Lianas in tropical dry forests have higher embolism resistance but similar hydraulic efficiency than lianas in rainforests

Lianas are increasing in relative abundance and biomass, mainly in seasonally dry forests, but it is unclear if this is associated with their hydraulic strategy. Here, we ask whether liana of seasonally dry forests are safer and more efficient in water transport than those of rainforest, which could explain liana distribution patterns and their recent increases. We measured hydraulic traits on five pairs of congeneric liana species (tribe Bignonieae) on one seasonal dry Atlantic forest and one Amazon rainforest. The predawn and minimum water potential, and the water potential at which 50% of the maximum gas amount was discharged were, on average, more negative in the liana species of the seasonal forest. However, these patterns were not constant at the genus level. The positive hydraulic safety margins and hydraulic efficiency were similar among species congeners across sites. The Bignonieae lianas studied likely experience equally low levels of embolism during drought, and maintain a high conductive capacity with efficient use of xylem space, which may favor survival and growth across tropical forests. The likely evolutionary convergence of high hydraulic safety associated with the opportunistic strategy of rapid growth, especially in disturbed areas can favor the abundant liana species in seasonal forests. HighlightTropical forest liana species have high hydraulic efficiency and high interspecific variability in hydraulic safety. Despite this variability, some seasonal forest liana species have greater hydraulic safety than rainforest lianas, indicating an evolutionary convergence across lineages.