To determine the variation and the limitation between species, many concepts have been proposed. When a taxonomist study a particular taxa, he/she must adopted a species concept and provide a species limitation to define this taxa. Plant kingdom as other living kingdoms has a hierarchy structure ends mostly with species rank. Species are one of the basic units to compare in almost all fields of biology. A species is defined as the largest group of organisms in which two individuals are capable of reproducing fertile offspring, typically using sexual reproduction. Definition of a species as a group of interbreeding individuals cannot be easily applied to organisms that reproduce only or mainly asexually. If two lineages of oak look quite different, but occasionally form hybrids with each other, should we count them as different species? Idea of a species is something that we humans invented for our own convenience. ‘‘No matter what variations occur in the individuals or the species, if they spring from the seed of one and the same plant, they are accidental variations and not such as distinguish a species permanently; one species never springs from the seed of another nor vice versa” - JOHN RAY. Used a sexual system ‘‘natural system” for defining species - LINNAEUS. ‘‘A species is a collection of all the individuals which resemble each other more than they resemble anything else, which can by natural fecundation produce fertile individuals, and which reproduce themselves by generation, in such a manner that we may from analogy suppose them all to have sprung from one single individual” - DE CANDOLLE.

1. SPECIES CONCEPT
ALEN SHAJI
1 MSC BOTANY
P1914015

2. INTRODUCTION
To determine the variation and the limitation
between species, many concepts have been
proposed.
When a taxonomist study a particular taxa, he/she
must adopted a species concept and provide a
species limitation to define this taxa.
Plant kingdom as other living kingdoms has a
hierarchy structure ends mostly with species rank.
Species are one of the basic units to compare in
almost all fields of biology.

4. A species is defined as the largest group of
organisms in which two individuals are capable of
reproducing fertile offspring, typically using sexual
reproduction.
These spiders are considered the same species.

5. Definition of a species as a group of interbreeding
individuals cannot be easily applied to organisms
that reproduce only or mainly asexually.
If two lineages of oak look quite different, but
occasionally form hybrids with each other, should
we count them as different species?
Idea of a species is something that we humans
invented for our own convenience.

6. VARIOS CONCEPTS OF SPECIES
1. ‘‘No matter what variations occur in the individuals or
the species, if they spring from the seed of one and
the same plant, they are accidental variations and not
such as distinguish a species permanently; one species
never springs from the seed of another nor vice versa”
- JOHN RAY.
2. Used a sexual system ‘‘natural system” for defining
species - LINNAEUS.
3. ‘‘A species is a collection of all the individuals which
resemble each other more than they resemble
anything else, which can by natural fecundation
produce fertile individuals, and which reproduce
themselves by generation, in such a manner that we
may from analogy suppose them all to have sprung
from one single individual” - DE CANDOLLE.

7. 4. Species as the fundamental units of evolution,
species could be produced rapidly if the conditions
were appropriate and in the absence of such
conditions, species might remain unchanged for a
long time - CHARLES DARWIN.

8. MODERN SPECIES CONCEPTS
Taxonomist proposed different approaches of
species concepts in modern science.
To approach a satisfactory and acceptable
classification the relationship between individuals
should be considered.
These relations could be phenetic or phylogenetic.

9. DEFINITION OF SPECIES CONCEPTS
1. BIOLOGICAL SPECIES CONCEPT.
2. MORPHOLOGICAL SPECIES CONCEPT.
3. ECOLOGICAL SPECIES CONCEPT.
4. EVOLUTIONARY SPECIES CONCEPT.
5. COHESION SPECIES CONCEPT.
6. PHENETIC SPECIES CONCEPT.
7. PHYLOGENETIC SPECIES CONCEPT.
8. PLURALISTIC SPECIES CONCEPT.
9. RECOGNITION SPECIES CONCEPT.
10. CLADISTIC SPECIES CONCEPT.

