Reproductive success (fruit set) and seed production (seed number and size) were analyzed in 15 populations of P. coronopus along the Atlantic East coast, from Morrocco to the European northern countries, covering the practical totality of the species latitudinal range. The spatial aggregation and distribution of seedlings relative to reproductive plants were examined at some contrasted populations, to test if the differences among populations in the production of each type of seed (with opposite dispersal capacities) entail differences in the spatial population structures. Variables like soil organic matter content and pH, and average precipitation, were used to characterize local environment in populations.
Results/Conclusions Fruit set was very high and did not differ among populations. Two groups of populations emerged, however, when fruits were further analyzed. One group contains most southern populations, located at dry places with poor soils, and the other consists of most northern populations, characterized by more water availability. Reproductive plants in the first group produce fewer seeds per fruit, lower proportion of small seeds, and heavier large seeds (in relation to small ones), than in the second group. The spatial pattern of seedlings did not correlate with the differential production of both types of seeds in populations.
A trade-off in number, type and size of seeds was found in this species, probably as a way to maximize seed production at each local environment. Soil properties, together with abundance and regularity in precipitation, stand out among the possible factors associated to the observed pattern. Despite clearly contrasted dipersal potential in P. coronopus seeds, other factors than dispersal could be more important in shaping quantitative and qualitative components of fecundity fitness along species latitudinal gradient.
