Genetic diversity of the macaronesian leafy liverwort Porella canariensis inferred from RAPD markers

Plant colonization of the North Atlantic raises the intriguing question of the relationships between extant island species with their continental coun terparts (European, African, and American), which may provide clues to past geographic distribution and colonization history. It has been suggested th at during past glaciations, many plant species with typical Mediterranean d istributions survived in the Atlantic islands that belong to what is today known as Macronesia. We used random amplified polymorphic DNA (RAPD) marker s to study 12 populations of the liverwort Porella canariensis partly cover ing its present-day distribution (Azores, Madeira, Canary and Cape Verde Is lands, and Iberian Peninsula). Unweighted pair-group (UPGMA) and principal component (PCO) analyses showed a similar geographical pattern that suggest ed a close relationship between Iberian populations and those from the Cana ries and Cape Verde Islands. Populations from Madeira had more genetic vari ation than those from the Azores, a result from either a richer diversity o f habitats in Madeira, which prompted more population diversification, succ essive colonization waves from different origins, or an older colonization of Madeira. The data show that continuous patches of liverworts are often c omprised of more than one individual. Finally, RAPDs can be used to investi gate intraspecific diversity within a comparatively large geographic area a nd, with utmost care, can be used to infer a historic context to explain th e patterns observed.