Can someone identify the species of this angiosperm?

It seems to be from the pea family (Fabaceae) due to the zygomorphic flowers and the pods. It also has stipules at the base of the composite leaves. It's quite high (~ 80 cm). Photographed in spring in Morocco. It was photographed in a dry riverbed.

This is a difficult one to identify down to the species from the photos. It very much looks like a member of the genus Ononis in the pea family. The leaves, flowers, and seed pods are all characteristic of Ononis. It might be Ononis spinosa, but that is a guess. The bright sunlight make it difficult to discern many morphological details. I can't see any visible spines on the plant to be certain. Links provided:

Classification of Angiosperms

Human interaction with the flowering plants is a fundamental biological activity. As we know all living animals even human being rely on angiosperms for substance. The world 20,000 years ago was probably much mere familiar with the local flora, in terms of species recognition than most people today because a local angiosperms flora offer a mosaic of valuable resources as food, medicine, etc.

It has always been important to be able to discuss pattern of flowering plant variation, recognize significant structural features and identify kinds. Thus the discipline of plant systematics has extremely deep cultural roots in all parts of the world.

Classification of plants is a necessity to study the number of plants available in the world.

Objectives of Classification:

Following are the objectives of classification:

1. First objective is to name all the plants of the world and fix their specificity to their habit, habitat, distribution, characters etc.

2. Second objective is to arrange them according to their characters in their particular place in the classification.

3. Name the plant according to International Code of Botanical Nomenclature in which it should have two epithets, the first in the generic name and the second is the specific name.

The ancient knowledge of Indians was very vast but their language was primarily Sanskrit which was not accessible by western people. Ancient Indians had the concept of life which can be compared to the modern one. It was given by Parashar in Vrikshayurveda.

It suggests that water transforms into kalalm (a jelly like substance) and a pindasthamukam (nucleus) is formed in it, which is regulated by terrestrial energies. The jelly is transformed into bija (germ).

They described protoplasm as Kalalibhutan (colloidal system). In their opinion plants preceded animals and man on earth. The great Indian writers Uddalaka and Yajnavalkya had thoughts of evolution and heredity even 2000 years before Darwin.

Apart of Vrikshayurveda there are several books on plant science mostly written by Varahmihir such as Brihatsamhita, Agnipurana, Sarangdhara etc.

In Vrikshayurveda, different subjects related to plants such as:

(a) Bijotptti vidhi (Seed biology),

(b) Drumraksha (Plant protection),

(d) Bhumi Nirupana (Soil science), and

(e) Upavanakriya (Horticulture) etc.

There are several examples which feel that these people know about soil fertility and necessity of water, how it travels up in the trees. They know that water not only moves up but also circulate in plant body as blood circulation in human system.

Though they were not aware of the mechanism of photosynthesis yet they were knowing the importance of leaves, the role of leaves and sunlight in the sustenance of plants. They knows about the diseases of plants the remedies and prevention. Our rishis like Gunaratna, Kasyapa and Sarangdhara etc. have worked upon it.

In the book The Positive Sciences of the Ancient Hindus, King George V professor of philosophy at Calcutta University told that ancient Hindu scriptures hold the plants have dormant or latent consciousness and are capable of pleasure and pain.

Gunaratna told that plants display the phenomenon of walking and sleeping. In Mimosa pudica he observed the leaves drop by touch and he called it as Lajjalu (a shy person). Plants also show the phenomenon of life, death, sleep, diseases etc.

In Ancient Indian literature the plant and plant parts have a definite terminology. Even they have the knowledge of area, season and plant germplasm etc.

Some of the terminology is given below:

Skandshakha (primary branches)

Triparna (Trifoliate leaves)

In ancient Indian literature the plant names are based on certain special features, characters, uses, properties, locality where they grow etc.

1. Dadrughna (cures ring worm e.g., Cassia fistula)

2. Arsoghna (cures pils e.g., Amorphophallus paeonifolius)

(B) Special characteristics:

1. Dwipatra (bifid leaves e.g., Bauhinia)

2. Satmuli (Hundred roots e.g., Asparagus)

3. Bahupada (Many columnar prop roots e.g., Ficus)

(C) Special association:

1. Yagnadumura (Association with Yagna e.g., Ficus glome rata)

2. Bodhi druma (association with ‘Budha’ enlightenment e.g., Ficus religiosa)

1. Dhanudruma (used for making bows e.g., Bambusa)

2. Lekhana (used for making pen e.g., Arundinaria).

1. Vaidehi (indigenous to Videh or e.g., Piper nigrum)

2. Magadhi (Indiginous to Magadh e.g., Piper betal)

(F) Ecological characteristics:

1. Kutja (growing on mountain peakse.g, Holarrhena pubescens)

2. Pankeriha (grouping in mud e.g., Nelumbium)

The different species of a genus may be differentiated on the basis of the colour of flowers e.g., Pitapushpa (yellow flower), Raktapushpa (Red flower), shweta pushpa (white flowered etc.)

Ancient Indian plant classification was based on three major considerations i.e.:

(b) Virechanadi (Medicinal), and

The necessacity of classification increased by the increase of knowledge of more and more plants. The classification of plants in Indian Vedas is the oldest where the saints have divided the plants based on their needs. The first literature is cited in Rigveda in 3000 BC. After that in Vrikshayurveda and Manusmriti also it could be seen. Plants were divided into 8 parts in Vrikshayurveda.

Fruit and flower bearing trees

Such type of classification of plants is also found in Charak and Sushrut Samhita. Where the plants are classified according to their uses. In Sushrut Samhita plants are divided into 37 orders on their medicinal value.

Prasastapada (medical practioners) classified plants as:

Arboreal plants and shrubs.

Trees with flowers and fruits.

Trees with fruits but no flower.

Ancient Indian plants were studied mostly in relation to medicinal uses. In Ayurveda most of the medicinal plants with their properties and uses for different ailments are included.

The History of classification of Angiosperms is divided differently. According to one view it is classified into two major periods.

A. Pre Darwinian period and B. Post Darwinian period.

Other ways of Classification are:

1. Classification based on habit.

2. Classification based on number of floral parts e.g., stamen etc.

3. Classification based on morphological characters or form and relationship.

4. Classification based on phylogeny.

Pre Darwinian period includes the time of Theophrastus i.e., 370-285 B.C. upto the time doctrine of Darwin was proposed. However, post Darwinian period includes all the classification after the Doctrine of Organic Evolution of Charles Darwin is 1859.

Another view of classifying the history of classification of angiosperms is as:

1. Artificial system:

Based on habit or one character.

2. Natural system:

Based on morphological structure.

3. Phylogenetic system:

Based on evolutionary trends.

Artificial System:

It starts with Theophrastus (370-285 BC). Theopharstus was a philosopher and naturalist of Greece. He is also known as father of Botany. Theophrastus, a Greek student of Plato and Successor to Aristotle as Director of the Lyceum and its botanical garden.

He proposed his classification in Historia plantarum He divided the plants into:

He included about 500 plants in it.

Intellectual stagnation of the middle age resulted in minimal original work in plant systematis Albertus Magnus (1200-1800 A.D) produced a classification system for the first time recognizing Monocots and Dicots.

After a very long, gap, Otto Brunfels (1464-1534) recognized plants and named Perfecti and Imperfecti respectively to the plants with and without flower.

Jean Bauhin (1541—1631) described 5000 plants in his book Historia plantarum universalis. He was a Swiss physician. His brother Gaspand Bauhin (1560-1654) wrote a book Pinax in 1623 and described 6000 plants. Carolus Linnaeus (1707—1778) gave Sexual system of classification. He was a physician. First he published some plants in Hortus uplandicus.

Thus his most popular classification based on stamen, type, absence or presence etc. was published in Species plantarum in 1753. He diagnosed nearly 6000 species of 1000 genera.

He used binomial nomenclature of plants in the 23 volumes of Species plantarum. In Philosophia Botanica (1751), Linneaus enumerated67 “natural orders” such as Palms, Orchids, grasses, conifers, borages, composites etc. But there is a mixing of dicots and monocots in these natural orders.

Classification Proposed By Linneaus:

Linneaus divided plant kingdom into 24 Klasses:

7. Heptandria (Seven stamen),

11. Dodecandria (Twelve stamen),

12. Icosandria (Twenty stamen),

13. Polyandria (Many free stamen),

15. Tetradynamia (Tetradynamous),

16. Monadelphia (One bundle),

18. Polyadelphia (Many bundles),

19. Syngenesia (Anther fused, filament free),

20. Gynandria (Stamen adnate to pistil),

21. Monoecia (Unisexual flowers on one plant),

22. Dioecia (Unisexual flowers on two different plants),

23. Polygamia (Flower Polygamous), and

24. Cryptogamia (Flowerless).

This classification was appreciated for more than 100 years. It aids to quick and easy identification of plants by means of one or few characters. The main demerit was Dicots, monocots and gymnosperm were not separated, e.g., Gynandria contain ordhids (monocot) and Passiflora (Dicots).

One genus can be placed in more than one class e.g., Brassica with six stamens is placed in hexandria as well as tetradynamia etc. Genera belonging to one family are placed in different classes.

Natural System of Classification:

It starts with.Bernard de Jussieu (1699-1777) who as centemporary of Linneaus. He was French man and professor of Botany at Royal Gardens. He modified the systems of Linneaus by dividing the flowering plants into Monocots and Dicots based on Positions of ovary, presence or absence of petals, free or fused petals etc.

His nephew Antonie Laurent de Jussieu in 1778 proposed the classification based on number of cotyledons, position, number of adhesion of petals. He published his work in Genera plantarum in 1979 and divided plants into 15 classes, 100 orders and families. He included cryptogames in Acotyledons.

Augustin P de Candolle published his classification of plants in 1819 in Prodromus systematis naturalis regni vegetabilis. Candolle published 7 volumes and his son Alphonse de Candolle continued the work and published 10 more volume, the last in 1873. The most popular and practical classification of Natural system was given by George Bentham (1800- 1884) and Joseph Dalton Hooker (1817-1911).

They jointly published their classification in Genera plantarum (in latin) in 3 volumes from 1862—83. They have taken into consideration many features of the plants. Joseph Dalton Hooker was a botanist and the first director of Kew Botanical Garden in 1865. Sir J.D. Hooker published 7 volumes of Flora of British India and Index Kewensis.

Bentham and Hooker classified only phanerogames or seed plants. They have distributed about 97,205 species in 202 families.

Bentham and Hooker’s Classification:

Bentham and Hooker divided the seed plants or spermatophytes into three divisions:

Division I Dicotyledons:

It includes plants with dicotyledonous seeds, Reticulate venation of leaves and Pentamerous flowers.

A. Polypetalae: with free petals.

B. Gamopetalae: with fused petals.

C. Monochlamydeae: Flowers have perianth i.e., calyx and corolla are either not distinguished or petals are absent.

This class is divided into 3 series:

Flowers with superior ovary. This series is divided into 6 orders. These are:

Nectar disc is present below the ovary. Ovary is superior.

