叶绿体序列和核微卫星显示同域分布润楠属物种杂交严重

Chloroplast sequences and nuclear microsatellites reveal extensive hybridization among sympatric species of the genus Machilus

关键词:  润楠属, 叶绿体序列, 核微卫星, 系统进化, 渐渗杂交

Key words:  Machilus, chloroplast sequence, nuclear microsatellites, phylogenetics, introgressive hybridization

摘要:

樟科润楠属(Machilus Nees)植物为常绿乔木,是亚热带常绿阔叶林常见的优势种,具有重要的经济价值,但属内分类和种间系统进化关系存在较大争议。为了解其可能的原因,该文选择12个同域分布的润楠属物种,采用72个叶绿体DNA序列片段和10个核微卫星位点进行分析。结果表明:(1)72个叶绿体DNA序列片段共44 025 bp的序列上仅有48个变异位点,多态性极低。(2)10个核微卫星标记在12个润楠属物种中通用性好、多态性高,不同物种间共享大量等位基因,独有等位基因少。(3)基于叶绿体DNA不能得到支持率高的一致系统进化树,微卫星标记支持建润楠(M. oreophila)、狭叶润楠(M. rehderi)和红楠(M. thunbergii)的分类地位,但其他物种间关系混乱且核-质系统进化关系冲突,其原因可能是种间频繁的杂交渐渗模糊了种间的界限。后续需综合形态学和多种分子标记,开发有效的分析工具,以理解润楠属内复杂的系统进化关系。

Abstract:

Plants of the genus Machilus Nees(Lauraceae)are evergreen trees and are common dominant species in subtropical evergreen broad-leaved forests, with significant economic value. However, there is considerable debate regarding the classification within the genus and the phylogenetic relationships among species. To explore the potential reasons behind this, this study selected 12 sympatric species of Machilus and analyzed 72 chloroplast fragments and 10 nuclear microsatellite loci. The results were as follows:(1)A total of only 48 variable sites were found across the 44 025 base pairs of the 72 chloroplast fragments, indicating extremely low polymorphism.(2)The 10 nuclear microsatellite markers showed good universality across the 12 species of Machilus, with high polymorphism, a large number of shared alleles among different species, and very few private alleles.(3)A high-support consensus phylogenetic tree could not be obtained based on chloroplast DNA, while microsatellite markers supported the taxonomic status of M. oreophila, M. rehderi, and M. thunbergii. However, those relationships among other species were confused and there was incongruence between nuclear and plastid phylogenies. This confusion is likely attributed to frequent interspecific hybridization that have blurred the boundaries between species. Further research is needed to integrate morphological data and multiple molecular markers, and to develop effective analytical tools to understand the complex phylogenetic relationships within the genus Machilus.