Opsin variation in a poison frog that shows color-associated behavioral biases

Abstract

Abstract Animals send and receive signals, which are honed by evolution for detection by their intended receiver, for a variety of purposes. For signals used in mate choice, selection should favor those that are easy to detect by the receiving sex’s sensory system(s). Here we test for genetic differences affecting color vision among populations and color morphs of the polytypic poison frog, Oophaga pumilio, a species where both males and females show color-assortative behavioral biases. Opsin genes, expressed in rod and cone cells in the retina, play an important role in the tuning of color vision. We therefore hypothesized that the frog’s behavioral biases may be underlain by differences in the expression or sequences of these genes. To test this, we compared closely related populations of O. pumilio containing red and green morphs to test for convergence in opsin expression and sequence by color. We also compared opsins in sympatric morphs from two polymorphic regions with those of neighboring monomorphic populations to test for differences that would confer improved color discrimination in the polymorphic area. We found no significant differences in opsin expression among red and green populations nor among frogs from one polymorphic (red/blue) zone. However, consistent with our predictions for greater color discrimination, we found greater RH1 expression in frogs from a second polymorphic (red/yellow) region. We found several opsin sequence variants that showed no clear association with color morph, though some mutations were only found in polymorphic populations and some mutations should have significant impacts on color vision in affected individuals. Overall, we found limited evidence that differences in color vision have evolved among distinctly colored O. pumilio populations, though the variation we observed within populations does suggest that the raw material needed for selection to act on color vision is present.