Data from: Diet is the primary determinant of bacterial community structure in the guts of higher termites

The gut microbiota of termites plays critical roles in the symbiotic digestion of lignocellulose. While phylogenetically “lower termites” are characterized by a unique association with cellulolytic flagellates, higher termites (family Termitidae) harbor exclusively prokaryotic communities in their dilated hindguts. Unlike the more primitive termite families, which primarily feed on wood, they have adapted to a variety of lignocellulosic food sources in different stages of humification, ranging from sound wood to soil organic matter. In this study, we comparatively analyzed representatives of different taxonomic lineages and feeding groups of higher termites to identify the major drivers of bacterial community structure in the termite gut, using amplicon libraries of 16S rRNA genes from 18 species of higher termites. In all analyses, the wood-feeding species were clearly separated from humus and soil feeders, irrespective of their taxonomic affiliation, offering compelling evidence that diet is the primary determinant of bacterial community structure. Within each diet group, however, gut communities of termites from the same subfamily were more similar than those of distantly related species. A highly resolved classification using a curated reference database revealed only few genus-level taxa whose distribution patterns indicated specificity for certain host lineages, limiting any possible cospeciation between the gut microbiota and host to short evolutionary time scales. Rather, the observed patterns in the host-specific distribution of the bacterial lineages in termite guts are best explained by diet-related differences in the availability of microhabitats and functional niches.

白蚁肠道微生物群（gut microbiota）在木质纤维素（lignocellulose）的共生消化过程中发挥关键作用。系统发育分类中的低等白蚁（lower termites）以与纤维素分解鞭毛虫的独特共生关联为典型特征，而高等白蚁（higher termites，白蚁科Termitidae）的扩张型后肠（hindguts）中仅栖息原核生物群落。与主要以木材为食的原始白蚁类群不同，高等白蚁已适应了腐殖化不同阶段的多种木质纤维素食物来源，从完好木材直至土壤有机质。本研究选取18种高等白蚁的16S rRNA基因（16S rRNA genes）扩增子文库（amplicon libraries），对不同分类谱系和取食类群的高等白蚁代表样本开展比较分析，以明确驱动白蚁肠道细菌群落结构的核心影响因子。所有分析结果均显示，取食木材的白蚁类群与取食腐殖质、土壤的类群界限清晰，且与其分类学归属无关，这为饮食是肠道细菌群落结构的主要决定因素这一结论提供了强有力的证据。然而在同一取食类群内部，同亚科白蚁的肠道群落相较于远缘物种更为相似。通过使用经过整理的参考数据库开展高精度分类学鉴定，仅发现少量属级分类单元的分布模式显示出对特定宿主谱系的特异性，这将肠道微生物群与宿主之间可能存在的共物种形成（cospeciation）限定在了较短的进化时间尺度内。与之相反，白蚁肠道细菌谱系的宿主特异性分布模式，最佳解释为微生境与功能生态位（functional niches）的可用性因饮食差异而产生分化。