Phylogenetic and biogeographic controls of plant nighttime stomatal conductance.

The widely documented phenomenon of nighttime stomatal conductance g could lead to substantial water loss with no carbon gain, and thus it remains unclear whether nighttime stomatal conductance confers a functional advantage. Given that studies of g have focused on controlled environments or small numbers of species in natural environments, a broad phylogenetic and biogeographic context could provide insights into potential adaptive benefits of g . We measured g on a diverse suite of species (n = 73) across various functional groups and climates-of-origin in a common garden to study the phylogenetic and biogeographic/climatic controls on g and further assessed the degree to which g co-varied with leaf functional traits and daytime gas-exchange rates. Closely related species were more similar in g than expected by chance. Herbaceous species had higher g than woody species. Species that typically grow in climates with lower mean annual precipitation - where the fitness cost of water loss should be the highest - generally had higher g . Our results reveal the highest g rates in species from environments where neighboring plants compete most strongly for water, suggesting a possible role for the competitive advantage of g .