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.