Leaf hydraulic vulnerability influences species' bioclimatic limits in a diverse group of woody angiosperms

The ability of plants to maintain water flow through leaves under water stress-induced tension (assessed as the leaf hydraulic vulnerability; <i>P50</i>_leaf) is intimately linked with survival. We examined the significance of <i>P50</i>_leaf as an adaptive trait in influencing the dry-end distributional limits of cool temperate woody angiosperm species. We also examined differences in within-site variability in <i>P50</i>_leaf between two high-rainfall montane rainforest sites in Tasmania and Peru, respectively. A significant relationship between <i>P50</i>_leaf and the 5th percentile of mean annual rainfall across each species distribution was found in Tasmania, suggesting that <i>P50</i>_leaf influences species climatic limits. Furthermore, a strong correlation between <i>P50</i>_leaf and the minimum rainfall availability was found using five phylogenetically independent species pairs in wet and dry evergreen tree species, suggesting that rainfall is an important selective agent in the evolution of leaf hydraulic vulnerability. Greater within-site variability in <i>P50</i>_leaf was found among dominant montane rainforest species in Tasmania than in Peru and this result is discussed within the context of differences in spatial and temporal environmental heterogeneity and parochial historical ecology.