Phylogenetic community structure of subtropical forests along elevational gradients in Ailao Mountains of southwest China

Understanding the maintenance of biodiversity and community assembly is a central issue in community ecology. Here, we examined patterns of the community phylogenetic structure of subtropical forests along an elevational gradient in the Ailao Mountains of southwest China. We surveyed all trees with diameter at breast height ≥1 cm in 16 plots, and constructed a community phylogeny from DNA barcode sequence data with a constraint tree based on Angiosperm Phylogeny Group (APG) III. We found that the community structure changed from phylogenetically clustered to phylogenetically overdispersed with increasing elevation. Co-occurring trees at low-elevation communities tended to be more closely related than expected by chance, implying that these communities were structured primarily by habitat filtering. Clustered and over-dispersed phylogenetic compositions were showed in mid-elevation communities, suggesting that these communities are structured by habitat filtering or competitive exclusion. At high-elevation sites, NRI (Net Relatedness Index) showed clustering, but NTI (Nearest Taxon Index) showed randomness or over-dispersion. We therefore interpreted our results with caution. It is possible that convergent evolution 第 4 期 卢孟孟等: 沿海拔梯度变化的哀牢山亚热带森林群落系统发育结构 439 may be occurred independently in distantly related lineages under higher environmental stress at high elevations. Taken together, the results of our study provide insight into the potential role of elevational gradients in shaping community composition and phylogenetic diversity.