Spatial Patterns of Species Diversity and Phylogenetic Structure of Plant Communities in the Tianshan Mountains, Arid Central Asia.

Hong-Xiang Zhang,Ming-Li Zhang

doi:10.3389/fpls.2017.02134

Abstract

The Tianshan Mountains, located in arid Central Asia, have a humid climate and are biodiversity hotspots. Here, we aimed to clarify whether the pattern of species diversity and the phylogenetic structure of plant communities is affected by environmental variables and glacial refugia. In this study, plant community assemblies of 17 research sites with a total of 35 sample plots were investigated at the grassland/woodland boundaries on the Tianshan Mountains. Community phylogeny of these plant communities was constructed based on two plant DNA barcode regions. The indices of phylogenetic diversity and phylogenetic community structure were calculated for these sample plots. We first estimated the correlation coefficients between species richness (SR) and environmental variables as well as the presence of glacial refugia. We then mapped the significant values of indices of community phylogeny (PD, RPD, NRI, and NTI) to investigate the correlation between community phylogeny and environmental structure or macrozones in the study area. The results showed that a significantly higher value of SR was obtained for the refugial groups than for the colonizing groups (P < 0.05); presence of refugia and environmental variables were highly correlated to the pattern of variation in SR. Indices of community phylogeny were not significantly different between refugial and colonizing regions. Comparison with the humid western part showed that plant communities in the arid eastern part of the Tianshan Mountains tended to display more significant phylogenetic overdispersion. The variation tendency of the PhyloSor index showed that the increase in macro-geographical and environmental distance did not influence obvious phylogenetic dissimilarities between different sample plots. In conclusion, glacial refugia and environmental factors profoundly influenced the pattern of SR, but community phylogenetic structure was not affected by glacial refugia among different plant communities on the Tianshan Mountains. This pattern of community phylogenetic structure could have resulted from shared ancestry and species pool among these sample plots.

Highlights

How species assemble in communities is a fundamental question in ecology and biogeography
For the three indices of phylogenetic community structure, the significantly high relative phylogenetic diversity (RPD) values occurred at the research sites of HTB, MNS, SHZ, and NLK (Figure 4, Table 1); the significant negative values of net relatedness index (NRI) and nearest taxon index (NTI) were shown at the research sites of FK, QT, and WLMQ (Figure 4, Table 1)
Species composition of sample plots showed that glacial refugial regions preserved significantly higher species richness (SR) than colonizing regions (Figure 2) on the Tianshan Mountains of arid Central Asia

Summary

Introduction

How species assemble in communities is a fundamental question in ecology and biogeography. Patterns of community assembly usually vary along temporal and spatial gradients (Freestone and Inouye, 2015), but underlying mechanisms of this variation are not clarified yet. A growing number of ecological and evolutionary hypotheses attempt to address this question. Community phylogenetics, which incorporates phylogenetic information into community ecology, provides an evolutionary framework for investigating community assembly (Webb et al, 2002). Based on the hypotheses on phylogenetic niche conservatism (Crisp and Cook, 2012), species with close phylogenetic relationships should have more similar ecological requirements than distantly related species. Habitat filtering and biotic interactions influence community phylogenies, while biogeographical and ecological processes influence the patterns of community assembly associated with temporal and spatial changes of the environment

Objectives

Methods

Results

Conclusion