Female preference for male color is necessary and sufficient for assortative mating in 2 cichlid sister species

Abstract

A critical step for speciation in the face of gene flow is the origination of reproductive isolation. The evolution of assortative mating greatly facilitates this process. Assortative mating can be mediated by one or multiple cues across an array of sensory modalities. We here explore possible cues that may underlie female mate choice in a sympatric species pair of cichlid fish from Lake Victoria, Pundamilia pundamilia and Pundamilia nyererei. Previous studies identified species-specific female preferences for male coloration, but effects of other cues could not be ruled out. Therefore, we assessed female choice in a series of experiments in which we manipulated visual (color) and chemical cues. We show that the visibility of differences in nuptial hue (i.e., either blue or red) between males of the 2 species is necessary and sufficient for assortative mating by female mate choice. Such assortment mediated by a single cue may evolve relatively quickly, but could make reproductive isolation vulnerable to environmental changes. These findings confirm the important role of female mate choice for male nuptial hue in promoting the explosive speciation of African haplochromine cichlids.

Differential Survival between Visual Environments Supports a Role of Divergent Sensory Drive in Cichlid Fish Speciation

“…This environmental difference coincides with species differences in visual pigment gene sequences and expression Seehausen et al 2008), as well as behavioral responses to blue and red light (Maan et al 2006). Male nuptial coloration and female mate preferences have diverged in parallel: P. pundamilia females prefer the blue coloration of P. pundamilia males, while P. nyererei females prefer the yellow and red coloration of P. nyererei males (Seehausen and Van Alphen 1998;Selz et al 2014), indicating that divergent visual adaptation may directly or indirectly affect sexual communication and reproductive isolation (Maan and Seehausen 2010).…”

“…Assortative mating could then emerge as an immediate by-product of depth segregation. Second, female P. pundamilia and P. nyererei exert species-assortative mating preferences that are mediated by male coloration (Seehausen and Van Alphen 1998;Selz et al 2014). These preferences may be influenced directly by visual adaptation: a general preference for conspicuous males, as documented in these and other haplochromine cichlids (Maan and Sefc 2013), would translate to different color preferences when visual adaptation affects the perceived conspicuousness of different colors (Endler 1992;Boughman 2002;Maan et al 2006;Seehausen et al 2008).…”

Differences in male coloration are predicted by divergent sexual selection between populations of a cichlid fish

“…Previous studies in Pundamilia suggest that males do not visually discriminate between females of own and other species based on colour or morphology [26,27]. In general, the males of P. nyererei are yellow between the bars on the lower flanks, but red around and above the lateral line.…”

“…The two species are geographically fully sympatric at several islands in Lake Victoria, but within an island, they inhabit subtly different depth ranges with different light environments [25]. Behavioural mating preference and mate choice experiments have shown that the differences in colour between males of the two species are necessary and sufficient for species-assortative mating [26,27]. Pundamilia nyererei inhabits deeper waters with more red-shifted light conditions and has a more red-shifted retinal visual pigment composition than P. pundamilia [17,28,29].…”

Differentiation of visual spectra and nuptial colorations of two Paratanakia himantegus subspecies (Cyprinoidea: Acheilognathidae) in response to the distinct photic conditions of their habitats

“…Variations in spectral sensitivity mainly result from the alternative usage of different opsin genes (Flamarique 2013;Johnson et al 2013;Kasagi et al 2015;Kondrashev et al 2013;Valen et al 2013). Furthermore, sexual selection favors individuals that can display visual signals that are readily distinguishable from the background (Hurtado-Gonzales et al 2014;Miyagi et al 2012;Morrongiello et al 2010;Selz et al 2014). Therefore, in addition to their link with visual properties, photic environments may also influence overall body coloration of fish.…”