The Relationship between the Algal-foraging Ability and Expression of Sexually Selected Traits in the Male Guppy

In the guppy Poecilia reticulata, males exhibit orange spots on their body and tail, and the orange spot patterns are often criteria of female mate choice. The orange spot coloration of the males is determined by the intake of algae, a natural source of carotenoids. Therefore, it is considered that males exhibiting conspicuous orange coloration possess high algal-foraging ability. In the present study, we examined the influence of the algal-foraging ability with regard to an algal-searching ability and algal-foraging frequency on the expression of the orange spot patterns and on other sexually selected traits in male guppies. The males exhibiting a greater performance in terms of both the algal-searching ability and algal-foraging frequency grew larger. The size of the orange spots of the males also increased with the algal-foraging ability. However, neither the algal-searching ability nor the algal-foraging frequency influenced the coloration of the orange spots of the males. In this experiment, it is possible that the shortage of carotenoids due to limited carotenoid supply prevented the males from completely developing their orange spots to the intrinsic size. The results of this study suggest that in male guppies under a carotenoid-limited situation, the allocation of carotenoids is based toward the enlargement of the size of the orange spots rather than the enhancement of coloration. Since both the body size and orange spot patterns of the males contribute to their sexual attractiveness to females, the high algal-foraging ability may enhance their mating success.