Tomato yellow leaf curl virus (TYLCV) is one of the major constraints for tomato production in Mediterranean and tropical environments. TYLCV has spread worldwide and has shown strong patterns of evolution with the emergence of several recombinant variants. Understanding the evolution of ensuing viral complexes is one of the keys to control and to predict viral emergence. Islands are particularly well adapted for such study because of the limited migration of viruses, and thus their isolated evolution. In Reunion Island, after the introduction of the mild strain of TYLCV (TYLCV-Mld) in 1997, the Israel strain (TYLCV-IL) was first reported in 2004. This recent introduction into an agroecological niche largely occupied by the TYLCV-Mld, provides an ideal field experiment to analyse the successive invasions and competition of two strains of one of the most emergent phytovirus species. In this study, we performed a five years' survey (2004 to 2008) of the viral population implicated in the tomato yellow leaf curl disease on Réunion. TYLCV-IL was found to rapidly displace TYLCV-Mld. In 2008, TYLCV-Mld was only found in co-infections with TYLCV-IL. To understand the factors associated with this displacement, efficiency of transmission, virulence and fitness of both strains were measured.