Drought tolerance of Hakea species (Proteaceae) from a range of biomes
and life-histories predicted by climatic niche.
Extreme drought conditions across the globe are impacting biodiversity
with serious implications for the persistence of native species.
However, quantitative data on drought tolerance is not available for
diverse flora to inform conservation management. We quantified
physiological drought tolerance in the diverse Hakea genus (Proteaceae)
to test predictions based on climatic-origin, life history and
functional traits. We sampled terminal branches of replicate plants of
16 species in a common garden. Xylem cavitation was induced in branches
under varying water potential (tension) in a centrifuge and the tension
generating 50% loss of conductivity (stem P50) was characterized as a
metric for drought tolerance. The same branches were used to estimate
plant functional traits, including wood density, specific leaf area, and
Huber value (sap flow area to leaf area ratio). There was significant
variation in stem P50 among species, which was negatively associated
with the species climate-origin (rainfall and aridity). Drought
tolerance did not differ among life histories; however, a drought
avoidance strategy with terete leaf form and greater Huber value may be
important for species to colonize and persist in the arid biome. Our
findings will contribute to future prediction of species vulnerability
to drought and adaptive management under climate change.