This series is divided into 4 orders.

Flowers are generally epigynous i.e., the ovary is inferior.

This series is divided into 5 orders:

The class is divided into 3 series.

Flowers with inferior ovary.

This series is divided into 3 orders:

This series is also divided into 3 orders:

(c) Bicarpellatae:

Flowers with bicarpellary, syncarpous, superior ovary, epipetafous stamen. The series is divided into 4 orders:

Class 3. Monochlamydeae:

The flowers are either apetalous or with perianth i.e., calyx and corolla are not distinguished. Generally incomplete flowers. The class is divided into 8 series. Series are not divided into orders but directly families are assigned to it.

(b) Multiovulate – terrestres

Division 2. Monocotyledons:

The plants have seeds with only one cotyledon. Leaves show parallel venation and flowers are trimerous. This division is divided into 7 classes. Each class includes families directly. There is no series or order.

The classes are as follows:

The classification of monocots is very unnatural. Gymnosperms are sandwiched between dicots and monocots.

1. The classification is very practical.

2. Ranales were considered as primitive dicots.

3. Placements is gamopetalae after polypetalae also is supported by evolutionary condition.

4. Presence of Cucurbitaceae and Apiaceae at the end of polypetalae i- justified.

5. The phanerogames were divided into 202 families (cohorts) startrr: Ranunculaceae and ending in Gramineae.

6. The monocots were categorized on the basis of positions of – r – and characters of perianth.

7. In Gamopetalae, the orders start with actinomorphic f.: Bt. m and ends with zygomorphic flowers (Personales and Lamiales).

1. Polypetalae starts with hypogyny (Thalamiflorae) to epigyny (Calycifloreae) but Gamopetalae starts with epigyny (Inferae) and ends in hypogyny (Bicarpellatae).

2. Gymnosperms are sandwitched between Dicots and Monocots.

3. Monochlamydeae is an artificial class with a single character i.e., one whorl of perianth. Related families of curvembryae could found place in caryophyllaceae.

4. Podostemaceae is related to Rosales, and Napenthaceae to Parietales etc.

5. Retention of Nyctaginaceae, Polygonaceae, Amaranthaceae, Chenop- odiaceae etc. in Monochlamydeae is not much justified as many of them have differentiated or dichlamydous perianth.

6. Monocots starts with epigynous flowers (Microspermae and Epigyneae), while it should be taken into the last.

7. Orchidaceae has been given a primitive position though it is highly advanced in characters.

8. Closely related Liliaceae and Amaryllidaceae are kept apart in two different classes only on the basis of ovary position.

9. Monochlamydeae is divided upon series only.

10. Monocotyledons were divided into classes only.

Phylogenetic System of Classification:

The period started a little knowledge of evolution in the beginning. The authors started incorporating evolutionary bases also. In this system the first was that of August Wilhelern Eichler’s system (1839-1887). Eichler was a professor of botany in Germany. He only modified Bentham and Hooker’s system by placing Gymnosperm before angiosperms (Dicot and Monocots).

The outline is as follows:

Engler and Prantl’s Semiphylosenetic Classification:

Adolf Engler (1844-1930) Karl Pranltl (1849- 1893) published their classification in their voluminous work “Die Naturlichen Pflanzen familien”. They modified Eichler’s classification. It was the first angiosperm system which considered anatomical data also. In this the families are arranged according to increasing complexity of the flower, fruit and seed development (Fig.).

The plant kingdom is divided into 13 divisions. The 13th division was Embryophyta Siphonogama. It was again divided into Gymnospermae and Angiospmermae. Which were then divided into classes, and orders and family.

The fourteen divisions are:

(14) Embryophyta Siphonogama.

Archichlamydeae includes 33 orders beginning from Verticillatae and ending in Umbelliflorae with 199 families: The first family was Casuarinaceae and the last Cornaceae.

Metachlamydeae includes 11 orders staring from Diapensiales and ending into Campanulatae, with 56 families. The first family was Diapensiaceae and the last Compositae.

Naked flowers were considered as Primitive and the families were kept under Amentiferae. While dichlamydous flower was considered as advanced.

Monochlamydeae of Bentham and Hooker was abolished and generally arranged in Archichlamydeae. The group Amentiferae was treated as most primitive and begins with Verticillatae and Piperales with naked, anemophilous, unisexual flowers.

Class Monocotyledonae was divided into 11 orders starting with Pandanales and ending in Microspermae. The class contains 45 families. The 5rst family in Pandanales is Typhaceae and the 45th family in Microspermae is Orchidaceae. It means that they considered Orchidaceae as the highly evolved family.

1. The large artificial group Monochlamydeae of Bentham and Hooker was merged in archichlamydeae.

2. Metachlamydeae or Sympetalae corresponds to Gamopetalae of Eentham and Hooker.

3. Gymnosperm are taken out from inbetween of Dicots and Monots and made separate sub division.

4. In both Archichlamydeae and Metachlamydeae the families with epigynous flowers were treated as advanced. The evolution is considered as hypogyny to epigyny.

5. Orchids were considered most advanced and evolved than grasses.

1. They considered the angiospermic flower as derived from gymnospermous strobilues. Primitive families bear catkin type of inflorescence (unisexual). The bisexual flower was derived from unisexual type.

2. Amentiferae is placed in the beginning of Archichlamydeae.

3. In Amentiferae, the flowers are generally naked or monochlamydous with bract like perianth.

4. They considered that Gymnosperm give rise to Amentiferae on one and monocots on the other hand.

5. Origin of angiosperm was considered as polyphyletic.

6. Primitive position of Amentiferae is critisised by many botanists.

7. Derivation of dichlamydous flower from monochlamydous was not accepted by many botanists.

8. Derivation of perietal placentation from axile placentation.

9. Monocots as more primitive than dicots.

The Englerian system positioned Coniferlike (unisexual) angiosperm at the phylogenetic base (e.g., Casuarinaceae) with taxa producing large, showy flower such as Magnoliidae as derived or specialized.

Taxa now treated as the Hamamelidae (Engler’s Amentiferae) represented the basal element and monocots are basal dicots. While this statement is abandoned by most involved with flowering plants classification.The Englerian system remain as significant cataloging device in that, due to the size, scope and quality of Die Naturlichen P flanzen familien.

Alexander Braun 1859 classified monocots on showing progression from simple to complex organization. He believed unisexual naked flower of Lamnaceae are most primitive and other originated from this with gradual complexity to Orchidaceae. In dicots he began with Apetalae → Sympetalae → ending with Leguminosae.

Eichler modified this system many a times in 1876, 1880, 1883 in the final version.

Engler and Prantl adopted this system and modified to certain extent. According to Englerian concept flower with only stamen or carpel from lowest grade of organization unisexual naked flower generally borne in Catkins are most primitive within angiosperm and probably arose from gyno-ancestors with unisexual strobilus.

Bisexual flowers are derived from a cluster of male and female flowers held together and forming a false flower (Pseudoanthum). Parianth evolved Later in evolution. This also believed in polyphyletic origin of angiosperm from gymnosperm and Ptderidophyota.

The Ranalian School:

The thought of Charles E. Bessey (1915) was modified by J. Hutchinson on angiosperm. According to which angiosperm arose from gymnosperm with female strobilus bearing megasporophyll on upper region and microspherophyll and lower region. The lower sporophylls developed with sepals and petals due progressive sterilisation. Upper one developed into stamen and Carpel.

The axis-, of strobilus condensed to from receptacle. That is why primary flower has indefinite number of perianth, stamen, free carpels, spirally arranged on receptacle. Ancestor of angiosperm was believed to be an undiscovered gymnosperm and the origin is monophyletic type.

Recent or Modern system of flowering plant classification is influenced by phylogenetic Dicots given by Charles Bessey (1845-1915) (Fig.).

Hutchinson’s Classification:

The classification based on principles of phylogeny was suggested by John Hutchinson in his 2 volumes of “The Families of Flowering Plants”. John Hutchinson was a British Botanists from England (1884-1972).

He proposed 24 principles of Phylogeny parallel to Bessey’s Dicta of phylogeny. In 19G9, he published “Evolution and Phylogeny of Flowering plants.” His other work is Genera of Flowering plants (1964-67). His classification was revised time to time (1955, 69) and finally appeared in 1973.

The main feature of classification suggests:

(1) Origin of Angiosperms is Monophyletic originating from unknown hypothetical proangioperms.

(2) Initially Angiosperms were regarded to have evolved along two separate parallel evolutionary lines.

(a) Herbaceae (Herbaceous families starting from Ranales to Lamiales, 28 orders)

(b) Lignosae (Arborescent or woody plants starting from Magnoliales to Verbenales, 54 orders)

(c) He considered monocots to be derived from Ranales. Monocots were divided into 3 groups based on nature of Perianth into Calyciferae, Corolliferae and Glumiflorae with in all 29 orders and 104 families.

(d) In the phylogenetic tree he did not drive one order from the other. Instead, that arose from the ancestrol stock.

(e) His system provided strong basis for the later phylogenetic systems of Takhtajan, Cronquist, Dahlgreen and Thorne etc.

According to Hutchinson, the origin of Angiosperm is from Hypothetical Proangiosperms. Whereas the evolution in Lignosae is from Magnolicaceae →Verbenaceae, in Herbacae from Ranunculaceae to Lamiaceae while in

Monocotyledones from Butomaceae to Poaceae:

In the new revised classification published in 1973 small alterations were made as: Lytherales were transferred to Myrtales in Lignosae from Herbacea. Now Dicots include 82 orders and 343 families while Monocots include 29 orders and 69 families.

Merits of Hutchinsons System:

(1) It is a phylogenetic system purely based on principles of phylogeny.

(2) This system provided a base for the phylogenetic system of Ostwald Tippo Cronquist, Takhtajan and Dahlgren etc.

(3) The system considers Ranales as primitive Herbaceous dicots while Magnoliales as primitive Lignoceous dicots.

(4) Families and orders are very small and comprises of only very much related taxa.

(5) The arrangement of families in Monocots is widely accepted.

(6) Monocots are considered to be more advanced than Dicots.

Demerits of Hutchinson’s System:

(1) Dicots were divided on the basis of habit into two major groups, i.e., Lignosae and Herbaceae. Lignosae includes woody plants. This was not accepted by many as otherwise closely related plants were kept for apart and the two evolutionary lines cannot considered distinct.

(2) The two related families on the basis of floral structure were separated, e.g., closely related families of Ranales as Ranunculaceae and Magnoliaceae were kept far away.

(3)This system did not derive one order directly from other but from ancestral stock.

(4) Several herbaceous families which are closely related or even derived from woody families e.g., Apiaceae (Herbaceous) is considered to be derived from Cornaceae and Araliaceae (woody) or Brassicaceae (Herbaceous) is derived from woody Capparidaceae via Cleomaceae.

