Host plant shifts are a common mode of speciation in herbivorous insects. Although insects can evolve adaptations to successfully incorporate a new host plant, it is becoming increasingly recognized that the gut bacterial community may play a significant role in allowing insects to detoxify novel plant chemical defenses. Here, we examined differences in gut bacterial communities between Altica flea beetle species that feed on phylogenetically unrelated host plants in sympatry. We surveyed the gut bacterial communities of three closely related flea beetles from multiple locations using 16S rRNA amplicon sequencing. The results showed that the beetle species shared a high proportion (80.7%) of operational taxonomic units. Alpha-diversity indicators suggested that gut bacterial diversity did not differ among host species, whereas geography had a significant effect on bacterial diversity. In contrast, analyses of beta-diversity showed significant differences in gut bacterial composition among beetle species when we used species composition and relative abundance metrics, but there was no difference in composition when species presence/absence and phylogenetic distance indices were used. Within host beetle species, gut bacterial composition varied significantly among sites. A metagenomic functionality analysis predicted that the gut microbes had functions involved in xenobiotic biodegradation and metabolism as well as metabolism of terpenoids and polyketides. These predictions, however, did not differ among beetle host species. Antibiotic curing experiments showed that development time was significantly prolonged, and there was a significant decline in body weight of newly emerged adults in beetles lacking gut bacteria, suggesting the beetles may receive a potential benefit from the gut microbe-insect interaction. On the whole, our results suggest that although the gut bacterial community did not show clear host-specific patterns among Altica species, spatiotemporal variability is an important determinant of gut bacterial communities. Furthermore, the similarity of communities among these beetle species suggests that microbial facilitation may not be a determinant of host plant shifts in Altica.

寄主植物转移是草食性昆虫的一种常见形态形成方式。尽管昆虫可以进化适应性机制以成功整合新的寄主植物，但人们越来越认识到，肠道细菌群落可能在允许昆虫解毒新的植物化学防御物中起重要作用。在这里，我们研究了以系统发育上不相关的寄主植物为食的Altica跳蚤甲虫物种之间肠道细菌群落的差异。我们使用16S rRNA扩增子测序技术，从多个位置调查了三个紧密相关的跳蚤甲虫的肠道细菌群落。结果表明，甲虫物种在操作分类单位中所占比例很高（80.7％）。Α多样性指标表明，肠道细菌的多样性在寄主物种之间没有差异，而地理位置对细菌的多样性有显着影响。相反，对beta的分析当我们使用物种组成和相对丰度度量标准时，甲虫物种的肠道细菌组成存在显着差异，但是当使用物种存在/不存在和系统发生距离指数时，组成没有差异。在寄主甲虫种内，肠道细菌的组成在各部位之间差异很大。宏基因组功能分析预测，肠道微生物具有异种生物降解和代谢以及萜类和聚酮化合物代谢的功能。但是，这些预测在甲虫寄主物种之间没有差异。抗生素治愈实验表明，在缺乏肠道细菌的甲虫中，发育时间显着延长，新成年成年人的体重显着下降，提示甲虫可能会从肠道微生物与昆虫的相互作用中获得潜在的好处。总体而言，我们的结果表明，尽管肠道细菌群落并未显示出明确的宿主特异性模式Altica物种的时空变异性是肠道细菌群落的重要决定因素。此外，这些甲虫物种之间的群落相似性表明，微生物的促进作用可能不是Altica宿主植物转移的决定因素。