Meeting Abstract
Gene expression and coding sequence changes both facilitate adaptive evolution at the molecular level, but to what extent? Because the functional significance and mechanistic pathways are relatively well understood, phototransduction is an excellent domain to test the patterns of molecular adaptation and their import to diversification. Among vertebrates, coral reef fishes are known for their hyperdiversity, but there is a clear juxtaposition between lineages inhabiting shallow euphotic reefs and those from deeper mesophotic habitats, which differ in the prevailing light intensity and spectrum. Phylogenetic data show that repeated transitions between habitats have occurred, suggesting that depth drives diversification in reef fishes. Intriguingly, the Athiadinae or anthias fishes, which are very common and colorful inhabitants of shallow reefs, also includes many mesophotic species which are similarly colorful and sexually dimorphic in the red-yellow hues that are reduced in the blue-dominated spectrum at these depths. By analyzing RNA-seq data from the eyes of two mesophotic and two euphotic non-sister lineages of Pseudanthias, we determined that adaptation to spectral environment included both expression and coding changes in opsin genes: deep and shallow lineages preferentially express different paralogs of the green-sensitive Rh2 genes, while the constitutively-expressed blue-sensitive SWS2B gene exhibited parallel differences in codon positions that likely cause differences in spectral sensitivity. We will also discuss the relevance of these changes to patterns of biofluorescence in anthias fishes.
