A molecular phylogeny for the genus Coccoloba (Polygonaceae) with an assessment of biogeographic patterns

Species in the genus Coccoloba are trees, shrubs, and lianas present in low elevation tropical and sub-tropical forests. Since 1756, well over 400 taxa have been described for Coccoloba. Coccoloba species are natively distributed throughout the New World in a variety of habitats. Despite being distributed throughout the Neotropics, the concentration of Coccoloba species in a given area varies considerably, with four centers of diversity for the genus: Southern and Coastal Brazil, the West Indies, Mesoamerica, and Amazonia. We here present the first molecular phylogeny of Coccoloba and use this phylogeny to investigate geographic patterns of diversity within the genus. The topology of the phylogeny and the closest related genera to Coccoloba suggest a Mesoamerican origin for the genus. The South American species are recovered as the crown group of the phylogeny with one instance of a separate migration event from Mesoamerica to South America. Coccoloba species in Mesoamerica and the Caribbean show little to no geographic pattern to their diversification. Mesoamerica and the Caribbean are best considered as one phytogeographic region for Coccoloba.

Methods
Concatenated DNA sequences from three chloroplast regions: rbcL, trnL-trnF, psbA-trnH. Sanger sequences generated from DNA extracted from leaf tissue. Raw sequences were aligned using MUSCLE and trimmed using MESQUITE.

海葡萄属（Coccoloba）的物种涵盖乔木、灌木与藤本，自然分布于低海拔热带及亚热带森林中。自1756年起，该属已发表的分类单元逾400个。海葡萄属物种原生分布于新世界的各类生境中。尽管该属遍布新热带界，但不同区域的物种丰度差异显著，该属共有4个多样性中心：巴西南部及沿海区域、西印度群岛、中美洲与亚马孙流域。

本研究首次构建了海葡萄属的分子系统发育树，并以此探讨该属的物种多样性地理分布格局。系统发育树的拓扑结构以及与海葡萄属亲缘关系最近的类群均表明，该属起源于中美洲。系统发育分析显示，南美物种构成该属的冠群，且存在一次独立的从中美洲向南美洲的迁移事件。中美洲与加勒比海地区的海葡萄属物种分化几乎无地理分布模式可循。就海葡萄属而言，中美洲与加勒比海地区可被视为同一个植物地理区。

## 方法
本研究采用三个叶绿体基因区域的拼接序列：rbcL、trnL-trnF及psbA-trnH。测序所用DNA提取自植物叶片组织，原始序列通过Sanger测序法获得。原始序列使用MUSCLE进行多序列比对，并通过MESQUITE完成剪切修剪。