蚜虫与其初级内共生菌（Buchnera）系统发育关系格局及演化机制

Aphids have a very strictly mutually beneficial relationship with their intracellular symbionts, Buchnera. They have complementary pathways related to nutritions metabolism. They can even share some amino acid metabolic pathways. Buchnera can not survive if without the intracellular environment of their aphid hosts. For many years, the interesting and important question, how the strictly endosymbiotic relationship between aphids and Buchnera has evolved, has been attracting scientists' attention. Previous studies showed that aphids codiversified with Buchnera, namely, parallel evolution. This was the first case for which codiversification was shown in insects. Until now, the parallelism hypothesis is still popular in literature. However, new evidences indicate some imperfection of the parallelism hypothesis, mainly due to this hypothesis was based on aphid and Buchnera phylogenies using very limited sampling. Therefore, based on informative exploratory researches related to this question, this proposing program will try to reveal the phylogenetic relationships between aphids and Buchnera across different taxonomic levels based on a wide range of taxon and molecular marker sampling. We will also try to disentangle the mechanisms underlying the phylogenetic patterns by revealing the evolutionary modes of Buchnera genes among different aphid lineages. The research of this program will not only provide a improved hypothesis on the evolution of aphids-Buchnera relationships, but also give implications for understanding the adaptive evolution of aphids and the evolution of Buchnera genomes.

蚜科昆虫正常的生长发育离不开其体内专性胞内共生菌Buchnera。两者有密切的营养代谢互补关系，同时共享某些代谢途径。Buchnera离开蚜虫宿主不能存活。多年来一个有趣且重要的科学问题是，两者严格的共生关系是如何演化的。早期研究基于少数蚜虫类群及Buchnera的系统发育关系提出平行演化假说，这是第一个昆虫和内共生菌平行演化的实例，该假说至今依然流行。然而，最近一些证据显示该假说可能存在问题，主要在于提出该假说的研究有先天取样缺陷。在良好的前期研究基础上，本项目将基于大范围取样和多个分子标记开展系统性研究，力求从不同阶元水平上揭示更清晰的蚜虫-Buchnera系统演化关系以及Buchnera基因在不同蚜虫支系中的演化模式，补充并修订平行演化假说，为更深入理解蚜虫类适应进化及Buchnera基因组进化提供证据和基础。本项目还将对共生关系演化的普遍性问题及其他昆虫和内共生菌关系研究有所启示。

蚜虫与其初级内共生菌Buchnera之间有密切的营养互补关系。早期研究基于少数蚜虫类群及其Buchnera的系统发育关系提出共分化假说，这是第一个昆虫和内共生菌平行演化的实例。然而，前人研究的取样缺陷使得该假说的广泛性有待检验。本项目基于大量实验研究，从高级阶元和低级阶元水平上全面揭示了蚜虫与其初级内共生菌Buchnera之间的进化关系，即两者进化在低级水平上具有平行分化关系，但在高级阶元水平上不具有平行对应关系，这些结果有助于完善修订第一例昆虫和细菌间的平行演化假说；还证明了Buchnera基因标记并不适用于研究蚜虫类本身的高级阶元进化关系，但可作为研究蚜虫属级以下包括种群水平问题的分子标记，对于科研实践有重要的指导价值。本项目的研究结果为更好地理解昆虫和内共生菌关系演化的普遍性问题提供了重要证据。