Institute of Botany, Leibniz University Hannover, Herrenhäuserstr, 2, D-30419 Hannover, Germany.
BMC Evol Biol. 2014 Apr 30;14:92. doi: 10.1186/1471-2148-14-92.
The Indo-Pacific region has the largest number of seagrass species worldwide and this region is considered as the origin of the Hydrocharitaceae. Halophila ovalis and its closely-related species belonging to the Hydrocharitaceae are well-known as a complex taxonomic challenge mainly due to their high morphological plasticity. The relationship of genetic differentiation and geographic barriers of H. ovalis radiation was not much studied in this region. Are there misidentifications between H. ovalis and its closely related species? Does any taxonomic uncertainty among different populations of H. ovalis persist? Is there any genetic differentiation among populations in the Western Pacific and the Eastern Indian Ocean, which are separated by the Thai-Malay peninsula? Genetic markers can be used to characterize and identify individuals or species and will be used to answer these questions.
Phylogenetic analyses of the nuclear ribosomal internal transcribed spacer region based on materials collected from 17 populations in the Western Pacific and the Eastern Indian Ocean showed that some specimens identified as H. ovalis belonged to the H. major clade, also supported by morphological data. Evolutionary divergence between the two clades is between 0.033 and 0.038, much higher than the evolutionary divergence among H. ovalis populations. Eight haplotypes were found; none of the haplotypes from the Western Pacific is found in India and vice versa. Analysis of genetic diversity based on microsatellite analysis revealed that the genetic diversity in the Western Pacific is higher than in the Eastern Indian Ocean. The unrooted neighbor-joining tree among 14 populations from the Western Pacific and the Eastern Indian Ocean showed six groups. The Mantel test results revealed a significant correlation between genetic and geographic distances among populations. Results from band-based and allele frequency-based approaches from Amplified Fragment Length Polymorphism showed that all samples collected from both sides of the Thai-Malay peninsula were clustered into two clades: Gulf of Thailand and Andaman Sea.
Our study documented the new records of H. major for Malaysia and Myanmar. The study also revealed that the Thai-Malay peninsula is a geographic barrier between H. ovalis populations in the Western Pacific and the Eastern Indian Ocean.
印度洋-太平洋地区拥有全球最多的海草物种，被认为是 Hydrocharitaceae 的起源地。海菖蒲属的海菖蒲及其近缘种由于具有高度的形态可塑性，是一个公认的复杂分类学挑战。该地区对海菖蒲属辐射的遗传分化与地理障碍之间的关系研究甚少。海菖蒲与其近缘种之间是否存在鉴定错误？海菖蒲不同种群之间是否仍然存在分类学上的不确定性？被泰国-马来半岛分隔的西太平洋和东印度洋的种群之间是否存在遗传分化？遗传标记可用于描述和鉴定个体或物种，我们将使用这些标记来回答这些问题。
对来自西太平洋和东印度洋 17 个种群的核核糖体内部转录间隔区进行的系统发育分析表明，一些被鉴定为海菖蒲的标本属于海菖蒲 major 分支，这也得到了形态学数据的支持。两个分支之间的进化分歧在 0.033 到 0.038 之间，远高于海菖蒲种群之间的进化分歧。发现了 8 种单倍型；来自西太平洋的单倍型都没有在印度发现，反之亦然。基于微卫星分析的遗传多样性分析表明，西太平洋的遗传多样性高于东印度洋。来自西太平洋和东印度洋的 14 个种群的无根邻接树显示了 6 个组。Mantel 检验结果表明，种群间的遗传距离与地理距离之间存在显著相关性。基于扩增片段长度多态性的带型和等位基因频率方法的结果表明，从泰国-马来半岛两侧采集的所有样本都聚类为两个分支：泰国湾和安达曼海。
我们的研究记录了马来西亚和缅甸的海菖蒲 major 的新记录。该研究还表明，泰国-马来半岛是西太平洋和东印度洋的海菖蒲种群之间的地理障碍。