(5) The system is not considered more useful in practical plant classification.

(6) All the emphasis has been placed on herbarium and woody habit and not on floral character.

Principles of Phyloseny given by Hutchinson: `

1. Evolution is both upward and downward.

2. Evolution does not necessarily take place in all the parts of the plant at one time.

3. Evolution has generally been consistent.

Habit and Habitat:

4. Trees and shrubs are primitive than herbs.

5. In one family or genus trees and shrubs are primitive then climbers.

6. Perennials are primitive the biennials and annuals are most advanced type.

7. Aquatic plants are derived from terrestrial plants.

8. Dicots (conjoint, collateral, open, vascular bundles arranged in a ring) are primitive than monocots (conjoint, collateral, closed, scattered, vascular bundles).

Vegetative Characters:

9. Spiral arrangements (alternate) is primitive than opposite than whorled.

10. Simple leaves are primitive than compound leaves.

Floral Characters:

11. Bisexual flowers are primitive than unisexual.

12. Solitary flowers are primitive than inflorescence, Hypanthodium is most advanced type.

13. Spirocyclic flowers are primitve than cyclic.

14. Polymery is primitive than oligomery.

15. Polypetaly is primitive than Gamopetaly, similarly polysepaly is primitve than gamosepaly.

16. Apetalous flowers are derived from petaliferous flowers.

17. Actinomorphy is primitve than Zygomorphy.

18. Hypogyny is primitive than epigyny and perigyny.

19. Apocarpy is primitive than syncarpy.

20. Polycarpy is primitive than monocarpy

21. Polyandry is primitive than synandry (Adelphous to Syngenesious).

22. Cauliflory is primitive than ramiflory.

23. Endospermic seeds are primitive.

24. Simple fruit is primitive- than aggregate than Composite. Syconus is the most advanced fruit.

Dahlgren’s System of Classification:

The system was proposed by RolfM.T. Dahlgren (1932-1987) in 1974 in his book A Text-book of Angiosperm Taxonomy. The system was revised in 1975 in Botanical notiser in 1980 in Botanical Journal of the Linnearn Society in 1981 in Phytochemistry and Angiosperm phylogeny and in 1983 in Nordiac Journal of Botany.

Dahlgren was professor at the Botanical Museum of the University of Copenhagen, Denmark. His classification is a phylogenetic classification. His classification is based on Anatomy, Phytochemistry and Embryology etc. He considered angiosperms to be Monophyletic origin angiosperms evolving from 4 Gymnosperms.

Dahlgren named Angiosperm Magnoliopsida and divided them into two subclass Magnolidae (Dicots) and Liliidae (Monocots). Magnolidae include 24 superorders, 80 orders and 346 families, and Liliidae includes 7 superorders, 26 orders and 92 families.

Merit of Dahlgren’s System:

(1) The system is a modified version of Takhtajan’s system. Data from anatomy, embryology and chemists are also considered.

(2) Dicots are considered to be more primitive than Monocots.

(3) Dahlgren illustrated his system as a phylogenetic shrub showing the relationship between orders. (Fig. 2).

Demerits of Dahlgren’s System

(1) Dahlgren made many unnatural orders and Superorders.

(2) He did not consider the Polyphyletic origin of Angiosperms from Gymnosperms.

(3) Dahlgren thought that 8 nucleate embryosac, companion-cell in phloem and secondary endosperm etc. have evolved independently.

(4) Nomenclature of various groups are criticized and the name Pseui suggested for a conjectural taxon.

Robert Thorne’s System of Classification:

Robert F.Thorne published his Phylogenetic type of classification as “a synopsis of a pultatively phylogenetic system of classification of flowering plants” in Aliso in 1968. He first proposed some phylogenetic guidelines and then elaborated his classification in 1976. He revised the classification in 1981 and published in Phytochemistry and Phylogeny and in 1983 in Nordiac Journal of Botany.

He included data form Phytochemistry, host- parasite relationships, pollen and seed morphology, comparative anatomy, microstructure, embryology, plant geography, palaeobotany and cytology in his classification. He believed that the origin, Angiosperms is Monophyletic. He divided Angiospermae (Annonopsida) in two subclass Dicotyledoneae (Annonidae) and Mono- cotyledoneae (Liliidae).

He divided Subclass Annonidae into 19 super-orders, 41 orders, 56 suborders, 297 families, 350 subfamilies 9640 genera, 1, 73,370 species and Subclass Liliidae into 9 Superorder 12 Orders, 17 Suborders, 53 families, 102 subfamilies, 2,615 genera and 52,120 species.

Robert F. Thorne revised his classification in “Classification and Geography of Flowering Plants” Which was updated once again in 1999 March.

According to which the classification is as follows:

Merits of Thorne’s System:

(1) Annonales are considered as primitive living angiotperms.

(2) Closely related taxa are placed nearer to one another.

(3) Orders Cornales and Dipsacales are placed under one superorder Corniflorae.

(4) Families of Amentiferae are distributed into different orders.

(5) Orders Malvales, Urticales, Rhamnales and Euphorbiales are included in one superorder Malviflorae (Fig. 3).

Demerits of Thorne’s System:

(1) The unnatural super-orders and suborders, subfamilies are much in number.

(2) It is not practical in identification of plants.

(3) Throne’s view was that angiosperms originated from some Pteridospermous members in early cretaceous period is not accepted by many taxonomists.

Armen Takhtajan’s System of Classification:

Armen Takhtajan was born in 1910. He was Head of Department of higher plants at Komarov Botanical in Leningrad (Russia), when his classification was first published in 1942. In 1959 in elaborated system of classification appeared in German in his “Die Evolution der Agniospermen” in 1966. He modified the classification and published in English in Flowering Plants Origin and Dispersal.

In 1980 A new version of his classification appeared in Botanical review. Takhtajan’s system is basically inspired by Bassey- Hallier tradition considering evidences from fields like Morphology, Anatomy, Embryology, Cytology, Palynology, Paleobotany, Chemistry, Ultrastructure etc. According to Takhtajan angiosperms are monophyletic in origin and have derived their ancestry from Gymnosperms. Monocots are derived from primitive dicots.

In 1980 Takhtajan divided Magnoliophyta (Angiosperms) into 2 classes Magnoliopsida and Liliopsida with about 10 Subclasses (7 in Megnoliopsida and 3 in Liliopsida).

In 1977 he revised his classification and now the two classes include 151 subclasses (11 in Magnoliopsda and 6 in Liliopsida). These are as follows:

According to Takhtajan among Magnoliopsida, Magnoliidae is the most primitive basal group from which others are derived and Asteridae is the most advanced one. However, in Liliopsida, Alismatidae, Lilidae and Arecidae are considered to be more primitive than the other subclass of Magnoliopsida, and have been derived from Magnolidae. Winterceae was considered to be the most primitive family and Poaceae to be the most advanced family among angiosperms.

Takhtajan’s system is based on some Phyletic principles.

The most important on which his classification was based are as follows (Fig. 4):

(1) Woody plants are more primitive than herbaceous plants.

(2) Deciduous woody plants are evolved from evergreen plants.

(3) Xylem fibres evolved from tracheids to libriform fibres, through fibre tracheids.

(4) Trilacunar or pentalacunar nodes are primitive to unilacunar nodes.

(5) Alternate leaf phyllotaxy is more primitive than other types.

(6) Parallel venation is advanced.

(7) Anomocytic stomata (Stomata without subsidiary cells) are more advanced than stomata with subsidiary cells.

(8) Cymose inflorscence is more primitive than recemose.

(9) Flowers with an indefinite or variable number of floral parts (Polymerous) are primitive.

(10) Pollen with unsculptured exine (smooth) is more primitive than sculptured exine.

(11) Apocarpous gynoecium is more primitive than syncarpous.

(12) Bitegmic ovules are primitive than unitegmie ovules.

(13) Anatropous ovule is more primitive than others.

(14) 8-nucleated Polygonum type embryosac (female gametophyte) is most primitive.

(15) Mesogamic and chalozogamic conditions have evolved from porogamic condition.

(16) Many seeded follicle fruits are most primitive.

Merits of Takhtajan’s System:

(1) Magnoliopsida is considered primitive to Liliopsida,

(2) Families are small in size and made up of every closely related genera.

(3) Dicots start with most primitive Magnoliales.

(4) Monocots start with most primitive Alismatales.

(5) Problems of Monophyly or Polyphyly, Inter-relationships of monocots and Dicots etc. are dealt satisfactorily.

Demerits of Takhtajan’s System:

(1) Derivation of Monocots from the stocks ancestral to the Nymphaeales.

(2) Extremely narrowly defined taxa have resulted in the unwarranted splitting of related groups.

Arthur Cronquist’s System of Classification:

Arthur Cronquist’s was born on March 19, 1919 in San Jose, California. He joined the University of Idaho with Prof. J Davis. He worked under the direction of Dr. Basselt Maguire on Aster Foliaceus complex. He worked at New York Botanical Garden in 1943. He left the Botanical garden in 1951 and joined Washington State University to teach Botany.

Again, he joined back the New York Botanical Garden in 1952 and worked on floristics with Henry A. Gleason. They published “New Britton and Broswon illustrated flora in 1952.

The second book was published with Gleason named Manual of Vascular Plants of Northeastern United Arthur Crofnquist (1919-92) States and Adjacent Canada in 1963 “The Natural Geography of Plants” in 1964.

Cronquist worked as Director of Botany from 1971-74 and Senior Scientist from 1974-92 at the New York Botanical Garden. He was president of American Society of Plant Taxonomists in 1962, Botanical Society of America in 1973, and Torrey Botanical Club in 1976. He received many Awards also.

He received Asa Gray Award of American Society of Plant Taxonomists in 1985, Medal for Botany from Linnean Society of London in 1986. He died on March 22, 1992 while studying plant specimens in the herbarium of Brigam Young, University in Utah.

The first classification of Dicotylodons was presented in 1957 by A. Cronquist. It was modified in 1966, 1981 and finally published in 1988 in his book Evolution and Classification of Flowering Plants. The first revision in 1966 with Sporne and Zimmerman. In 1968 the classification was published in a book called Evolution and Classification of Flowering Plants.

In 1981 it was again revised and appeared in Integrated Systematics of Classification of Flowering Plants. The classification is based on observations and discussions with other botanists. Classification is based on evidences from Morphology, Anatomy, Embryology, Palynology, Serology, Phytochemistry, Cytology etc.

Important Features of Classification:

1. Traditional nomenclature of angiosperm, dicots and monocots is replaced as has been done by Takhtajan.

2. Synthetic system of classification taken help from other fields of botany to deduce his interpretation.

3. Key for each group upto family is useful.

4. System appears more natural.

5. Evolution relationship amongst the subclasses of dicots has shown in the form of balloon. The size of balloon is proportionate to member of species in each group (Fig. 5).

