Department of Evolution, Ecology, & Organismal Biology, The Ohio State University, Columbus, OH, 43210, USA.
Institutt for Biovitenskap, Universitetet i Bergen, 5006, Bergen, Norway.
Am J Bot. 2023 Jan;110(1):e16118. doi: 10.1002/ajb2.16118. Epub 2022 Dec 23.
Hybridization is increasingly being identified in the genomes of species across the tree of life, leading to a general recognition that hybridization plays an important role in the generation of species diversity. While hybridization may increase species diversity directly via the formation of new taxa through hybrid speciation, it may also act indirectly via the exchange of phenotypic and genetic variance between species, which may in turn stimulate future speciation events.
Using high-throughput sequence data, we resolved phylogenetic relationships and investigated the role of hybridization as a diversification mechanism in the shrubby beardtongues (Penstemon subgenus Dasanthera), a group of North American wildflowers that has undergone a recent and rapid adaptive radiation. Specifically, we tested four hypotheses of hybrid taxon formation resulting from hybridization between P. davidsonii and P. fruticosus.
Species tree inference supports the monophyly of subgenus Dasanthera and elucidates relationships between taxa distributed in the Cascades and Sierra Nevada Mountains. Results also provide evidence of gene flow between P. davidsonii and P. fruticosus and support at least one hybrid origin hypothesis (P. davidsonii var. menziesii) in a region of contemporary distributional overlap. Hybridization may have also been facilitated by historical overlap in geographic distribution caused by species' responses to climatic changes during the Pleistocene.
Our results support a history of hybridization between focal taxa in a rapidly radiating clade of plants and more broadly contribute to our growing understanding of the role of hybridization as a diversification mechanism in plants.
杂交在生命之树的各个物种的基因组中越来越多地被发现，这导致人们普遍认识到杂交在物种多样性的产生中起着重要作用。虽然杂交可能通过杂种形成新的分类单元直接增加物种多样性，但它也可能通过在物种之间交换表型和遗传方差间接起作用，这反过来可能刺激未来的物种形成事件。
我们使用高通量测序数据解决了系统发育关系，并研究了杂交作为一种多样化机制在北美野花灌木须苞石竹（Penstemon 亚属 Dasanthera）中的作用，该组植物经历了最近和快速的适应性辐射。具体来说，我们测试了四种由 P. davidsonii 和 P. fruticosus 杂交形成杂交分类单元的假设。
物种树推断支持 Dasanthera 亚属的单系性，并阐明了分布在喀斯喀特山脉和内华达山脉的分类单元之间的关系。结果还提供了 P. davidsonii 和 P. fruticosus 之间基因流的证据，并支持至少一个杂交起源假说（P. davidsonii var. menziesii）在当代分布重叠的地区。杂交可能也受到历史上地理分布重叠的促进，这是物种对更新世气候变化的反应造成的。
我们的结果支持在一个快速辐射的植物类群的焦点类群之间存在杂交的历史，并更广泛地促进了我们对杂交作为植物多样化机制的作用的认识。
