Department of Ecology, Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China.
Guangdong Key Laboratory of Animal Conservation and Resource Utilization, Guangdong Public Laboratory of Wild Animal Conservation and Utilization, Guangdong Institute of Applied Biological Resources, Guangzhou, China.
Mol Biol Evol. 2019 Oct 1;36(10):2171-2183. doi: 10.1093/molbev/msz127.
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.
饮食是决定和构建动物多样性和适应性辐射的关键因素。哺乳动物化石记录保存了许多饮食变化的表型证据，而遗传变化后哺乳动物的饮食多样化在很大程度上仍然未知。为了测试现存哺乳动物是否保留了饮食变化的分子证据，我们研究了海藻糖酶基因（Treh），该基因编码一种能够消化昆虫血液中海藻糖的酶，在蝙蝠和其他饮食多样的哺乳动物中。蝙蝠是所有哺乳动物目中最大的饮食辐射群体，具有独立起源的果食性、蜜食性、肉食性、杂食性，甚至在原本以昆虫为食的分支中也有血食性。我们发现，Treh 在与独立辐射到非昆虫食性生态位的无关蝙蝠谱系中已失活。一致地，非昆虫食性蝙蝠中的净化选择明显放松，与它们的昆虫食性亲属相比。蝙蝠肠道海藻糖酶的酶活性测定表明，与昆虫食性亲属相比，非昆虫食性蝙蝠的海藻糖酶活性往往丧失或明显降低。此外，我们对 119 种哺乳动物物种Treh 的调查，代表了更深的进化时间框架，还在非昆虫食性物种中发现了其他几个独立的Treh 缺失，再现了我们在蝙蝠中发现的进化模式。这些结果记录了哺乳动物饮食多样化的分子记录，并表明这种饮食变化的分子特征将有助于我们理解动物饮食的历史和现代变化。
