Asking the pikas politely…
Abstract Premise Leaves lose water in parallel between stomata and the cuticle. Plants regulate stomata to reduce leaf water loss in response to atmospheric demand. However, water may still be lost through leaky stomata and the cuticle, as measured by minimum leaf conductance ( g min ). We compared g min between co‐occurring diploid and triploid individuals of Populus tremuloides to determine whether ploidy, leaf traits, or microclimate explain variation in g min . We hypothesized that g min may increase with increasing ploidy because higher ploidy influences traits related to plant water loss, resulting in greater triploid water loss. Methods We measured g min in five leaves each of 32 aspen genets in Colorado. We also measured traits associated with plant water‐use and structure. We then assessed predictors of differences in g min , including ploidy level. Results Minimum leaf conductance differed by ploidy level, with higher g min in triploids than in diploids. Although leaf area and surface‐area‐to‐volume ratio were significant predictors of g min , neither variable accounted for the difference by ploidy level. Slope and aspect explained additional variation in g min , suggesting important microsite effects. However, ploidy level remained a significant predictor of g min across all models, indicating the effect on g min is robust and not due to covariation with structural traits and topography. Conclusions Triploids consistently had higher g min than diploids across models; accounting for structural traits and topography. Higher g min in triploids is consistent with hypothesized physical or genetic effects of a larger genome on leaf traits, resulting in differential drought vulnerability across ploidy levels.