Disentangling the biogeographical origins of threatened species of the Macaronesian bryophythe flora

Abstract

Historical biogeographic knowledge of island colonization is unevenly spread across insular regions and taxonomic groups. While in the case of vascular plants, the biogeographical origins of a limited number of insular floras are relatively well known, there is still a long way to go to reach a similar knowledge for insular bryophyte floras. Most of this knowledge is highly concentrated in a few archipelagos distributed across the Northeastern Atlantic Ocean, a region known as Macaronesia. The Macaronesian bryophyte flora has been thus object of a number of publications focussing on phylogenetic and biogeographic aspects, but aspects such as the geographic origins of its bryophyte flora remains largely unknown. This contrast with the case of the Macaronesian angiosperm flora, for which there is mounting evidence that the main species pools are inferred to have been in the Mediterrean and northern regions in Europe. In the present Master Thesis, we implement an integrative biogeographical quantitative-approach in order to improve our understanding on the evolutionary origins and post-colonization diversification events of the Macaronesian bryophyte flora. Specifically, we target species groups that include threatened bryophyte taxa, which have been analysed in BEAST and BioGeoBEARS in order to estimate their colonization and divergence times and their ancestral areas, respectively. Our results support the role of the Macaronesian archipelagos as a crossroad for bryophyte species pools from different geographic origins, with a principal influence of Palearctic, Nearctic and Neotropical regions. The dating approach also provides preliminary evidence for the apparent predominance of neoendemic species in detriment of palaeoendemic species, which departs from previous hypotheses on the origins of the Macaronesian flora, in particular for species associated with the different types of the laurel forest. The implications of our findings for island plant conservation are discussed.