Integrating Phylogenetic and Experimental Analyses: The Evolution of Male and Female Nuptial Coloration in the Stickleback Fishes (Gasterosteidae)

Both male and female gasterosteid fishes display nuptial coloration. Male nuptial coloration originated in the ancestor of the Pungitius + Culaea + Gasterosteus clade. Patterns of origin and diversification of characters involved in male-male, male-female, and parental interactions indicate that the evolution of male color was influenced by intersexual selection, natural selection during parental care, and intrasexual selection, in decreasing order of importance. This macroevolutionary hypothesis was corroborated by examining changes in male color across the breeding cycle for two stickleback species, Gasterosteus aculeatus and Culaea inconstans. Female nuptial coloration may have originated before the male signal. The phylogenetic diversification of the male and female signals are decoupled, suggesting that they have been subject to different selection pressures throughout their evolutionary histories. Macroevolutionary patterns and experimental studies indicate that color signal evolution has been more complex in this group of fishes than was previously thought.