Colour vision and speciation in Lake Victoria cichlids of the genus Pundamilia

Abstract

Lake Victoria cichlids are one of the most speciose groups of vertebrates. Selection on coloration is likely playing an important role in their rapid speciation. To test the hypothesis that sensory biases could explain species differences in mating preferences and nuptial coloration, we studied seven populations of four closely related species of the genus Pundamilia that differ in visual environment and male nuptial colour. Microspectrophotometry determined that the wavelength of maximum absorption (lambdamax) of the rod pigment and three cone pigments were similar in all four species. Only the long wavelength sensitive (LWS) pigment varied among species, with 3-4 nm shifts in lambdamax that correlated with differences in the LWS opsin sequence. These subtle shifts in lambdamax coincided with large shifts in male body colour, with red species having longer LWS pigments than blue species. Furthermore, we observed within and between species a correlation between water transparency and the proportion of red/red vs. red/green double cones. Individuals from turbid water had more red/red double cones than individuals from clear water. The variation in LWS lambdamax and in the proportion of red/red double cones could lead to differences in perceived brightness that may explain the evolution of variation in male coloration. However, other factors, such as chromophore shifts and higher order neural processing, should also be investigated to fully understand the physiological basis of differential responses to male mating hues in cichlid fish.

The fiddler crabUca mjoebergiuses colour vision in mate choice

“…For instance, the females of two sympatric species of Lycaena butterflies appear to use wing colour to identify conspecific males and their visual pigments are well matched to facilitate such discriminations (Bernard & Remington 1991). The coloration of cichlid fish is believed to play a role in speciation (Seehausen & von Alphen 1998;Couldridge & Alexander 2001) and there is some evidence that their spectral sensitivities match their nuptial coloration (Carleton et al 2005). Reproductive isolation in fiddler crabs may be aided by their species-specific coloration, but whether their colours evolved in response to a pre-existing sensory bias or drove the evolution of the visual pigments is unknown.…”

“…Species-specific colours, like those common in fiddler crabs (Crane 1975), may influence the evolution of visual pigments (Goldsmith 1991;Endler 1992) and vice versa (Endler 1992;Ryan & Keddy-Hector 1992;Ryan 1998;Carleton et al 2005). For instance, the females of two sympatric species of Lycaena butterflies appear to use wing colour to identify conspecific males and their visual pigments are well matched to facilitate such discriminations (Bernard & Remington 1991).…”

The Causes and Consequences of Color Vision

“…Male cichlids exhibit very vivid colors during the mating season (their nuptial colors) that are specific to a given species and are likely to serve as signals to help females identify mates of the right species. It turns out that photopigments can be very different in different species, suggesting that the eyes of individuals of the different species are specifically "tuned" to see the nuptial colors of the males from their species (Carleton et al 2005). Behavioral studies that examine female mating preferences have shown that when you mask the color differences between males in the laboratory by using monochromatic light, the females show no preference between their own males and those of a closely related species (Mann et al 2004).…”

Male courtship decisions are influenced by light environment and female receptivity

“…Variation in light environments within a habitat causes associated changes in sensed colour signal parameters [1][2][3][4][5]. This results from interactions among the spectral composition of light (relative light intensity at each wavelength or 'colour'), the total intensity of light, the medium through which light travels to the eye, and the surrounding visual backgrounds.…”

“…Thus, the received signal can be different under different light environments, altering the perceived conspicuousness of a colour pattern. Visual spectral sensitivities [2,3] also change in response to the predominant light environment, causing changes in signal perception that can result in long-term changes in colour patterns [4]. These processes can lead to polymorphism, population divergence, or speciation [3,5,6].…”