Resource-sharing strategies in ecotypes of the invasive clonal plant Carpobrotus edulis: specialization for abundance or scarcity of resources

Aims Carpobrotus edulis (L.) N.E.Br. is known to invade many coastal ecosystems around the world, and it has been considered as one of the most severe threats to numerous terrestrial plant communities. Therefore, the study of the relationships between life-history traits that may favour its invasiveness and the invasibility of the environments is necessary to improve our knowledge about invasion success. In this research, we specifically tested the effects of physiological integration in genotypes from contrasting habitats, where the importance of integration is expected to differ. Thus, the main objective of this work was to detect the presence of adaptive plasticity in the capacity for clonal integration in this aggressive invader. Methods In a greenhouse experiment, we compared the performance, in terms of growth and photochemical efficiency, of two C. edulis ecotypes. Connected and severed ramet pairs from coastal sand dunes and rocky coast habitats were grown in substrates of different quality and heterogeneity. Important Findings Our study clearly indicates that clonal integration improves growth and photosynthetic efficiency in the aggressive invader C. edulis. Two different aspects of clonal integration determine site-specific strategies in this species in order to optimize its successful propagation in a particular habitat. We demonstrated that the adaptation of C. edulis to local environments has led to a differential selection of two complex clonal traits associated with the capacity for clonal integration. In patchy sand dunes, C. edulis has evolved ecotypes with ramets highly plastic in patterns of biomass allocation, which allows ramets to specialize in the acquisition of the resource that is locally most abundant, i.e., a spatial division of labour among ramets. However, in the harsher rocky coast habitats, local adaptation produced highly integrated ecotypes, where resource sharing is not combined with a specialization of resource acquisition.