Theoretical Biology, Centre for Ecological and Evolutionary Studies, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands.
Mol Ecol. 2012 Sep;21(17):4257-69. doi: 10.1111/j.1365-294X.2012.05701.x. Epub 2012 Jul 16.
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. However, 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 obligately associated with the ant Lasius flavus. We assessed the genetic population structure of four species (Geoica utricularia, Tetraneura ulmi, Forda marginata and Forda 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) occurred 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 L. flavus populations, so that all four root aphid species would have realistic opportunities for completing their sexual life cycle.
具有偶发性有性生殖的克隆生物对于我们全面了解维持有性生殖的成本和收益至关重要。周期性孤雌生殖的蚜虫在有性生殖的频率上变化很大。然而，研究大多集中在地面上的自由生活的蚜虫上，而扩散限制和对蚂蚁饲养的依赖可能会对地下蚜虫有性生殖的成本和收益产生不同的影响。在这里，我们研究了与蚂蚁 Lasius flavus 强制性相关的根蚜虫群落中的生殖模式和扩散。我们评估了荷兰种群中四个物种（Geoica utricularia、Tetraneura ulmi、Forda marginata 和 Forda formicaria）的遗传种群结构，发现所有物种主要或完全无性繁殖，因此种群由多个克隆谱系组成。我们表明种群粘性很高，有翅蚜虫很少，这与蚂蚁宿主群体之间水平传播很少一致。主要宿主灌木（黄连木）的缺失可能解释了研究的三个物种中没有性别的原因，但作为第四个物种（T. ulmi）主要宿主的榆树（榆树）距离研究种群只有几公里。我们讨论了强制性蚂蚁饲养和主要宿主缺失对永久性孤雌生殖选择的影响程度，并强调需要进一步研究这些蚜虫在南欧的情况，在那里主要宿主可能与 L. flavus 种群相邻，因此所有四个根蚜虫物种都有现实的机会完成它们的有性生命周期。
