Data from: Sympatric diversification vs. immigration: deciphering host-plant specialization in a polyphagous insect, the stolbur phytoplasma vector Hyalesthes obsoletus (Cixiidae)

The epidemiology of vector transmitted plant diseases is highly influenced by dispersal and the host-plant range of the vector. Widening the vector's host range may increase transmission potential, whereas specialization may induce specific disease cycles. The process leading to a vector's host shift and its epidemiological outcome is therefore embedded in the frameworks of sympatric evolution vs. immigration of preadapted populations. In this study, we analyse whether a host shift of the stolbur phytoplasma vector, Hyalesthes obsoletus from field bindweed to stinging nettle in its northern distribution range evolved sympatrically or by immigration. The exploitation of stinging nettle has led to outbreaks of the grapevine disease bois noir caused by a stinging nettle-specific phytoplasma strain. Microsatellite data from populations from northern and ancestral ranges provide strong evidence for sympatric host-race evolution in the northern range: Host-plant associated populations were significantly differentiated among syntopic sites (0.054 < FHT < 0.098) and constant over 5 years. While gene flow was asymmetric from the old into the predicted new host race, which had significantly reduced genetic diversity, the genetic identity between syntopic host-race populations in the northern range was higher than between these populations and syntopic populations in ancestral ranges, where there was no evidence for genetic host races. Although immigration was detected in the northern field bindweed population, it cannot explain host-race diversification but suggests the introduction of a stinging nettle-specific phytoplasma strain by plant-unspecific vectors. The evolution of host races in the northern range has led to specific vector-based bois noir disease cycles.

虫媒植物病害的流行病学（epidemiology）极易受到媒介昆虫的扩散能力及其寄主植物范围的影响。拓宽媒介昆虫的寄主范围或可提升病害传播潜能，而寄主特化则可能催生特定的病害循环。因此，媒介昆虫发生寄主转移的过程及其对应的流行病学后果，均隶属于同域演化与预适应种群迁入这两大理论框架。本研究针对分布北限范围内的stolbur植原体（phytoplasma）媒介凹缘菱纹叶蝉（Hyalesthes obsoletus），分析其从田旋花（field bindweed）向荨麻（stinging nettle）的寄主转移，究竟是通过同域演化还是种群迁入形成。对荨麻的利用已催生由荨麻专化型植原体菌株引发的葡萄黑果病（bois noir）暴发事件。对分布北限与祖先分布区种群的微卫星（microsatellite）数据分析，为北限范围内的寄主宗（host-race）演化提供了强有力证据：同域分布的寄主关联种群间存在显著遗传分化（0.054 < FHT < 0.098），且该分化状态在5年时间内保持稳定。尽管基因流呈不对称性：从旧寄主宗流向遗传多样性显著降低的新预测寄主宗，但北限范围内同域分布的寄主宗种群间的遗传相似度，高于这些种群与祖先分布区无寄主宗遗传分化证据的同域种群间的相似度。虽然在北限的田旋花种群中检测到了种群迁入现象，但该现象无法解释寄主宗的分化形成，却提示存在通过非寄主专化媒介传入荨麻专化型植原体菌株的可能。北限范围内寄主宗的演化，已催生了基于媒介昆虫的特异性葡萄黑果病循环。