Résumé
This article documents the differentiation among populations for quantitative traits and for achene morph proportions in the heterocarpic species Crepis sancta (Asteraccae). The descendants of plants from three populations from northeastern France, two northwestern populations, and three southern populations were compared in a common garden experiment in the south of France. Phenological characters, such as age at reproduction, and some fitness-related traits (seedling size, fecundity of head) showed genetic differentiation among the three population groups that can be considered as an adaptive pattern. In contrast, there was no consistent difference among regions or populations in achene morph proportions. Developmental constraints occurring during the ontogeny of the capitulum lead to some allometric relationships between head traits. In particular, within a head, the number of peripheral achenes cannot be as variable as the number of central achenes. However, these constraints do not explain the reduced variation in achene morph proportions observed in C. sancta. Therefore, the reproductive system of C. sancta-insect pollinated and highly allogamous-should contribute to the observed patterns by constraining capitulum size. Finally, since achene morphs differ for their dispersal and competitive ability, this result could be related to the colonizing aptitude of the species.