Natural variation of fecundity components in a widespread plant with dimorphic seeds

The number and size of seeds are the basis of the quantity and quality components of female reproductive fitness in plants, playing a central role in the evolutionary ecology of life history diversification. In this study we show and analyze the natural variability of several fecundity variables (fruit set, seed production per fruit, seed size, total seed production per plant, and proportion of small seeds) in Plantago coronopus, a widespread, short-lived herb with dimorphic seeds. The structure of such variability was examined at the individual, population (eight locations with different environments within the same region), and life history levels (annual vs perennial), and correlated to soil fertility. There was no divergence associated to the life history for any of the variables studied. Total seed production (the quantity component of female fitness) was correlated with maternal resources, while the size of the large mucilaginous, basal seeds, and the proportion of the small apical seeds (quality component) were more associated to environmental resources. Thus, internal and external resources shape different fitness components, maximizing seed production, and fitting the size and proportion of different kind of seeds to local conditions irrespective of life history. P. coronopus illustrates the versatility of short-lived widespread plants to combine fecundity traits in a flexible manner, in order to increase fitness at each of the many possible habitats they occupy over heterogeneous environments.