Differentiation among populations for life history, morphology, head traits, and achene morph proportions in the heterocarpic species Crepis sancta (L.) bornm. (Asteraceae)

This article documents the differentiation among populations for quantitati ve traits and for achene morph proportions in the heterocarpic species Crep is sancta (Asteraccae). The descendants of plants from three populations fr om northeastern France, two northwestern populations, and three southern po pulations were compared in a common garden experiment in the south of Franc e. Phenological characters, such as age at reproduction, and some fitness-r elated traits (seedling size, fecundity of head) showed genetic differentia tion among the three population groups that can be considered as an adaptiv e pattern. In contrast, there was no consistent difference among regions or populations in achene morph proportions. Developmental constraints occurri ng during the ontogeny of the capitulum lead to some allometric relationshi ps between head traits. In particular, within a head, the number of periphe ral achenes cannot be as variable as the number of central achenes. However , these constraints do not explain the reduced variation in achene morph pr oportions observed in C. sancta. Therefore, the reproductive system of C. s ancta-insect pollinated and highly allogamous-should contribute to the obse rved patterns by constraining capitulum size. Finally, since achene morphs differ for their dispersal and competitive ability, this result could be re lated to the colonizing aptitude of the species.