Distribution of Plant Species and Dispersal Traits along Environmental Gradients in Central Mediterranean Summits

High-mountain ecosystems are spots of plant diversity in which species composition and traits depict a long evolutionary history of species adaptation to steep environmental gradients. We investigated the main trends in plant species composition and reproductive and dispersal traits (pollen vector, diaspore appendages, dispersal of diaspores and fruit type) in central Mediterranean summits in relation to environmental factors (altitude, aspect, debris cover and slope). Based on 114 plots, with floristic and environmental data collected in the year 2016 on alpine calcareous grasslands in the central Apennines, we explored how species composition varies in relation to environmental factors using CCA (canonical correspondence analysis). Then, we analyzed the relationships among species presence, the occurrence of reproductive and dispersal traits and environmental variables. We used for this analysis the fourth-corner model approach. Our results highlight a consistent response of floristic composition and of structural and ecological characteristics to environmental gradients, with elevation and debris cover being the most important ones. The environmental characteristics of the analyzed ecosystems (e.g., steep slopes and harsh environments) combined with the persistence of perennial plant species already present in each stand, the high precision of pollination and the prevalence of short-distance dissemination strategies should allow the calcareous endemic plant communities of the analyzed Mediterranean summits to be conserved at least for a mid-term period slowing down the expansion of the warm-adapted species, less adapted to the local environmental constrains