Soil properties drive a negative correlation between species diversity and genetic diversity in a tropical seasonal rainforest.

Jie Li,Wumei Xu,Min Cao,Tianhua He,Qiaoming Li,Lu Liu,Yuehua Hu,Liqing Sha

doi:10.1038/srep20652

Abstract

A negative species-genetic diversity correlation (SGDC) could be predicted by the niche variation hypothesis, whereby an increase in species diversity within community reduces the genetic diversity of the co-occurring species because of the reduction in average niche breadth; alternatively, competition could reduce effective population size and therefore genetic diversity of the species within community. We tested these predictions within a 20 ha tropical forest dynamics plot (FDP) in the Xishuangbanna tropical seasonal rainforest. We established 15 plots within the FDP and investigated the soil properties, tree diversity, and genetic diversity of a common tree species Beilschmiedia roxburghiana within each plot. We observed a significant negative correlation between tree diversity and the genetic diversity of B. roxburghiana within the communities. Using structural equation modeling, we further determined that the inter-plot environmental characteristics (soil pH and phosphorus availability) directly affected tree diversity and that the tree diversity within the community determined the genetic diversity of B. roxburghiana. Increased soil pH and phosphorus availability might promote the coexistence of more tree species within community and reduce genetic diversity of B. roxburghiana for the reduced average niche breadth; alternatively, competition could reduce effective population size and therefore genetic diversity of B. roxburghiana within community.

Highlights

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A positive Species-genetic diversity correlations (SGDCs) was the typical result found in previous studies that examined the parallel effects of the environment on the two levels of diversity[4,5,7,15,19]; negative SGDCs are observed less often, and the drivers of negative SGDCs are rarely discussed in the literature on empirical studies[13]
A negative correlation was found between the tree diversity and the genetic diversity of B. roxburghiana (Fig. 1)

Summary

Introduction

Code P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 P15. B. roxburghiana and tree diversity within the plots, respectively. The relationships between the distributions of plants and soil properties have long attracted the interest of ecologists[24,25,26,27,28,29]; relatively little is known about the effect of soil properties on the genetic diversity of a population of a focal species. Research that addresses this gap in our understanding could provide new perspectives on the consequences of global ecological issues such as atmospheric nitrogen deposition and eutrophication on the biodiversity of diverse ecosystems. Our goal was to answer two fundamental questions: 1) Are the tree diversity of a community and the genetic diversity of a common tree species correlated? 2) What are the possible drivers of the SGDC pattern in these species-diverse communities?

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Conclusion