Rhodopsin Molecular Evolution in Mammals Inhabiting Low Light Environments

Zhao, Huabin; Ru, Binghua; Teeling, Emma C.; Faulkes, Christopher G.; Zhang, Shuyi; Rossiter, Stephen J.

Relatively fewer studies have been undertaken on the molecular evolution of vertebrate rhodopsin genes in spite of its key function in conferring monochromatic vision in low light. The molecular mechanism of spectral tuning in rhodopsin appears to be influenced by 13 amino acids [17, [23] [24] . Shifts in spectral tuning appear to correlate with foraging depth in marine mammals [14] and have also been linked to differential light environments in some fishes [15, [25] [26] [27] [28] . Darwinian selection along the rhodopsin gene has been detected during the adaptive radiation of cichlid fishes [15] . In this study we present the most detailed comparative phylogenetic study of mammal rhodopsins to date. We include several groups that are highly specialized for living in low light conditions, including bats, subterranean mole-rats, pinnipeds and cetaceans. We test the hypotheses that the rhodopsin gene has undergone molecular adaptation associated with evolutionary switches to different niches characterized by low light conditions, and, more specifically, that these changes will have coincided with losses of the SWS1 gene. In addition, we undertake a more detailed study of rhodopsin evolution among several clades of bats that use different sensory modalities and in which SWS1 has undergone differential psuedogenisation among lineages [22] .