Aim

The mechanisms underlying the maintenance of biodiversity remain to be elucidated. Taxonomic diversity alone remains an unresolved issue, especially in terms of the mechanisms of species co-existence. We hypothesized that phylogenetic information could help to elucidate the mechanism of community assembly and the services and functions of ecosystems. The aim of this study was to explore the mechanisms driving floral diversity in subtropical forests and evaluate the relative effects of these mechanisms on diversity variation, by combining taxonomic and phylogenetic information.

Location

We examined 35 1-ha tree stem-mapped plots across eight National Nature Reserves in Guangxi Zhuang Autonomous Region, China.

Taxon

Trees.

Methods

We quantified the taxonomic and phylogenetic β-diversity between each pair of plots using the (abundance-based) Rao’s quadratic entropy and the (incidence-based) Sørensen dissimilarity indices. Using a null model approach, we compared the observed β-diversity with the expected diversity at random and calculated the standard effect size of the observed β-diversity deviation. Furthermore, we used distance-based redundancy analysis (dbRDA) to partition the variations in taxonomic and phylogenetic observed β-diversity and β-deviation into four parts to assess the environmental and spatial effects.

Results

The taxonomic β-deviation was related to and higher than the phylogenetic β-deviation (r = 0.74). This observation showed that the species turnover between pairwise plots was mainly the turnover of closely related species. Higher taxonomic and phylogenetic β-deviation were mainly concentrated in the pairwise karst and non-karst forest plots, indicating that the species in karst forests and in other forests were predominantly from distantly related clades. A large proportion of the variation in β-deviation was explained by the joint effect of environmental and spatial variables, while the relative importance of environmental variables was greater than that of spatial variables, probably owing to the influence of glacial refuge, and the migration and dispersal of plant species under the postglacial rapid climate change.

Main conclusions

Our study emphasized the importance of phylogeny in biodiversity research. The incorporation of taxonomic and phylogenetic information provides a perspective to explore potential underlying mechanisms that have shaped species assemblages and phylogenetic patterns in biodiversity hotspots.