LIFE 102 Lecture Notes - Lecture 54: Allopatric Speciation, Sympatric Speciation, Ensatina
Document Summary
Prevent the hybrid zygote from developing into a viable fertile adult: Genes of the different parent species may interact and impair the hybrid"s development. Even if hybrids are vigorous, they may be sterile. Some first-generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of the next generation are feeble or sterile. *reproductive isolation may then arise by natural selection, genetic drift, or sexual selection in the isolated populations. *even if contact is restored between populations, interbreeding is prevented. Gene flow is interrupted or reduced when a population is divided into geographically isolated subpopulations. Squirrels on either side of the grand canyon. *the definition of barrier depends on the ability of a population to disperse. *separate populations may evolve independently through mutation, natural selection, and genetic drift. *regions with many geographic barriers typically have more species than do regions with fewer barriers.
