Leaf habit affects the distribution of drought sensitivity but not water transport efficiency in the tropics

Considering the global intensification of aridity in tropical biomes due
to climate change, we need to understand what shapes the distribution of
drought sensitivity in tropical plants. We conducted a pantropical data
synthesis representing 1117 species to test whether xylem-specific
hydraulic conductivity (KS), water potential at leaf turgor loss (ΨTLP),
and water potential at 50% loss of KS (ΨP50) varied along climate
gradients. The ΨTLP and ΨP50 increased with climatic moisture only for
evergreen species, but KS did not. Species with high ΨTLP and ΨP50 values
were associated with both dry and wet environments. However,
drought-deciduous species showed high ΨTLP and ΨP50 values regardless of
water availability whereas evergreen species only in wet environments. All
three traits showed a weak phylogenetic signal and a short half-life.
These results suggest that environmental controls on trait variance, which
in turn is modulated by leaf habit along climatic moisture gradients in
the tropics.