FECUNDITY ALLOCATION IN HERBACEOUS PLANTS

The relationship between fecundity and plant size (fecundity allocation) was studied in twenty-one herbaceous species collected from natural populations. Within species, size/fecundity regressions were predominantly linear but the slopes often varied significantly among sites. Species varied widely in r2 and slope. Monocarpic species generally had greater r2 values and steeper slopes than polycarpic species, especially clonal perennials. The implications of variation in fecundity allocation among species are explored in terms of its role as a component of competitive ability (i.e. fitness under competition). For linear relationships, the role of fecundity allocation as a component of competitive ability is defined by both the slope and the X-intercept of the fecundity versus size regression. Their relative roles depend on the intensity of competition (i.e. the resource supply/demand ratio). We predict that a greater slope becomes more important in defining relative competitive abilities when plants are. allowed to get relatively large (under relatively weak competition or resource-rich conditions), whereas a smaller X-intercept becomes more important when plants are forced to be relatively small (under relatively intense competition or resource-impoverished conditions).