Role of male-male competition and female choice in the development of breeding coloration in pupfish (Cyprinodon pecosensis)

Abstract

The function of male breeding coloration and the conditions under which it is expressed were investigated using two experimental protocols that differed in the degree of control of social factors. In tank experiments, focal males were separated by opaque or clear partitions or allowed to interact freely without partitions. In lake experiments, males were introduced into opaque or clear enclosures in the lake from which they were collected. This design tested the relative importance of breeding substrate, social interactions with other males, and presence of females and juveniles on the expression of breeding coloration and agonistic and mating behavior in pupfish. Breeding coloration was not expressed in the absence of conspecifics, even in the presence of suitable breeding substrate, or in the presence of juveniles. Breeding coloration was poorly developed when only males were present, was more intense in the presence of females, and darkened significantly after a spawning bout Males in clear enclosures in their natural lake habitat were in visual contact with conspecifics of both sexes and developed more intense blue breeding coloration than males in the tank experiments that were in visual contact only with other males. Uncon-fined males with territories in the lake developed the most intense breeding coloration. Breeding coloration of male pupfish is a facultative trait that is well developed when breeding females are present and plays a major role in the attraction and courtship of mates. However, maximum development of breeding coloration by territorial males suggests that intrasexual and intersexual selection act concordantly on this trait.[Behav Ecol 7: 431-437 (1996)]