Nettel Alejandro, Dodd Richard S
Department of Environmental Science, Policy, and Management, 137 Mulford Hall, University of California, Berkeley, California 94720-3114, USA.
Evolution. 2007 Apr;61(4):958-71. doi: 10.1111/j.1558-5646.2007.00070.x.
Two issues that have captured the attention of tropical plant evolutionary biologists in recent years are the relative role of long distance dispersal (LDD) over vicariance in determining plant distributions and debate about the extent that Quaternary climatic changes affected tropical species. Propagules of some mangrove species are assumed to be capable of LDD due to their ability to float and survive for long periods of time in salt water. Mangrove species responded to glaciations with a contraction of their range. Thus, widespread mangrove species are an ideal system to study LDD and recolonization in the tropics. We present phylogenetic and phylogeographic analyses based on internal transcribed spacers region (ITS) sequences, chloroplast DNA (cpDNA), and amplified fragment length polymorphisms (AFLPs) of genomic DNA that demonstrate recent LDD across the Atlantic, rejecting the hypothesis of vicariance for the widespread distribution of the black mangrove (Avicennia germinans). Northern latitude populations likely became extinct during the late Quaternary due to frosts and aridification; these locations were recolonized afterward from southern populations. In some low latitude regions populations went extinct or were drastically reduced during the Quaternary because of lack of suitable habitat as sea levels changed. Our analyses show that low latitude Pacific populations of A. germinans harbor more diversity and reveal deeper divergence than Atlantic populations. Implications for our understanding of phylogeography of tropical species are discussed.
近年来，吸引热带植物进化生物学家关注的两个问题是长距离扩散（LDD）相对于隔离分化在决定植物分布中的相对作用，以及关于第四纪气候变化对热带物种影响程度的争论。由于某些红树物种的繁殖体能够漂浮并在盐水中长时间存活，因此被认为具备长距离扩散的能力。红树物种对冰川作用的响应是其分布范围的收缩。因此，广泛分布的红树物种是研究热带地区长距离扩散和重新定殖的理想系统。我们基于内部转录间隔区（ITS）序列、叶绿体DNA（cpDNA）以及基因组DNA的扩增片段长度多态性（AFLP）进行了系统发育和系统地理学分析，结果表明近期存在跨大西洋的长距离扩散，这一结果否定了关于黑红树（Avicennia germinans）广泛分布是由于隔离分化的假说。由于霜冻和干旱，北纬地区的种群可能在第四纪晚期灭绝；这些地区后来由南方种群重新定殖。在一些低纬度地区，由于海平面变化导致缺乏适宜栖息地，红树种群在第四纪期间灭绝或数量大幅减少。我们的分析表明，低纬度太平洋地区的黑红树种群比大西洋种群拥有更多样性，且分化程度更深。文中还讨论了这些结果对我们理解热带物种系统地理学的意义。
