Data from: Evolutionary and demographic history of the Californian scrub white oak species complex: an integrative approach

Understanding the factors promoting species formation is a major task in evolutionary research. Here, we employ an integrative approach to study the evolutionary history of the Californian scrub white oak species complex (genus Quercus). To infer the relative importance of geographical isolation and ecological divergence in driving the speciation process, we (i) analyzed inter- and intra-specific patterns of genetic differentiation and employed an approximate Bayesian computation (ABC) framework to evaluate different plausible scenarios of species divergence. In a second step, we (ii) linked the inferred divergence pathways with current and past species distribution models, and (iii) tested for niche differentiation and phylogenetic niche conservatism across taxa. ABC analyses showed that the most plausible scenario is the one considering the divergence of two main lineages followed by a more recent pulse of speciation. Genotypic data in conjunction with species distribution models and niche differentiation analyses support that different factors (geography vs. environment) and modes of speciation (parapatry, allopatry and maybe sympatry) have played a role in the divergence process within this complex. We found no significant relationship between genetic differentiation and niche overlap, which probably reflects niche lability and/or that multiple factors have contributed to speciation. Our study shows that different mechanisms can drive divergence even among closely related taxa representing early stages of species formation and exemplifies the importance of adopting integrative approaches to get a better understanding of the speciation process.阐明推动物种形成的核心因子，是进化生物学研究的重要课题。本研究采用整合分析方法，对加州灌丛白栎物种复合群（栎属 Quercus）的进化历史展开系统探究。为解析地理隔离与生态分化在物种形成过程中的相对重要性，本研究其一分析了物种间及物种内的遗传分化模式，并采用近似贝叶斯计算（approximate Bayesian computation）框架，评估多种合理的物种分化情景；其二将推断得到的分化路径与当前及历史物种分布模型进行关联；其三对不同类群间的生态位分化与系统发育生态位保守性开展检验。ABC分析结果显示，最符合实际的情景为：两个主要支系先发生分化，随后在更近的地质时期出现一次物种形成脉冲事件。基因型数据结合物种分布模型与生态位分化分析结果表明，地理隔离与环境差异等不同因子，以及邻域、异域乃至可能的同域等不同物种形成模式，均在该物种复合群的分化过程中发挥了作用。本研究未发现遗传分化与生态位重叠间存在显著关联，这一结果或反映了生态位易变性，亦或表明多种因子共同推动了物种形成。本研究证实，即使在处于物种形成早期阶段的近缘类群中，不同的演化机制也可推动分化过程，同时也彰显了采用整合研究方法以更深入解析物种形成过程的重要性。