BIOL 3130 Study Guide - Quiz Guide: Allopatric Speciation, Introgression, Parapatric Speciation
23 Oct 2016
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Document Summary
Population splits into two geographically isolated populations. Key issues: founder effects, bottlenecks, genetic drift & random allelic selection. Only partial separation of the zones of two diverging populations afforded by geography. Individuals may come in contact but reduced offspring fitness leads to selection of mechanisms that prevent inter-breeding. Two or more descendant species from a single ancestral species all occupying the same geographic location. Mechanism: individuals switching to different microhabitats, creating fitness differences that become reinforced by sexual selection. Directional: selection against phenotype at one extreme. Darwinian island: populations never come into contact with source of individuals (mainland). If isolation persists, species formation results in neo-formation. With extreme isolation, the ecological space will be filled by speciation. Fragment island: ecological space initially filled by connection to mainland prior to separation. # of species declines following fragmentation due to the process of relaxation. If islands become more isolated, species will arise due to allopatric speciation leading to paleo-endemics .
