Department of Biological Sciences, Mississippi State University, Mississippi State, MS, USA.
Florida Museum of Natural History, University of Florida, Gainesville, FL, USA.
Syst Biol. 2023 Aug 7;72(4):856-873. doi: 10.1093/sysbio/syad018.
Applications of molecular phylogenetic approaches have uncovered evidence of hybridization across numerous clades of life, yet the environmental factors responsible for driving opportunities for hybridization remain obscure. Verbal models implicating geographic range shifts that brought species together during the Pleistocene have often been invoked, but quantitative tests using paleoclimatic data are needed to validate these models. Here, we produce a phylogeny for Heuchereae, a clade of 15 genera and 83 species in Saxifragaceae, with complete sampling of recognized species, using 277 nuclear loci and nearly complete chloroplast genomes. We then employ an improved framework with a coalescent simulation approach to test and confirm previous hybridization hypotheses and identify one new intergeneric hybridization event. Focusing on the North American distribution of Heuchereae, we introduce and implement a newly developed approach to reconstruct potential past distributions for ancestral lineages across all species in the clade and across a paleoclimatic record extending from the late Pliocene. Time calibration based on both nuclear and chloroplast trees recovers a mid- to late-Pleistocene date for most inferred hybridization events, a timeframe concomitant with repeated geographic range restriction into overlapping refugia. Our results indicate an important role for past episodes of climate change, and the contrasting responses of species with differing ecological strategies, in generating novel patterns of range contact among plant communities and therefore new opportunities for hybridization. The new ancestral niche method flexibly models the shape of niche while incorporating diverse sources of uncertainty and will be an important addition to the current comparative methods toolkit. [Ancestral niche reconstruction; hybridization; paleoclimate; pleistocene.].
分子系统发育方法的应用揭示了生命众多分支中杂交的证据，但导致杂交机会的环境因素仍不清楚。人们经常援引涉及在更新世将物种聚集在一起的地理范围变化的口头模型，但需要使用古气候数据进行定量测试来验证这些模型。在这里，我们使用 277 个核基因座和几乎完整的叶绿体基因组，为 Saxifragaceae 科的 15 属 83 种的 Heuchereae 类群产生了一个系统发育，对公认的物种进行了完整采样。然后，我们采用改进的框架和合并模拟方法来测试和确认以前的杂交假说，并确定一个新的属间杂交事件。我们专注于 Heuchereae 的北美分布，引入并实施了一种新的方法，用于重建该类群中所有物种和跨越从上新世晚期开始的古气候记录的祖先谱系的潜在过去分布。基于核和叶绿体树的时间校准恢复了大多数推断出的杂交事件的中到晚更新世日期，这一时间框架与物种的地理范围限制到重叠避难所相一致。我们的结果表明，过去的气候变化事件以及具有不同生态策略的物种的不同反应在产生植物群落之间的新范围接触模式方面起着重要作用，因此为杂交提供了新的机会。新的祖先生态位方法灵活地模拟了生态位的形状，同时结合了各种来源的不确定性，这将是当前比较方法工具包的重要补充。[祖先生态位重建；杂交；古气候；更新世。]
