Twenty-eight legume species (14% Caesalpinieae, 29% Mimosoideae, and 57% Papilionoideae) were found growing actively in the wetlands and riversides of Guadeloupe. Only 11% of the checked species appeared not to be nodulated after repeated investigation in the field, and all belong to the Caesalpinieae tribe. The legume distribution brings out the importance of this family in the wetlands in terms of abundance of legume trees and shrubs. In wet meadows, herb and liana legumes have low cover and species richness, allowing the Poaceae to dominate. Of the 19 species of trees and shrubs, 17 have shown efficient N-fixing symbiosis in natural conditions. N-fixing legume predominance seems to be a biotic characteristic that recurs in perennial plant communities of flooded habitats. Efficient N-fixing symbiosis under flood conditions is achieved through various nodulation strategies including (i) waterlogging tolerance with aquatic nodules associated with aerenchymateous tissue, (ii) seasonal avoidance brought about by short-lived determinate nodules, and (iii) spatial stress avoidance with aerial nodules developing on root, plank buttress or stem.