André Andrian Padial

Dispersal Ability Determines the Role of Environmental, Spatial and Temporal Drivers of Metacommunity Structure

Recently, community ecologists are focusing on the relative importance of local environmental factors and proxies to dispersal limitation to explain spatial variation in community structure. Albeit less explored, temporal processes may also be important in explaining species composition variation in metacommunities occupying dynamic systems. We aimed to evaluate the relative role of environmental, spatial and temporal variables on the metacommunity structure of different organism groups in the Upper Paraná River floodplain (Brazil). We used data on macrophytes, fish, benthic macroinvertebrates, zooplankton, periphyton, and phytoplankton collected in up to 36 habitats during a total of eight sampling campaigns over two years. According to variation partitioning results, the importance of predictors varied among biological groups. Spatial predictors were particularly important for organisms with comparatively lower dispersal ability, such as aquatic macrophytes and fish. On the other hand, environmental predictors were particularly important for organisms with high dispersal ability, such as microalgae, indicating the importance of species sorting processes in shaping the community structure of these organisms. The importance of watercourse distances increased when spatial variables were the main predictors of metacommunity structure. The contribution of temporal predictors was low. Our results emphasize the strength of a trait-based analysis and of better defining spatial variables. More importantly, they supported the view that “all-or- nothing” interpretations on the mechanisms structuring metacommunities are rather the exception than the rule.

Homogenization dynamics of the fish assemblages in Neotropical reservoirs: comparing the roles of introduced species and their vectors

Non-native species introduced into reservoirs cause major changes in biodiversity, resulting in spatial and temporal biotic homogenization and/or differentiation. We used a sampling standardized temporally and spatially in reservoirs of basins located in the Neotropics, the Coastal, Iguaçu, and Upper Paraná basins. Our analyses were conducted at the interbasin and intrabasin scales, aimed at: (i) identifying the non-native species and their major vectors of introductions, (ii) assessing temporal and spatial changes in the fish assemblages, and (iii) evaluating temporal changes in the beta diversity of the basins/reservoirs. The spatial occupation of non-native species was variable, with Tilapiarendalli, Cyprinus carpio and Oreochromis niloticus the most frequently introduced species. This highlights aquaculture as the main vector of invasives on a large spatial scale. The percentage of non-native species at the interbasin and intrabasin scales increased over time. Temporal comparisons of the fishes support the hypothesis that biotic homogenization occurred at the interbasin scale, whereas the biotic differentiation was observed at the intrabasin scale. Beta diversity decreased over time at the interbasin and intrabasin scales, with decrease in species richness serving as the variable that best explained changes in biological diversity. There was no relation between beta diversity and time for the Iguaçu.

Nutrient enrichment is related to two facets of beta diversity for stream invertebrates across the United States.

Beta diversity, the spatial or temporal variability of species composition, is a key concept in community ecology. However, our ability to predict the relative importance of the main drivers of beta diversity (e.g., environmental heterogeneity, dispersal limitation, and environmental productivity) remains limited. Using a comprehensive data set on stream invertebrate assemblages across the continental United States, we found a hump-shaped relationship between beta diversity and within-ecoregion nutrient concentrations. Within-ecoregion compositional dissimilarity matrices were mainly related to environmental distances in most of the 30 ecoregions analyzed, suggesting a stronger role for species-sorting than for spatial processes. The strength of these relationships varied considerably among ecoregions, but they were unrelated to within-ecoregion environmental heterogeneity or spatial extent. Instead, we detected a negative correlation between the strength of species sorting and nutrient concentrations. We suggest that eutrophication is a major mechanism disassembling invertebrate assemblages in streams at a continental scale.

Floods decrease zooplankton beta diversity and environmental heterogeneity in an Amazonian floodplain system

Floods are major determinants of ecological patterns and processes in river-floodplain systems. Although some general predictions of the effects of water level changes on ecological attributes have been identified, specific tests using the flood pulse concept are scarce, mainly in tropical areas, where large river-floodplain systems abound. We tested the hypothesis that floods decrease environmental and biological variability using data from a near-pristine floodplain in Central Amazon (Brazil). We recorded nine limnological variables and the zooplankton community structure at eleven sites during one low and one high water period. During the low water period, when the levels of hydrological connectivity were low, asynchronous processes (e.g., sediment disturbance by biota, decomposition, and predation) likely determined the large environmental and biological heterogeneity in the floodplain. On the other hand, environmental variability and zooplankton beta diversity were significantly decreased by the flood. We postulate that floods act as “rubber erasers”, reducing the environmental and ecological idiosyncrasies created during low water periods. Also, we suggest that dilution effects and enhanced connectivity during the high water period, along with species sorting during the low water period, may determine zooplankton beta diversity patterns in river-floodplain systems.

Removing the abyss between conservation science and policy decisions in Brazil

The executive and legislative branches of Brazilian government have either proposed or taken a variety of initiatives that threaten biodiversity and ecosystems. Opposition by the scientific community has largely been ignored by decision-makers. In this short essay, we present recent examples of harmful policies that have great potential to erode biodiversity, and we suggest ways to communicate scientific knowledge to decision- makers. If the current gap between conservation science and policies is not filled, the country will threaten the maintenance of its natural capital and, consequently, the sustainability of essential societal activities in the long term.

