According to the competitive exclusion principle, species with low competitive abilities should be excluded by more efficient competitors, and yet they generally remain as rare species. Here, we describe the positive and negative spatial association networks of 326 disparate assemblages, showing a general organization pattern that simultaneously supports the primacy of competition and the persistence of rare species. Abundant species monopolize negative associations in about 90% of the assemblages. Contrarily, rare species are mostly involved in positive associations, forming small network modules. Simulations suggest that positive interactions among rare species and microhabitat preferences are the most likely mechanisms underpinning this pattern and rare species persistence. The

One of the most valuable initiatives on massive availability of biodiversity data is the Global Biodiversity Information Facility, which is creating new opportunities to develop and test macroecological knowledge. However, the potential uses of these data are limited by the gaps and biases associated to large-scale distributional databases (the so-called Wallacean shortfall). Describing and quantifying these limitations are essential to improve knowledge on biodiversity, especially in poorly-studied groups, such as mosses. Here we assess the coverage of the publicly-available distributional information on Iberian mosses, defining its eventual biases and gaps. For this purpose, we compiled IberBryo v1.0, a database that comprises 82,582 records after processing and checking the geospatial and taxonomical information. Our results show the limitations of data and metadata of the publicly-available information. Particularly, ca. 42% of the records lacked collecting date information, which limits data usefulness for time coverage analyses and enlarges the existing knowledge gaps. Then we evaluated the overall coverage of several aspects of the spatial, temporal and environmental variability of the Iberian Peninsula. Through this assessment, we demonstrate that the publicly-available information on Iberian mosses presents significant biases. Inventory completeness is strongly conditioned by the recorders' survey bias, particularly in northern Portugal and eastern Spain and the spatial pattern of surveys is also biased towards mountains. Besides, the temporal pattern of survey effort intensifies from 1970 onwards, encompassing a progressive increase in the geographic coverage of the Iberian Peninsula. Although we just found 5% of well-surveyed cells of 30’ of resolution over the 1970-2018 period, they cover about a fifth of the main climatic gradients of the Iberian Peninsula, which provides a fair – though limited – coverage. Yet, the well-surveyed cells are biased towards anthropised areas and some of them are located in areas under intense land-use changes, mainly due to the wood-fires of the last decade. Despite the overall increase, we found a noticeable gap of information in the south-west of Iberia, the Ebro river basin and the inner plateaus. All these gaps and biases call for a careful use of the available distributional data of Iberian mosses for biogeographical and ecological modelling analysis. Further, our results highlight the necessity of incorporating several good practices to increase the coverage of high-quality information. These good practices include digitalisation of specimens and metadata information, improvement on the protocols to get accurate data and metadata or revisions of the vouchers and recorders' field notebooks. These procedures are essential to improve the quality and coverage of the data. Finally, we also encourage Iberian bryologists to establish a series of re-surveys of classical localities that would allow updating the information on the group, as well as to design their future surveys considering the most important information gaps on IberBryo.

Background We identified and classified damselfly (Zygoptera) and dragonfly (Anisoptera) metacommunities in Brazilian Amazonia, relating species distribution patterns to known biological gradients and biogeographical history. We expected a random distribution of both Zygoptera and Anisoptera within interfluves. At the Amazonian scale, we expected Anisoptera metacommunities to be randomly distributed due to their higher dispersal ability and large environmental tolerance. In contrast, we expected Zygoptera communities to exhibit a Clementsian pattern, limited by the large Amazonia rivers due to their low dispersal ability. Methods We used a dataset of 58 first-to-third order well-sampled streamlets in four Amazonian interfluves and applied an extension of the Elements of Metacommunity Structure (EMS) framework, in which we order Zygoptera and Anisoptera metacommunities by known spatial and biogeographic predictors. Results At the Amazonian scale, both Zygoptera and Anisoptera presented a Clementsian pattern, driven by the same environmental and biogeographical predictors, namely biogeographic region (interfluve), annual mean temperature, habitat integrity and annual precipitation. At the interfluve scale, results were less consistent and only partially support our hypothesis. Zygoptera metacommunities at Guiana and Anisoptera metacommunities at Tapajós were classified as random, suggesting that neutral processes gain importance at smaller spatial scales. Discussion Our findings were consistent with previous studies showing that environmental gradients and major rivers limit the distribution of Odonata communities, supporting that larger Amazonian rivers act as barriers for the dispersal of this group. In addition, the importance of habitat integrity indicates that intactness of riparian vegetation is an important filter shaping metacommunity structure of Amazonian stream Odonata.

Aim Nearly 40 different hypotheses have been put forward to explain the latitudinal diversity gradient, implying that geographical variations of biodiversity may be the result of a complex array of factors affecting organisms in different ways. Our main goal was to identify the most important drivers of local dung beetle species richness in the Neotropics. Location Neotropics. Taxon Dung Beetles (Coleoptera: Scarabaeinae). Methods We used a multi‐model approach to identify which potential drivers correlate better with the variations in local dung beetle species richness. We surveyed published literature on dung beetle communities to extract information on species richness, abundance, type of bait, type of habitat and sampling effort (as hours/pitfall) for different localities, discarding sites with low sampling effort. We used environmental variables to account for six possible explanations of species richness gradients: productivity, water–energy, ambient energy, habitat heterogeneity, resource heterogeneity and seasonality, as well as spatial data to account for other geographically structured phenomena. We used mixed models—with abundance, ecoregion and bait type as random factors—to select the best model among the variables accounting for each explanation. Finally, we used structural equation models to assess which explanations are associated with variations in dung beetle diversity and how they interact. Results Resource heterogeneity was the best single correlate of dung beetle richness. However, the best multiple model comprises three different explanations: productivity, resource heterogeneity and other spatially structured factors. Structural equation models show that abundance is directly (positively) associated with richness, followed by primary productivity and soil variables (a proxy for environmental heterogeneity), together with mammal richness, (a proxy for resource heterogeneity). Main conclusions Several explanations need to be considered to account for Scarabaeinae local richness patterns. The diversity of dung beetle communities correlates with the interaction of water–energy dynamics and heterogeneity in both resources and habitats. However, while heterogeneity variables are directly associated with richness, energy relates with it through abundance, and water through resource diversity.

