Influence of elevation on bioregionalisation: A case study of the Sino-Himalayan flora

Aim: Elevation is an important factor that influences bioregionalisation in mountainous areas, but its effects are not well known. Taking the Sino-Himalayan flora as a case, we aimed to test the effect of elevation on bioregionalisation and provide a regionalisation scheme of the Sino-Himalayan flora.

Location: The Sino-Himalaya (East Himalaya, the Hengduan Mountains and the Yunnan Plateau in China).

Taxon: Angiosperms.

Methods: We compiled distribution data and elevation ranges of angiosperms in the Sino-Himalaya and adjacent areas and reconstructed a species-level phylogenetic tree of 19,313 angiosperm species. The area was divided into 398 grid cells, each 1 × 1°. Nine datasets of different elevation ranges were then used to delineate the flora of the Sino-Himalaya and adjacent areas using the phylogenetic dissimilarity approach.

Results: A comparison of nine regionalisation schemes of the Sino-Himalayan flora based on different elevation range datasets revealed that more than half of grid cells were allocated to more than one subregion. Most of these grid cells were located in areas with a wide range of elevation and/or at the boundaries between subregions. After revising the subregion allocations of eight shifting grid cells, we generated a phylogeny- and elevation-based regionalisation scheme of three regions, comprising eight subregions, for the Sino-Himalayan flora.

Main conclusions: By integrating phylogenetic and elevational information, the Sino-Himalaya can be divided into three floristic regions: the Yunnan Plateau region, the Hengduan Mountains region, and the East Himalaya region. Our study provides novel insights into the regionalisation of the flora and highlights the importance of incorporating elevation data in the bioregionalisation of areas with a broad elevational range.