Conclusion
This study highlights climate (rainfall and aridity), rather than life history and functional traits, as the key predictor of variation in drought tolerance (stem P50). Rainfall for species origin was the best predictor of hydraulic trait, explaining variation in stem P50, which appears to be a major determinant of species distribution. This study also indicates that stem P50 is an adaptive trait, genetically determined, and hence reliable and robust for predicting species vulnerability to climate change. This provides support for climate as a predictor of species suitability under climate change using species distribution models. Our results show that Hakea species in humid biomes are more vulnerable to future droughts compared to species in arid biomes. Alternative avoidance or recovery strategies may still be important for diverse flora to colonise and persist in the arid biome. We provide evidence for avoidance via terete leaves and enhanced HV, however the role of resprouting in recovery from drought was not supported. Findings from this study will provide the scientific basis for adaptive management strategies for Hakea , including conservation of threatened and widespread species through translocations and assisted migration respectively.
Acknowledgement : We appreciate the support of Benedict Lyte from The Australian Botanic Garden, Mount Annan for granting us excess to their collections and Nzie Peter for support in data collection and Rosana Lopez for technical insights into the hydraulic techniques. Australian Postgraduate Award (Western Sydney University), Ecological Society of Australia-Holsworth Wildlife Research Endowment grant to O.O.O and NSW Department for Planning, Industry and Environment, Saving Our Species grant to P.D.R and D.T.