THE ALLOMETRY OF SEED PRODUCTION IN HERBACEOUS ANGIOSPERMS

The number of seeds produced per ramet of 285 ramets of 57 species of herbaceous angiosperms in 1 yr was regressed on aboveground vegetative weight and average individual seed weight, as well as on categorical variables indicating minimum time to reproduction, growth form, occurrence in disturbed habitats, and phylogeny. Seed number per ramet (N(s)) was weakly correlated to average seed weight (W(a), r2 = 0.36) and to vegetative ramet weight (W(v), r2 = 0.38), but a combination of these two variables accounted for 81% of the variance in seed number. The allometric equation was N(s) = 1.4 W(v)0.93W(a)-0.78. The main source of variation was interspecific. The nonphylogenetic categorical variables accounted for little of the residual variance, with occurrence in disturbed habitats being the most important. This indicates that most of the variation in seed output among plants of different habitats or successional status is due to size-related effects.