The South West Indian Ocean islands are an official hotspot of biodiversity and endemism (Myers et al., 2000). Among these islands, the Mascarenes consist of three main islands: La Reunion, Mauritius and Rodrigues. These islands differ in size, elevation profile, age, distance to the next larger land mass (Madagascar) and biodiversity. The Mascarenes are particularly rich in plants species, with about 1,300 vascular plants, of which 585 are endemics. Ferns form an important flora component in the very diverse biotas of the islands, especially in tropical forest. Most ferns disperse easily via their spores, allowing frequent colonization from Madagascar but also exchange among the Mascarene islands. We propose to perform an integrated phylogeographic study of selected groups of ferns with a view to elucidating the processes creating these islands diversity. To this end, we will integrate ecological data to explore the biotas of each island, population genetics, and cytological data to explore polyploidy. The study will also take into account the fern gametophytic phase, too often neglected in fern studies. We will particularly investigate the importance of apomixis. This study is expected to help identify characteristics that allow ferns to successfully colonize islands.