Plasticidade fenotípica de Calotropis procera (Aiton) W.T.Aiton (Gentianales: Apocynaceae) como resposta a estresse e competição

Abstract

The phenotypic plasticity of invasive species is considered as a contributing factor to their successful invasion in different habitats, whether under favorable or unfavorable conditions. The plasticity of architecture and leaf traits in response to stress conditions, especially regarding height, number of leaves, leaf size, and dry mass, is an important characteristic that can partly explain why these species achieve success, as these traits can confer competitive advantages over native species. Thus, this study aimed to understand how an exotic species present in the state of Ceará responds to nutritional and wind stress, as well as competition, in two different relief features with presumed distinct soil, wind, and competitive conditions. We hypothesized that plants under wind and nutritional stress would have shorter height, smaller and more resistant leaves, a smaller number of leaves, and a lower proportion of live stems compared to those under less stress but more competition. Allometric (height, diamter and number of leaves) and leaves were collected from populations or invasion cores for subsequent laboratory analysis of leaf traits (leaf area, specific leaf area and leaf dry matter content) and statistical analysis. The results confirmed the expected patterns for some leaf traits but showed little overall investment by plants under nutritional and wind stress, suggesting a nutritional limitation for investing in more robust leaves. The relationship between height and diameter was consistent with expectations, but the proportion of live stem numbers was contrary to the hypothesis, which can be explained by a greater investment in rapid growth to cope with competition at the expense of branch robustness. Finally, the number of leaves was lower in more competitive areas, but this can be partly explained by the reduced load on longer and fragile branches and larger leaves compensating for reduced photosynthesis. Therefore, the stress and competition factors caused plastic responses in allometric parameters and leaf traits, which may be related to their success in invading different habitats. However, additional studies evaluating fitness associated with observed plasticity are necessary to provide more certainty to this assertion.