Percy Diana M, Garver Adam M, Wagner Warren L, James Helen F, Cunningham Clifford W, Miller Scott E, Fleischer Robert C
National Museum of Natural History, Box 37012, Smithsonian Institution, Washington, DC 20013, USA.
Proc Biol Sci. 2008 Jul 7;275(1642):1479-90. doi: 10.1098/rspb.2008.0191.
Knowledge of the evolutionary history of plants that are ecologically dominant in modern ecosystems is critical to understanding the historical development of those ecosystems. Metrosideros is a plant genus found in many ecological and altitudinal zones throughout the Pacific. In the Hawaiian Islands, Metrosideros polymorpha is an ecologically dominant species and is also highly polymorphic in both growth form and ecology. Using 10 non-coding chloroplast regions, we investigated haplotype diversity in the five currently recognized Hawaiian Metrosideros species and an established out-group, Metrosideros collina, from French Polynesia. Multiple haplotype groups were found, but these did not match morphological delimitations. Alternative morphologies sharing the same haplotype, as well as similar morphologies occurring within several distinct island clades, could be the result of developmental plasticity, parallel evolution or chloroplast capture. The geographical structure of the data is consistent with a pattern of age progressive island colonizations and suggests de novo intra-island diversification. If single colonization events resulted in a similar array of morphologies on each island, this would represent parallel radiations within a single, highly polymorphic species. However, we were unable to resolve whether the pattern is instead explained by ancient introgression and incomplete lineage sorting resulting in repeated chloroplast capture. Using several calibration methods, we estimate the colonization of the Hawaiian Islands to be potentially as old as 3.9 (-6.3) Myr with an ancestral position for Kaua'i in the colonization and evolution of Metrosideros in the Hawaiian Islands. This would represent a more ancient arrival of Metrosideros to this region than previous studies have suggested.
了解在现代生态系统中占据生态主导地位的植物的进化历史，对于理解这些生态系统的历史发展至关重要。铁树属植物分布于太平洋地区的许多生态和海拔区域。在夏威夷群岛，多形铁树是一种生态优势物种，在生长形态和生态方面也具有高度多态性。我们利用10个非编码叶绿体区域，研究了目前公认的5种夏威夷铁树属物种以及来自法属波利尼西亚的一个既定外类群——科利纳铁树的单倍型多样性。我们发现了多个单倍型组，但这些单倍型组与形态学界定并不匹配。具有相同单倍型的不同形态，以及在几个不同岛屿分支中出现的相似形态，可能是发育可塑性、平行进化或叶绿体捕获的结果。数据的地理结构与年龄递进的岛屿殖民化模式一致，并表明存在岛内的从头多样化。如果单次殖民事件在每个岛屿上导致了相似的形态排列，这将代表一个单一的、高度多态性物种内的平行辐射。然而，我们无法确定这种模式是否反而可以用古老的基因渗入和不完全谱系分选导致的重复叶绿体捕获来解释。我们使用了几种校准方法，估计夏威夷群岛的殖民化可能早在390万（-630万）年前，考艾岛在夏威夷群岛铁树属的殖民化和进化中处于祖先位置。这将意味着铁树属到达该地区的时间比以前的研究所表明的要早得多。
