The ecological drivers of nuptial color evolution in darters (Percidae: Etheostomatinae)

Abstract

Closely related animal lineages often vary in male coloration, and ecological selection is hypothesized to shape this variation. The role of ecological selection in inhibiting male color has been documented extensively at the population level, but relatively few studies have investigated the evolution of male coloration across a clade of closely related species. Darters are a diverse group of fishes that vary in the presence of elaborate male nuptial coloration, with some species exhibiting vivid color patterns and others mostly or entirely achromatic. We used phylogenetic logistic regression to test for correlations between the presence/absence of color traits across darter species and the ecological conditions in which these species occur. Environmental variables were correlated with the presence of nuptial color in darters with colorful species tending to inhabit environments that would support fewer predators and potentially transmit a broader spectrum of natural light compared to species lacking male coloration. We also tested the color preferences of a common darter predator, largemouth bass, and found that it exhibits a strong preference for red, providing further evidence of predation as a source of selection on color evolution in darters. Ecological selection therefore appears to be an important factor in dictating the presence or absence of male coloration in this group of fishes.

Male behaviour predicts trait divergence and the evolution of reproductive isolation in darters (Percidae: Etheostoma)

“…The colour of male dewlaps in Anolis lizards has diverged to maximize brightness contrast in populations occupying distinct signalling environments , and across numerous species of antbirds, the frequency (pitch) of male song is correlated with the sound transmission properties of distinct habitats . In darters, the extent of sexual dichromatism (colour differences between the sexes within a species) and the presence/absence of nuptial coloration covaries with habitat use across the genus Ciccotto & Mendelson, 2015). However, among very closely related darter species, such as the focal species examined here, sexual signal differences are not associated with environmental differences , and sympatric darter species often express different colour signals in the same habitats .…”

Agonistic character displacement of genetically based male color patterns across darters

“…In addition, the traits that are most strongly implicated in species-specific differences between orangethroat and rainbow darters (i.e., the proportion of red and blue coloration on the body, anal fin, and caudal fin) have intermediate values in F1 hybrid males [29], suggesting that introgression can cause increased trait similarity between species. Second, although large-scale transitions between genera and sub-genera are associated with ecological divergence in darters [41,42], there is strong evidence that differences in male color pattern among more closely related species are primarily driven by intrasexual selection rather than ecological differences [24,26,43,44].…”

The evolution of male nuptial colour in a sexually dimorphic group of fishes (Percidae: Etheostomatinae)

“…Alternatively or additionally, a bias for red may only be maintained in populations that are free from ecological constraints. Concurrent work shows that red species tend to inhabit streams with fewer piscivorous fishes and that at least one darter predator has a strong preference for red prey items (Ciccotto & Mendelson, 2016). Thus, darters in habitats with limited predation pressure may be free from an ecological constraint against a preference for red.…”

“…Colour data from Ciccotto & Mendelson () were used for phylogenetic comparative analyses. In brief, the presence of step‐shaped colours (red, red–orange and orange) and peak‐shaped colours (blue, blue–green, green and turquoise), two classes of colour that have been confirmed with reflectance spectrophotometry in darters (Gumm et al ., ; Gumm & Mendelson, ; P. J. Ciccotto, unpub.…”