Cronquist divided Angiosperms Magnoliophyte into 2 classes Magnoliopsida and Liliopsida. Classes are divided into subclass, orders and families. No super orders are formed. Magnoliopsida is divided into 6 subclasses and Liliopsida is divided into 5 subclasses.

Merits of Cronquist’s Classification:

1. It is a phylogenetic classification.

2. He compared all the previous classification and discussing their merits and demerits proposed a new classification.

3. He considered morphology, anatomy, embryology, palynology, serology, cytology, and phytochemistry in his classification.

4. Key for each group upto families is useful.

Demerits of Cronquist’s Classification:

1. Arrangement of some families in Liliales is criticized.

2. Submergence of Amaryllidaceae into Liliaceae is not satisfactory.

3. It shows too much reliance on single character, e.g., free central placentation and centifugal stamen etc. many times which is not accepted.

4. Traditional nomenclature is replaced.

Differences between Magnoliopsida and Liliopsida:

3. Roots primary and adventitious,

4. Vascular Cambium present,

5. Vascular bundles arranged in a ring in stem,

6. Flower Tetra or Pentamerous, and

7. Pollen grains of various types.

3. Roots only adventitious,

4. Vascular Cambium absent,

5. Scattered Vascular Bundles in stem,

6. Flowers usually Trimerous, and

7. Pollen grains mainly monosulcate types.

Important Characters of Different Subclasses Magnoliopsida

Subclass 1 Magnoliidae:

It includes 8 orders, 39 families. The families show primitive characters. Plants generally are woody (shrubs or arborescent). Leaves evergreen, stipulate or existpulate simple, alternate.

Flowers solitary, actinomoprhic, polymerous, floral axis elongated. Calyx and Corolla not much distinct, i.e., generally perianth. Numerous stamens with laminar to terete filament. Numerous carpels, apocarpous. Fruits generally follicle entomophilous.

The orders start from Magnoliales to Papaverales (herbaceous, syncarpous plants).

Subclass 2. Hamamelidae:

It includes 11 orders and 24 families. Typically plants are woody except order Urticales. Flowers are unisexual (imperfect) perianth apetalous (absent) or reduced, inflorescence with numerous reduced apetalous flowers arranged in catkin or ament. The group as named is Amentiferae.

Primitive order is Trochodendrales and advance is Casurinales (multiple fruiting structures).

Subclass 3. Caryophyllidae:

It includes 3 orders, 14 families. Caryophyllales in the largest order. The plants in this order lack anthocyanin instead possess Betalins (Betacyanin and Betaxanthin). Betalins are otherwise found in fungi only. Perianth is uniseriate. Placentation is either basal or free central.

The older name of the group is Centrospermae as the ovules are present around in placenta in the centre of the ovary. In most of the caryophyllales perisperm is present which is derived from sporophytic tissue (2N) instead of endosperm. Embryo takes a peripheral position in the seed and produced a Beaked (protrusion of radial)

The families start from Phytolaccaceae to Caryophyllaceae come under the order caryophyllales.

The 3 orders are Caryophyllales, Polygonales and Plumbaginales.

Subclass 4. Dilleniedae:

This subclass includes 13 orders and 78 families. The plants show diverse characters. All the plants have synacarpous flowers except Dilleniales where flowers are apocarpous. Generally perietal, free central axile or basal placentation and Gamopetatous flowers.

Rarely they are poly or apetalous flowers. Lack of connection in gynoecium, e.g., Paeonia-Paeoniaceae order Dilleniales. Dilleniales from a link between Dileniidae and Magnoliidae. It starts form Dilleniales order and ends in Primulates. Dillenidae is divided into Pinnate Dilleniales and Palmate Dilleniada.

It includes 18 orders 114 families. It is the largest subclass. It includes flowers with diverse characters. Generally the leaves are pinnately compound, polypetalous, very rarely gamoptalous, nectary disks are present, Gynoecium generally synacarpous, Apocarpous in Fabales and Proteales, and apocarpous- synacarpous in Resales. Placentation marginal, Basal or Axial. Orders start from Rosales to Apiales.

Flowers hypogynous → Perigynous → Epigynous, Polypetalous or basally connate or reduced, nectarias often staminodal in origin, frequently from intra or extrastaminal disc.

Stamen initiate in centripetal sequence (except Punicaceae), Gynoecium apocarpous in monocarpellary condition as in Fabales, Proteals etc. Many Rosales have syncarpous gynoecium with ovary sperior semi inferior → inferior condition. Placentation varies but majority its in axile less commonly parietal or basal.

Subclass includes 11 orders and 49 families. One third of the total plants belong to Asteraceae. Flowering actinomorphic or zygomorphic hypogynous- epigynous……. gamopetalous Gynoecium 2-5 carpels synacarpous, usually are necterifereous disc is style terminal or gynobasic with basal to axial placentation and stamens epipetalous.

Asteridae is considered to be most advanced dicotyledonous plant. Some of the orders included in it are hypogynous to the Advanced Asteraceae as epigynous. The order starts from Gentianales to Asterals.

Subclass 1 Alismatidae:

Subclass Alismatidae includes 4 orders and 16 families. It is considered to be the smallest subclass of Magnoliophyta. Gynoecium 1-α and apocarpous. It may be 2-3 carpels fused below forming pseudomonomerous unilocular. Generally aquatic plants except Triuridales. Orders start from Alismatales to Triuridales. Subclass is considered to be nearer to Magnoliidae through Nymphaeales.

Subclass 2. Arecidae:

It includes 4 orders and 5 families. Flowers small often crowed in spadix, hypogynous, ovary sunken in axis. It includes smallest flowering plants (Lemnaceae) in Arales and the largest monocots (Arecaceae) in Arecales. Largest Angiospemic seed is Lodoicea maldivica belongs to Arecaceae. The largest leaves of Raphia regalis are also considered in Arecaceae. The order starts from Arecales to Arales.

Subclass 3. Commelinidae:

It includes 7 orders and 16 families. Flowers bi or unisexual hypogynous nectaries rarely present pollination by wind, Trimerous apomicts. It includes the largest monocot family, the grasses Poaceae. The family is economically as well as ecologically very important. Flowers entomophilous to anemophilous. The orders follow a phyletic pattern. The orders start from Commelinales, to the Typhals.

Subclass 4. Zingiberidae:

The subclass includes 2 orders and 9 families. The two orders are Bromeliales and Zingiberales. Bromeliales show diverse characters. Bromeliales is a monotypic order including epiphytes. Flowers are actinomorphic trimerous hypo or epigynous and hexandrous. In Zingiberales plants are mesophytes with zygomorphic, 6 stamens but 1-5 stamens are functional in flowers. Sometimes flowers are functionally unisexual. They are Bird or Bat pollinated.

Subclass 5. Liliidae:

The last subclass includes 2 orders and 19 families. Flowers are very large and showy generally petaloid sepals. The orders are Liliales and Orchidales. Liliales include actinmorpic flowers with superior or inferior ovary. Orchidales are characterized by mycotropic plants, epiphytes, flowers, zygomorphic with inferior ovary numerous seeds, anemophilous pollination and non-endospermic embryo.

Angiosperm Phylogeny Group (APG) System:

Recent cladistic analyses have revealed that the phylogeny of Angiospems is supported for monophyly by many major groups above the family level. With many elements of the major branching scheme of phylogeny of these groups being established by now, a revised suprafamilial classification of flowering plants becomes both feasible and desirable.

APG system organizes plants into a “selected number of monophyletic suprafamilial groups”. The system was proposed in “An ordinal classification for the families of flowering plants” in 1998 and 2003 in “The Annals of the Missouri Botanical Garden” Compiled by Kare Bremer, Mark W. Chase and Peter F. Stevens, et al.

Based on a cladistic methodology, the grouping presents in this system are viewed by the authors as monophyletic clades. The higher levels are described as in informal and many families and orders are unassigned to higher level grouping.

The classification shows 462 families in 40 putatively monophyletic, order and a small number of monophyletic informal higher groups. The latter are monocots, commelinoids, eudicots, core eudicots, rosids including eurosids I and II and asterids including euasterids I and II. Informal groups include a number of families without assignment to order.

At the end of system an additional list of families of uncertain position is given for which no firm data exist regarding placement anywhere within the system. Phylogenetic naming is adopted as under current International Code of Botanical Nomenclature (Greuter et al. 1994).

Principle of priority is not mandatory for texa above the rank of family but the authors tried to balance priority with general usage while assigning names to orders. Generally, the well known orders are retained with the discoveries of new species, genera, and families, the size of genera, families, and orders have increased and many orders are now comprised of 10—20 families or even more.

A number of small orders are also recognised because these represent clades for which monophyly and relationships are well supported. It better conveys the interrelationships of the families included rather than leaving them unclassified to order. APG group recognises 462 families and 40 orders while Cronquist (1981) recognised 321 families 64 orders. Thorne (1992) 440 families and 69 orders, Takhtajan (1997) and 589 families in 232 orders.

In this ordinal classification, the principle of monophyly in combination with their desirability of maintaining already well established and familiar entities has largely been considered. Monofamilial orders and monogeneric families are avoided minimizing redundancy in classification.

Some monofamilial orders, e.g., Ceratophyllales, Accorales and Arecales are recognised because these are sister groups of more than one order. So, the families of these monofamilial order cannot be included in any other order without isolating monophyly.

Monophyly Principle in combination with mandatory usage of the family category leads to the recognition of many families, e.g., In Dipsacales, if Dipsacaceae and Valerianaceae are to be retained as families from Caprifoliaceae, the principle monophyly requires the recognition also of Diervillaceae, Linnaeaceae and Morinaceae because each of these families is the sister group of more than one family, so they cannot be merged with other family without violating monophyly.

These are small families that may be reduced to synonymy of their sister group if the latter consists of a single family., e.g., Cabombaceae may be merged with Nymphaeaceae, and Kingdoniaceae may be merged with Circaesteraceae (Ranunculales).

Some families may be non-monophyletic, revised circumscriptions, either by merging or splitting, into monophyletic taxa, e.g., Euphorbiaceae and Flacourtiaceae of Malpighiales several families of Myrtales, core Caryophyllales comprising of Achatocarpaceae, Aizoaceae, Amaranthaceae. Basellaceae, Cactaceae, Caryophyliaceae, Didiereaceae, Molluginaceae, Nyctaginaceae, Phytolaccaceae, Portulaccaceae, Sarcobalaceae and Stegnospermataceae.

The APG classification gives a major difference in the expansion of Alismatales including Araceae, Caryophyllales including Droseraceae, Nepenthaceae, Polygonaceae, Plumbaginaceae etc.

The recognition of a comparatively widely circumscribed Rosales including Rhamnaceae. Urticaceae, Moraceae etc. in addition of a number of smaller orders like Ceratophyllales, Acorales, Arecales, Proteales Carryales, Aquifoliales, and in deletion of Aristolochiales, Nymphaeales, Bromeliales, Trochodendrales, Zygophyllales etc. Monocots and Eudicots are not formally ranked and named.

