Class Year



coloration, frequency-dependent selection, genetic diversity, predation, mating


The Trinidad guppy, Poecilia reticulata, is one of the most polymorphic species in existence. Guppies exhibit predominantly Y-linked inheritance of male color patterns, which appear on the body, caudal fin, or dorsal fin and are highly variable between individuals. Little investigation behind the mechanism maintaining polymorphism in guppies has been done. One hypothesis is that guppy polymorphism results from frequency-dependent selection. My study sought to investigate whether reduced sexual attractiveness of "redundant" males, with similar color patterns, may contribute to polymorphism. Experimental groups consisted of two males with similar color patterns (redundant) and two males with distinctly different color patterns (unique). The four males were placed in a tank with four virgin females. I compared sexual responsiveness of female guppies to the redundant vs. the unique males. Females were significantly less likely to show sexual response to the redundant males than they were to the unique males. This suggests that female guppies preference for unique males contributes to the maintenance of polymorphism in this population.


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