Evidence for Evolution For female isopods, size doesn't matter In the marine isopod Paracerceis sculpta , there are three discrete male morphologies. These are determined by a single allele change at one locus. The largest of the three males, the alpha males, defend harems of isopod females. The intermediate size male, the beta, mimics female morphology and behavior and the gamma males, the smallest of the three morphs, attempt to hide in large harems and not attract the attention of the alpha male(s). The larger the male, the slower it matures. But larger males, although they reach reproductive age later in life, live longer and therefore have more reproductively active years. In the paper I will summarize here, the authors demonstrate that each male morph enjoys equal mating success. Male reproductive success in these isopods depends on many factors. Each male morph is able to sire roughly the same amount of offspring when isolated from other males. Differences in male reproductive success occur when males are mixed in the mating area, the spongocoel. For
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