Dick Christopher W, Abdul-Salim Kobinah, Bermingham Eldredge
Smithsonian Tropical Research Institute, Unit 0948 APO AA 34002-0948, USA.
Am Nat. 2003 Dec;162(6):691-703. doi: 10.1086/379795. Epub 2003 Nov 4.
The broad geographic range of many Neotropical rain forest tree species implies excellent dispersal abilities or range establishment that preceded the formation of current dispersal barriers. In order to initiate historical analyses of such widespread Neotropical trees, we sequenced the nuclear ribosomal spacer (ITS) region of Symphonia globulifera L. f. (Clusiaceae) from populations spanning the Neotropics and western Africa. This rain forest tree has left unmistakable Miocene fossils in Mesoamerica (15.5-18.2 Ma) and in South America ( approximately 15 Ma). Although marine dispersal of S. globulifera is considered improbable, our study establishes three marine dispersal events leading to the colonization of Mesoamerica, the Amazon basin, and the West Indies, thus supporting the paleontological data. Our phylogeographic analysis revealed the spatial extent of the three Neotropical S. globulifera clades, which represent trans-Andes (Mesoamerica+west Ecuador), cis-Andes (Amazonia+Guiana), and the West Indies. Strong phylogeographic structure found among trans-Andean populations of S. globulifera stands in contrast to an absence of ITS nucleotide variation across the Amazon basin and indicates profound regional differences in the demographic history of this rain forest tree. Drawing from these results, we provide a historical biogeographic hypothesis to account for differences in the patterns of beta diversity within Mesoamerican and Amazonian forests.
许多新热带地区雨林树种广泛的地理分布范围意味着它们具有出色的扩散能力，或者在当前扩散障碍形成之前就已建立了分布范围。为了对这些分布广泛的新热带树木进行历史分析，我们对新热带地区和西非各地种群的球花金莲木（Symphonia globulifera L. f.，藤黄科）的核糖体间隔区（ITS）进行了测序。这种雨林树木在中美洲（1550 - 1820万年前）和南美洲（约1500万年前）留下了明确无误的中新世化石。尽管球花金莲木通过海洋扩散的可能性被认为不大，但我们的研究确定了三次海洋扩散事件，这些事件导致了中美洲、亚马逊盆地和西印度群岛的殖民化，从而支持了古生物学数据。我们的系统地理学分析揭示了新热带地区球花金莲木三个分支的空间范围，它们分别代表跨安第斯地区（中美洲 + 厄瓜多尔西部）、安第斯地区东部（亚马逊地区 + 圭亚那）和西印度群岛。在球花金莲木跨安第斯种群中发现的强烈系统地理结构与亚马逊盆地ITS核苷酸无变异形成对比，这表明这种雨林树木在种群历史方面存在深刻的区域差异。基于这些结果，我们提出了一个历史生物地理学假设，以解释中美洲和亚马逊森林中β多样性模式的差异。
