Does light modulate the success of the invasive species Cryptostegia madagascariensis Bojer ex Decne. over native species in the early stages of growth?

Invasive climbing plants are among the most aggressive groups in tropical ecosystems, largely due to their high competitive capacity, which is still poorly understood in the early stages of growth. In this study, we investigated the effects of interactions between the invasive Cryptostegia madagascariensis and two native species from Northeast Brazil, Cenostigma bracteosum and Piptadenia retusa, during initial establishment under two light conditions. We conducted experiments on intra- and interspecific competition, varying the combinations of species while maintaining a density of two plants per pot and including a control treatment (single plants), under two light conditions (full sun and 50% shade). Native species showed productivity declines of more than 30% when competing with the invasive species in the brighter environment. Intraspecific competition, observed only in C. madagascariensis , reduced the productivity of this species by 30% in the shade. C. madagascariensis maintained high productivity and relative dominance under both light conditions, although its competitive effects on native species were stronger under full sunlight. Under shade, the invasive species showed greater height and SLA, consistent with a morphological response to reduced light availability. These results indicate that light availability modulates competitive outcomes during early establishment and that disturbed, well-lit sites may be especially susceptible to invasion by C. madagascariensis.