Modeling species distributions from heterogeneous data for the Biogeographic Regionalization of the European Bryophyte Flora

摘要

The definition of biogeographic regions provides a fundamental framework for a range of basic and applied questions in\udbiogeography, evolutionary biology, systematics and conservation. Previous research suggested that environmental forcing\udresults in highly congruent regionalization patterns across taxa, but that the size and number of regions depends on the\uddispersal ability of the taxa considered. We produced a biogeographic regionalization of European bryophytes and\udhypothesized that (1) regions defined for bryophytes would differ from those defined for other taxa due to the highly\udspecific eco-physiology of the group and (2) their high dispersal ability would result in the resolution of few, large regions.\udSpecies distributions were recorded using 10,000 km2 MGRS pixels. Because of the lack of data across large portions of the\udarea, species distribution models employing macroclimatic variables as predictors were used to determine the potential\udcomposition of empty pixels. K-means clustering analyses of the pixels based on their potential species composition were\udemployed to define biogeographic regions. The optimal number of regions was determined by v-fold cross-validation and\udMoran’s I statistic. The spatial congruence of the regions identified from their potential bryophyte assemblages with largescale\udvegetation patterns is at odds with our primary hypothesis. This reinforces the notion that post-glacial migration\udpatterns might have been much more similar in bryophytes and vascular plants than previously thought. The substantially\udlower optimal number of clusters and the absence of nested patterns within the main biogeographic regions, as compared\udto identical analyses in vascular plants, support our second hypothesis. The modelling approach implemented here is,\udhowever, based on many assumptions that are discussed but can only be tested when additional data on species\uddistributions become available, highlighting the substantial importance of developing integrated mapping projects for all\udtaxa in key biogeographically areas of Europe, and the Mediterranean peninsulas in particular.