Investigating the genetic basis of dietary specialization can provide insights into the evolution of niche breadth. In this study, we used comparative genomics methods to analyze two seasonally avivorous bats (Nyatalus aviator and Ia io) to elucidate the mechanism of adaptation to the expansion of their dietary niche from insectivory to avivory. Our findings revealed that genes related to immunity and lipid metabolism underwent positive selection and convergent evolution among two avivorous bat species. We also found that immune-related genes in avivorous bats are under greater compared to bat species with other diets selective pressure and harbor fewer endogenous retroviral elements in their genomes. We also found that TLR10 is absent in the two avivorous bat species. These findings emphasized the significance of immune-driven adaptive evolution in avivory. Additionally, our results showed that the dietary evolution of avivorous bats is accompanied by convergent evolution associated with the PPAR pathway. Notably, CEPT1, the upstream gene required for the activation of the PPAR pathway, underwent positive selection and convergence, which may have affected lipid metabolism. These findings not only provided comprehensive insights into the adaptive evolution underlying the unique diet of avivorous bats but also offered novel perspectives on the molecular mechanisms underlying ecological niche evolution in a dietary context.

Understanding the adaptive evolution of species has long interested evolutionary biologists. Adaptive phenotypes can result from changes in protein-coding sequences that affect protein structure and function. The Rhinolophus macrotis group as a specific group has low echolocation frequency relative to body size compared with other rhinolophids, suggesting a special evolutionary process of this group. Transcription bridges genetic information and phenotypes. Here, we sequenced transcriptomes of the brain, liver, and cochlea for five species of the macrotis group and its closely related species, R. pusillus, to explore the molecular basis of the adaptation in the macrotis group at the sequence level. Strong and significant positive selection signals for species within the macrotis group was detected in seven genes (CRYM, FOXM1, MAP6, PYCARD, SLC35A2, WRB and SPRY2) linked to hearing. Unexpectedly, we also detected five PSGs (ARRDC3, LZTFL1, RAB8A, IGFBPL1 and TRNT1) linked to vision in species with relatively low frequencies. These results suggested that natural selection has led to the positive selection of some sensory-related genes. Furthermore, PSGs identified in the macrotis group significantly enriched in GO categories related to metabolism (e.g. catalytic activity and oxidoreductase activity), which provided evidence to parse the genetic adaptations of the species with low frequencies within the macrotis group. This is the first attempt to detect genome-wide sequence evolution across the macrotis group and our study provided valuable resources for studying the genetic mechanisms of rhinolophids adaptation.

The circadian rhythm is an adaptive biological process, allows organisms to anticipate daily environmental changes and implement appropriate strategies. Circadian rhythms play a crucial role in the health and survival of organisms. However, little is known concerning how intrinsic and extrinsic factors affect animal daily rhythms in the field, especially in nocturnal animals. Here, we investigated the emergence and return times of Vesperilio sinensis, and also integrated environmental conditions (temperature, humidity and light intensity) and biotic factors (reproductive status and predation risk) to determine causes of variation in the activity rhythms of the bats. We found that variation in the first emergence time, the mid-emergence time, and the final return time were distinct. The results demonstrated that the emergence and return times of bats were affected by light intensity, reproductive status, and predation risk in a relatively complex pattern. Light intensity had the greatest contribution to activity rhythms. Moreover, we first investigated the effects of actual predators on the activity rhythms of bats; the results showed that the mid-emergence time of bats was earlier as predators were hunting, but the final return time was later when predators were present. This challenges the traditional view that high predation risk leads to later emergence and earlier return. Finally, our results also highlighted the importance of higher energy demands during the lactation period in bats to variation in activity rhythms. These results improve our understanding of the patterns and causes of variation in activity rhythms in bats and other nocturnal animals.