The ecophysiological responses of Copernicia prunifera palm trees to soil constraints and competition with invasive Cryptostegia madagascariensis in tropical dryland

Biological invasions have modified the terrestrial biota worldwide, reducing biodiversity, and causing economic loss. Copernicia prunifera (Carnauba), a palm tree native to the semi-arid region of Brazil (Caatinga ecosystem), has high economic and social importance, but has been impacted by the invasive climbing shrub Cryptostegia madagascariensis (Madagascar rubber vine). We evaluated physiological, biochemical, and nutritional responses in mature plants of both species in two locations: Catuana (where there is an intense water-deficit during the dry season) and Minguaú (where there is high salinity and sodicity, and excess water throughout the year). Our results show that competitive interaction between the two species is mainly defined by their adaptability to abiotic soil constraints. C. prunifera is better adapted to severe water-deficit conditions, but its ecophysiological performance is not sufficient to withstand invasion by C. madagascariensis . The invader is more competitive in flooded, salt-affected soils, and is not severely impacted even with high sodium accumulation in its leaves. Our results also show that the negative impacts on C. prunifera intensify at the final stage of infestation, when the shading caused by C. madagascariensis restricts access to solar radiation and accelerates leaf senescence. However, the impact on C. prunifera precedes the permanent shading, as evidenced by the inhibition of net assimilation of CO 2 under intermediate levels of infestation. These results reinforce the vulnerability of carnauba populations in the Caatinga ecosystem, which may be severely impacted without the development of technologies to mitigate the impact of invasion.