guppies, sexual selection, visual barriers
Sexual selection is the outcome of behavioral interactions within and between the sexes. Numerous studies show how individuals modify their behavior in response to ecological or social conditions, and such changes may therefore affect the evolutionary outcome of sexual selection. This study examined the effect of habitat structure on the sexual behavior of male and female guppies (Poecilia reticulata). I wished to determine whether the ability of males to observe other courting males would affect the rates of male courtship, courtship interference, and the sexual responsiveness of females. Specifically, I manipulated visibility using opaque barriers in laboratory aquaria and found that there was less male interference behavior in aquaria containing visual obstructions than in aquaria without barriers, regardless of whether the male was courting virgin ("responsive") or non-virgin ("unresponsive") females. In addition, the sexual responsiveness of virgin females to male displays was significantly increased, and the frequency of male displays when courting virgin females was significantly reduced in aquaria with barriers. The presence of visual barriers, however, did not appear to affect the rates of male courtship displays to non-virgins or the responsiveness of non-virgins. Evidently, the barriers impede visibility enough that males are less likely to observe and interfere with the courtship activity of other males, and therefore, females are less likely to flee or lose interest in a courting male. Such habitat related changes in male-male competition and female responsiveness could potentially affect female choice and the evolutionary outcome of sexual selection.
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