Hibernation is an energy-saving and adaptive strategy adopted by a diverse array of animals, rarely including warm-climate species, to survive in the harsh winter environment. Here, we collected large-intestinal microbial samples from two species of warm-climate lizards, one (the Reeves’ butterfly lizard Leiolepis reevesii) hibernating in the winter months and one (the many-lined sun skink Eutropis multifasciata) not doing so, in summer and winter to analyze and compare their microbiota using 16S rRNA gene amplicon sequencing technology. Gut microbiota were seasonally variable in L. reevesii but not in E. multifasciata. The decreased Firmicutes/Bacteroidetes ratio and increased relative abundance of Verrucomicrobia in hibernating butterfly lizards in a state of long-term fasting should help them live through the winter months, as bacteria of the phyla Bacteroidetes and Verrucomicrobia can use host-derived mucin glycans in the absence of dietary substrates. Facultative plant feeding by omnivorous butterfly lizards resulted in a significant increase in the relative abundance of bacteria of the phylum Firmicutes (e.g., Lachnospiraceae) with the ability to degrade plant fibers. This study not only validates the role of gut microbiota in dietary adaptation in lizards but also shows that gut microbial communities are seasonally variable in warm-climate lizards hibernating in the winter months.

Climatic niche breadth is defined as the range of climatic conditions (e.g., temperature and precipitation) under which a species occurs. However, the relationship between niche breadth variation and climatic factors remains poorly studied, and existing results require more general testing. We studied spatial patterns of variation in climatic niche breadths in lizards of the family Agamidae and compared patterns within and across regions to see if they parallel or differ from each other using geo-referenced occurrence records, climatic data and phylogenetic comparative methods. We found that (1) species in warmer environments have narrower temperature niche breadths; (2) precipitation niche breadths are positively correlated with precipitation niche position, and also with temperature niche breadths; and (3) most of the variation in temperature niche breadths is explained by within-locality variation in climatic conditions, whereas most of the variation in precipitation niche breadths is explained by among-locality variation. The patterns of climatic niche breadth in agamids are consistent across regional and global scales, similar to those in other amphibians and reptiles. This suggests that this is a widespread phenomenon among ectothermic vertebrates.