Data from: A multilocus phylogenetic analysis of Escallonia (Escalloniaceae): diversification in montane South America

The mountains of South America are hotspots of plant diversity. How this diversity originated and evolved, and what roles geographic and environmental factors may have played in the diversification of lineages occurring in these regions is not well understood. Escallonia, a morphologically and ecologically diverse group of shrubs and trees widely distributed in these mountains, provides an ideal opportunity for studying the historical underpinnings that have shaped the extraordinarily distinctive, diverse, and endangered flora of these regions, and for evaluating the role of abiotic factors in the process of lineage divergence. I analyzed neutral DNA sequence data from two nuclear loci and one chloroplast locus using maximum parsimony, maximum likelihood, and Bayesian phylogenetic approaches. I used a Bayesian approach to analyze the geographic structure of gene trees, and a phylogenetically controlled decomposition of the variance in bioclimatic variables to analyze the eco-climatic structure of gene trees. I found i) that Escallonia is monophyletic, ii) a remarkable level of geographical and climatic phylogenetic structure, iii) that Escallonia likely originated in the tropical Andes, and iv) a widespread absence of species exclusivity. Geography played an important role early on the history of Escallonia by separating populations that later diversify likely in isolation. Although geographic isolation was generally accompanied by changes in climate, it is not clear whether environmental gradients along elevation have influenced more recent diversification events, or species have evolved broader environmental tolerances.

南美山地是植物多样性的热点区域。目前学界对这类区域的植物多样性如何起源与演化，以及地理与环境因子在该区域内类群分化过程中发挥的作用尚未形成清晰认知。杯萼属（Escallonia）是一类在形态与生态上均具丰富多样性的灌木与乔木类群，广泛分布于上述山地中，为研究塑造该区域极具特色、多样且濒危的植物区系的历史成因，以及评估非生物因子在类群分化过程中的作用提供了理想契机。本研究采用最大简约法、最大似然法以及贝叶斯系统发育分析方法，对两个核基因座与一个叶绿体基因座的中性DNA序列数据进行了分析。本研究采用贝叶斯方法分析基因树的地理结构，并通过系统发育控制下的生物气候变量方差分解，解析基因树的生态气候结构。研究结果显示：其一，杯萼属（Escallonia）为单系类群；其二，该类群具备显著的地理与气候系统发育结构；其三，杯萼属可能起源于热带安第斯山脉；其四，类群普遍缺乏物种排他性。在杯萼属的演化早期，地理隔离通过将种群分隔开来，为后续种群的独立分化奠定了重要基础。尽管地理隔离通常伴随气候变迁，但目前仍无法明确：沿海拔梯度分布的环境因子是否对近期的类群分化事件产生了影响，亦或是物种已演化出更广泛的环境耐受能力。