Population structure of Betula albosinensis and Betula platyphylla: evidence for hybridization and a cryptic lineage
Population structure of Betula albosinensis and Betula platyphylla: evidence for hybridization and a cryptic lineage
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白桦和白桦的种群结构：杂交和神秘谱系的证据
DOI：
10.1093/aob/mcz024
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发表时间：
2019-06-04
期刊：
影响因子：
4.2
通讯作者：
Wang, Nian
中科院分区：
文献类型：
--
作者：
Hu, Ya-Nan;Zhao, Lei;Wang, Nian
背景与目的预测不同地区的丰度和倍性水平的差异会影响物种间的基因渐渗方向。本文以被认为在倍性水平上存在差异的白桦（Betula albosinensis，红桦）和白桦（Betula platyphylla，白桦）为研究对象，对上述假设进行了验证。方法对中国9个地区的391棵桦树进行取样，并根据叶片形态对其进行分类。每个样本中12个核微卫星标记进行基因分型，并利用主坐标分析和STRUCTURE软件进行分析。我们比较了两种不同多倍体基因型评分方法对群体遗传分析的影响。我们分析了倍性、本地物种丰度和纬度对种间渗透水平的影响。叶片形态将样品分为红桦和白桦，但遗传分析意外地发现红桦中有两组，其中一组如预期的那样是四倍体，而另一组似乎是二倍体微卫星基因型。5个个体被鉴定为白桦与红桦的早代杂交或回交，5个个体被鉴定为红桦与“二倍体”红桦的杂交。克莱恩分析表明，外加剂的水平与纬度不显著相关。在确定的四倍体和未确定的四倍体基因型之间，物种间估计的遗传分化没有显著差异。结论红桦与白桦之间存在着有限的杂交和基因流动。相对物种丰度和倍性水平不影响它们之间的渗透方向，因为遗传混合大致对称。我们意外地发现了明显为二倍体的红桦种群，该分类群可能是异源四倍体红桦种群的祖先。不完全谱系分选可以解释明显二倍体和异源四倍体红桦的遗传混合模式。
Background and Aims Differences in local abundance and ploidy level are predicted to impact the direction of introgression between species. Here, we tested these hypotheses on populations of Betula albosinensis (red birch) and Betula platyphylla (white birch) which were thought to differ in ploidy level, the former being tetraploid and the latter diploid.Methods We sampled 391 birch individuals from nine localities in China, and classified them into species based on leaf morphology. Twelve nuclear microsatellite markers were genotyped in each sample, and analysed using principal coordinates analysis and STRUCTURE software. We compared the effects of two different methods of scoring polyploid genotypes on population genetic analyses. We analysed the effect of ploidy, local species abundance and latitude on levels of introgression between the species.Key Results Leaf morphology divided our samples into red and white birch, but genetic analyses unexpectedly revealed two groups within red birch, one of which was tetraploid, as expected, but the other of which appeared to have diploid microsatellite genotypes. Five individuals were identified as early-generation hybrids or backcrosses between white birch and red birch and five were identified between red birch and 'diploid' red birch. Cline analysis showed that levels of admixture were not significantly correlated with latitude. Estimated genetic differentiation among species was not significantly different between determined tetraploid and undetermined tetraploid genotypes.Conclusions Limited hybridization and gene flow have occurred between red birch and white birch. Relative species abundance and ploidy level do not impact the direction of introgression between them, as genetic admixture is roughly symmetrical. We unexpectedly found populations of apparently diploid red birch and this taxon may be a progenitor of allotetraploid red birch populations. Incomplete lineage sorting may explain patterns of genetic admixture between apparently diploid and allotetraploid red birch.