Key Laboratory of Biodiversity and Biogeography, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, China.
Ann Bot. 2013 May;111(5):873-86. doi: 10.1093/aob/mct053. Epub 2013 Mar 10.
Pantropical intercontinental disjunction is a common biogeographical pattern in flowering plants exhibiting a discontinuous distribution primarily in tropical Asia, Africa and the Americas. Only a few plant groups with this pattern have been investigated at the generic level with molecular phylogenetic and biogeographical methods. Paederia (Rubiaceae) is a pantropical genus of 31 species of woody lianas, with the greatest species diversity in continental Asia and Madagascar and only two species from tropical America. The aim of this study was to reconstruct the biogeographical history of Paederia based on phylogenetic analyses to explore how the genus attained its pantropical distribution.
Maximum parsimony and Bayesian inference were used for phylogenetic analyses using sequences of five plastid markers (the rbcL gene, rps16 intron, trnT-F region, atpB-rbcL spacer and psbA-trnH spacer). Biogeographical inferences were based on a Bayesian uncorrelated lognormal relaxed molecular clock together with both Bayesian and likelihood ancestral area reconstructions.
The data suggest an early diverged Asian lineage sister to the clade of the remaining species consisting of a predominantly Asian sub-clade and a primarily Malagasy sub-clade. Paederia is inferred to have originated in the Oligocene in tropical continental Asia. It then reached Africa in the early to middle Miocene, most probably via long-distance dispersal across the Indian Ocean. The two Neotropical species are inferred to have derived independently in the late Miocene from ancestors of Asia and East Africa, respectively.
The results demonstrate the importance of post-Boreotropical long-distance dispersals (across three major oceans) in shaping the global pantropical disjunction in some plants, such as Paederia, with small, winged diaspores adapted to long-distance dispersal by various agents including wind, ocean currents or birds. Overland migration is less likely to explain its palaeotropical disjunction between Asia and Africa.
泛热带洲际间断分布是开花植物中常见的生物地理模式，主要分布在热带亚洲、非洲和美洲。仅有少数具有这种模式的植物类群在属级水平上通过分子系统发育和生物地理方法进行了研究。鸡矢藤属（茜草科）是一个泛热带木质藤本植物属，有 31 个种，主要分布在亚洲大陆和马达加斯加，仅有两个种分布在热带美洲。本研究的目的是基于系统发育分析重建鸡矢藤属的生物地理历史，以探讨该属如何获得其泛热带分布。
使用五个质体标记（rbcL 基因、rps16 内含子、trnT-F 区、atpB-rbcL 间隔区和 psbA-trnH 间隔区）的最大简约法和贝叶斯推断进行系统发育分析。生物地理推断基于贝叶斯不相关对数正态松弛分子钟以及贝叶斯和似然祖先区重建。
数据表明，一个早期分化的亚洲谱系与其余物种的分支关系最密切，其余物种的分支包括一个主要分布在亚洲的亚分支和一个主要分布在马达加斯加的亚分支。鸡矢藤属被推断起源于渐新世的热带亚洲大陆。然后在早至中中新世到达非洲，最有可能是通过长距离扩散穿越印度洋。两个新热带物种被推断分别在晚中新世从亚洲和东非的祖先中独立衍生而来。
研究结果表明，在某些植物中，后始新世的长距离扩散（穿越三大洋）在塑造全球泛热带间断分布方面非常重要，例如鸡矢藤属，其具有适应长距离扩散的小而带翅的种子，通过各种媒介，包括风、洋流或鸟类进行扩散。陆地迁徙不太可能解释它在亚洲和非洲之间的古热带间断分布。
