Functional traits determine why species belong to the dark diversity in a dry grassland fragmented landscape

A challenge for nature conservation is to know why many species are absent from suitable habitats and whether they might be able to disperse and to establish. Here, we used 272 dry grassland patches within a fragmented landscape to investigate the role of local abiotic conditions and dispersal filtering in determining the likelihood of vascular plants to belong to the dark diversity (i.e. absent portion of the species pool). First, we quantified the species (SD), functional (FD) and phylogenetic (PD) diversity of both observed and dark communities. Second, we determined the roles of abiotic, present-day and historical landscape configuration variables in shaping their patterns. Third, we evaluated the importance of each variable in determining their species compositions. Environmental filtering was assessed as effects of local abiotic conditions and dispersal filtering as the effects of present-day and historical landscape configuration. Dispersal filtering was also estimated by compari...