Data from: Host associated genetic differentiation in a seed parasitic weevil Rhinusa antirrhini (Coleptera: Curculionidae) revealed by mitochondrial and nuclear sequence data

Plant feeding insects and the plants they feed upon represent an ecological association that is thought to be a key factor for the diversification of many plant feeding insects, through differential adaptation to different plant selective pressures. While a number of studies have investigated diversification of plant feeding insects above the species level, relatively less attention has been given to patterns of diversification within species, particularly those that also require plants for oviposition and subsequent larval development. In the case of plant feeding insects that also require plant tissues for the completion of their reproductive cycle through larval development, the divergent selective pressure not only acts on adults, but on the full life history of the insect. Here we focus attention on Rhinusa antirrhini (Curculionidae), a species of weevil broadly distributed across Europe that both feeds on, and oviposits and develops within, species of the plant genus Linaria (Plantaginaceae). Using a combination of mtDNA (COII) and nuclear DNA (EF1-α) sequencing and copulation experiments we assess evidence for host associated genetic differentiation within R. antirrhini. We find substantial genetic variation within this species that is best explained by ecological specialisation on different host plant taxa. This genetic differentiation is most pronounced in the mtDNA marker, with patterns of genetic variation at the nuclear marker suggesting incomplete lineage sorting and/or gene flow between different host plant forms of R. antirrhini, whose origin is estimated to date to the mid-Pliocene (3.77 mya; 2.91-4.80 mya).

植食性昆虫（plant feeding insects）与其取食的植物所形成的生态关联，被认为是驱动多数植食性昆虫物种分化的关键因子——该分化过程依赖于昆虫对不同植物选择压力的差异化适应。尽管已有诸多研究探讨了物种以上阶元的植食性昆虫物种分化模式，但针对物种内分化格局的关注相对匮乏，尤其是那些同时需要植物作为产卵及幼虫发育场所的昆虫类群。对于需依赖植物组织完成从幼虫发育到生殖周期的植食性昆虫而言，差异化选择压力不仅作用于成虫阶段，更贯穿昆虫的完整生活史。本研究聚焦于柳穿鱼沟眶象（Rhinusa antirrhini，象甲科Curculionidae）：该类群广泛分布于欧洲，既取食柳穿鱼属（Linaria，车前科Plantaginaceae）植物，同时也在该属植物体内产卵并完成幼虫发育。本研究结合线粒体DNA（mtDNA）的COII基因与核DNA（EF1-α）测序技术，以及交配实验，评估了R. antirrhini种群内宿主相关遗传分化的证据。研究发现该物种内存在显著的遗传变异，该变异可通过昆虫对不同宿主植物类群的生态特化得到最优解释。其中，线粒体DNA标记所呈现的遗传分化最为显著；而核DNA标记的遗传变异模式则暗示，不同宿主植物关联型的R. antirrhini之间存在不完全谱系分选（incomplete lineage sorting）及/或基因流（gene flow）。经估算，该类群的分化起源时间可追溯至上新世中期（3.77百万年前；95%置信区间：2.91-4.80百万年前）。