Rainfall and temperature variation does not explain arid species diversity in outback Australia

Lochran W Traill,¹ Thomas C Wanger,^2,3,4 Siobhan C de Little,¹ Barry W Brook<sup>1

1</sup>Environment Institute and School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA, Australia; ²Center for Conservation Biology, Department of Biology, Stanford University, CA, USA; ³Ecosystem Functions, Leuphana University Lüneburg, Lüneburg, Germany; ⁴Agroecology, Department of Crop Sciences, University of Göttingen, Göttingen, Germany

Abstract: Steps toward conserving biodiversity should start at understanding the components across spatial scales and a determination of the drivers of these. Here we determine additive species diversity for arid South Australia, based on over 50 years of survey data. Elevation and soil data were sourced through the Australian Government, and climate data from the WorldClim database. Alternative hypotheses relating the effect of climatic and environmental parameters to diversity were tested using generalized linear models and ranked according to information-theoretic statistics. Total species richness for the region was 1824, similar to all arid regions. α-diversity values were low, relative to the contributions made by β-diversity toward total γ-diversity, similar to additive diversity indices for nonarid biomes. There was a lack of statistical support for our hypothesis that regional spatial variation in arid region diversity can be explained by climate topography. Arid South Australian species diversity appears to be largely driven by environmental parameters at the localized scale – beyond the resolution of available survey data. Heterogeneity in habitat, provided by mountainous regions, likely contributes toward the high β-diversity values. Our research is the first application of the additive (not multiplicative) approach toward understanding diversity within arid Australia.

Keywords: additive diversity, arid biome, South Australia, generalized linear models, global climate models, species richness