Data from: Demographic processes shaping genetic variation of the solitarious phase of the desert locust

Between plagues, the solitarious desert locust (Schistocerca gregaria) is generally thought to exist as small populations, which are particularly prone to extinction events in arid regions of Africa and Asia. Given the high genetic structuring observed in one geographical area (the Eritrean coast) by former authors, a metapopulation dynamics model involving repeated extinction and colonization events was favored. In this study, we assessed the validity of a demographic scenario involving temporary populations of the solitarious phase of the desert locust by analyzing large-scale population genetic data. We scored 24 microsatellites in 23 solitarious population samples collected over most of the species range during remission. We found very little genetic structuring and little evidence of declining genetic diversity. A Bayesian clustering method distinguished four genetically differentiated units. Three groups were largely consistent with three population samples which had undergone recent bottleneck events. Nevertheless, the last genetically homogeneous unit included all individuals from the remaining 18 population samples and did not show evidence of demographic disequilibrium. An approximate Bayesian computation treatment indicated a large population size for this main genetic group, moderately reduced between plague and remission but still containing tens of thousands of individuals. Our results diverge from the hypothesis of a classical metapopulation dynamics model. They instead support the scenario in which large populations persist in the solitarious phase of the desert locust.

在蝗灾间歇期，散居型沙漠蝗（Schistocerca gregaria）通常被认为以小型种群形式存续，在非洲与亚洲的干旱区域中，这类种群尤其易于发生灭绝事件。既往研究人员在厄立特里亚海岸这一地理区域中观测到显著的遗传结构分化，因此学界曾更倾向于采用包含反复灭绝与定殖事件的集合种群动态模型。本研究通过分析大规模种群遗传数据，对涉及沙漠蝗散居型临时种群的种群动态假说的有效性进行了评估。研究人员对蝗灾平息期内采集的、覆盖该物种绝大多数分布范围的23个散居型种群样本的24个微卫星（microsatellite）位点进行了基因分型。结果显示，种群间的遗传结构极弱，遗传多样性出现下降的证据也十分有限。通过贝叶斯聚类方法（Bayesian clustering method），我们区分出了4个遗传分化单元：其中三个组与近期经历过瓶颈效应（bottleneck event）的3个种群样本基本吻合。然而，最后一个遗传均一的单元包含了其余18个种群样本的全部个体，且未表现出种群动态失衡的迹象。近似贝叶斯计算（approximate Bayesian computation, ABC）分析结果表明，这一主要遗传类群的种群规模庞大：在蝗灾间歇期虽有所小幅缩减，但仍保有数万个体。本研究结果与经典集合种群动态模型的假说相悖，反而支持沙漠蝗散居型以大型种群持续存续的理论场景。