Diet is a key factor in determining and structuring animal diversity and adaptive radiations. The mammalian fossil record preserves phenotypic evidence of many dietary shifts, whereas genetic changes followed by dietary diversification in mammals remain largely unknown. To test whether living mammals preserve molecular evidence of dietary shifts, we examined the trehalase gene (Treh), which encodes an enzyme capable of digesting trehalose from insect blood, in bats and other mammals with diverse diets. Bats represent the largest dietary radiation among all mammalian orders, with independent origins of frugivory, nectarivory, carnivory, omnivory, and even sanguivory in an otherwise insectivorous clade. We found that Treh has been inactivated in unrelated bat lineages that independently radiated into noninsectivorous niches. Consistently, purifying selection has been markedly relaxed in noninsectivorous bats compared with their insectivorous relatives. Enzymatic assays of intestinal trehalase in bats suggest that trehalase activity tends to be lost or markedly reduced in noninsectivorous bats compared with their insectivorous relatives. Furthermore, our survey of Treh in 119 mammal species, which represent a deeper evolutionary timeframe, additionally identified a number of other independent losses of Treh in noninsectivorous species, recapitulating the evolutionary pattern that we found in bats. These results document a molecular record of dietary diversification in mammals, and suggest that such molecular signatures of dietary shifts would help us understand both historical and modern changes of animal diets.

The evolution of taste perception is usually associated with the ecology and dietary changes of organisms. However, the association between feeding ecology and taste receptor evolution is unclear in some lineages of vertebrate animals. One example is the sweet taste receptor gene Tas1r2. Previous analysis of partial sequences has revealed that Tas1r2 has undergone equally strong purifying selection between insectivorous and frugivorous bats. To test whether the sweet taste function is also important in bats with contrasting diets, we examined the complete coding sequences of both sweet taste receptor genes (Tas1r2 and Tas1r3) in 34 representative bat species. Although these two genes are highly conserved between frugivorous and insectivorous bats at the sequence level, our behavioral experiments revealed that an insectivorous bat (Myotis ricketti) showed no preference for natural sugars, whereas the frugivorous species (Rousettus leschenaultii) showed strong preferences for sucrose and fructose. Furthermore, while both sweet taste receptor genes are expressed in the taste tissue of insectivorous and frugivorous bats, our cell-based assays revealed striking functional divergence: the sweet taste receptors of frugivorous bats are able to respond to natural sugars whereas those of insectivorous bats are not, which is consistent with the behavioral preference tests, suggesting that functional evolution of sweet taste receptors is closely related to diet. This comprehensive study suggests that using sequence conservation alone could be misleading in inferring protein and physiological function and highlights the power of combining behavioral experiments, expression analysis, and functional assays in molecular evolutionary studies.

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Rhinolophus malayanus has been found in several countries in Southeast Asia, including Vietnam, Thailand, Malaysia, Laos, and Myanmar. In 2015, we found three small Rhinolophus bats in Mengla County, Yunnan, China. Results of morphological and molecular examinations identified them as R. malayanus. This is the first record of existence of R. malayanus in China. This study advanced our knowledge of bat distribution and provided important information for further studies of various aspects of R. malayanus in China.

Grooming is a common behavior of some mammals. Previous studies have shown that grooming is a means by which animals clean themselves, remove ectoparasites, and lower their body temperature. It is also involved in olfactory communication. Bats belong to the order Chiroptera and, like most mammals, are the natural host of many ectoparasites. Bat grooming, including licking and scratching, is one of the ways to reduce the adverse effects caused by ectoparasites. Bat grooming may also be induced by exogenous odor. In this study, we used lesser flat‐headed bats ( Tylonycteris pachypus ) to test the hypothesis that exogenous odor affects the self‐grooming behavior of bats. Results showed that external odor from distantly related species caused lesser flat‐headed bats to spend more time in self‐grooming. Lesser flat‐headed bats that received odor from humans spent the longest time in self‐grooming, followed by those that received odor from a different species of bats ( T. robustula ). Lesser flat‐headed bats that received odor form the same species of bats, either from the same or a different colony, spent the least amount of time in self‐grooming. These results suggest that bats can recognize conspecific and heterospecific through body scent.

Hypsugo cadornae bats have been found in India, Myanmar, Thailand, Vietnam, Laos, and Cambodia. In 2017 and 2018, 15 medium size Hypsugo bats were collected from Shaoguan, Guangzhou, and Huizhou in Guangdong, China. Molecular and morphological examinations identified them as H. cadornae. This is the first record of H. cadornae in China. Morphological and ultrasonic characteristics of H. cadornae were compared with its close relative, Hypsugo pulveratus.