Species Concept

• Species concept are still subject to debate. An idea of what kind of entity is represented by the word SPECIES
• There are several concepts recognizing the special reality of species
• SPECIES CRITERIA = standards used for species recognition = operationalism

What is a species?

A group or class of animals or plants (usually constituting a subdivision of a genus) having a certain common and permanent characterstics which clearly distinguish it from other groups.

BIOLOGICAL SPECIES CONCEPT

• Given by Mayr in 1942
• Species are groups of interbreeding natural population that are reproductively isolated from other such groups.
• Species are designated on absence of gene flow
• Emphasis on REPRODUCTIVE ISOLATION

REPRODUCTIVE ISOLATING MECHANISM

PHYLOGENETIC SPECIES CONCEPT

• Species is a group of organism whose members are descended from common ancestor and have unique evolutionary history.
• Subspecies not recognized
• STRENGTH: considers ancestry, genetic similarity, evolutionary process
• WEAKNESS: Does not consider reproductive habitats

EVOLUTIONARY SPECIES CONCEPT

• Given by Simpson in 1951.
• A single lineage of ancestor-descendant populations which maintains its identity from other such lineages and has its own evolutionary tendencies and historical fate.
• It considers the species as an evolutionary entity.

NOMINALISTIC SPECIES CONCEPT

• Given by Occan and his followers
• Nature produces individuals only and nothing more, species have no actual existence in nature
• DRAWBACKS-: Nominalist misinterpreted the relation between similarity and relationship
• It is a established fact that species are products of evolution.

RECOGNITION SPECIES CONCEPT

• A Species is a set of organism that recognize one another as potential mates, they have a
• shared recognition system.”
• Emphasis on reproductive isolationing mechanism to keep species apart
• Sometimes referred to as REPRODUCTIVE SPECIES CONCEPT
• EXAMPLE: AMERICAN CRICKET

MORPHOLOGICAL SPECIES CONCEPTS

• Given by Cronquist in 1978.
• “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.”
• May be applied to both sexual and asexual organisms.

ECOLOGICAL SPECIES CONCEPTS

• Focus of species characterization is on similarity of niche and ecological role.
• Strength : considers species role in an ecosystem.
• Weakness : geographically widespread populations that don’t actually interbreed may be considered the species.

Conclusion

• The categorization and maintenance of species records is important for science and conservation.
• For identifying an individual species, typically scientists will first consider Biological Species Concept, then descent from common ancestry and genotypic and phenotypic cohesion.

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