Temporal changes in the structure of the male nuptial signal in the brook stickleback, Culaea inconstans (Kirtland)

Abstract

Within the Gasterosteidae, only members of the clade Culaea + Pungitius + Gasterosteus contain nuptially coloured males. Of these males, the nuptial signal has been subjected to detailed experimental examination in one species, the three-spined stickleback, Gasterosteus aculeatus. Since most components of the signal did not originate in G. aculeatus, descriptions of signal structure and variability for other members of the Gasterosteidae are a critical prerequisite to discussions of the processes underlying the evolution of male nuptial colouration in these fish. In this paper I investigated the changes in the male nuptial signal for another member of the clade, the brook stickleback, Culaea inconstans. The results of this investigation revealed that as in G. aculeatus, the signal is a complex mosaic, in this case representing the interaction between changes in the intensity of black pigmentation in the ventral – lateral body surface, the dorsal – lateral body surface, the eye bar, the fins, and the spines. These variables interacted to produce four distinct male colour mosaics corresponding to the stage a male had reached in the breeding cycle and the sex of an intruding conspecific.