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Aim Our aim was to determine the relative contribution of species replacement and richness differences to overall beta diversity in Macaronesian spiders, the influence of several biogeographical drivers in shaping such dissimilarity patterns, and how these change according to the dispersal ability of spiders. Location Four Macaronesian archipelagos: the Azores, Madeira, Selvagens and the Canary Islands. Methods Each spider species was assigned to a group relative to its ballooning propensity (frequent, occasional or rare), used as a surrogate of dispersal ability, based on its family membership. Beta diversity was decomposed for each group, by disentangling all compositional differences (overall beta diversity, βtotal) into two components, species replacement (βrepl) and species richness differences (βrich). The effects of island area, environmental heterogeneity, geological age, distance to mainland and inter-island distances on βrepl and βrich were tested by partial Mantel tests and hierarchical partitioning of variation for each mobility group. Results The archipelagos studied had similar intra-archipelagic richness differences, but species replacement was lower within the Azores for the three groups of spiders. The variation in community composition among the archipelagos was determined by species replacement for frequently ballooning spiders, while richness differences dominated for less mobile spiders. Island area was more important for species with higher mobility, while less mobile species were mostly affected by the distance to mainland and inter-island distances. Environmental heterogeneity had an effect, mostly on richness differences, across the three spider groups. Time had only a weak effect on species replacement for less mobile species. Main conclusions The partition of βtotal into βrepl and βrich identified different causes of beta-diversity patterns as driven by the dispersal ability of spiders. Dispersal-limited species responded more strongly to isolation than more mobile species. In contrast, the latter were influenced more by island area. Thus our findings emphasize the importance of interspecific traits and dispersal limitation for structuring species assemblages on islands. [ABSTRACT FROM AUTHOR]

Aim To propose a unified framework for quantifying taxon ( Tβ), phylogenetic ( Pβ) and functional ( Fβ) beta diversity via pairwise comparisons of communities, which allows these types of beta diversity to be partitioned into ecologically meaningful additive components. Location Global, with case studies in Europe and the Azores archipelago. Methods Using trees as a common representation for taxon, phylogenetic and functional diversity, we partition total beta diversity (βtotal) into its replacement (turnover, βrepl) and richness difference (βrich) components according to which part of a global tree was shared by or unique to communities that were being compared. We demonstrate the application of this framework using artificial and empirical examples (mammals in Europe and epigean arthropods in the Azores). Results Our empirical examples show that comparing Pβ and Fβ with the most commonly used Tβ revealed previously hidden patterns of beta diversity. More importantly, we demonstrate that partitioning Pβtotal and Fβtotal into their respective βrepl and βrich components facilitates the detection of more complex patterns than using the overall coefficients alone, further elucidating the different forces operating in community assembly. Main conclusions The methods presented here allow the integration and full comparison of Tβ, Pβ and Fβ. They provide a tool for effectively disentangling the replacement (turnover) and richness difference components of the different biodiversity facets within the same methodological framework. [ABSTRACT FROM AUTHOR]