Figure 2 explains the inter-relationships among the basal branches of the tree and the position of the root of the flowering plant phylogny remain elusive.

Under each of the superaordinal groups of monocots, commelinoids, core eudicots, rosids etc., there are a number of families listed without assignment to order as their ordinal position is still uncertain. Amborellaceae, Austrobaileyaceae and Canellaceae are listed at the beginning as they belong in neither any of the phylogenetically based orders at the beginning nor in the monocots or eudicots.

Families listed directly under monocots without an order are monocots and not commelinoids, families listed directly under Eudicots and Core-eudicots are Eudicots oe Core eudicots and not Rosids or Asterids. The families listed in the last are of uncertain position. They are probably eudicots.

Comparison between Bentham and Hooker, Engler and Prantl and Hutchinson’s Classification

1. The system was proposed in “Genera plantarum.”

2. The system was published in 1862.

3. It is a natural system of classification.

4. This system was based on de Candolle’s system (1818) which was the modification of Jussieu’s system.

5. Flowering plants are divided into Dicotyledons Gymnospermae and Monocotyledons.

6. Flowering plants were divided into 202 families.

7. Gymnosperms are placed between Dicots and Monocots.

8. Dicots kept before monocots.

9. Dicots divided into three classes polypetalae, Gamopetalae, and Monochlamydeae.

10. Dicots were further divided into series, order etc.

11. Monocots were divided into 7 classes, no orders.

12. Polypetate is divided into 3 series. Thalamiflorae, Disciflorae and Calyciflorae. Polypetalae has 15 orders starting with Ranales to Umbellales.

13. Gamopetalae is divided into 3 series Inferae, Heteromerae and Bicarpellatae. It has 10 orders starting with Rubiales to Lamiales.

14. Cucurbitaceae with gamopetalous flowers is included in Passiflorales of Polypetalae.

15. Highly evolved Asteraceae is placed in the beginning of Gamopetalae in the series Inferae and order Asterals.

16. Orchidaceae is placed in the beginning of Monocots in class Microspermae.

17. Gramineae is considered most advanced and placed in the end of Monocots.

1. The system was published in Die naturalichen pftenzen familien.

2. The system was published in 1931.

3. It is semi-phylogenetic system.

4. The system was modification of Bentham and Hooker’s system where Monochlamydeae is merged into Archichlamydeae. It is based on Eicher’s system mainly.

5. Flowering plants called Embryophyta siphonogama has been divided into Gymnospermae and Angiosprmae.

6. Flowering plants were divided into 280 families.

7. Gymnosperms are placed before angiosperms.

8. Monocots kept before dicots.

9. Dicots divided into Archichlamydeae and Metachlamydeae.

10. Dicots were divided directly into orders.

11. Monocots were divided into orders.

12. Archiclilamydeae divided into 31 orders starting with Vertioillate and ending with Umbelliflorae. Amentiferae is the primitive group.

13. Sympetalae is divided into 11 orders starting with Dispansiales to Companulatae.

14. Cucurbitaceae is placed in Cucurbitales of Sympetalae.

15. Asteraceae is placed in Sympetalae and the last order Campanulatae.

16. Orchidacae is placed at the end of Monocots under order Microspermae.

17. Gramineae is placed between Heiobiales and Princeps in the order Glumiflorae.

1. The system was published in “Families of flowering plants.”

2. The system was published in 1959.

3. It is purely a phylogenetic system.

4. This system was based on 24 principles of Phylogeny suggested by him. The Dicots are not divided on petal position. Dichlamydous plants where considered primitive.

5. Angiosperms are divided into Dicots and Monocots.

6. Flowering plants were divided into 411 families.

7. Same as Engler and Prantl’s system.

8. Dicots are kept before monocots.

9. Dicots are divided into Lignosae and Herbaceae.

11. Monocots were divided into calyciferae, corolliferae and glumiflorae.

12. Lignosae is divided into 54 orders. It starts with Magnoliales end with Verbenales.

13. Herbaceae is divided into 28 orders, starting with Ranales to Lamiales.

14. Cucurbitaceae is placed in Lignosae in the order Cucurbitales.

15. Asteraceae is placed in Herbaceae under Asterales.

16. Orchidaceae is placed as the last family of Corolliferae.

17. Gramineae is placed in the last under Glumiflorae.

Five Kingdom Classifications:

Living organisms are subdivided into 5 major kingdoms including Monera, Protista (Protoctista), Fungi, Plantae and the Animalia. Each kingdom is further subdivided into separate Phyla or divisions. Generally Animals are subdivided into Phyla while plants into Division. Living have two major characters the prokaryote and eukaryote.

A. Prokaryotic Cells without Nuceli and Membrane bound organelle

1. Kingdom Monera [10,000 Species]:

Unicellular and colonial including the true Bacteria (Eubacteria) and Cyanobacteria (Blue-green algae).

B. Eukaryotic Cells with nuclei and Membrane bound organelle

2. Kingdom Protista (Protoctista) [250,000 Species]:

Unicellular protozoan unicellular and multicellular macroscopic algae with 9+2 cilia or flagella or undulopodia.

3. Kingdom Fungi [100,000 Species]:

Haploid and diKaryotic (binucleate) cells, multicellular generally heterotrophic without cilia and eukaryotic (9+2) flagella (undulopodia).

4. Kingdom Plantae [2,50,000 Species]:

Haplo-diploid life cycles, mostly autotropic, retaining embryo within female sex organ on parent plant.

5. Kingdom Animalia [10,00000 Species]:

Multicellular animals, without cell walls and photosynthetic pigments, forming diploid blastula.

The discovery of Archaebacteria complicated this classification as it is different from eubacteria and cyanobacteria included in Monera. Lipids of Archeo-bacterial cell membrane is different from prokaryote and eukaryote cell membrane. The cell wall composition is different.

The sequence of its rRNA subunit is also different. Recent studies show that archaebacterial RNA polymerases resemble the eukaryotic enzymes, not the eubacterial RNA polymerase. Archaebacteria have introns in some genes like advance eukaryots.

Some scientists put Archaebacteria in separate kingdom making 6 Kingdom classification. The data from DNA and RNA comparison indicate that Archaebacteria are so different that it cannot be classified with bacteria. Systematists daised a classification level higher than kingdom, called a domain or Superkingdom to accommodate Archaebacteria. Now it is placed under domain Archaea.

Now there is seven kingdom classification suggested. It is based on molecular evidence base sequences from ribosomal RNA.

Guillaume Le Cointre and Herve Le Guyader (2006) published a book The Tree of Life: A Phylogenetic Classification. It includes the three major domains which are in turn subdivided into numerous branches (Clades).

  1. Essay on the Definition of Taxonomy
  2. Essay on Taxonomy and Systematics
  3. Essay on the Aims of Taxonomy
  4. Essay on the Principles of Taxonomy
  5. Essay on the Phases of Taxonomy
  6. Essay on Key to Identify Taxon

Essay # 1. Definition of Taxonomy:

Taxonomy (Greek, taxis = arrangement, nomous = law, rule) means the “arrangement by rules” or “lawful arrangement”. The botanists agreed on a nomenclature — arrangement of plants into convenient groups for the proper and easy handling of vast number of plants in a sui­table process following certain principles or rules.

The term Taxonomy was first introduced in plant science by A. P. de Candolle (1813), a French botanist, as the theory of plant classification. Later on and till date, it is considered as a part of plant science which includes identification, nomencla­ture and classification.

According to G. H. M. Lawrence (1955) “Taxonomy is a science which includes identification, nomenclature and classi­fication of objects and is usually restricted to objects of biological origin”. When the taxonomy is concerned with plants, it is referred to as systematic botany.

In respect to plant, both the terms are consi­dered as synonym but are not accepted by all. Both the terms are often used variously, like chemotaxonomy (based on chemical content), cytotaxonomy (based on chromosome structure and numbers), biosystematics (systematics of living organisms), etc.

Initially, the taxonomy was based on a few macro morphological informations like habit, sex organ, etc. i.e., the artificial system. Later on, the classification was developed after considering many morphological characteristics, the natural systems. During the post-Darwinian period the taxonomy was based on evolutionary relation­ships i.e., the phylogenetic systems.

However, modern taxonomy is not restricted on morphology only. It depends on other branches of botany for good information like anatomy, cytology, physiology, phytochemistry, genetics, embryology, ecology etc.

The term ‘taxon’ was first introduced by Adolf Meyer (1926), a German biologist, for the animal groups. Later, in 1948, it was Herman J. Lam who proposed the term in plant science and it was accepted in the Seventh International Congress (1950). The term “taxon” indicates a taxonomic group like a variety, species, genus or any higher group.

Essay # 2. Taxonomy and Systematics:

There is no harmonic opinion in the mea­ning and use of both the terms taxonomy and systematics. Mason (1950) considered taxonomy as a vast field in biological science including four main streams. These are systematics i.e., comparative study of the organisms, taxonomic systems, nomenclature, and documentation.

On the other hand, authors like Simpson (1961), Heywood (1967), Ross (1974) and many others have treated systematics as a field which covers the study of diversity, differentiation and the relationship that exists among the organisms. According to them, taxonomy is a part of syste­matics.

According to Solsbrig (1966), taxonomy includes nomenclature and classification but tilt massively on systematics for its concept. Later, Small (1989) reviewed the above and defined systematics as ‘The science of organisation and pattern of heritable relationships among the kinds and diversity of organisms’ and, on the other hand, taxonomy as ‘a very substantial but imprecisely separated part of systematics, that is especially concerned with the production of for­mal classifications of living things on the basis of genetic relationships’.

Finally, it can be concluded that due to loose and interchangeable use in past, a proper expla­nation at present is very difficult. The literal meaning of Taxonomy in Greek is putting in order or lawful arrangement and Systematics means putting together. Lam (1959) and Turrill (1964) boldly expressed their opinion to treat these terms synonymously and later it was followed by many others.

Essay # 3. Aims of Taxonomy:

The aim of taxonomy includes three aspects I. Identification, II. Nomenclature, and III. Classi­fication of plants. But to develop the construction of the above, the taxonomists approach in diffe­rent ways.

These are of two types:

2. Interpretative approach.

This type of approach is based on the thorough observation and characterisation of the organism which finally leads to the construction of a classi­fication. Due to thorough observation of many characteristics of the specimens and development of a classification, this type becomes popularly acceptable. This type of approach was developed during pre- Darwinian period.

2. Interpretative Approach:

This type of approach of classification is based on the interpretation of evolution of a taxon. This is called phylogenetic classification, which developed during post-Darwinian period (i.e., after the publication of ‘The Origin of Species by Means of Natural Selection’ (1859). This type of classification needs the data from the past history of a taxon.

The modern taxonomy made an attempt to merge the above two approaches.

