Leaf trait divergence between Azadirachta indica (exotic) and native species of the northern Brazilian coast

The introduction of exotic plants can pose ecological threats as they may become invasive. We investigated leaf traits potentially linked to competitive advantage and invasiveness in Azadirachta indica, a widely used exotic tree in northeastern Brazil's urban forestry, compared to native species Ouratea fieldingiana and Myrcia multiflora. We tested the limiting similarity hypothesis, evaluating how leaf characteristics influence the ecological responses of these species and A. indica's potential invasiveness. A. indica exhibited larger leaf area, specific leaf area (SLA), and leaf area ratio (LAR) compared to native species, but lower specific petiole length (SPL) and specific internode length (SIL). Additionally, A. indica displayed greater phenotypic variation in these traits. The larger leaf area, SLA, and LAR suggest a strategy in A. indica favoring rapid carbon gain through increased growth. The higher phenotypic variation observed may facilitate adaptation to new habitats, potentially enhancing its competitive ability and invasiveness. These findings highlight distinct functional strategies between exotic and native species, raising concerns regarding the potential invasiveness of A. indica in northeastern Brazil's natural ecosystems.