Elevational pattern of species range size of vascular plants in Changbai Mountain, China:A test of Rapo-port's rule.

Species range size is closely related to its ability to migrate and adapt to environmental change. Rapoport's rule predicts that species range size would become larger with increasing latitude or elevation. Empirical evidence for Rapoport's rule are controversial, and the comparisons among different groups and families are lacking. We analyzed the elevational patterns of species range size with a dataset of 1505 vascular plant species in Changbai Mountain of Northern China, including 249 woody species, 1168 herbaceous species, and 88 fern species. We used four methods (Stevens method, mid-point method, Pagel method and cross-species method) to test the effectiveness of Rapoport's rule for all plant species, among two growth forms, among ferns, and among 19 families. The results showed that richness of two growth forms and ferns all monotonically decreased along the elevation, but for three groups of range size, richness and its proportion had various patterns along the elevation: narrow-range species had the highest proportion in low elevation, medium-range species had two peaks at low and high elevations respectively, and the proportion of wide-range species increased first and then decreased with elevation. The results for Rapoport's rule varied among different methods. Range size patterns of all plants generally support Rapoport's rule expect for the mid-point method. Woody plants showed stronger evidence than herbaceous plants, while the support of ferns was the weakest and Stevens method did not support the rule. Eight out of the 19 families with no less than 20 species had the support from at least three methods, while four families had only one method to support. Species range size patterns along elevations and the support of Rapoport's rule were inconsistent among two growth forms, ferns and 19 families of vascular plants in Changbai Mountain, suggesting the dramatic differences in their evolutionary history and the abilities to response and adapt environment changes.