Projected climate change implications for the South Australian flora testing title

Abstract

South Australia has warmed since 1950 and further temperature increases are forecast this century. We explore the implications of climatic warming for individual plant species and the State’s plant biodiversity, which is significant and includes 418 endemic taxa. Environmental constraints and interspecific interactions operate on species to determine which survive in which environment, with resulting compositional signatures. Climate change influences such ‘filtering’ processes via mechanisms such as altered mortality or recruitment rates and indirectly through fire regimes. While modest environmental changes can be absorbed within a given ecological community, significant change will eventually drive species turnover. We use the Hopbush, Dodonaea viscosa subsp. angustissima (DC.) J.G.West as a case study that shows morphological adaptations to arid conditions (narrower leaves and higher stomatal densities), observed in more northern populations in South Australia. Leaves of this species have narrowed through time in conjunction with climatic warming, matching predictions from the spatial cline. Genomic sequencing has also revealed genetic correlations with temperature and aridity, suggesting key climate change variables are impacting the selection of functional genes including those linked to leaf characters. Despite such adaptations in individual species, plant community composition is sensitive to small changes in climate. As a result, predicted climatic changes may ultimately drive complete species turnover, if the more severe scenarios are realised. Spatial analysis highlights a climatic transition zone, between desert and Mediterranean South Australia, where community composition changes more rapidly with climate and this area is therefore likely to be more vulnerable to climate change. Notwithstanding potential evolutionary adaptation, significant climate change will influence ecophysiology, leading to changes in primary productivity and water stress and is predicted to ultimately lead to lower species richness, altered species composition and more uneven abundances. Although we have an empirical understanding of climate sensitivity for South Australian plant communities, we need sophisticated ecological forecasting that considers complex interactions with fire, habitat configuration and evolutionary adaptation.