Abstract The population dynamics of freshwater organisms are expected to be related to the connectivity among comparable streams, ponds, or rivers in a patchy habitat. Here, we investigated the population dynamics of the giant water bug, Belostoma angustum Lauck 1964 (Hemiptera: Belostomatidae), in a fine-scale spatial sampling, and evaluated which gene flow model previously described for freshwater organisms could explain the genetic–morphological variation in this species. For these purposes, we evaluated genetic and morphological variations, as well as the demographic history of this freshwater insect. Our genetic analyses showed a lack of geographical structure within B. angustum populations across the evaluated range, concordant with widespread gene flow model. Our findings of the demographic history of B. angustum suggest recent and rapid expansion beginning during the late Pleistocene after the Last Glacial Maximum. Likewise, we did not find geographically structured morphological variation in B. angustum, except for body size. The lack of structure of genetic–morphological variation in B. angustum could be explained by a stepping ponds system resulting in the widespread gene flow detected among populations of this species. The warmer and wetter climatic conditions after the last glacial period may have favored the demographic expansion of B. angustum populations due to the increasing of potential freshwater habitats and food resources. This favorable habitat probably allowed the stepping ponds dispersal mode resulting in the verified geographically unstructured genetic–morphological variation.

中文翻译：

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广泛的基因流模型解释了精细空间采样下巨型水虫物种的遗传形态变异

摘要 淡水生物的种群动态预计与斑驳栖息地中可比溪流、池塘或河流之间的连通性有关。在这里，我们在精细空间采样中研究了巨型水虫 Belostoma angustum Lauck 1964（半翅目：Belostomatidae）的种群动态，并评估了先前描述的淡水生物基因流模型可以解释这个物种。出于这些目的，我们评估了这种淡水昆虫的遗传和形态变异以及人口统计历史。我们的遗传分析表明，在整个评估范围内的 B. angustum 种群中缺乏地理结构，这与广泛的基因流模型一致。我们对 B. angustum 表明在末次盛冰期之后的更新世晚期开始最近的快速扩张。同样，我们没有在 B. angustum 中发现地理结构的形态变异，除了体型。B. angustum 缺乏遗传形态变异的结构可以通过阶梯池塘系统来解释，该系统导致在该物种的种群中检测到广泛的基因流。由于潜在淡水栖息地和食物资源的增加，末次冰期后温暖潮湿的气候条件可能有利于 B. angustum 种群的人口扩张。这种有利的栖息地可能允许阶梯池扩散模式，从而导致经过验证的地理非结构化遗传形态变异。