Data from: Aphid specialization on different summer hosts is associated with strong genetic differentiation and unequal symbiont communities despite a common mating habitat

Specialization on different host plants can promote evolutionary diversification of herbivorous insects. Work on pea aphids (Acyrthosiphon pisum) has contributed significantly to the understanding of this process, demonstrating that populations associated with different host plants exhibit performance trade-offs across hosts, show adaptive host choice and genetic differentiation, and possess different communities of bacterial endosymbionts. Populations specialized on different secondary host plants during the parthenogenetic summer generations are also described for the black bean aphid (Aphis fabae complex) and are usually treated as different (morphologically cryptic) subspecies. In contrast to pea aphids, however, host choice and mate choice are decoupled in black bean aphids, because populations from different summer hosts return to the same primary host plant to mate and lay overwintering eggs. This could counteract evolutionary divergence, and it is currently unknown to what extent black bean aphids using different summer hosts are indeed differentiated. We addressed this question by microsatellite genotyping and endosymbiont screening of black bean aphids collected in summer from the goosefoot Chenopodium album (subspecies A. f. fabae) and from thistles of the genus Cirsium (subspecies A. f. cirsiiacanthoides) across numerous sites in Switzerland and France. Our results show clearly that aphids from Cirsium and Chenopodium show strong and geographically consistent genetic differentiation, and that they differ in their frequencies of infection with particular endosymbionts. The dependence on a joint winter host has thus not prevented the evolutionary divergence into summer host-adapted populations that appear to have evolved mechanisms of reproductive isolation within a common mating habitat.

取食不同寄主植物的特化行为，可促进植食性昆虫的演化分化。针对豌豆蚜（Acyrthosiphon pisum）的相关研究，极大推动了学界对这一过程的认知：依附不同寄主植物的豌豆蚜种群，在不同寄主上的适合度存在权衡，展现出适应性寄主选择与遗传分化特征，且其体内细菌内共生菌的群落组成亦存在差异。在孤雌生殖的夏季世代阶段，取食不同次生寄主植物的特化种群，在黑豆蚜（Aphis fabae复合体）中亦有报道，这类种群通常被视为不同的（形态隐存）亚种。但与豌豆蚜不同的是，黑豆蚜的寄主选择与配偶选择相互分离：来自不同夏季寄主的种群，会回到同一原生寄主植物上完成交配并产下越冬卵。这一特性可能会抵消演化分化的进程，目前学界尚不清楚，取食不同夏季寄主的黑豆蚜种群的实际分化程度究竟如何。本研究通过微卫星基因分型与内共生菌筛查技术，对在瑞士与法国多地夏季采集自藜（Chenopodium album，对应A. f. fabae亚种）以及蓟属（Cirsium）植物（对应A. f. cirsiiacanthoides亚种）的黑豆蚜样本开展分析，以此解答上述问题。研究结果清晰显示：取自蓟属植物与藜的黑豆蚜种群，存在显著且地理一致的遗传分化，且二者在特定内共生菌的感染频率上亦存在差异。由此可见，依赖共同冬季寄主的特性，并未阻碍这些种群演化分化为适应不同夏季寄主的类群；这些类群似乎已在共同的交配生境中演化出了生殖隔离机制。