Department of Biology, Georgia Southern University, Statesboro, Georgia, United States of America.
PLoS One. 2011 Mar 9;6(3):e17524. doi: 10.1371/journal.pone.0017524.
The importance of genetic diversity in successful biological invasions is unclear. In animals, but not necessarily plants, increased genetic diversity is generally associated with successful colonization and establishment of novel habitats. The Oleander aphid, Aphis nerii, though native to the Mediterranean region, is an invasive pest species throughout much of the world. Feeding primarily on Oleander (Nerium oleander) and Milkweed (Asclepias spp.) under natural conditions, these plants are unlikely to support aphid populations year round in the southern US. The objective of this study was to describe the genetic variation within and among US populations of A. nerii, during extinction/recolonization events, to better understand the population ecology of this invasive species.
METHODOLOGY/PRINCIPAL FINDINGS: We used five microsatellite markers to assess genetic diversity over a two year period within and among three aphid populations separated by small (100 km) and large (3,700 km) geographic distances on two host plant species. Here we provide evidence for A. nerii "superclones". Genotypic variation was absent in all populations (i.e., each population consisted of a single multilocus genotype (MLG) or "clone") and the genetic composition of only one population completely changed across years. There was no evidence of sexual reproduction or host races on different plant species.
CONCLUSIONS/SIGNIFICANCE: Aphis nerii is a well established invasive species despite having extremely low genetic diversity. As this aphid appears to be obligatorily asexual, it may share more similarities with clonally reproducing invasive plants, than with other animals. Patterns of temporal and geographic genetic variation, viewed in the context of its population dynamics, have important implications for the management of invasive pests and the evolutionary biology of asexual species.
遗传多样性在生物成功入侵中的重要性尚不清楚。在动物中，但不一定在植物中，遗传多样性的增加通常与成功的殖民和新栖息地的建立有关。夹竹桃蚜虫，Aphis nerii，虽然原产于地中海地区，但在世界上许多地区都是一种入侵性害虫。在自然条件下，这些蚜虫主要以夹竹桃（Nerium oleander）和乳草（Asclepias spp.）为食，在美国南部，这些植物不太可能全年支持蚜虫种群。本研究的目的是描述 A. nerii 在美国种群内和种群间的遗传变异，在灭绝/再殖民事件中，以更好地了解这种入侵物种的种群生态学。
方法/主要发现：我们使用五个微卫星标记，在两年内评估了三种蚜虫种群内和种群间的遗传多样性，这三种蚜虫种群分布在两种宿主植物上，地理距离小（100 公里）和大（3700 公里）。在这里，我们提供了 A. nerii“超级克隆”的证据。所有种群的基因型变异均不存在（即每个种群由一个多基因座基因型（MLG）或“克隆”组成），并且只有一个种群的遗传组成在两年内完全发生了变化。在不同的植物物种上没有发现有性繁殖或宿主种族的证据。
结论/意义：尽管 A. nerii 的遗传多样性极低，但它仍是一种成熟的入侵物种。由于这种蚜虫似乎是强制性无性繁殖的，它可能与无性繁殖的入侵植物有更多的相似之处，而不是与其他动物。在其种群动态的背景下，时间和地理遗传变异模式对入侵害虫的管理和无性物种的进化生物学具有重要意义。
