Abstract
Geckos are a species-rich clade of primarily nocturnal lizards and adaptations to nocturnality has dramatically reshaped the gecko eye. Perhaps the most notable change is the loss of rod cells in the retina and subsequent “transmutation” of cones into a rod-like morphology. While many studies have noted the absence of the rod opsin RH1, in geckos, these studies have focused on a handful of species that are nested deep in the gecko phylogeny. Thus, it is not clear whether these changes are ubiquitous across geckos or restricted to a subset of species. Here, we used eye transcriptomes from five gecko species, representing the breadth of extant gecko diversity, to show that geckos lost expression of multiple rod cell phototransduction genes in the eye, distinct from other reptiles. Furthermore, all sampled species lost expression of the SWS2 visual opsin. Together, these results suggest a “nocturnal bottleneck” in the MRCA of geckos.