Effects of resource sharing directionality on physiologically integrated clones of the invasive Carpobrotus edulis

Abstract

Aims: One of the key traits associated with clonal growth in plants is the capacity for physiological integration, which allows resource sharing between connected ramets within a clonal system. Resource transport is expected to occur following a source-sink relationship: from ramets established in rich patches to ramets growing in poor patches. However, some experiments have shown that acropetal transport (from basal to apical modules) usually exceeds basipetal transport (from apical to basal ramets). In this study, we aimed to determine the resource transport directionality in physiologically integrated modules of the invader Carpobrotus edulis. Methods: We conducted two manipulative experiments under common garden conditions that studied the effect of different nutrient levels located at different positions (basal, medial and apical) on connected and disconnected clonal systems of C. edulis. We compared the biomass partitioning patterns and final biomass of ramets to elucidate whether the effect of physiological integration is affected by the directionality of the resource transport. Important Findings: Results indicate a prevalent acropetal transport of resources in C. edulis, with a developmentally programmed division of labor where basal ramets were specialized in obtaining soil-based resources and apical ramets specialized in aboveground growth. This biomass partitioning pattern was not affected by the nutrient conditions in which basal or apical ramets were growing, although the highest benefit was achieved by apical ramets growing under the most stressed conditions. This developmentally programmed division of labor is expected to increase the lateral growth of C. edulis, and therefore could have meaningful implications for the expansion of this invasive species.