Different ecological processes determined the alpha and beta components of taxonomic, functional, and phylogenetic diversity for plant communities in dryland regions of Northwest China.

Jianming Wang,Qi Lu,Yiming Feng,Chen Chen,Jingwen Li

doi:10.7717/peerj.6220

Abstract

Drylands account for more than 30% of China’s terrestrial area, while the ecological drivers of taxonomic (TD), functional (FD) and phylogenetic (PD) diversity in dryland regions have not been explored simultaneously. Therefore, we selected 36 plots of desert and 32 plots of grassland (10 × 10 m) from a typical dryland region of northwest China. We calculated the alpha and beta components of TD, FD and PD for 68 dryland plant communities using Rao quadratic entropy index, which included 233 plant species. Redundancy analyses and variation partitioning analyses were used to explore the relative influence of environmental and spatial factors on the above three facets of diversity, at the alpha and beta scales. We found that soil, climate, topography and spatial structures (principal coordinates of neighbor matrices) were significantly correlated with TD, FD and PD at both alpha and beta scales, implying that these diversity patterns are shaped by contemporary environment and spatial processes together. However, we also found that alpha diversity was predominantly regulated by spatial structure, whereas beta diversity was largely determined by environmental variables. Among environmental factors, TD was most strongly correlated with climatic factors at the alpha scale, while with soil factors at the beta scale. FD was only significantly correlated with soil factors at the alpha scale, but with altitude, soil and climatic factors at the beta scale. In contrast, PD was more strongly correlated with altitude at the alpha scale, but with soil factors at the beta scale. Environment and space explained a smaller portion of variance in PD than in TD and FD. These results provide robust evidence that the ecological drivers of biodiversity differ among different scales and facets of diversity. Future research that focuses on the comparisons among TD, FD and PD would likely provide new insights into elucidating the underlying community assembly.

Highlights

Understanding the fundamental processes that underlie biogeographic patterns of biodiversity has been a focus of biogeography and ecology (Gaston, 2000; Anderson et al, 2011)
The Pagel’s l and Blomberg’s K values for each functional trait were less than 1, implying weak phylogenetic signals. These results suggest that evolutionary history or phylogenetic relationships may only significantly influence a part of functional traits types, and phylogenetic diversity (PD) could not be used as a simple proxy for taxonomic diversity (TD) in dryland regions of China
Our study found that environment and pure spatial factors could significantly influence TD, functional diversity (FD) and PD at both alpha and beta scales, implying that contemporary environment and spatial processes are two important drivers for these diversity facets (Blundo, González-Espinosa & Malizia, 2016; Liu, Tang & Fang, 2015)

Summary

Introduction

Understanding the fundamental processes that underlie biogeographic patterns of biodiversity has been a focus of biogeography and ecology (Gaston, 2000; Anderson et al, 2011). Niche theory emphasizes the importance of contemporary environment, such as abiotic (e.g., climate and soil attributes) and biotic factors (Chase & Leibold, 2003; Tang et al, 2012; Ulrich et al, 2014). It suggests that diversity patterns are largely determined by environmental filtering (Chesson, 2000; Chase & Leibold, 2003). The influence of spatial processes was highlighted by neutral theory. It is widely reported that both environmental and spatial factors could strongly influence plant diversity, yet no consensus has been reached on the relative contribution of niche and neutral processes to plant diversity across different geographic regions and scales (Steinitz et al, 2006; Legendre et al, 2009)

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Results

Discussion

Conclusion