A comparison of the moss flora of the Mascarenes

Based upon recent checklists, the moss floras of the Mascarenes (Seychelles, Réunion, Mauritius) is compared. The diversity of species varies much amongst the islands and is lowest in the Seychelles (110 species) but highest in Réunion (366 species), whereas Mauritius has 246 species. Interestingly the young volcanic islands Réunion and Mauritius have much higher species numbers as the Seychelles which were part of the Gondwana continent. The richness of mosses in Réunion is due to the higher altitude (3069m), higher rainfall and the better state of conservation (30% of surface consist of intact forest), whereas the maximum altitude of the other islands hardly exceeds 800 m and most forests are destroyed. The moss flora of the islands have only few species on common and are thus almost not related. All islands have only 33 species in common. The Seychelles, which are situated about 1900 km from Réunion and Mauritius, share only 42 viz. 49 species with the latter. Réunion and Mauritius, which are 170 km away, share only 107 species. This indicates that the factor chance played an important role in the colonization of the islands. Insofar the term “Mascarenes” is a geographical but not a floristic one. The Mascarenes were mainly colonized by species from Africa and Madagascar, but also from SE-Asia und the austral region. The main floristic element is African, which is in contrast to the prevailing trade winds and might indicate that the colonization at least of the young volcanic islands happened during a different wind system in the past