10. BIOLOGICAL SPECIES CONCEPT
1. ‘‘Groups of actually or potentially interbreeding
natural populations which are reproductively
isolated from other such groups” – MAYR.
 Groups of related plants which are distinct at the
level of biological species do not interbreed when
growing in the same area in nature.
 Biological Species Concept which is a non-
phylogenetic species concept because it is
potentially interbreeding process with no
references of ancestry.

11. Biological species concpts defines a species as
members of populations that actually or potentially
interbreed in nature, not according to similarity of
appearance.
2. “ Species are the members in aggregate of a group
of populations that breed or potentially interbreed
with each other under natural conditions” –
FUTUYMA.

12. 3. “A species is a group of reproducing natural
populations incapable to effectively mate or breed
with other such groups, and which inhabits a
particular niche in nature” -
MAYR,BISBY,CODDINGTON.
DISADVANTAGES.
1. Inapplicable onto asexual organisms.
2. impractical in instances of allopatric populations.
Both isolating species concept and recognition
species concept can be part of biological concept or
genetic concept because both see the species as a
field for gene recombination.

13. Isolating concept stresses on reproductive isolation
as the mechanism responsible for discontinuity
between species.
Recognition concept stresses on reproductive
coherence as the factor responsible for continuity
within species.

14. Organisms may appear to be alike and be different
species.
Western meadowlarks and Easternmeadowlarks
look almost identical to one another, yet donot
interbreed with each other.

15. Organisms may look different and yet be the same
species.
Two ants of the species Pheldolebarbata, fulfilling
different roles in the same colony.

16. RING SPECIES
Coloured bars show a number of natural
populations, each population represented by a
different colour, varying along a cline.
A. Variation may occur in a straight line.
B. Variation may bend right around.
C. Cline bends around, populations next to each other on the
cline can interbreed, but at the point that the beginning
meets the end again.

17. Gap between pink and green on the diagram
represents the differences that have accumulated
along the cline are great enough to prevent
interbreeding.
Interbreeding populations in this circular breeding
group are then collectively referred to as a ring
species.
Cline describes an ecotone in which a series of
biocommunities display ac ontinuous gradient.
Ecotone is a transition area between two biomes.

18. They all interbreed with their immediate neighbors
with one exception – where the extreme ends of
the range overlap in Southern California, E.klauberi,
E.eschscholtzii donot interbreed.

19. CHRONOSPECIES
Group of one or more species derived from a
sequential development pattern which involves
continual and uniform changes from an extinct
ancestral form on an evolutionary scale.

20. MORPHOLOGICAL SPECIES CONCEPT
1. “Species as the smallest groups that are constantly
and determinedly distinctive and distinguishable
by average means, species are the smallest natural
populations permanently separated from each
other by a distinct discontinuity in the series of
biotype” - CRONQUIST.
2. ‘‘A species is a community, or a number of related
communities, whose distinctive morphological
characters are, in the opinion of a competent
systematist, sufficiently definite to entitle it, or
them, to a specific name” – REGAN.

21. ADVANTAGES
1. Applied to sexual and asexual organisms.
2. Useful for species concepts in the fossil record.

22. ECOLOGICAL SPECIES CONCEPT
About ecological competition.
‘‘A species is a lineage which occupies an adaptive
zone minimally different from that of any other
lineage in its range and which evolves separately
from all lineages outside its range” - VAN VALEN.
“Species is a number of related populations the
members of which compete more with their own
kind than with members of other species” -
COLINVAUX.

23. When two organisms are similar to each other, their
needs are more likely to overlap, therefore, they are
expected to contest, and consequently the more
likely that they are of the same species.
DISADVANTAGES
1. At what point does one stop the process of splitting
divergent forms into new species?

24. EVOLUTIONARY SPECIES CONCEPT
‘‘It is a single lineage of ancestordescendant
populations of organisms which maintains its
identity from other such lineages and which has its
own evolutionary tendencies and historical fate” –
WILEY.
“Concept was developed by Simpson” - include
asexual organisms and extinct species.

25. COHESION SPECIES CONCEPT
‘‘It is an evolutionary lineage that serves as the
arena of action of basic micro evolutionary forces,
such as gene flow (when applicable), genetic drift
and natural selection” – TEMPLETON.
“Cohesion concept is similar to the evolutionary
species concept” - population genetic stress on the
origins of phenotypic similarity within species.

