The present study aimed to investigate ecophysiological traits and water relations strategies that contribute to the faster expansion of invasive alien species, Lantana camara L. (Verbenaceae), compared to the native Adhatoda vasica Nees. (Acanthaceae). We measured physiological traits, i.e., stomatal conductance, photosynthetic rate, intracellular carbon dioxide concentration, transpiration rate, leaf temperature, morphological traits (i.e., specific leaf area, leaf area), biochemical traits (i.e., chlorophyll contents, leaf pH, and leaf carbon) and relative water content openly connected to three primary resources that strongly affect plant growth under varying light conditions (i.e., sun and shade). We also measured the twig water potential (& psi;) of plants under sun and shade during predawn and midday and developed the pressure-volume (PV) curve during the peak growing season. Lantana camara exhibited a higher capacity to adapt to semi-arid environmental conditions presenting lower water use efficiency and higher transpiration, photosynthetic rate, and stomatal conductance than native A. vasica. The leaf chlorophyll content of L. camara in the shade was higher than L. camara in the sun and A. vasica. The predawn (& psi;(pd) = - 0.80 & PLUSMN; 0.10 MPa) and mid-day twig water potential (- 2.25 & PLUSMN; 0.18 MPa) of L. camara sun plant were the lowest, followed by L. camara under the shade and A. vasica. The difference in the PV curve between the two species indicated that the tolerance range for L. camara was more than the A. vasica. The ability of drought-adaption of L. camera to adjust osmotic pressure, turgor pressure, and elasticity represents some of the key adaptations that helps L. camara as a successful invader in harsh environmental conditions.
