Landscape pattern and plant biodiversity in Mediterranean coastal dune ecosystems: Do habitat loss and fragmentation really matter?

Aim: Habitat fragmentation and loss are two of the most important factors drivingcurrent biodiversity decline. Nonetheless, the relationship between biodiversity andlandscape patterns appears more complex than generally expected, depending onthe species and communities involved. We aim to enrich knowledge concerning therelationship between plant diversity and landscape patterns along linear landscapes,such as Mediterranean coastal dunes. A dedicated buffering method consideringmultiple nested extents was developed for sampling linear landscapes (e.g. coastalor fluvial), which traditionally present a challenge for standard round or square sam-pling buffering approaches.Location: Tyrrhenian coast of central Italy.Methods: Based on a database of plant community plots and functional traits fromfield measurements, for each plot we calculated taxonomic (TD) and functional (FD)diversity, which was further decomposed in functional evenness (FDeven) and meantrait dispersion (FDdisp). Relying on a land-cover map, we computed a set of land-scape metrics describing habitat loss, fragmentation and direct human disturbanceat multiple extents around each plot. Diversity measures (TD, FD, FDevenand FDdisp)were then related to the landscape metrics at different scales via linear mixed-effectmodels.Results: Overall, the relationship between plant species diversity and landscape pat-terns was weak. We observed different responses of TD, FD, FDevenand FDdisp,which only emerged at fine-medium scales. TD decreased with habitat loss and dis-turbance, while FD only with disturbance. FDevendecreased in more fragmentedareas, while FDdispwas not affected by the selected landscape parameters.Main conclusions: Like other transitional areas, coastal strand and dune ecosystemsexhibit steep gradients in biotic and environmental factors, are dynamic in location,and could be among the earliest to be affected by environmental drivers. However,the response of Mediterranean coastal dune plant diversity to habitat loss and frag-mentation is weak. For these reasons, we propose that these plant communities areadapted to the ever-changing nature of the coastal environment and consequentlyto changes in landscape pattern.