BIOL 2P92 Lecture Notes - Allele Frequency, Mutation, Polyploid
19 Jan 2013
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Document Summary
Species are named on the basis of statistically significant differences in the traits used to estimate the phylogeny. Recent analyses have found that the phylogenetic species concept often distinguishes a series of cryptic species in populations that were formerly considered a single species. Species can be identified by distinctive morphological traits, reproductive isolation, and/or phylogenetic independence. Employing more than one species concept can help biologists recognize diversity and organize research on its consequences. Read example on marine copepods and elephants on pages 609-610. Speciation has been hypothesized to be a three-stage process: Initial step that isolates populations: second step that results in divergence in traits such as mating system or habitat use, final step that produces reproductive isolation. Isolation and divergence steps were thought to take place over time and to occur while populations were located in different geographic areas. Isolation/divergence/secondary contact hypothesis provides a useful framework for analyzing how speciation takes place. First step in speciation is genetic isolation.
