SPECIES CONCEPT -
- According to Davis and Heywood species define as assemblage of individuals with morphological features in common and separable from other such assemblage by correlated morphological discontinuities in a number of features.
- Lumpers tend to combine populations into single species or groups.
- Splitters tend to separate the same populations into different species or groups.
BIOLOGICAL SPECIES CONCEPT -
- A species is a sexually interbreeding or potentially interbreeding group of individuals separated from other species by reproductive isolation that is by absence of genetic exchange.
SIBLING SPECIES CONCEPT -
- When the two species are morphologically almost identical but do not interbreed. e.g., Drosophila pseudoobscura and Drosophila persimilis are two species, do not cross-fertilize.
POLYTYPIC SPECIES CONCEPT -
- Morphologically and geographically separated species into a single species on the basis of their successful interbreeding is called polytypic species. e.g., North American sparrows - Passarella melodia.
EVOLUTIONARYCHRONO SPECIES CONCEPT -
- According to George Gaylord Simpson (1961) A species as a group of organism that is derived from its ancestor by a process of slow, steady evolutionary change and is not regarded as members of the same species as its ancestor.