Institute of Evolutionary Biology and Environmental Studies, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
Mol Ecol. 2011 Oct;20(19):4165-81. doi: 10.1111/j.1365-294X.2011.05242.x. Epub 2011 Aug 29.
Aphid species may exhibit different reproductive modes ranging from cyclical to obligate parthenogenesis. The distribution of life cycle variation in aphids is generally determined by ecological forces, mainly climate, because only sexually produced diapausing eggs can survive harsh winters or periods of absence of suitable host plants. Aphids are thus interesting models to investigate intrinsic and environmental factors shaping the competition among sexual and asexual lineages. We conducted a Europe-wide sampling of black bean aphids, Aphis fabae, and combined population genetic analyses based on microsatellite data with an experimental determination of life cycle strategies. Aphids were collected from broad beans (Vicia faba) as well as some Chenopodiaceae, but we detected no genetic differentiation between aphids from different host plants. Consistent with model predictions, life cycle variation was related to climate, with aphids from areas with cold winters investing more in sexual reproduction than aphids from areas with mild winters. Accordingly, only populations from mild areas exhibited a clear genetic signature of clonal reproduction. These differences arise despite substantial gene flow over large distances, which was evident from a very low geographic population structure and a lack of isolation-by-distance among 18 sites across distances of more than 1000 km. There was virtually no genetic differentiation between aphids with different reproductive modes, suggesting that new asexual lineages are formed continuously. Indeed, a surprising number of A. fabae genotypes even from colder climates produced some parthenogenetic offspring under simulated winter conditions. From this we predict that a shift to predominantly asexual reproduction could take place rapidly under climate warming.
蚜虫物种可能表现出不同的繁殖模式，从周期性到强制性孤雌生殖。蚜虫生命周期变化的分布通常由生态力量决定，主要是气候，因为只有有性产生的滞育卵才能在恶劣的冬季或缺乏合适的寄主植物的时期存活下来。因此，蚜虫是研究内在和环境因素塑造有性和无性谱系之间竞争的有趣模型。我们在欧洲范围内对黑豆蚜（Aphis fabae）进行了采样，并结合基于微卫星数据的种群遗传分析和对生命周期策略的实验确定。蚜虫从蚕豆（Vicia faba）以及一些藜科植物上采集，但我们没有检测到来自不同寄主植物的蚜虫之间存在遗传分化。与模型预测一致，生命周期变化与气候有关，冬季寒冷的地区的蚜虫比冬季温和的地区的蚜虫更多地投资于有性生殖。因此，只有来自温和地区的种群表现出明显的无性繁殖遗传特征。尽管存在大量的远距离基因流，但这些差异仍然存在，这从 18 个地点之间的极低地理种群结构和 1000 多公里以上距离的隔离无关中显而易见。具有不同繁殖方式的蚜虫之间几乎没有遗传分化，这表明新的无性谱系在不断形成。事实上，即使在较冷的气候下，来自不同繁殖模式的 A. fabae 基因型在模拟冬季条件下也会产生一些孤雌生殖后代。由此我们预测，在气候变暖的情况下，向主要无性生殖的转变可能会迅速发生。
