Sexually asymmetric colour-based species discrimination in orangethroat darters

Abstract

Female mate preferences, male mate preferences and male–male competition can all potentially play roles in promoting speciation by sexual selection. The orangethroat darter, Etheostoma spectabile , is a sexually dichromatic fish in which males compete for access to females. We quantified male and female responses to conspecific versus heterospecific fish under normal light, dim light and blue light, the last of which impaired colour perception. We found that behavioural isolation was likely mediated primarily by male behavioural discrimination against heterospecific fish, with females showing no evident mate preferences. Furthermore, male aggression towards conspecific rivals was reduced in blue light, suggesting that the evolution of male coloration may contribute to speciation through male–male interactions. • We examined behavioural isolation in two Etheostoma darters with dichromatic colour vision. • Male, but not female, E. spectabile discriminated between conspecific and heterospecific males. • Male E. caeruleum did not respond to heterospecific fish of either sex. • Perception of reddish coloration was necessary for conspecific male–male aggression.