Phytogeographical and community similarities of alpine tundras of Changbaishan Summit, China, and Indian Peaks, USA

We compared the diversity, phytogeography, and plant communities in two mid -latitude alpine tundras with comparable aerial and elevational extents: Ch angbaishan Summit in eastern Asia and Indian Peaks in western North America . Despite wide separation, the two areas shared 72 species. In all, 43 % of the species on Changbaishan Summit are also distributed in the alpine zone s of western North America, while 22 % of the species on Indian Peaks are a lso distributed in the alpine zones of eastern Asia. Almost all the shared species also occur in the Beringian region. Phytogeographical profiles of s pecies and genera showed that 69 % of species and over 90 % of genera in bo th alpine tundras belong to the three phytogeographical categories: cosmopo litan, circumpolar, and Asian-North American. We attributed the current flo ristic relationship between these widely separated areas to the periodic pa st land connection between the two continents during the Tertiary and Pleis tocene. Indian Peaks has a closer floristic relationship with the Arctic tu ndra than does Changbaishan Summit. Indian Peaks also has 45 % higher speci es richness and lower vegetation cover than Changbaishan Summit. Plant communities from the two areas were completely separated in the two-w ay indicator species analysis and nonmetric multidimensional scaling on flo ristic data at both species and generic levels, whereas ordination of commu nities by soil data produced a greater overlap. The plant communities on Ch angbaishan Summit in general have lower alpha diversity, higher beta divers ity (lower between-community floristic similarity), and more rare species t han does Indian Peaks. Mosaic diversity does not differ in the two alpine t undras, although the analysis suggests that Changbaishan Summit communities are more widely spaced on gradients than the Indian Peaks communities.