Abstract
Large-scale patterns of biodiversity and the underlying mechanisms that regulate these patterns are central topics in biogeography and macroecology. The Qinghai-Tibet Plateau serves as a natural laboratory for studying these issues. However, most previous studies have focused on the entire Qinghai-Tibet Plateau, leaving independent physical geographic subunits in the region less well understood. We studied the current plant diversity of the Kunlun Mountains, an independent physical geographic subunit located in northwestern China on the northern edge of the Qinghai-Tibet Plateau. We integrated measures of species distribution, geological history, and phylogeography, and analyzed the taxonomic richness, phylogenetic diversity, and community phylogenetic structure of the current plant diversity in the area. The distribution patterns of 1911 seed plants showed that species were distributed mainly in the eastern regions of the Kunlun Mountains. The taxonomic richness, phylogenetic diversity, and genera richness showed that the eastern regions of the Kunlun Mountains should be the priority area of biodiversity conservation, particularly the southeastern regions. The proportion of Chinese endemic species inhabiting the Kunlun Mountains and their floristic similarity may indicate that the current patterns of species diversity were favored via species colonization. The Hengduan Mountains, a biodiversity hotspot, is likely the largest source of species colonization of the Kunlun Mountains after the Quaternary. The net relatedness index indicated that 20 of the 28 communities examined were phylogenetically dispersed, while the remaining communities were phylogenetically clustered. The nearest taxon index indicated that 27 of the 28 communities were phylogenetically clustered. These results suggest that species colonization and habitat filtering may have contributed to the current plant diversity of the Kunlun Mountains via ecological and evolutionary processes, and habitat filtering may play an important role in this ecological process.