The “Tilapia Law” encouraging non-native fish threatens Amazonian River basins

Freshwater ecosystems in Brazil, arguably the most diverse on the planet, have been disturbed by several threats in the past years, particularly competition for water and subsequent water abstraction, urbanization, severe drought, dam construction/water diversion, pollution from different sources, commercial exploitation, and the introduction of non-native species (Agostinho et al. 2005; Vitule et al. 2015; Lima et al. 2015; Winemiller et al. 2016). A worrying example is the federal law 5989/2009 that intends to naturalize non-native fish species by decree in Brazil, some of which have a high invasion potential, such as the carps Aristichthys nobilis, Ctenopharyngodon idella, Cyprinus carpio, Hypophthalmichthys molitrix and tilapias Oreochromis spp. (Lima et al. 2012; Vitule

We need better understanding about functional diversity and vulnerability of tropical freshwater fishes

Here we extend a discussion initiated by Toussaint et al. (Sci Rep 6:22125, 2016) concerning the relationship between global patterns of freshwater fish functional diversity (FD) and its vulnerability to human impacts. Based on a set of morphological traits, they concluded that Neotropical freshwater fishes have highest FD, but low vulnerability given high levels of functional redundancy. This conclusion implies that conservation efforts for freshwater fishes should emphasize temperate regions. This perspective is risky, because Toussaint et al.’s study seriously underestimates the full scope of FD, including important ecosystem services provided by fishes in the tropics. We briefly discuss some additional and well-documented aspects of tropical freshwater fish FD and conclude that tropical fish FD is highly vulnerable.

Human-Induced Landscape Changes Homogenize Atlantic Forest Bird Assemblages through Nested Species Loss.

The increasing number of quantitative assessments of homogenization using citizen science data is particularly important in the Neotropics, given its high biodiversity and ecological peculiarity, and whose communities may react differently to landscape changes. We looked for evidence of taxonomic homogenization in terrestrial birds by investigating patterns of beta diversity along a gradient of human-altered landscapes (HAL), trying to identify species associated with this process. We analyzed bird data from 87 sites sampled in a citizen science program in the south Brazilian Atlantic Forest. Regional-scale taxonomic homogenization was assessed by comparing beta diversity among sites in different HALs (natural, rural or urban landscapes) accounting for variation derived from geographical distance and zoogeographical affinities by georeferencing sites and determining their position in a phytogeographical domain. Beta diversity was calculated by multivariate dispersion and by testing compositional changes due to turnover and nestedness among HALs and phytogeographical domains. Finally, we assessed which species were typical for each group using indicator species analysis. Bird homogenization was indicated by decreases in beta diversity following landscape changes. Beta diversity of rural sites was roughly half that of natural habitats, while urban sites held less than 10% of the natural areas’ beta diversity. Species composition analysis revealed that the turnover component was important in differentiating sites depending on HAL and phytogeography; the nestedness component was important among HALs, where directional species loss is maintained even considering effects of sampling effort. A similar result was obtained among phytogeographical domains, indicating nested-pattern dissimilarity among compositions of overlapping communities. As expected, a few native generalists and non-native urban specialists were characteristic of rural and urban sites. We generated strong evidence that taxonomic homogenization occurs in the south Brazilian Atlantic Forest as a result of a directional and nested species loss, with the resultant assemblages composed of few disturbance-tolerant birds.

The strength of species sorting of phytoplankton communities is temporally variable in subtropical reservoirs

Recent studies have found that the relative importance of predictors of metacommunity structure is dependent on different factors. Low explanatory power of multivariate models is a frequent result. To increase this power, ecologists have suggested different strategies, including the use of functional approaches. Using a phytoplankton dataset from 17 reservoirs in Southern Brazil, sampled seasonally over eight years, we tested the hypothesis that the explanatory power of multivariate models would be higher when the analyses were based on functional groups than when based on a taxonomic approach. We also modeled the temporal variation in the strength of species sorting (as given by the adjusted coefficient of determination derived from environmental variables). We found high temporal variability in the strength of species sorting, indicating that results from snapshot surveys should be interpreted cautiously. When compared to the taxonomic approach, we did not find an increase in the explanatory power of multivariate models when the analyses were based on a functional approach. The main correlates of the temporal variation in the strength of species sorting were insolation, water temperature, and environmental heterogeneity, suggesting that conditions related to productivity and heterogeneity are important in determining the role of species sorting in phytoplankton communities.

ESTRUTURA DO COMPONENTE DE REGENERAÇÃO NATURAL E ARBÓREO DE DOIS MANGUEZAIS NO ESTADO DO PARANÁ

We analyzed the structures of two mangrove forests of Parana (Brazil) (Antonina Bay and Guaratuba Bay), considering adult trees and regeneration component. In each area, we marked three sub-areas and sampled five plots of 10 x 10 m, equivalent to 0.05 ha to adults trees and fifteen 1 x 1m sub-plots to assess the regeneration component. Avicennia schaueriana, Rhizophora mangle and Laguncularia racemosa exhibited distinct dominance and relative density between the areas. Mangroves of Antonina and Guaratuba differed both in the structure of natural regeneration as the tree component. The Principal Coordinates Analysis (PCoA) show that differences between areas in relation to abiotic variables of soil are strongly related to the structural parameters of trees. The different types of mangrove soil are the most significant factor in the differentiation between the mangrove areas since influences the salinity values ​​and consequent adaptability of plants.