Large Amazonian rivers may act as dispersal barriers for animals with low dispersal abilities, limiting their distribution to certain interfluves. Consequently, the distribution of these taxa would be less affected by macroclimatic gradients. Conversely, high‐dispersal taxa would be less constrained by large rivers and may track suitable climates. We evaluate whether Zygoptera and Anisoptera, two Odonata suborders with different dispersal abilities, show differences in distribution patterns across Amazonian interfluves. We further assess the relative importance of macroclimatic and habitat factors in their community assembly. We used network modularity analyses to identify biogeographic species pools and spatial buffers to define metacommunity species pools. Then, we used structural equation models to estimate the relative importance of multi‐scale factors on species richness patterns. Zygoptera communities are more similar in species composition within than between interfluves, suggesting that large Amazonian rivers indeed limit the distribution of Zygoptera species. Conversely, the distribution of Anisoptera extends across Amazonian interfluves. Seasonality has a strong positive effect on Zygoptera and Anisoptera richness across scales. In addition, habitat integrity is negatively correlated with the regional species richness and abundance of Anisoptera and positively correlated with Zygoptera local richness. The contrasting effects of habitat integrity on Anisoptera and Zygoptera suggest that the former is favored in open habitats, whereas the latter is so in forests. Despite these differences, both suborders appear to follow similar community assembly mechanisms in Amazonia, with a strong climatic control across scales and an effect of habitat filters on local communities.

Agricultural practices such as livestock grazing and tilling can result in soil erosion and runoff of fine sediments, nutrients (e.g. nitrogen, phosphorus, potassium) and pesticides, leading to degradation of aquatic environments. Urbanization is also responsible for a variety of impacts on fluvial ecosystems, including pollution by heavy metals, oil, domestic sewage and garbage. In this study, we evaluate the impact of land use on stream health of the Uberabinha river catchment. Overall, rural streams presented better ecological conditions than urban streams. Both species composition and abundance of benthic communities showed significant differences between rural and urban streams. Urban streams presented a higher dominance of Oligochaeta, Hirudinea and Gastropoda, bioindicators of poor water quality. Rural streams presented significantly greater richness and diversity. Compared to urban streams, rural streams presented a significantly higher number of Ephemeroptera, Plecoptera, Trichoptera, Odonata and Hemiptera taxa. Our analyses also showed congruence (high correlation) among the classical biodiversity metrics (Shannon-Wiener index -H', Pielou's measure of eveness -J) and monitoring parameters (% Ephemeroptera, Plecoptera and Trichoptera -EPT, Biological Monitoring Work Party -BMWP, bioindicator approach and Rapid Assessment Protocol -RAP, a habitatbased approach). Five from seven rural streams presented good water quality according to both BMWP and RAP and none of the urban streams presented good water quality. Our results show that the urban streams of Uberlândia municipality are poor ecosystems, and require improved management actions by environmental authorities. We also encourage that the riparian forest restoration and management carried out in the upper portion of Uberabinha River catchment to be extended to the urban area of the municipality.

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Spiders are ubiquitous in most vegetation, however very little empirical data are available on specific spider–plant interactions and their reciprocal outcomes. In the Brazilian Cerrado, the plant Mimosa setosa var. paludosa, (Fabaceae) has glandular trichomes in its leaves and stems, commonly entrapping insects (i.e. carrion) as well as hosting the lynx spider, Peucetia flava. We hypothesized that: (1) the damage inflicted by exophytic (leaves) and endophytic (seeds) herbivore insects that overcome the glandular trichomes is lower in plants where the lynx spider is present; and (2) the presence of this predator is positively related to food availability (live insects and/or carrion) and plant size. We performed field observations and an experimental field study in terms of the spider's presence versus absence on the Fabaceae plants. Our results showed that the proportion of damaged foliolules on the Fabaceae plants differed between the spiders‐present and spiders‐absent treatments, and that the absence of spiders led to a 3.3‐fold increase in the number of damaged foliolules. However, there was no significant difference in the proportion of seeds taken by endophytic herbivores from branches with and without spiders. We also found that the presence of Peucetia flava was positively related to the presence of entrapped carrion on plants, and that there was a positive and marginally significant effect of increasing abundance of the spiders on taller plants. The results of this study suggest that it is more common to find lynx spiders interacting with M. setosa var. paludosa in larger plants with higher carrion abundance (food source), and that P. flava and M. setosa var. paludosa interact in a facultative mutualism, in which plants provide entrapped carrion for spiders to feed on and possibly facilitate prey manipulation. In return, lynx spiders decrease the damage inflicted by exophytic, but not by endophytic herbivores. These results also contribute to a better understanding of which ecological factors may affect plant selection by lynx spiders and what the influence of this predator is on the structure of food webs in glandular plants.