STAT 2230 Lecture Notes - Assortative Mating, Hybrid Zone, Allopatric Speciation
Document Summary
Dispersal, vicariance, and polyploidization only create the conditions for speciation: for speciation to take place, genetic drift & natural selection have to act on mutations in a way that creates divergence in the isolated populations. Effects of genetic drifts are random fixation of alleles and random loss of alleles. Drift can produce rapid genetic divergence in small, isolated populations. Its effects are most pronounced in small populations. A general model of speciation: small populations that become isolated start out as a non-random sample of the ancestral population. As drift continues to occur in the small, derived population, it leads to a random loss of allele and the random fixation of existing and new alleles. As a result, the isolated population should undergo rapid genetic divergence from the ancestral population. For drift to change allele frequencies dramatically, the founding population has to be extremely small and remain small for a significant period of time.