An endemic fish living in freshwater blue hole in the Bahamas, Poecilia bahamani

Question

An endemic fish living in freshwater blue hole in the Bahamas, Poecilia bahamania, has two color morphs, a red and blue morph. You have observed that an invasive species of cichlid that was introduced to the blue hole five years before seems to prefer to eat the red morph of the native fish. You even go so far as to conduct an experiment that the cichlid will eat the red Poecilia twice as often as the blue. However, in those five years, the relative frequency of Poecilia has not noticeably changed. What might account for this observation and might natural selection ever cause the population to lose the red morph?

Explanation / Answer

Although conspicuous visual sexual signals, such as bright colors, in males serve to attract females in numerous species, they may also attract the attention of potential predators and thus may be costly in terms of increasing individual risk of mortality to predation. Most models of the evolution of extravagant male sexual traits and female preferences for them assume that the sexually preferred male trait is costly to produce and maintain. However, there is surprisingly little empirical evidence for direct fitness costs associated with sexually selected visual traits that enhance male mating success. In the present study, we report a direct fitness cost for sexually selected, bright body-color patterns in males in the form of an associated greater risk of mortality to predation. By using the guppy (Poecilia reticulata) and the blue acara cichlid fish (Aequidens pulcher) as a model prey

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