Rapid speciation events, with taxa generated over a short time period, are among the most investigated biological phenomena. However, molecular systematics often reveals contradictory results compared with morphological/phenotypical diagnoses of species under scenarios of recent and rapid diversification. In this study, we used molecular data from an average of over 29 000 loci per sample from RADseq to reconstruct the diversification history and delimit the species boundary in a short‐winged grasshopper species complex (Melanoplus scudderi group), where Pleistocene diversification has been hypothesized to generate more than 20 putative species with distinct male genitalic shapes. We found that, based on a maximum likelihood molecular phylogeny, each morphological species indeed forms a monophyletic group, contrary to the result from a previous mitochondrial DNA sequence study. By dating the diversification events, the species complex is estimated to have diversified during the Late Pleistocene, supporting the recent radiation hypothesis. Furthermore, coalescent‐based species delimitation analyses provide quantitative support for independent genetic lineages, which corresponds to the morphologically defined species. Our results also showed that male genitalic shape may not be predicted by evolutionary distance among species, not only indicating that this trait is labile, but also implying that selection may play a role in character divergence. Additionally, our findings suggest that the rapid speciation events in this flightless grasshopper complex might be primarily associated with the fragmentation of their grassland habitats during the Late Pleistocene. Collectively, our study highlights the importance of integrating multiple sources of information to delineate species, especially for a species complex that diversified rapidly, and whose divergence may be linked to ecological processes that create geographic isolation (i.e. fragmented habitats), as well as selection acting on characters with direct consequences for reproductive isolation (i.e. genitalic divergence).

中文翻译：

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不再有并系物种——基因组数据解析更新世辐射并验证 Melanoplus scudderi 复合体的形态物种（昆虫纲：直翅目）

快速物种形成事件，在短时间内产生类群，是研究最多的生物现象之一。然而，在最近和快速多样化的情况下，与物种的形态学/表型诊断相比，分子系统学经常揭示矛盾的结果。在这项研究中，我们使用来自 RADseq 的每个样本平均超过 29 000 个位点的分子数据来重建多样化历史并划定短翅蚱蜢物种复合体（Melanoplus scudderi group）中的物种边界，其中更新世多样化已被假设产生超过 20 种具有不同雄性生殖器形状的假定物种。我们发现，基于最大似然分子系统发育，每个形态物种确实形成了一个单系群，与先前线粒体 DNA 序列研究的结果相反。通过确定多样化事件的年代，估计该物种复合体在晚更新世期间已经多样化，支持最近的辐射假说。此外，基于聚结的物种定界分析为独立的遗传谱系提供了定量支持，这对应于形态学定义的物种。我们的研究结果还表明，雄性生殖器形状可能无法通过物种间的进化距离来预测，这不仅表明这种性状是不稳定的，而且还暗示选择可能在性状分化中发挥作用。此外，我们的研究结果表明，这种不会飞的蚱蜢复合体中的快速物种形成事件可能主要与晚更新世期间草原栖息地的破碎化有关。总的来说，我们的研究强调了整合多种信息来源来描述物种的重要性，特别是对于快速多样化的物种复合体，其分化可能与造成地理隔离（即破碎的栖息地）的生态过程以及选择作用有关。对生殖隔离有直接后果的角色（即生殖器分歧）。