26. PHENETIC SPECIES CONCEPT
‘‘A species is a set of organisms that look similar to
each other and distinct from other sets” – RIDLEY.
Phenetic concept measures as many characters as
possible in as many organisms as possible.
It identifies phenetic clusters by multivariate
statistics.
Smallest unit in these clusters has sufficient
similarity to be called a species.

27. Since the frogs depicted here look the same —even
though they are prevented from mating with each
other - they would be considered the same species
according to the pheneticspecies concept.

28. To achieve a better classification based on phenetic
similarity some principals should be followed –
STACE.
1.
• A great content of information and more characters in the taxa
concerned should be attained
2.
• Each trait has an equal weight when forming natural taxa
3.
• Overall similarity between two taxa is a result of their individual
resemblance among the many traits used to compare them
4.
• Taxa can be identified and recognized because correspondences of
characters differ in the groups of organisms under investigation
5.
• Taxonomy is usually viewed and practiced as an empirical science

29. PHYLOGENETIC SPECIES CONCEPT
Species as a group of organisms that share an
ancestor.
Species are individuals show a high degree of
resemblances in many unique traits which give a
monophyletic clusters based on discriminative
phenotypes.
It is applicable on both sexual and allopatric
populations.

30. DISADVANTAGES
1. It is rarely possible to reconstruct with certainty
the past evolutionary pathway.
2. It is hardly possible to devise a satisfactory method
of designation a branching pattern by means of a
single linear sequence.
Many attempts have been made to produce a
system – to construct a sequence starting with the
most primitive and ending with the most advanced.
Ensuring that each taxon recognized is a
monophyletic or polyphyletic.

31. PLURALISTIC SPECIES CONCEPT
‘‘Factors that are most important for the cohesion
of individuals as a species vary” – CAMPBELL,
REECE.
Use more than one species concepts in order to be
applicable arose the idea of a pluralistic species
concept.
For understanding all species living at all times, a
broader concept of species should be applied.
When a given species concept is favored in a given
conditions, that does not mean it could be
universally applicable.

32. RECOGNITION SPECIES CONCEPT
Species is a set of organisms thst can recognize each
other as potential mates.
1. American crickets – different species sings
different songs.
2. As many as 30 or40 different species of crickets
may be breeding.
3. Female cricket recognizes the song of amles of her
own species and will breed only with a male who
sings that songs.
 Recognition concept should define very similar
species to the biological concept.

33. Even though these two frogs have been prevented
from mating, the fact that they recognize each
other as potential mates makes them the same
species under ther ecognition species concept.

34. CLADISTIC SPECIES CONCEPT
Species as a set of organisms between two
speciation events, or between one speciation event
and one extinction event.
According to this, species comes to exist when a
lineage of organisms is split into two.
When a speciation event occur, the ancestral
species becomes extinct, giving rise to two new
species.

35. Every time a speciation event occur, two new
species are created and the ancestral species
becomes extinct.

36. CONCLUSION
With this large number of concepts it is not an easy
or simple decision to adapt one.
It depends on the criteria and the aim of each
project.
Species is a group of individuals sufficiently distinct
from other groups to be considered by taxonomist
to worth specific rank.
Term ‘‘sufficiently distinct” here is the most
important one.
Taxonomists decide these sufficient distinct
according to what information they have.

37. Taxonomists use one or more of the following main
criteria as in – STACE.
1.
• Individuals should bear a close resemblance to one another such
that they are always readily recognizable as members of that group
2.
• There are gaps between the spectra of variation exhibited by related
species; if there are no such gaps then there is a case for
amalgamating the taxa as a single species
3.
• Each species occupies a definable geographical area and is
demonstrably situated to the environmental conditions which it
encounters
4.
• In sexual taxa, the individuals should be capable of interbreeding
with little or no loss of fertility, and there should be some reduction
in the level or success of crossing with other species

38. THANK YOU