分子和形态分析阐明了 Costatae 组内的物种界限，并在中国揭示了新种 Betula buggsii sp. nov.（Betulaceae 科 Costatae 组）。
Molecular and morphological analyses clarify species delimitation in section Costatae and reveal Betula buggsii sp. nov. (sect. Costatae, Betulaceae) in China.
机构信息
State Forestry and Grassland Administration Key Laboratory of Silviculture in Downstream Areas of the Yellow River, College of Forestry, Shandong Agricultural University, Tai'an, China.
Mountain Tai Forest Ecosystem Research Station of State Forestry and Grassland Administration, College of Forestry, Shandong Agricultural University, Tai'an, China.
出版信息
Ann Bot. 2022 Mar 23;129(4):415-428. doi: 10.1093/aob/mcac001.
BACKGROUND AND AIMS
Delineating closely related and morphologically similar species is difficult. Here, we integrate morphology, genetics, ploidy and geography to resolve species and subspecies boundaries in four trees of section Costatae (genus Betula): Betula ashburneri, B. costata, B. ermanii and B. utilis, as well as multiple subspecies and polyploid races.
METHODS
We genotyped 371 individuals (20-133 per species) from 51 populations at 15 microsatellite markers, as well as a subset of individuals, using restriction-site associated DNA sequencing and nuclear internal transcribed spacers. We determined the ploidy level of eight individuals using flow cytometry and characterized leaf variation for a subset of 109 individuals by morphometric analysis.
KEY RESULTS
Integration of multiple lines of evidence suggested a series of revisions to the taxonomy of section Costatae. Betula costata and B. ermanii were found to be valid. Molecular and leaf morphology analyses revealed little differentiation between diploid B. albosinensis and some samples of B. utilis ssp. utilis. By contrast, other B. utilis ssp. utilis samples and ssp. albosinensis formed a morphological continuum but differed based on genetics. Specifically, B. utilis ssp. albosinensis was divided into two groups with group I genetically similar to B. utilis ssp. utilis and group II, a distinct cluster, proposed as the new diploid species Betula buggsii sp. nov. Phylogenomic analysis based on 2285 620 single nucleotide polymorphisms identified a well-supported monophyletic clade of B. buggsii. Morphologically, B. buggsii is characterized by elongated lenticels and a distinct pattern of bark peeling and may be geographically restricted to the Qinling-Daba Mountains.
CONCLUSIONS
Our integrated approach identifies six taxa within section Costatae: B. ashburneri, B. buggsii, B. costata, B. utilis ssp. utilis, B. utilis ssp. albosinensis and B. ermanii. Our research demonstrates the value of an integrative approach using morphological, geographical, genetic and ploidy-level data for species delineation.
背景与目的
密切相关且形态相似的物种的划分具有一定难度。本研究整合了形态学、遗传学、倍性和地理信息，以解决桦木属（Betula）Costatae 组内的四个树种（Betula ashburneri、B. costata、B. ermanii 和 B. utilis）以及多个亚种和多倍体的种和亚种界限问题。
方法
我们在 51 个种群中对 371 个个体（每个物种 20-133 个个体）进行了 15 个微卫星标记的基因型分析，同时还对部分个体进行了基于限制性位点相关 DNA 测序和核内转录间隔区的分析。我们使用流式细胞术确定了 8 个个体的倍性水平，并通过形态计量分析对 109 个个体中的一部分进行了叶片变异的特征描述。
主要结果
综合多种证据表明，对 Costatae 组的分类学进行了一系列修订。发现 B. costata 和 B. ermanii 是有效的。分子和叶片形态分析表明，二倍体 B. albosinensis 和一些 B. utilis ssp. utilis 样本之间几乎没有分化。相比之下，其他 B. utilis ssp. utilis 样本和 ssp. albosinensis 形成了一个形态连续体，但在遗传学上有所不同。具体来说，B. utilis ssp. albosinensis 分为两组，第 I 组在遗传上与 B. utilis ssp. utilis 相似，第 II 组是一个明显的聚类，被提议为新的二倍体物种 Betula buggsii sp. nov. 基于 2285620 个单核苷酸多态性的基因组分析确定了一个支持良好的单系 B. buggsii 聚类。形态上，B. buggsii 的特征是延长的皮孔和独特的树皮剥落模式，其地理分布可能局限于秦岭-大巴山地区。
结论
本研究在 Costatae 组内确定了 6 个分类群：B. ashburneri、B. buggsii、B. costata、B. utilis ssp. utilis、B. utilis ssp. albosinensis 和 B. ermanii。本研究证明了使用形态学、地理信息、遗传学和倍性水平数据进行物种划分的综合方法的价值。
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