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Biological Species Concepts
To maintain species
Prezygotic Barriers
- Habitat isolation
- Behavioral isolation
- Temporal isolation
- Mechanical isolation
- Gamete isolation
Postzygotic Barriers
- Reduced hybrid viability
- Reduced hybrid fertility
- Hybrid breakdown
Where the Biological concept DOES NOT work –
• Inadequates for grouping extinct forms of life.
• Meaningless for organisms that reproduce asexually.
• Some species interbreed and produce viable hybrids but maintain separate species.
Ex. Wolves, domestic dogs and coyotes. Also deer mouse that maintain fore
subspecies.
• Discovering more cases of “ what is a subspecies and what is a full species?”
• Catching populations at different stages of evolution.
For these reasons, other species concepts are being evaluated.
1. Morphological – taxonomy
2. Recognition – mating adaptations (rituals).
3. Cohesion – each species is defined by its set of genes. Can use this to include organisms
that reproduce asexually and hybrids.
4. Ecological – Where organisms live and what they do (roles) rather than phenotype.
5. Evolutionary – Defines a species as a sequence of ancestral populations with a specific
set of forces of natural selection and unique role in the environment.
• Biological concept needs isolation of the gene pool.
• The other concepts recognize genetic exchange between species.
• Which concept(s) depends on the question you are asking about a species.
Talking about populations that are genetically discrete, that have originated from genetic
isolation.