Estrutura taxonômica, funcional e filogenética de metacomunidades de anuros do extremo sul do Brasil

Abstract

[Capítulo 1:] 1. We evaluated seasonal variation in taxonomic, functional and phylogenetic diversity and redundancy of tadpoles present in 401 points of 10 ponds in southern Brazil. We predicted i) congruent patterns between all components of diversity and environmental descriptors; ii) higher effects of descriptors in the three components in seasons with high hydric stress; iii) all components would be influenced by different sets of environmental descriptors in each season. Predictions were tested using Linear Mixed Models. 2. Taxonomic, functional but mainly the phylogenetic diversity, responded similarly to water depth during the low hydric stress period. This also was observed for functional redundancy. This influence was positive for all components of diversity. Phylogenetic redundancy was not explained by any of environmental descriptors. In the period of higher hydric stress components of diversity were not significantly affected by environmental descriptors. 3. Environmental filtering seems to strongly influence tadpole community structure in temporary ponds, at least during the winter. Water depth gradients create a variety of micro-habitat conditions allowing diverse sets of species to settle and co-occur in ponds. These sets are then filtered according to their swimming and foraging abilities along the depth gradient, where intermediate depths should contain the greatest tadpole diversity. [Capítulo 2:] Anurans exhibit limited dispersion ability and have physiological and behavioural characteristics that narrow their relationships with both environmental and spatial predictors. So, the relative contributions of environmental and spatial predictors in the patterns of taxonomic and functional anuran beta diversity were examined in a metacommunity of 33 ponds along the coast of south Brazil.. We expected that neutral processes and, in particular, niche-based processes could have similar influence on the taxonomic and functional beta diversity patterns. Distance-based methods (db-RDA) with variation partitioning were conducted with abundance data to examine taxonomic and functional facets and components (total, turnover and nestedness) in relation to environmental and spatial predictors. Processes determining metacommunity structure differed between the components of beta diversity and among taxonomic and functional diversity. While taxonomic beta diversity was further accounted by both environmental and spatial predictors, functional beta diversity responded more strongly to spatial predictors. These two contrasting patterns were different to what we had predicted, suggesting that while there is a taxonomic turnover mediated by environmental filters, the spatial distance promotes the trait dissimilarity between sites. In addition, our data confirm that neutral and niche-based processes operate on anuran metacommunities even at short geographic scales. Our results reinforce the idea that studies aiming to evaluate the patterns of structure in metacommunities should include different facets of diversity so that better interpretations can be achieved. [Capítulo 3:] Trait variation across environmental gradients results from two processes: intraspecific variation (ITV) and turnover. Tadpoles are known to exhibit phenotypic plasticity in several traits in response to the environment, resulting from intra or interspecific variation. Here we evaluate patterns of intraspecific variation in functional traits of adult anurans (head shape, eye size and position, limb length and body mass) and their relationship with environmental variables in an anuran metacommunity in southern Brazil. From anurans sampled from 33 ponds, we decomposed trait variation into ITV and turnover and modelled trait-environment relationships. We predict that the contribution of ITV and turnover to trait variation and trait-environment relationships should vary according to the preferred habitat of the species and the analysed traits. Intraspecific variation accumulated the highest rate of trait variation for arboreal species, while interspecific variation was greater for aquatic-terrestrial species and for the whole set of species. The contributions of turnover and ITV to shifts in community mean trait values were similar between traits, but differed between species sets. Depth, distance between ponds, area of Pinus surrounding the ponds, and types of pond vegetation and substrate strongly influenced trait variation, but their relative contribution depended on the analysed traits and species sets. The great contribution of ITV for head shape and eye size and position suggests the existence of intraspecific adaptations to microhabitats, while turnover dominance in the variation of body mass and limb length suggests differences in dispersal and trophic segregation between species. [Capítulo 4:] Amphibians represent a significant part of the biomass of aquatic systems contributing to several ecosystem services in these environments. Amphibian populations are undergoing global-scale declines due to the increased incidence anthropogenic stressors. The loss of anuran species with unique evolutionary histories and functional traits poses a serious risk to the maintenance of ecosystem functions in aquatic environments already directly affected by several anthropogenic land-use changes. Here we investigate the influence of ecological variables, including anthropogenic, local environmental and spatial factors on functional, phylogenetic and taxonomic composition of anuran assemblages from a metacommunity of 33 ponds in southern Brazil. We expect the relative influence of ecological predictors to vary according to the compositional facet. We also expect stronger influence of spatial predictors on functional composition, while anthropogenic and environmental predictors should affect mostly phylogenetic and taxonomic compositions. To evaluate this we used redundancy analyses with partition variance (pRDA) for each of the compositional facets evaluated – functional, phylogenetic, and taxonomic and for each type of ecological factor – anthropogenic, local environmental and spatial. Although the sets of selected ecological predictors were similar for the three compositional facets, ecological predictors explained varying degrees of variation in functional, phylogenetic and taxonomic compositions. These varying patterns may result from different responses of species with distinct functional traits and belonging to distinct evolutionary clades. Anuran functional structure fits mostly the pattern predicted by the neutral theory of metacommunities, phylogenetic structure the species sorting paradigm, and taxonomic structuring the pattern predicted by the mass effects model. Our results suggest that the distinct metacommunity paradigms may concurrently explain different facets of anuran assemblage structuring and that the effects of different sets 272 of ecological predictors should be considered when designing management plans for anuran assemblages of subtropical ponds.