Adaptive Evolution of the Greater Horseshoe Bat : Insights into the Link between and Hibernation Rhythms.

Arylalkylamine N-acetyltransferase (AANAT) is a crucial rate-limiting enzyme in the synthesis of melatonin. has been confirmed to be independently duplicated and inactivated in different animal taxa in order to adapt to the environment. However, the evolutionary forces associated with having a single copy of remain unclear. The greater horseshoe bat has a single copy of but exhibits different hibernation rhythms in various populations. We analyzed the adaptive evolution at the gene and protein levels of from three distinct genetic lineages in China: northeast (NE), central east (CE), and southwest (SW). The results revealed greater genetic diversity in the loci of the NE and CE lineage populations that have longer hibernation times, and there were two positive selection loci. The catalytic capacity of AANAT in the Liaoning population that underwent positive selection was significantly higher than that of the Yunnan population ( < 0.05). This difference may be related to the lower proportion of α helix and the variation in two interface residues. The adaptive evolution of was significantly correlated with climate and environment ( < 0.05). After controlling for geographical factors (latitude and altitude), the evolution of by the negative temperature factor was represented by the monthly mean temperature (r = -0.6, < 0.05). The results identified the gene level variation, functional adaptation, and evolutionary driving factors of , provide an important foundation for further understanding the adaptive evolution of the single copy of in pteropods, and may offer evidence for adaptive hibernation rhythms in bats.