Reproductive allometry in Pedicularis species changes with elevation

1. Plants produce biomass and then allocate some of it to reproductive structures, so the relation-ship between reproductive (R) and vegetative (V) mass is a fundamental aspect of a plant’s repro-ductive strategy. 2. Differences among populations or taxa in the allometric relationship betweenR and V have been attributed to environmental conditions. We hypothesize that populations and taxa living at high elevations should exhibit a lower log R vs. log V slope than those in more benign environments, because the environmental limits on size in alpine environments should favour a relatively large reproductive allocation at smaller sizes and a smaller investment in reproduction per additional unit of biomass accumulated. 3. We investigated variation in the allometric relationship between R and V among 44 naturally occurring populations representing 24 species of Pedicularis in the Tibetan Plateau, to test the hypothesis that the slope of the relationship declines with increasing elevation. 4. There was a significant negative relationship between the slope of the log R vs. log V relationship and elevation among populations, although the relationship among populations within species var-ied. We interpret this in terms of abiotic limitations on size and decreasing efficiency of resourc