The aims of modern taxonomy are:

1. To supply an appropriate method of identi­fication

2. To contribute classification based on natural affinities of the specimens

3. To contribute a catalogue of taxa by studying the different flora

4. To trace the evolution after proper observa­tion and interpretation

5. To supply an integrating and synthetic role to maintain the relationship among the diffe­rent biological fields.

Essay # 4. Principles of Taxonomy:

Taxonomy is the oldest branch of Botany and was practiced in many countries like India, Greece, Rome, China, England from long back. During early part, taxonomy was mainly aimed to develop some convenient methods of classifi­cation. One of the earliest known Indian works dealing with plants in a scientific manner is Vrikshayurveda.

Later, it was completed by Parasar before Christ. This book contained a classification based on comparative morphology of plants. The artificial system reached its climax in Carolus Linnaeus (1707-1778), the Father of modern taxonomy. Later, Michel Adanson (1727-1806) was perhaps the first person to reject all artificial systems in favour of natural system.

He proposed the idea that all characte­ristics are important in grouping of plants, which in the recent years came as Numerical Taxonomy. At that time, it was very difficult to consider all the characteristics of a plant in grouping of plants. For the above problem, importance was given on flower characteristics. In this system, a group of characteristics are con­sidered in grouping of plants.

The natural system reached its climax in George Bentham and Joseph Dalton Hooker in their book ‘Genera Plantarum’ in July 1862 and the last part in April 1883. Before the publication of their book, the phylogenetic concept came in focus after the publication of Darwin’s concept of ‘Origin of Species’ (1859).

This system is still continuing with eminent personalities like Engler (1886-1892), Hutchinson (1926-1973), Takhtajan (1969, 1980), Cronquist (1968, 1981) and many others. Thus, the principles have evolved through time.

However, Cronquist (1968) has formulated certain basic principles of Taxonomy in “Evolution and Classification of Flowering Plants”:

1. Taxa are properly established on the basis of multiple correlations of characters.

2. Taxonomic importance of a character is determined by how well it correlates with other characters. This means that the taxonomic importance of a character is determined by a posteriori rather than a priori.

3. An important feature of taxonomy is its predative value.

The most important principle of taxonomy is the multiple correlations of characters. To find out correlation of taxa with others, single character should not be considered, it should always be considered along with other characters.

The selected characters should show maxi­mum correlation with other characters. The significance of a selected characters depends on the degree of correlation. Characters with no distinct correlation with other characters is often accepted as an anomalous one and usually it is not important from the taxonomic point of view.

Thus, the regular flower (Scoparia dulcis) of Scrophulariaceae, exstipulate leaves (Corculum leptopus) of Polygonaceae, zygomorphic flower (Delphinium ajacis) of Ranunculaceae and many such exceptional characters are taken as anomalous, because they are not correlated with common characters of taxa.

The above exam­ples clearly indicate that they are not significant taxonomically, but are important from their identification. But the anomalous characters often help the taxa with other groups of plants where these same characters are normally available.

Essay # 5. Phases of Taxonomy:

The taxonomy includes identification, nomenclature and classification.

According to Davis and Heywood (1963) the classification is achieved in four (4) different consecutive phases:

This is also called explora­tory phase. In this phase, different plants of a taxon have to be collected throughout the world and identified.

2. Consolidation Phase:

In this phase, plant is studied both in field as well in the herbarium and a range of variations are evaluated. The new group or groups, if discovered, are fully described. Thus a monograph is obtained.

3. Biosystematic or Experimental Phase:

This phase deals with much more detailed know­ledge of a taxon based on the above two phases along with the geographical varia­tion, physiological characteristics, cytological characteristics, etc. The progress of this phase is very slow and it requires a team work rather than individual effort. The suc­cess in this phase is remarkable in some countries (U.K., U.S.A. etc.) but at and below the generic level.

4. Encyclopaedic or Holotaxonomic Phase:

This phase is a coordination of the above three phases.

According to Turrill (1938) the classification is of two types:

1. Alpha Classification:

The first two phases i.e., pioneer and consolidation phases are based on gross morphological characteristics and the classifications of these phases are called Alpha classification or Alpha taxo­nomy.

2. Omega Classification:

The last two phases, i.e., biosystematic and encyclopaedic phase, are based on the data collected from fields, herbarium, laboratory and library and then properly analysed with the help of compu­ter. The classifications of plants of these phases are called Omega classification or Omega taxonomy.

Essay # 6. Key to Identify Taxon:

It consists of cards of appropriate size where the names of all taxa like families, genera or species for which the key have to be prepared should be printed on each. Each card has to be numbered serially. Each card should be printed with any one characteristic at any corner. All the taxa having the characteristics should be indicated by a hole in front of their name and others remain without it.

Many set of cards have to be developed, one set for each characteristics. During identification of a specimen, select the cards showing charac­teristics possessed by the specimens. The charac­teristic combination shown by the specimen will permit only one hole in the set of cards chosen. The particular sample of specimen is then assigned to that family to which the cards indi­cate the hole.

Advantages of Punched Card Key:

The punched card key is tackled by the beginners like college stu­dents, who find more interest in taxonomy. But the system is very costly for the cards, printing of names etc.

The dichotomous key consists of the following characteristics:

i. It consists of a pair of contrasting cha­racteristics i.e., cuplets and each state­ment of a couplet is called a lead.

ii. Lead should be numbered.

iii. Both the leads of a couplet begins with same word as far as possible.

iv. The characteristics used in the key should be easily observable and con­trast.

v. The quantitive characteristics are usu­ally preferred than qualitative characte­ristics.

vi. More than one contrasting characteris­tics should be selected to differentiate the closely related taxa with overlap­ping characteristics.

The dichotomous key is of two types:

In this type the collateral leads of a couplet are arranged in yokes and leads are identified by a figure or letter. Successive yokes are arranged one above the other.

An example of dichotomous key with indented or yoked leads is given:

In this type both the leads of each couplet always remain together.

Advantage of Dichotomous Key:

This key is very suitable for the taxonomists and is far less costly. The indented key gives a visual representa­tion of the group, thereby the user can read­ily obtain a picture about the taxon. But if the key is too large then the leads of a cou­plet get widely separated from each other, on the other hand, in bracketed or parallel leads, the advantage lies that the couplets occur side by side.

Good knowledge of characteristic diffe­rences and sound knowledge of the flora is essential in the construction of a key.

Distribution of Basal angiosperms

Basal angiosperms are found all around the world, with a few exceptions in extreme climates such as Antarctica and the Saharan desert. They enjoy most of their success in tropical and warm-temperate rainforests.

A number of the ANITA basal angiosperms are confined within Australia, Asia and Oceania a fact that supports the idea that the basal angiosperms originated in Australia. In comparison, Magnoliid species tend to have much more variable distributions.

Saw this flower today, can someone help identify it?

Edit: Some places seem to name them "Tulipa parrot". You can alternatively google search "white fringed tulip". You should see some more examples there.

Thanks for that! It was a pretty sweet looking flower, I was really curious as it what it was. The field looked like something from a Tim Burton film.

Definitely a Parrot Tulip. Since modern Tulips are so varied in their backgrounds horticulturalists divide tulips up into 15 divisions 'Parrot' being one of them:

In the case of this particular tulip the proper binomial name would be "Tulipa cv. 'White Parrot' with the "cv" denoting the cultivar name.

BTW OP, I'm assuming you are in the Southern Hemisphere? Otherwise this is a really weird time for a Tulip to be blooming.

You can't find a good binomial because it's not a natural species. It's an abomination created by scientists and selective breeding.

I used to have tulips like that on my lawn, but they were red. Like this

Where did you find it? And on what kind of ground?

At a Flower festival in the city I live in.

Is somebody breeding white Audrey Twos?

It is a tulip. Its petals are frayed because it has a virus. People like how they look so we purposefully innoculate them.

Sorry no. The petals are frayed because that's the type of tulip it is. The mosaic virus you are talking about that was around during the Dutch Tulip Mania caused streaking and variegation in color not the shape of the petals. Also no one purposefully inoculates with the virus as 1. the virus eventually kills the tulip and this would be catastrophic in a production field and 2. there is absolutely no need given the variation in shapes, sizes and colors that have been achieved through artificial breeding alone.

Families in Angiosperms

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The interaction between pollen and stigma is one of the most important stages in the life cycle of a flowering plant, because its outcome determines whether fertilization will occur and thus whether seed will be set. This critical cellular dialogue between the haploid pollen (grain and tube) and the diploid cells of the stigma (and style) is one of the most precisely adapted of all activities of the plant – morphologically, physiologically and biochemically ( Heslop-Harrison, 1978 ) – and has become a paradigm for the study of cell recognition and cell signalling in plants.

For fertilization to be achieved, pollen must establish molecular congruity/compatibility with the stigma and then, following production of a pollen tube, with the transmitting tissue of the style and ovary as the pollen tube grows through the pistil to deliver its two sperm cells to an ovule. Thus there must be a continuous exchange of signals, both physical and chemical, between pollen and pistil from the moment a pollen grain arrives on the stigma to the moment the pollen tube enters the ovule. Identifying these signals and the responses they induce has been the subject of intense research for the past three decades and a picture is emerging of a diverse array of signals that influence pollen germination and pollen tube growth and guidance within the pistil ( Franklin-Tong, 2002 Johnson & Preuss, 2002 Feijo et al., 2004 Dresselhaus, 2006 ). Recently the animal neurotransmitter, gamma-aminobutyric acid (GABA), was identified as a potential chemoattractant for pollen tubes in Arabidopsis ( Palanivelu et al., 2003 ), whilst in Lilium longiflorum, nitric oxide (NO) has been implicated in pollen tube guidance as a putative negative regulator of pollen tube growth able to induce tip reorientation ( Prado et al., 2004 ).

When a pollen grain lands on a stigma, specific recognition events must take place to establish that: (a) the object that has alighted is a pollen grain and not a fungal spore or bacterium (b) it is a pollen grain of the correct species, or a closely related species (interspecific hybridization is fairly common in angiosperms) and (c) in most hermaphrodite flowering plants, it is not a self-pollen grain ( Heslop-Harrison, 1978 Franklin-Tong, 2002 Hiscock, 2004 ). Whilst the last of these three recognition events (self-incompatibility) has been studied extensively (reviewed in Hiscock & McInnis, 2003 ), relatively little is known about molecular signals and interactions mediating the first two recognition events.

The stigma surface is only receptive to pollen for a relatively short period, so the timing of pollination is critical. Pollination either side of this period of optimal female receptivity results in reduced seed set, or no seed set ( Herrero, 2003 ). It has long been known that receptive stigmas ‘ripe’ for pollination are characterized by high levels of peroxidase activity ( Dupuis & Dumas, 1990 McInnis et al., 2006 ) and tests most widely used to determine pistil receptivity measure stigma peroxidase activity ( Dafni & Motte Maues, 1998 ). Nevertheless, the function of these ubiquitous enzymes in stigmas is not known ( McInnis et al., 2006 ).

