Miller Institute for Basic Research in Science, University of California, Berkeley, CA 94720;
Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720.
Proc Natl Acad Sci U S A. 2017 Dec 26;114(52):13768-13773. doi: 10.1073/pnas.1700122114. Epub 2017 Dec 11.
The gut bacterial communities of mammals have profound effects on host fitness, but the processes that generate and maintain gut bacterial diversity remain poorly understood. We mapped compositional variation (i.e., β-diversity) in the gut microbiotas of 136 pairs of wild mammalian species living throughout the Americas to assess how the distribution of mammals across geographic space influences the diversification of their gut bacteria. Comparing the gut microbiotas of sympatric and allopatric mammalian populations provided insights into the flow of gut bacteria within and between mammalian communities, revealing that spatial limits on bacterial dispersal promote β-diversity between the gut microbiotas of mammalian species. Each geographic locale displayed a unique gut-microbiota composition that could not be fully explained by the diets and phylogenetic histories of the resident mammalian hosts, indicating that some gut bacteria are geographically restricted. Across the western hemisphere, the compositional overlap between the gut microbiotas of allopatric mammalian populations decayed exponentially with the geographic distance separating the hosts. The relationship between geographic distances among hosts and compositional differences among their gut microbiotas was independent of dietary and phylogenetic divergence among hosts. Within mammalian communities, we observed widespread sharing of gut bacteria between predator-prey host-species pairs, indicating horizontal transfer of gut bacteria through mammalian food chains. Collectively, these results indicate that compositional differences between the gut microbiotas of mammalian taxa are generated and maintained by limits to bacterial dispersal imposed by physical distance between hosts.
哺乳动物的肠道细菌群落对宿主的适应性有深远的影响，但产生和维持肠道细菌多样性的过程仍知之甚少。我们绘制了生活在整个美洲的 136 对野生哺乳动物物种的肠道微生物群落组成变化（即β多样性），以评估哺乳动物在地理空间中的分布如何影响其肠道细菌的多样化。比较同域和异域哺乳动物种群的肠道微生物组，深入了解了肠道细菌在哺乳动物群落内部和之间的流动情况，揭示了细菌扩散的空间限制促进了哺乳动物物种肠道微生物组之间的β多样性。每个地理区域都显示出独特的肠道微生物组成，这不能完全用居住哺乳动物宿主的饮食和系统发育历史来解释，这表明一些肠道细菌在地理上受到限制。在整个西半球，异域哺乳动物种群的肠道微生物组之间的组成重叠随宿主之间的地理距离呈指数衰减。宿主之间的地理距离与它们肠道微生物组之间的组成差异之间的关系独立于宿主之间的饮食和系统发育分歧。在哺乳动物群落中，我们观察到捕食者-猎物宿主物种对之间的肠道细菌广泛共享，这表明通过哺乳动物食物链发生了肠道细菌的水平转移。总的来说，这些结果表明，宿主之间的物理距离对细菌扩散的限制产生并维持了哺乳动物分类群肠道微生物组之间的组成差异。
