Concept of species-Morphological, Biological and
Phylogenetic
Species is the fundamental unit of taxonomic classification.
Greek philosopher Plato proposed
concept of “eidos” or species and
believed that all objects are shadows of the “eidos”. According to Stebbins (1977) species is the
basic unit of evolutionary process. Species is a group of individual organisms
which have the following characters.
1.
A population of organisms which closely resemble
each other more than the other population.
2.
They descend from a common ancestor.
3.
In sexually reproducing organisms, they interbreed
freely in nature, producing fertile offspring.
4.
In asexually reproducing organisms, they are
identified by their morphological resemblance.
5.
In case of fossil organisms, they are identified by
the morphological and anatomical resemblance.
Species concepts can be classified into two general groups. Concept emphasizing process of evolution that maintains the species as a unit and that can result in evolutionary divergence and speciation.
Another concept emphasises the
product of evolution in defining a species.
There are different types of species and they are
as follows:
1. Process
of evolution - Biological Species
2. Product
of evolution - Morphological Species and Phylogenetic Species
When the individuals are similar to one another in
one or more features and different from other such groups, they are called morphological species. These species
are defined and categorized with no knowledge of phylogenetic history, gene
flow or detailed reproductive mechanisms.
According to Ernest
Mayr 1963,“ these are groups of populations that interbreed and are
reproductively isolated from other such groups in nature”.
This concept was developed by Meglitsch (1954), Simpson (1961) and Wiley (1978). Wiley defined phylogenetic species as “an
evolutionary species is a single lineage of ancestor descendent populations
which maintains its identity from other such lineages which has its own
evolutionary tendencies and historical fate”.
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