Recently we identified and characterized a stigma-specific peroxidase (SSP) from the ragwort Senecio squalidus ( McInnis et al., 2005 ). As part of ongoing work to determine the function of SSP and stigmatic peroxidases generally, we showed that Senecio stigmas accumulate high amounts of ROS, particularly H2O2, in their epidermal cells (papillae) where SSP is localized ( McInnis et al., 2006 ). The presence of such high amounts of ROS/H2O2 in the papillae, which receive and discriminate pollen, suggested that ROS/H2O2 (and, by potential association, SSP) may be important for stigma function. ROS/H2O2 have a variety of roles in cell metabolism but also act as signalling molecules mediating a range of cellular processes from development to defence, often in association with NO ( Hancock et al., 2006 ), so it was not unreasonable to speculate that ROS/H2O2 might be involved in pollen–stigma interactions. Here we expand upon these preliminary findings in Senecio and show for the first time that stigmas from a range of different species, including Arabidopsis thaliana, accumulate high amounts of ROS/H2O2. In species with papillate stigmas ROS/H2O2 accumulation was confined almost exclusively to the papillae. We further show that pollen of S. squalidus and A. thaliana produce NO and that exogenous NO can reduce ROS/H2O2 amounts in stigmas. These observations are discussed in the context of possible functions for ROS/H2O2, peroxidases and NO in pollen–stigma interactions and defence.


Coevolution is the evolution of two or more species which reciprocally affect each other, sometimes creating a mutualistic relationship between the species. Such relationships can be of many different types. [6] [7]

Flowering plants Edit

Flowers appeared and diversified relatively suddenly in the fossil record, creating what Charles Darwin described as the "abominable mystery" of how they had evolved so quickly he considered whether coevolution could be the explanation. [8] [9] He first mentioned coevolution as a possibility in On the Origin of Species, and developed the concept further in Fertilisation of Orchids (1862). [10] [11] [12]

Insects and insect-pollinated flowers Edit

Modern insect-pollinated (entomophilous) flowers are conspicuously coadapted with insects to ensure pollination and in return to reward the pollinators with nectar and pollen. The two groups have coevolved for over 100 million years, creating a complex network of interactions. Either they evolved together, or at some later stages they came together, likely with pre-adaptations, and became mutually adapted. [13] [14]

Several highly successful insect groups—especially the Hymenoptera (wasps, bees and ants) and Lepidoptera (butterflies and moths) as well as many types of Diptera (flies) and Coleoptera (beetles)—evolved in conjunction with flowering plants during the Cretaceous (145 to 66 million years ago). The earliest bees, important pollinators today, appeared in the early Cretaceous. [15] A group of wasps sister to the bees evolved at the same time as flowering plants, as did the Lepidoptera. [15] Further, all the major clades of bees first appeared between the middle and late Cretaceous, simultaneously with the adaptive radiation of the eudicots (three quarters of all angiosperms), and at the time when the angiosperms became the world's dominant plants on land. [8]

At least three aspects of flowers appear to have coevolved between flowering plants and insects, because they involve communication between these organisms. Firstly, flowers communicate with their pollinators by scent insects use this scent to determine how far away a flower is, to approach it, and to identify where to land and finally to feed. Secondly, flowers attract insects with patterns of stripes leading to the rewards of nectar and pollen, and colours such as blue and ultraviolet, to which their eyes are sensitive in contrast, bird-pollinated flowers tend to be red or orange. Thirdly, flowers such as some orchids mimic females of particular insects, deceiving males into pseudocopulation. [15] [1]

The yucca, Yucca whipplei, is pollinated exclusively by Tegeticula maculata, a yucca moth that depends on the yucca for survival. [16] The moth eats the seeds of the plant, while gathering pollen. The pollen has evolved to become very sticky, and remains on the mouth parts when the moth moves to the next flower. The yucca provides a place for the moth to lay its eggs, deep within the flower away from potential predators. [17]

Birds and bird-pollinated flowers Edit

Hummingbirds and ornithophilous (bird-pollinated) flowers have evolved a mutualistic relationship. The flowers have nectar suited to the birds' diet, their color suits the birds' vision and their shape fits that of the birds' bills. The blooming times of the flowers have also been found to coincide with hummingbirds' breeding seasons. The floral characteristics of ornithophilous plants vary greatly among each other compared to closely related insect-pollinated species. These flowers also tend to be more ornate, complex, and showy than their insect pollinated counterparts. It is generally agreed that plants formed coevolutionary relationships with insects first, and ornithophilous species diverged at a later time. There is not much scientific support for instances of the reverse of this divergence: from ornithophily to insect pollination. The diversity in floral phenotype in ornithophilous species, and the relative consistency observed in bee-pollinated species can be attributed to the direction of the shift in pollinator preference. [18]

Flowers have converged to take advantage of similar birds. [19] Flowers compete for pollinators, and adaptations reduce unfavourable effects of this competition. The fact that birds can fly during inclement weather makes them more efficient pollinators where bees and other insects would be inactive. Ornithophily may have arisen for this reason in isolated environments with poor insect colonization or areas with plants which flower in the winter. [19] [20] Bird-pollinated flowers usually have higher volumes of nectar and higher sugar production than those pollinated by insects. [21] This meets the birds' high energy requirements, the most important determinants of flower choice. [21] In Mimulus, an increase in red pigment in petals and flower nectar volume noticeably reduces the proportion of pollination by bees as opposed to hummingbirds while greater flower surface area increases bee pollination. Therefore, red pigments in the flowers of Mimulus cardinalis may function primarily to discourage bee visitation. [22] In Penstemon, flower traits that discourage bee pollination may be more influential on the flowers' evolutionary change than 'pro-bird' adaptations, but adaptation 'towards' birds and 'away' from bees can happen simultaneously. [23] However, some flowers such as Heliconia angusta appear not to be as specifically ornithophilous as had been supposed: the species is occasionally (151 visits in 120 hours of observation) visited by Trigona stingless bees. These bees are largely pollen robbers in this case, but may also serve as pollinators. [24]

Following their respective breeding seasons, several species of hummingbirds occur at the same locations in North America, and several hummingbird flowers bloom simultaneously in these habitats. These flowers have converged to a common morphology and color because these are effective at attracting the birds. Different lengths and curvatures of the corolla tubes can affect the efficiency of extraction in hummingbird species in relation to differences in bill morphology. Tubular flowers force a bird to orient its bill in a particular way when probing the flower, especially when the bill and corolla are both curved. This allows the plant to place pollen on a certain part of the bird's body, permitting a variety of morphological co-adaptations. [21]

Ornithophilous flowers need to be conspicuous to birds. [21] Birds have their greatest spectral sensitivity and finest hue discrimination at the red end of the visual spectrum, [21] so red is particularly conspicuous to them. Hummingbirds may also be able to see ultraviolet "colors". The prevalence of ultraviolet patterns and nectar guides in nectar-poor entomophilous (insect-pollinated) flowers warns the bird to avoid these flowers. [21] Each of the two subfamilies of hummingbirds, the Phaethornithinae (hermits) and the Trochilinae, has evolved in conjunction with a particular set of flowers. Most Phaethornithinae species are associated with large monocotyledonous herbs, while the Trochilinae prefer dicotyledonous plant species. [21]

Fig reproduction and fig wasps Edit

The genus Ficus is composed of 800 species of vines, shrubs, and trees, including the cultivated fig, defined by their syconiums, the fruit-like vessels that either hold female flowers or pollen on the inside. Each fig species has its own fig wasp which (in most cases) pollinates the fig, so a tight mutual dependence has evolved and persisted throughout the genus. [25]

Acacia ants and acacias Edit

The acacia ant (Pseudomyrmex ferruginea) is an obligate plant ant that protects at least five species of "Acacia" (Vachellia) [a] from preying insects and from other plants competing for sunlight, and the tree provides nourishment and shelter for the ant and its larvae. [26] [27] Such mutualism is not automatic: other ant species exploit trees without reciprocating, following different evolutionary strategies. These cheater ants impose important host costs via damage to tree reproductive organs, though their net effect on host fitness is not necessarily negative and, thus, becomes difficult to forecast. [28] [29]

Parasites and sexually reproducing hosts Edit

Host–parasite coevolution is the coevolution of a host and a parasite. [30] A general characteristic of many viruses, as obligate parasites, is that they coevolved alongside their respective hosts. Correlated mutations between the two species enter them into an evolution arms race. Whichever organism, host or parasite, that cannot keep up with the other will be eliminated from their habitat, as the species with the higher average population fitness survives. This race is known as the Red Queen hypothesis. [31] The Red Queen hypothesis predicts that sexual reproduction allows a host to stay just ahead of its parasite, similar to the Red Queen's race in Through the Looking-Glass: "it takes all the running you can do, to keep in the same place". [32] The host reproduces sexually, producing some offspring with immunity over its parasite, which then evolves in response. [33]

The parasite–host relationship probably drove the prevalence of sexual reproduction over the more efficient asexual reproduction. It seems that when a parasite infects a host, sexual reproduction affords a better chance of developing resistance (through variation in the next generation), giving sexual reproduction variability for fitness not seen in the asexual reproduction, which produces another generation of the organism susceptible to infection by the same parasite. [34] [35] [36] Coevolution between host and parasite may accordingly be responsible for much of the genetic diversity seen in normal populations, including blood-plasma polymorphism, protein polymorphism, and histocompatibility systems. [37]

Brood parasites Edit

Brood parasitism demonstrates close coevolution of host and parasite, for example in some cuckoos. These birds do not make their own nests, but lay their eggs in nests of other species, ejecting or killing the eggs and young of the host and thus having a strong negative impact on the host's reproductive fitness. Their eggs are camouflaged as eggs of their hosts, implying that hosts can distinguish their own eggs from those of intruders and are in an evolutionary arms race with the cuckoo between camouflage and recognition. Cuckoos are counter-adapted to host defences with features such as thickened eggshells, shorter incubation (so their young hatch first), and flat backs adapted to lift eggs out of the nest. [38] [39] [40]

Antagonistic coevolution Edit

Antagonistic coevolution is seen in the harvester ant species Pogonomyrmex barbatus and Pogonomyrmex rugosus, in a relationship both parasitic and mutualistic. The queens are unable to produce worker ants by mating with their own species. Only by crossbreeding can they produce workers. The winged females act as parasites for the males of the other species as their sperm will only produce sterile hybrids. But because the colonies are fully dependent on these hybrids to survive, it is also mutualistic. While there is no genetic exchange between the species, they are unable to evolve in a direction where they become too genetically different as this would make crossbreeding impossible. [41]

Predators and prey interact and coevolve: the predator to catch the prey more effectively, the prey to escape. The coevolution of the two mutually imposes selective pressures. These often lead to an evolutionary arms race between prey and predator, resulting in anti-predator adaptations. [42]

