Data from: Reproduction and dispersal in an ant-associated root aphid community

Clonal organisms with occasional sex are important for our general understanding of the costs and benefits that maintain sexual reproduction. Cyclically parthenogenetic aphids are highly variable in their frequency of sexual reproduction and studies have mostly focused on free-living aphids above ground, whereas dispersal constraints and dependence on ant-tending may differentially affect the costs and benefits of sex in subterranean aphids. Here, we studied reproductive mode and dispersal in a community of root aphids that are obligatorily associated with the ant Lasius flavus. We assessed the genetic population structure of four species (Geoica utricularia, Tetraneura ulmi, Forda marginata and F. formicaria) in a Dutch population and found that all species reproduce predominantly if not exclusively asexually, so that populations consist of multiple clonal lineages. We show that population viscosity is high and winged aphids rare, consistent with infrequent horizontal transmission between ant host colonies. The absence of the primary host shrub (Pistacia) may explain the absence of sex in three of the studied species, but elm trees (Ulmus) that are primary hosts of the fourth species (T. ulmi), occured within a few km of the study population. We discuss the extent to which obligate ant-tending and absence of primary hosts may have affected selection for permanent parthenogenesis and we highlight the need for further study of these aphids in Southern Europe where primary hosts may occur close to Lasius flavus populations, so that all four root aphid species would have realistic opportunities for completing their sexual life-cycle.

兼具偶发性有性生殖的无性系生物，对于我们理解维持有性生殖的演化成本与收益具有核心学术意义。周期性孤雌生殖的蚜虫类群，其有性生殖频率存在显著变异，过往研究多聚焦于地表自由生活的蚜虫，而扩散限制与专性蚁栖共生的依赖关系，或会差异化地影响地下蚜虫有性生殖的成本与收益。

本研究针对专性与黄足蚁（Lasius flavus）共生的根蚜虫群落，开展了生殖模式与扩散特性的探究。我们对荷兰种群中的4个物种（Geoica utricularia、Tetraneura ulmi、Forda marginata及F. formicaria）的遗传种群结构进行了系统评估，结果显示所有物种即便并非完全排他性地进行无性生殖，也主要以无性方式繁殖，种群由多个无性系谱系构成。

研究发现该群落的种群粘性较高，有翅蚜虫极为罕见，这与蚁宿主巢群间罕见的水平传播现象相符。本研究中3个物种未出现有性生殖，或许可归因于其原生寄主灌木黄连木属（Pistacia）的缺失；而第四种物种的原生寄主榆树（Ulmus），距离研究种群仅数公里之遥。

我们探讨了专性蚁栖共生与原生寄主缺失在多大程度上影响了永久性孤雌生殖的选择压力，并强调需在南欧开展此类蚜虫的进一步研究：该区域内原生寄主可能紧邻黄足蚁种群分布，从而让4种根蚜虫均具备完成有性生殖生命周期的现实条件。