Female color preferences, ecological selection, and the evolution of male coloration in darters (Percidae: Etheostomatinae)

Since Charles Darwin's initial observations and hypotheses, the evolution of elaborate male coloration in sexually dichromatic species has been the subject of great interest. Of particular recent interest is how sexual and ecological selection interact to shape variation in male coloration between closely-related species. Using darters (Percidae: Etheostomatinae), a group of fishes that vary in male coloration as a model system, my goal is to determine how sexual and ecological selection interact to shape variation in male coloration between as well as within species lineages. In Chapter 1, I used reflectance spectrophotometry to examine correlations between spectral properties of orange and blue pigmentation in the rainbow darter, Etheostoma caeruleum, with parasite load and observed a correlation between the chroma of orange bars with parasite counts. In Chapter 2, I quantified color preferences in the darter genus Etheostoma to determine if the strengths of attraction to different colors coincided with variation in male coloration between species. The females of most achromatic species exhibited no significant color preferences, while chromatic species varied in preferences, with a positive association between the presence of red or orange on the flanks and preference for red detected across all species. In Chapter 3 I utilized phylogenetic comparative approaches and a laboratory experiment of predator color preferences to quantify the role of ecological variables in shaping variation in male coloration in darters. Compared to achromatic species, chromatic darters tend to inhabit environments where predation risk would be lower; specifically, shallower, faster-flowing upland streams with a lower number of overlapping predatory species. Additionally, a common darter predator, largemouth bass (Micropterus salmoides), exhibited significant preferences for red stimuli in a color choice experiment. Finally, in Chapter 4 I investigated color and size correlations, as well as male and female preferences for different sized and colored mates, in the Roanoke darter, Percina roanoka. Using digital photography I found correlations between size and color, but no preferences for larger or more colorful mates were observed in either sex. The results of this dissertation suggest that sexual and ecological selection do interact to shape color variation between darter species