The same applies to herbivores, animals that eat plants, and the plants that they eat. Paul R. Ehrlich and Peter H. Raven in 1964 proposed the theory of escape and radiate coevolution to describe the evolutionary diversification of plants and butterflies. [43] In the Rocky Mountains, red squirrels and crossbills (seed-eating birds) compete for seeds of the lodgepole pine. The squirrels get at pine seeds by gnawing through the cone scales, whereas the crossbills get at the seeds by extracting them with their unusual crossed mandibles. In areas where there are squirrels, the lodgepole's cones are heavier, and have fewer seeds and thinner scales, making it more difficult for squirrels to get at the seeds. Conversely, where there are crossbills but no squirrels, the cones are lighter in construction, but have thicker scales, making it more difficult for crossbills to get at the seeds. The lodgepole's cones are in an evolutionary arms race with the two kinds of herbivore. [44]

Both intraspecific competition, with features such as sexual conflict [45] and sexual selection, [46] and interspecific competition, such as between predators, may be able to drive coevolution. [47]

The types of coevolution listed so far have been described as if they operated pairwise (also called specific coevolution), in which traits of one species have evolved in direct response to traits of a second species, and vice versa. This is not always the case. Another evolutionary mode arises where evolution is reciprocal, but is among a group of species rather than exactly two. This is variously called guild or diffuse coevolution. For instance, a trait in several species of flowering plant, such as offering its nectar at the end of a long tube, can coevolve with a trait in one or several species of pollinating insects, such as a long proboscis. More generally, flowering plants are pollinated by insects from different families including bees, flies, and beetles, all of which form a broad guild of pollinators which respond to the nectar or pollen produced by flowers. [48] [49] [50]

The geographic mosaic theory of coevolution was developed by John N. Thompson as a way of linking the ecological and evolutionary processes that shape interactions among species across ecosystems. It is based on three observations that are taken as assumptions: (1) species are usually groups of populations that are somewhat genetically distinct from each other, (2) interacting species often co-occur in only parts of their geographic ranges, and (3) interactions among species differ ecologically among environments.

From these assumptions, geographic mosaic theory suggests that natural selection on interactions among species is driven by three sources of variation:

1. Geographic selection mosaics occur in interactions among species, because genes are expressed in different ways in different environments and because different genes are favored in different environments. For example, natural selection on an interaction between a parasite population and a host population may differ between very dry environments and very wet environments. Alternatively, an interaction between two or more species may be antagonistic in some environments but mutualistic (beneficial to both or all species) in other environments.

2. Coevolutionary hotspots and coldspots occur because natural selection on interactions among species is reciprocal in some environments but not in others. For example, a symbiont population may decrease the survival or reproduction of its hosts in one environment, but it may have no effect on host survival or reproduction in another environment. When detrimental, natural selection will favor evolutionary responses in the host population, resulting in a coevolutionary hotspot of ongoing reciprocal evolutionary changes in the parasite and host populations. When the symbiont has no effect on the survival and reproduction of the host, natural selection on the symbiont population will not favor an evolutionary response by the host population (i.e, a coevolutionary coldspot).

3. Finally, there is constant remixing of the traits on which natural selection acts both locally and regionally. At any moment in time, a local population will have a unique combination of genes on which natural selection acts. These genetic differences among populations occur because each local population has a unique history of new mutations, genomic alterations (e.g., whole genome duplications), gene flow among populations from individuals arriving from other populations or going to other populations, random loss or fixation of genes at times when populations are small (random genetic drift), hybridization with other species, and other genetic and ecological processes that affect the raw genetic material on which natural selection acts. More formally, then, the geographic mosaic of coevolution can be viewed as a genotype by genotype by environment interaction (GxGxE) that results in the relentless evolution of interacting species.

Geographic mosaic theory has been explored through a wide range of mathematical models, studies of interacting species in nature, and laboratory experiments using microbial species and viruses. [5] [3]

Coevolution is primarily a biological concept, but has been applied to other fields by analogy.

In algorithms Edit

Coevolutionary algorithms are used for generating artificial life as well as for optimization, game learning and machine learning. [51] [52] [53] [54] [55] Daniel Hillis added "co-evolving parasites" to prevent an optimization procedure from becoming stuck at local maxima. [56] Karl Sims coevolved virtual creatures. [57]

In architecture Edit

The concept of coevolution was introduced in architecture by the Danish architect-urbanist Henrik Valeur as an antithesis to "star-architecture". [58] As the curator of the Danish Pavilion at the 2006 Venice Biennale of Architecture, he created an exhibition-project on coevolution in urban development in China it won the Golden Lion for Best National Pavilion. [59] [60] [61] [62]

At the School of Architecture, Planning and Landscape, Newcastle University, a coevolutionary approach to architecture has been defined as a design practice that engages students, volunteers and members of the local community in practical, experimental work aimed at "establishing dynamic processes of learning between users and designers." [63]

In cosmology and astronomy Edit

In his book The Self-organizing Universe, Erich Jantsch attributed the entire evolution of the cosmos to coevolution.

In astronomy, an emerging theory proposes that black holes and galaxies develop in an interdependent way analogous to biological coevolution. [64]

In management and organization studies Edit

Since year 2000, a growing number of management and organization studies discuss coevolution and coevolutionary processes. Even so, Abatecola el al. (2020) reveals a prevailing scarcity in explaining what processes substantially characterize coevolution in these fields, meaning that specific analyses about where this perspective on socio-economic change is, and where it could move toward in the future, are still missing. [65]

In sociology Edit

In Development Betrayed: The End of Progress and A Coevolutionary Revisioning of the Future (1994) [66] Richard Norgaard proposes a coevolutionary cosmology to explain how social and environmental systems influence and reshape each other. [67] In Coevolutionary Economics: The Economy, Society and the Environment (1994) John Gowdy suggests that: "The economy, society, and the environment are linked together in a coevolutionary relationship". [68]

In technology Edit

Computer software and hardware can be considered as two separate components but tied intrinsically by coevolution. Similarly, operating systems and computer applications, web browsers, and web applications.

All of these systems depend upon each other and advance step by step through a kind of evolutionary process. Changes in hardware, an operating system or web browser may introduce new features that are then incorporated into the corresponding applications running alongside. [69] The idea is closely related to the concept of "joint optimization" in sociotechnical systems analysis and design, where a system is understood to consist of both a "technical system" encompassing the tools and hardware used for production and maintenance, and a "social system" of relationships and procedures through which the technology is tied into the goals of the system and all the other human and organizational relationships within and outside the system. Such systems work best when the technical and social systems are deliberately developed together. [70]

Evolution and the Angiosperms

The angiosperms are a relatively recent group of land plants, and are thought to have originated in the early Cretaceous, only 130 million years ago. The angiosperms increased dramatically in abundance during the Cretaceous. This sudden, dramatic appearance of large numbers of very diverse flowering plant species in the fossil record was referred to by English naturalist Charles Darwin as an ⊫ominable mystery." It is postulated that coevolution with animal pollinators, especially insects, may have contributed to the explosion and abundance of angiosperm species which characterize the modern earth's flora. However, even today, it is not clear what group of nonflowering plants the angiosperms are most closely related to, or what the relationships of the early lineages of flowering plants are to one another. This is in part due to the extremely fast evolution of this group of plants, over a relatively short period of time, and the extinction of many closely related lineages of seed plants, some of which may be more closely related to the modern angiosperms than extant seed plant lineages.

Most contemporary studies, which are based on phylogenetic analysis of deoxyribonucleic acid (DNA) sequence data from as many as six different genes, suggest that the closest relatives of the angiosperms are the gymnosperms, which include cycads, Ginkgo, conifers (the group that contains the pines, spruces, firs, and relatives), and Gnetales (a group containing three ancient genera: Ephedra, the Mormon tea Welwitschia, a bizarre plant of southwest African deserts and Gnetum, a genus of mostly tropical vines). The origins of angiosperms are not well understood and remain problematic, in part because many seed plant lineages have already gone extinct. However, studies indicate that the earliest lineage of flowering plants, or basal angiosperms, may include the family Amborellaceae (with the single living species Amborella trichopoda, a shrub from the South Pacific island of New Caledonia). Other early diverging lineages of angiosperms include Nympheales, the water lilies Illiciales, or star anise a group called the magnoliids, which includes magnolias, laurels, and black pepper and the very large group called the monocots . A final lineage, the eudicots , contains all other flowering plants and comprises the bulk (approximately three-quarters) of the flowering plant species.

The size of the Angiosperms is various. You can find the smallest to the tallest ones. The smallest one is watermeal. It has the size at less than 0.08 inch or 2 millimetres.

Facts about Angiosperms 8: the tallest one

The example of the tallest Angiosperm is Eucalyptus regnans or the Australia’s mountain ash tree. It has the height at 330 feet or 100 metres.

Evolutionary Innovations

Over time, specific evolutionary features, have distinguished angiosperm reproduction. The development of non-exposed seeds, housed within a flower structure, defines the group. This evolutionary feature has led to an abundance of morphological variation and widespread distribution of this group. Angiosperm flower structures have evolved in response to ecological pressures rapidly, and this success has led to the group’s survival, nearly universally, across the diverse ecosystems of our planet (Carter 1997).

Spider Wasp, under a dissection microscope. This organism is a common pollinator and of the family Pompilidae. Photo by Nick White.

Flowers come in an astounding number of colors, shapes, sizes, arrangements, and smells. All of these are evolutionary innovations which assist in attracting pollinators. Attraction is effected by color, scent, and the production of nectar, which may be secreted in some part of the flower. Pollinator’s relationship with their flowers are a textbook example of coevolution, as some animals evolve specifically to cater to a flowers pollination needs. These animals transport the flowers pollen to a wider geographic range to give them an excellent diversity within the population. (Carter, 1997)

Flower organs help to facilitate the reproductive cycle of angiosperms.
Each flower part has a specific function.

A labelled, bisected specimen of the Erigeron glaucus, more commonly known as the Daisy. The reproductive (carpel, stamen, anther, and sepals) and non-reproductive structures (receptacle and pedicel) of the flower are displayed. Photo by Nick White.

Pedicel: The stalk of the flower

Receptacle: The part of the stalk where the various parts of the flower are attached

Sepal: Acts as the base for the flower

Petal: Aids in attracting pollinators

Stamen: The male part of a flower

Anther: The part of the stamen where pollen (male gametophytes) is made

Carpel: Houses female gametophytes

Example of the most commonly cultivated fruit, the citrus fruit of a Rutaceae, commonly called an orange. Photo by Nick White.

After fertilization, the ovule transforms into a seed, and it is surrounding tissues evolve into a fleshy fruit. The fruit protects the seed and also promotes it’s dispersal to a wide geographic range. Much like flowers, fruit also has a large diversity among species. Some is meant to be dispersed by the wind, but many rely on animals to disperse it. Whether by having hooks to hook on to an animal’s skin or fur or being sweet and nutrient rich to promote being eaten, digested, and fertilized by the animals that carry them off (Carter, 1997).