Environmental heterogeneity–species richness relationships from a global perspective

Anke Stein

doi:10.21425/f57427952

Abstract

Spatial environmental heterogeneity (EH) is considered one of the most important factors promoting species richness, but no general consent about the EH–richness relationship exists so far. This is because research methods and study settings vary widely, and because non-significant and negative associations have also been reported. My thesis provides a comprehensive review of the different measurements and terminologies of EH used in the literature, and presents strong quantitative evidence of a generally positive relationship between biotic and abiotic EH and species richness of terrestrial plants and animals from landscape to global extents. In a meta-analysis and a subsequent case study comparing multiple EH measures and their association with mammal species richness worldwide, I furthermore reveal that the outcome of EH–richness studies depends strongly on study design, including both the EH measure chosen and spatial scale. My research contributes to a better understanding of the EH–richness relationship, while identifying future research needs.

Highlights

Introduction and MethodsSpatial environmental heterogeneity (EH) has fascinated researchers from ecology, biogeography, conservation biology, and evolutionary biology for decades, and is considered one of the most important factors determining species richness (Tews et al 2004, Field et al 2009)
I revealed how heterogeneous and ambiguous the quantification and terminology of EH have been in past research: I identified 165 different EH measures, with even more measure variants, related to biotic EH in land cover and vegetation, and abiotic EH in climate, soil and topography
An important finding was that spatial grain, spatial extent and the use of equal-area study units clearly influenced the strength of EH– richness relationships, at least for the data subset including measures related to land cover types and elevation

Summary

Introduction

Introduction and MethodsSpatial environmental heterogeneity (EH) has fascinated researchers from ecology, biogeography, conservation biology, and evolutionary biology for decades, and is considered one of the most important factors determining species richness (Tews et al 2004, Field et al 2009). EH has been quantified with regard to vegetation structure, plant diversity, topographical complexity and habitat diversity, and with many different measures based on indices, ranges and other calculation methods. The variability in EH–richness research hampers attempts to find and compare studies and limits our understanding of the general EH– richness relationship.

Results

Conclusion