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Disentangling the drivers of taxonomic and phylogenetic beta diversities in disturbed and undisturbed subtropical forests.

ABSTRACT: Understanding the relative importance of dispersal limitation and environmental filtering processes in structuring the beta diversities of subtropical forests in human disturbed landscapes is still limited. Here we used taxonomic (TBD) and phylogenetic (PBD), including terminal PBD (PBDt) and basal PBD (PBDb), beta diversity indices to quantify the taxonomic and phylogenetic turnovers at different depths of evolutionary history in disturbed and undisturbed subtropical forests. Multiple linear regression model and distance-based redundancy analysis were used to disentangle the relative importance of environmental and spatial variables. Environmental variables were significantly correlated with TBD and PBDt metrics. Temperature and precipitation were major environmental drivers of beta diversity patterns, which explained 7-27% of the variance in TBD and PBDt, whereas the spatial variables independently explained less than 1% of the variation for all forests. The relative importance of environmental and spatial variables differed between disturbed and undisturbed forests (e.g., when Bray-Curtis was used as a beta diversity metric, environmental variable had a significant effect on beta diversity for disturbed forests but had no effect on undisturbed forests). We conclude that environmental filtering plays a more important role than geographical limitation and disturbance history in driving taxonomic and terminal phylogenetic beta diversity.

SUBMITTER: Liu J

PROVIDER: S-EPMC5075936 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Recently, new alternative matrices of biodiversity such as phylogenetic and functional diversity as a complement to species diversity have provided new insights into the mechanisms of community assembly. In this study, we analyzed the phylogenetic signals of five functional traits and the relative contribution of environmental variables and distance matrices to the alpha and beta components of taxonomic, phylogenetic and functional diversity in woody plant assemblages along four local elevational transects on two different mountains. We observed low but significant phylogenetic signals of functional traits, which suggest that phylogenetic dispersion can provide a rough approximation of functional dispersion but not perfect correlations between phylogenetic and functional diversity. Taxonomic alpha diversity showed a monotonic decline with elevation, and climatic variables were the main drivers of this pattern along all studied transects. Furthermore, although the phylogenetic and functional alpha dispersions showed different elevational patterns including increase, decrease and no relationship, the underlying processes driving the patterns of both types of alpha dispersion could be explained by the gradients of climatic and habitat variables as well as biotic interactions such as competition. These results suggest that both alpha dispersion patterns may be significantly controlled by niche-based deterministic processes such as biotic interactions and environmental filtering in our study areas. Moreover, the beta diversity with geographical distances showed distance-decay relationships for all transects. Although the relative importance of the environmental and geographical distances for beta diversity varied across the three facets of diversity and the transects, we generally found that environmental distances were more important for the beta components of the three facets of diversity. However, we cannot discriminate the effects of both distances on the three facets of diversity. Therefore, our study suggests that niche-based deterministic processes, potentially combined with neutral processes such as dispersal limitation and demographic stochasticity, may influence patterns of woody plant assemblage turnover in our study areas.

Project description:AimThe 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.LocationWe examined 35 1-ha tree stem-mapped plots across eight national nature reserves in Guangxi Zhuang Autonomous Region, China.TaxonTrees.MethodsWe 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.ResultsThe taxonomic β-deviation was related to and higher than the phylogenetic β-deviation (r = .74). This indicated 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 nonkarst forest plots, indicating that the species in karst forests and nonkarst forests were predominantly from distantly related clades. A large proportions of the variation in taxonomic and phylogenetic β-deviation were explained by the joint effect of environmental and spatial variables, while the contribution of environmental variables was greater than that of spatial variables, probably owing to the influence of the sampling scale dependence, integrality of sampling size and species pool, and the unique climatic and geomorphic characteristics.Main conclusionsOur study highlights 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.

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Disentangling the drivers of taxonomic and phylogenetic beta diversities in disturbed and undisturbed subtropical forests.

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