ALBERT

Description: Abstract Questions Despite the increasing scientific interest in distance decay of compositional similarity in ecology, the scale‐dependence of geographical vs environmental control on distance decay of biological communities has not been properly addressed so far. The present work highlights the relative importance of niche‐based processes vs dispersal limitations on distance decay patterns of epilithic bryophyte assemblages at different spatial scales. Location Serra de Sintra, central Portugal. Methods We adopted a nested sampling design with 32 selected sampling sites in each of which two clusters, each with five rocks, were surveyed. Each cluster was characterized by a set of 15 macro‐scale variables, which were divided into environmental and anthropogenic. For each rock eight micro‐scale variables were recorded. Partial Mantel tests were used to assess the relative importance of geographical and environmental distance on community dissimilarity for each grain size (site, cluster, rock). Quantile regressions were used to describe the decay patterns of community similarity with respect to geographical and environmental distances. Ordination analyses and variation partitioning techniques were applied to assess the pure and shared effects of measured variables on bryophyte community composition. Results Environmental distance based upon macro‐scale predictors was significantly correlated to community similarity, while no significant correlation was found for ecological distance calculated for micro‐scale predictors, except at the largest grain size. The decrease of community similarity with geographical and environmental distance was thus consistently strengthened with increasing sample grain. Compositional variation was best explained by anthropogenic variables. Conclusions The relative importance of environmental vs geographical distance on compositional similarity in epilithic bryophyte communities varies with the spatial scale of the predictors and with the sample grain. The decrease of similarity with increasing distance is related to changes in habitat features, especially those driven by human disturbance, while is weakly affected by variations in substrate features. This article is protected by copyright. All rights reserved.

Description: Abstract Questions 1) Are there differences in abundance‐weighted functional trait values between native and alien species in coastal plant communities? 2) Which functional traits are associated with a higher level of invasion in these communities? 3) Do functional diversity patterns differ between native and alien species? 4) Is alien species occurrence linked to small‐scale functional homogenization effects on the resident native species?. Location N‐Adriatic coastal ecosystems (Marano and Grado lagoon, Friuli Venezia Giulia region, Italy) Methods We sampled coastal vegetation within two habitats (foredunes and saltmarshes) along 9 belt transects in two sampling sites. Plant species richness and abundance were assessed in 128 plots along with a suite of plant functional traits. We tested for differences in CWMs between native and alien species within the two habitats, and a Linear Mixed Model (LMMs) provided insights on traits fostering the invasion success among alien species. To check for potential functional homogenization driven by alien species invasion, we explored functional diversity patterns of native and alien species (β and γ functional diversity) and the relationship between α functional diversity and alien cover. Results Alien species had lower functional diversity than natives and were characterized by lower leaf construction costs coupled with lower drought resistance and higher water transport efficiency. The most abundant aliens were the ones minimizing carbon investment for leaf construction. In addition, we also found evidence for small‐scale functional homogenization driven by alien invasion. Conclusions Our results suggested that native species adopt a resource conservative strategy whereas alien species are characterized by a higher resource acquisition capacity (i.e. acquisitive strategy). Our data also confirmed that alien species are less functionally diverse than natives, potentially driving the community towards small‐scale functional homogenization, resulting in a loss of species and a reduction in the functional space.