Biodiversity Science ›› 2010, Vol. 18 ›› Issue (3): 312-322.

• Special Issue •

### Altitudinal gradients of species richness and range size of vascular plants in Taiwan: a test of Rapoport’s rule

Wanjun Zhang; Qiyan Lu; Jun Liang; Zehao Shen*

1. Department of Ecology, College of Urban & Environmental Sciences, Peking University, Beijing 100871
• Received:2010-01-13 Online:2012-02-08
• Zehao Shen

Spatial patterns of species richness and range size along environmental gradients have long been central issues to biogeography and biodiversity. Because of their unique isolation effects on species distributions, much emphasis has been put on insular environments in developing and testing biogeography theories. Rapoport’s rule suggested an increasing trend of species range width along with increasing altitude. Taiwan, the largest island in China, is characterized by a significant altitudinal gradient, subtropical monsoon climate, as well as a rich and unique flora. Here, we offer the first report on the altitudinal patterns of species richness and species range size of Taiwan’s vascular plants, and analyze the relationship between altitudinal range size and range midpoint to test Rapoport’s rule. We established a database of 4,751 plant species (including subspecies levels), belonging to 241 families and 1,466 genera. Among these, 3,330 species have altitudinal range records and were analyzed. Taxonomic richness at the family, genus and species levels decreased with increasing elevation in terms of all plants and invasive species, and a hump-shaped altitudinal pattern of species richness was found for endemic plants. With regard to taxonomic groups, pteridophytes and gymnosperms richness exhibited hump-shaped patterns, while decreasing richness with increasing altitude was found for three subgroups in angiosperm (i.e. herbs, evergreen and deciduous woody plants). Relationships between species range size and midpoint elevation varied among assemblages as well as among methods applied to the same assemblage. The distribution of invasive plants supported Rapoport’s rule, while that of endemic species and overall species did not. The distribution of pteridophytes supported Rapoport’s rule, while gymnosperms did not. For angiosperms, no consistent patterns were found when different methods were applied. By comparing Taiwan and adjacent large insular and continental mountains, we suggest that the altitudinal patterns of precipitation might contribute to that of species richness. Our test of Rapoport’s rule suggested that, even on the same mountain, altitudinal variation of distributional patterns among different assemblages can result from different mechanisms.

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