Résumé
Invaders have often been said to display traits that favor colonisation (r-traits). However, while these traits may allow a species to reach empty habitats before other species do, they are usually associated with low competitive ability. More competitive species, even if they have lower colonisation ability, may prevent the permanent installation of an r-selected invader. Competition rather than colonisation may therefore limit invasion. The best situations to test this hypothesis are "invasive series", when successive invasions by related taxa occur in the same place. Phylogenetic proximity of the taxa and common environment ensure that trade-offs between colonization- and competition-oriented traits can be detected. We expect biological traits to change from colonisation-oriented to increasingly competition-oriented strategies along the invasive series. This prediction was tested using two different model systems, both of which invade tropical insular habitats: freshwater snails of the Thiaridae family in Martinique and Tephritid flies in La Réunion. In both systems, in consistency with our hypothesis, the first invaders were relatively r-selected, and were later replaced by new genotypes and/or taxa with increasingly lower fecundity and higher investment per offspring. (Résumé d'auteur)