ESPM 108B Chapter 1: More on Selection
23 Dec 2018
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Incompatibility alleles - excellent ex: maint at a more/less = freq bc rarer alleles will more likely be successful at pollination. Bc of drift, selection becomes less effective. Chance that neutral allele goes to xation within an avg of 4n gens. It can be shown that the prob of xation of an adaptive allele depends on. 2ns - so, as n is large, it approx 2s. Allele freq are determined mostly by drift when nes is less than 1, where the allele is advantageous. Therefore, a new allele w/ selection adv of . 01 will act as a neutral allele in pops of less than 100, but adaptive in pops larger than 100. When drift prevents selection from removing deleterious alleles, they can accum increasing genetic load. As deleterious alleles become expressed in homozygotes, pop size can further decrease, leading to mutational meltdown. When spp. are dist across heterogeneous landscapes, divergent selection pressures can result in adaptive evol to local conditions.
