Ecophysiological and clonal traits associated with the invasive success of carpobrotus n.E.Br. (aizoaceae)Adaptive capacity and responses to climate change

Resumo

The invasive species Carpobrotus edulis (L.) N.E.Br. and Carpobrotus acinaciformis (L.) L.Bolus (Aizoaceae), are succulent perennial herbs native from South Africa. They were first planted as ornamental and for dune or soil stabilization purposes, and by the end of the 19th century naturalized populations were recorded elsewhere in Southern Europe. Both species, together with their potential “hybrid swarm” C. aff. acinaciformis, are prominent taxa that threat the native biodiversity of Mediterranean coastal ecosystems. To gain insights on how the recent introduction of these invasive species in NW of Spain has resulted in a rapid modification of invaded coastal communities, we have studied the invasive ecology of the taxa, including the analysis of several ecophysiological and clonal traits in order to evaluate their capacity for local adaptation and habitat colonization. We have also studied how the performance of C. edulis would be affected by the new climatic scenarios projected for the NW of Spain, in order to predict the potential of this species to spread into new areas. Finally, to explain its rapid adaptative processes in the introduced range, we have also examined if Northern Iberian invasive populations of C. edulis have diverged evolutionarily from those populations in the native territories. As general conclusions of the different researchers conducted and the bibliographical review of the genus Carpobrotus, we can highlight: 1) There is evidence of the occurrence in Europe of a new large “hybrid swarm”, referred as C. aff. acinaciformis in the scientific literature. In NW of Spain, C. edulis and C. aff. acinaciformis, besides differ phenotypically, also diverge in growth, functional traits, competitive ability and the extent of sexual reproduction in response to different soil conditions. 2) Although some morphological characters are useful for the identification of these taxa, misidentifications, hybridization potential and nomenclature ambiguity, both in native and invaded areas, raise doubts on the taxonomy of these species. Thereby a full review of the genus is required to elucidate this taxonomic conflict. 3) A high plasticity in morphological and ecophysiological traits allows C. edulis to adjust the morphology of their clonal growth organs and physiological responses to a wide range of ecological conditions. 4) Physiological integration and division of labor are attributes of clonal growth subjected to evolutionary adaptation during the invasion process of C. edulis, which may determine site-specific resource-sharing strategies in order to optimize its successful propagation and the survival chances in hostile habitats. 5) The review of the studies regarding the reproductive biology of the taxa indicates that besides an intense vegetative clonality, the ability of C. edulis to produce apomictic seeds, its self and cross-pollination, a large seed bank with a moderate short-term persistence, and the effective dispersal of seeds by mammals, represent an optimal strategy to facilitate local adaptation and habitat colonization. 6) C. edulis is likely to continue threatening biodiversity of coastal ecosystems due to its capacity to rapidly evolve locally adapted genotypes, and probably this species will increase its distribution range under the increased temperature and reduced rainfall predicted for our latitudes. 7) The significant differences observed in survival, growth, functional and clonal traits between Northern Iberian Peninsula and South African populations of C. edulis demonstrate that both groups of populations have diverged evolutionarily since they invaded the Iberian Peninsula. These findings are essential to predict their potential distributions and to design appropriate management strategies for conservation of coastal habitats.