赖草属的地理分布及其起源散布

为了探讨赖草属（Leymus Hochst.）植物的地理分布及起源散布，通过野外调查、标本查阅和文献搜集，同时结合地史、气候及类群演化关系的综合分析，对其地理分布及起源散布进行了整理和研究。结果显示，赖草属植物有3组53种（含变种），主要分布于欧亚大陆和北美地区；中国有3组40种（含变种），主要分布于西北、华北、东北以及西南地区，也是该属种类最为集中的区域；尤其是新疆北部的阿尔泰地区及青藏高原东北部的唐古特地区又是中国该属分布相对密集之地，有3组22种，并且其间不同等级、不同系统演化水平的类群均有分布，是该属的现代分布中心。同时，阿尔泰地区多汇集赖草属不同等级的原始类群和外类群，故该地区极有可能是该属的起源地，起源时间大约在第三纪渐新世。赖草属起源后，在渐新世末期青藏高原不断隆升、气候与环境发生巨变，其在中国境内地质活动较为剧烈的区域得到进一步发展和分化，主要通过两个阶段和三条路径扩散成现今的地理分布格局。

Geographical distribution,origin, and dispersal of Leymus Hochst. (Poaceae)

The geographical distribution,origin,and dispersal of Leymus Hochst (Triticeae,Poaceae) were studied through field investigation,specimen collection,literature review,and comprehensive analysis of geological,climatic,and evolutionary relationships between groups.Results showed there were 53 species (including varieties) of Leymus belonging to three sections,mainly distributed in Eurasia and North America.In China,there were 40 species (including varieties) of Leymus belonging to three sections,mainly distributed in the northwest,north,northeast,and southwest regions of China. Leymus species mostly concentrated in these areas.The most abundant region for sections (three) and species (22) was in the Altai area of northern Xinjiang and the Tangut region of the northeastern Qinghai-Tibet Plateau,which included the most primitive and the most advanced in the genus,suggesting that this area was probably the distribution center of Leymus.The Altai area also possessed many primitive taxa and outgroups of Leymus,and hence was likely the region of origin sometime during the Oligocene.The climate and environment changed dramatically with the uplifting of the Qinghai-Tibet Plateau at the end of Oligocene,and thus the genus further developed and differentiated into other areas of China undergoing significant geological activities.Therefore,the geographical distribution pattern today formed mainly through two stages and three path diffusions.