CONICET | Buscador de Institutos y Recursos Humanos

Background and Aims: Phenotypic plasticity and local adaption can contribute to the success of invasive species. While the former is an environmentally induced trait, the latter involves a selection process to filter the best genotype for a location. We examined the evidence for phenotypic plasticity and local adaptation for seed and seedling traits of the invasive tree Gleditsia triacanthos, with three origins distributed along ~10{degree sign} latitude gradient across three biomes. Methods: In subtropical forests, dry woodlands and secondary temperate grasslands in Argentina, we harvested seeds from clusters of neighbouring trees (i.e. families) distributed within 15-20 km in each origin (biome). We manipulated the environmental conditions relevant to each biome, assuming propagule availability did not represent an ecological barrier. In growth chambers, we evaluated seed imbibition and seed germination under different light, temperature and water potential. In a 2-yr common garden, we evaluated the impact of resident vegetation removal on seedling survival and growth. Key Results: Mean time to complete seed imbibition differed among origins; seeds from temperate grasslands reached full imbibition before seeds from dry woodlands and subtropical forests. Germination was always above 70 %, but differentially affected by water potential, light quantity (dark- light) and quality (red-far red) among origins, suggesting local adaptation. In the common garden, vegetation removal rather than origin negatively affected seedling survival and enhance seedling growth. Vegetation removal increased basal diameter, leaves per plant and spine number, and reduced height:basal diameter ratio. Conclusions: We conclude that local adaptation in seed germination traits and plastic changes in seedling allometry (e.g. heigh:diameter) may allow this tree to respond over the short and long term to changes in environmental conditions, and lastly contribute to shape G. triacanthos as a successful woody invader. Overall our study revealed how local adaptation and plasticity can explain different aspects of tree invasion capacity across biomes.