Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, 95060, USA.
Department of Biological Sciences, California State Polytechnic University, Humboldt, Arcata, CA, 95521, USA.
New Phytol. 2024 Dec;244(6):2548-2560. doi: 10.1111/nph.20187. Epub 2024 Oct 14.
Hybridization is increasingly recognized as an important evolutionary process across the tree of life. In many clades, phylogenomic approaches have permitted unparalleled insight into the extent and frequency of hybridization. However, we continue to lack a deep understanding of the factors that limit and shape patterns of hybridization, especially in evolutionary radiations. In this study, we characterized patterns of introgression across Costus (Costaceae), a young evolutionary radiation of tropical understory plants that maintain widespread interfertility despite exhibiting strong prezygotic reproductive isolation. We analyzed a phylogenomic dataset of 756 genes from 54 Costus species using multiple complementary approaches - D-statistics, gene-tree-based tests, and phylogenetic network analyses - to detect and characterize introgression events throughout the evolutionary history of the radiation. Our results identified a moderate number of introgression events, including a particularly ancient, well-supported event spanning one of the deepest divergences in the clade. Most introgression events occurred between taxa or ancestral lineages that shared the same pollination syndrome (bee-pollinated or hummingbird-pollinated). These findings suggest that prezygotic barriers, including pollinator specialization, have been key to the balance between introgression and reproductive isolation in Costus.
杂交是生命之树中越来越被认可的一种重要进化过程。在许多类群中，基因组学方法使得我们能够以前所未有的方式深入了解杂交的程度和频率。然而，我们仍然缺乏对限制和塑造杂交模式的因素的深刻理解，特别是在进化辐射中。在这项研究中，我们描述了 Costus（姜科）中基因渐渗的模式。Costus 是一个年轻的热带林下植物进化辐射群，尽管表现出强烈的合子前生殖隔离，但仍保持着广泛的可交配性。我们使用多种互补的方法——D 统计、基于基因树的测试和系统发育网络分析——从 54 种 Costus 物种中分析了一个包含 756 个基因的基因组数据集，以检测和描述整个辐射进化历史中的基因渐渗事件。我们的结果确定了中等数量的基因渐渗事件，包括一个特别古老的、得到很好支持的事件，跨越了该类群中最深的分歧之一。大多数基因渐渗事件发生在具有相同传粉综合征（蜜蜂传粉或蜂鸟传粉）的分类单元或祖先谱系之间。这些发现表明，合子前障碍，包括传粉者的专业化，是 Costus 中基因渐渗和生殖隔离之间平衡的关键。
