Match and mismatch between dietary switches and microbial partners in plant sap-feeding insects

Some animal groups associate with the same vertically-transmitted microbial symbionts over extended periods of evolutionary time, punctuated by occasional symbiont switches to different microbial taxa. Here we test the oft-repeated suggestion that symbiont switches are linked with host diet changes, focusing on hemipteran insects of the suborder Auchenorrhyncha. These insects include the only animals that feed on plant xylem sap through the life cycle, as well as taxa that feed on phloem sap and plant parenchyma cells. Ancestral state reconstruction provides strong statistical support for a xylem-feeding auchenorrhynchan ancestor bearing the dual symbiosis with the primary symbiont Sulcia (Bacteroidetes) and companion symbiont “β-Sym” (β-proteobacteria). We identified 7 dietary transitions from xylem-feeding (six to phloem-feeding, one to parenchyma-feeding), but no reversions to xylem-feeding; five evolutionary losses of Sulcia, including replacements by yeast symbionts, exclusivel...

部分动物类群在漫长的进化历程中，始终与同一种垂直传播的微生物共生体保持稳定共生关系，其间偶有共生体转换事件，即转向不同的微生物类群。本研究针对“共生体转换与宿主饮食改变存在关联”这一广为提及的观点展开验证，研究对象为半翅目颈喙亚目（Auchenorrhyncha）昆虫。该类群包含了整个生命周期均取食植物木质部汁液的唯一已知动物类群，同时也涵盖取食韧皮部汁液与植物薄壁组织细胞的类群。祖先状态重建分析得到了强有力的统计学支持，表明颈喙亚目昆虫的祖先类群为木质部取食者，其与初级共生菌Sulcia（拟杆菌门Bacteroidetes）及伴随共生菌“β-Sym”（β-变形菌门β-proteobacteria）形成双重共生关系。我们共鉴定出7次从木质部取食向其他饮食模式的转换（其中6次转为韧皮部取食，1次转为薄壁组织取食），且未发现向木质部取食的反向转换；同时检测到5次Sulcia的进化丢失事件，其中包括被酵母类共生菌替代的情况，仅……