Environmental filtering and dispersal limitation jointly shaped the taxonomic and phylogenetic beta diversity of natural forests in southern China

Abstract

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 = .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 conclusions Our 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.

Abiotic Drivers of Seedling Bank Diversity in Subtropical Forests of Southern China

“…Specifically, the karst forest of Mulun presents a much more distinct community, as it would be expected given the peculiar landscape features and species adaptations to this environment (Geekiyanage et al, 2019). Greater beta-diversity between karst and non-karst adult tree communities compared to non-karst forests was also recently reported in the same region (Shi et al, 2021). Variation in soil nutrients availability has also been linked to gradients of species richness and diversity in different forest ecosystems (Huston, 1980;Cornwell and Grubb, 2003;Nadeau and Sullivan, 2015).…”

“…Community composition and diversity at the seedling stage are linked to the composition of reproductive individuals found in the area investigated, both at local scale but also as the species pool at large spatial scales that can act as a species source (Zobel, 1997). Dispersal limitation was highlighted as a source of variation in beta diversity in this region (Shi et al, 2021). In addition, the strength of negative density dependence is considered a major reason for the higher diversity in tropical compared to temperate forests (Bagchi et al, 2014).…”

“…We decided to study seedlings because they represent a critical bottleneck in plant recruitment and understanding their regeneration dynamics in relation to their environment is important to better comprehend forest community structure (Grubb, 1977;Queenborough et al, 2007). Further, recent studies in this region provided initial evidence on the important role of environmental filtering in shaping seedling emergence and tree diversity in these forests (Castillo-Díaz et al, 2021;Shi et al, 2021). Using data from four subtropical forests distributed along an elevation gradient of 1500 m, our goal was to elucidate the main abiotic drivers that determine seedling bank composition, abundance, and diversity, by investigating both direct and indirect relationships.…”

The Diversity and Community Assembly Process of Wetland Plants from Lakeshores on the Qinghai-Tibetan Plateau

“…The Mantel test with 999 permutations was used to investigate the relationships between sample ordination on taxonomic (Bray-Curtis distance) and geographic distance and environmental similarity (Euclidean distance) [16]. The variation partitioning analysis (VPA) is widely used in ecological research to evaluate the relative contribution of the pure effects of geospatial variables (the effects of potential dispersal limitation) and the pure effects of environmental factors (deterministic process) [44][45][46]. Non-metric multidimensional scaling (NMDS) ordination was performed based on unweighted Unifrac distances by using the GUniFrac and the vegan package to visualize the similarity of community structure among study sites.…”

“…Quantifying stochasticity and determinism in governing community assembly is important but difficult [56]. Here, the community assembly process of the wetland plants on the QTP was clarified in three contexts: the null-model-based phylogenetic and taxonomic diversity metrics [56], the correlations between taxonomic/phylogenetic diversity and geospatial and environmental factors [46,57], and the components of geography and environment contributed to the similarity of community structure among sites [58]. Based on the performance of these three contexts, we inferred that stochastic and deterministic processes only played modest roles in the community structure of wetland plants.…”