柳属植物在秦岭地区的分布和分化

STUDIES ON THE DISTRIBUTION AND DIFFERENTIATION OF WILLOWS (SALIX) IN QINLING MOUNTAIN

本文对秦岭地区41种柳属植物采用简约性分析讨论形态演化,采用聚类分析讨论地理分布式样和分化。秦岭地区有较完整的多雄蕊类群→两雄蕊类群→单雄蕊类群的演化。其分布式样和区系特征和邻近地区即华北、华中和西南成分联系密切,表现出明显的过渡性质,其中青藏高原成分占重要地位,特别可以从太白山分布上去说明。本区的地理分化也被青藏高原成分和华中成分所作用。

Qinling Mountain is the natural geographic dividing line between Southand North China. Taibai Mountain about altitute of 3767 m above sealevel is the highest in this region and eastward to Qinghai-Xizang (Tibet)Plateau. There are 41 species in this region, belonging to 14 sections and3 subgenera. This paper deals with the morphological variation and evol-ution of the said genus by means of parsimony analysis, the presentationof the floristic feature and geographic differentiation is by means of clu- ster analysis. The results are as following: 1. The cladogram indicates that the directions of morphological evol-ution are from multistaminal willows, two-staminal willows to one-sta-minal willows, from Subgen. Salix, Subgen. Vetrix to Subgen. Helix, andfrom the groups in the southern slope to that of the northern slope ofQinling Mountain. The groups of Qinghai-Xizang Plateau elements haveobvious variation in this region. 2. This region is influenced striking by the floristic elements of adj-iacent regions including North China Temperate, Central China Subtropicand Southwest China Subtropic elements. The transition could be seen insome groups. Sect. Wilsonianae with multistamens endemic to China, isextending from the southern China northwards to the southern slope ofthis region, such as S. wilsonii, S. rosthornii and S. paraplesia. Sect. Pe-ntandrae, Sect. Vetrix, Sect. Vimen and Sect. Haoanae are dispersing north-ward from Qinling Mountain or its northern slope, such as S. chaenomeldoi-des, S. matsudana, S. sinica, S. characta, S. viminalis and S. sinopurpurea. 3. There are more than 22 species (4 endemic species) of Salix in Tai-bai Mountain. It is the richest region in Qinling Mountain. The floristicelements are mainly belonging to North Temperate and Qinghai-XizangPlateau elements. Species distributed above 3000 m are chief the alpineelements of Qinghai-Xizang Plateau and endemic distributions. Form Salixcupularis is peculiar in the alpine meadow zone above 3500m. 4. The phenogram for area of species shows that there are threecenters of the species differentiation, namely, Ningshan-Shiquan conunties(42、51 in Fig. 1) representing Central China elements, Wenxian-Wuducounties (48、34) representing Southwest China elements and Taibai Mou-ntain (26) representing North China and Qinghai-Xizang Plateau elements.The ancient roads from the southern to the northern slope may be thepathways of dispersal and migration of the species, the Hanshui Riverand Jialing River is reponding respectively to the elements of CentralChina and Qinghai-Xizang Plateau.