Global patterns and determinants of phylogenetic beta diversity among liverwort floras

AimInvestigating phylogenetic beta diversity, and its turnover and nestedness components, can shed light on the evolutionary causes shaping the similarity (or dissimilarity) in composition between biological assemblages. Liverworts are important constituents of most terrestrial ecosystems worldwide but studies on phylogenetic beta diversity in liverworts are scarce. Here, we explore geographic patterns of phylogenetic beta diversity and its two components in liverworts across the world and evaluate the relative importance of dispersal limitation and environmental filtering processes in shaping beta diversity patterns at different spatial extents by relating phylogenetic beta diversity or phylogenetic turnover to geographic and climatic distances.LocationGlobal.TaxonLiverworts.MethodsWe conducted correlation and regression analyses to relate phylogenetic beta diversity and its two components (turnover and nestedness) to six variables representing current climate conditions and two variables representing historical (Quaternary) climate change, and to geographic and climatic distances at different spatial extents (global, continental, and regional).ResultsWe found that of the eight variables of current and historical climates considered, precipitation seasonality was the strongest determinant of phylogenetic beta diversity in liverworts. At the global extent, geographic and climatic distances explained similar amounts of the variation in phylogenetic turnover, whereas at the continental extent, climatic distance explained more variation than geographic distance in five of the seven continents, and at a regional extent (roughly a circle of 4000 km in diameter), geographic distances generally had a greater effect than climatic distance on phylogenetic turnover.Main ConclusionsWe conclude that both dispersal limitation and environmental filtering played an important role in shaping phylogenetic structure of liverwort floras, but their relative importance varies at different spatial scales and among geographic regions.