Species and Speciation
Big idea: Speciation occurs when gene flow is reduced and populations accumulate differences that produce reproductive isolation; species concepts provide different operational ways to recognize lineages.
Learning goals
- species concept
- reproductive isolation
- allopatric speciation
- sympatric speciation
- hybrid zone
Core concepts
species concept
An operational rule for identifying independently evolving lineages using reproduction, form or ancestry.
reproductive isolation
Biological barriers that prevent populations from exchanging genes successfully.
allopatric speciation
Divergence after a geographic barrier reduces gene flow between populations.
sympatric speciation
Divergence without geographic separation, often through ecological, behavioral or chromosomal differences.
hybrid zone
A region where differentiated populations meet and produce some hybrid offspring.