基于序列trnL-trnF和ITS的榉属系统发育与地理分布格局的初步分析

A preliminary study of molecular phylogeny and biogeography distribution pattern of Zelkova inferred from trnL-trnF and nrITS sequences

榉属(Zelkova)是包含6个种的榆科小属,呈东亚、西亚和南欧间断分布。该文基于DNA序列trnL-trnF和ITS构建了榉属的分子系统发育树,大体上把此属分为3个分支,分别对应东亚、西亚和南欧的种类,与前人仅依据ITS序列的结果不同。生物地理的扩散和隔离分化分析(DIVA)表明,榉属的原始祖先分布区可能是欧亚北温带,包括了东亚、西亚和南欧的某个大的区域。分化过程以隔离分化为主要特征,即3个分布区域是逐步隔离分化的。由于东亚的物种多样性,北太平洋有可能是起源中心。榉属的现代分布格局可能主要是由于渐新世发生的古地中海西退、中新世发生的青藏高原大范围隆升,以及第四纪冰川活动引起的分布区的收缩。

Aims Zelkova, belongs to the Ulmaceae, consists of only six species and has a disjunct distribution in East Asia, West Asia and South Europe. Molecular phylogenetic analysis and dispersal and vicariance analysis （DIVA） were employed to analyze phylogenetic relationships and biogeographic pattem of Zelkova. Methods The phylogenetic tree was reconstructed based on DNA sequences of trnL-trnF and ITS regions. The analysis of DIVA was used to deduce the biogeographic pattern. Important findings Results showed that three phylogenetic clades exist in Zelkova, and they correspond to groups from East Asia, West Asia and South Europe. The present phylogenetic tree is different from that in previ- ous study based on nrlTS region. DIVA analyses of this genus indicated that the ancestral area of Zelkova was a larger area including East Asia, West Asia and South Europe. The speciation process was dominant by vicariance. Each of the three areas was gradually separated from vicariant events. Based on the high level of species diversity of Zelkova in East Asia, the center of origin is probably the northern Pacific, i.e., north of China and Japan. The current distribution pattern of this genus was likely shaped by historical geological and environmental events, such as the retreat of Tethys, the Qinghai-Xizang Plateau uplift and the Quaternary glaciations that shrank distribution areas.