Clonal integration facilitates the colonization of drought environments by plant invaders

Biological invasion represents one of the main threats for biodiversity conservation at the global scale. Identifying the mechanisms underlying the process of biological invasions is a crucial objective in the prediction of scenarios of future invasions and the mitigation of their impacts. In this sense, some plant attributes might better explain the success of invasive plant species than others. Recently, clonal growth has been identified as an attribute that could contribute to the invasiveness of plants. In this experiment, we aim to determine the effect of physiological integration (one of the most striking attributes associated with clonal growth) in the performance (at morphological and physiological levels) of the aggressive invader Carpobrotus edulis, when occupying stressful environments. To achieve this objective we performed a greenhouse experiment in which apical ramets of C. edulis were water-stressed and the connection with the basal ramets was either left intact (physiological integration is allowed) or severed (physiological integration is impeded). Our results show that clonal integration allowed apical ramets to buffer drought stress in terms of photochemical activity, and as a consequence, to increase their growth in comparison with severed apical ramets. Interestingly, this increase in biomass was mainly due to the production of aboveground structures, increasing the spread along the soil surface, and consequently having important implications for the colonization success of new environments by this aggressive invader.