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The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted by insect group, latitude, spatial extent, altitudinal range, and dataset properties across multiple drainage basins throughout the world. Second, we assessed the relative roles of environmental and spatial factors in driving variation in assemblage composition within each drainage basin. Our analyses were based on a dataset of 95 stream insect metacommunities from 31 drainage basins distributed around the world. We used dissimilarity‐based indices to quantify beta diversity for each metacommunity and, subsequently, regressed beta diversity on insect group, latitude, spatial extent, altitudinal range, and dataset properties (e.g., number of sites and percentage of presences). Within each metacommunity, we used a combination of spatial eigenfunction analyses and partial redundancy analysis to partition variation in assemblage structure into environmental, shared, spatial, and unexplained fractions. We found that dataset properties were more important predictors of beta diversity than ecological and geographical factors across multiple drainage basins. In the within‐basin analyses, environmental and spatial variables were generally poor predictors of variation in assemblage composition. Our results revealed deviation from general biodiversity patterns because beta diversity did not show the expected decreasing trend with latitude. Our results also call for reconsideration of just how predictable stream assemblages are along ecological gradients, with implications for environmental assessment and conservation decisions. Our findings may also be applicable to other dynamic systems where predictability is low. Beta diversity should vary along major ecological gradients. We used data for 95 stream insect metacommunities to examine if beta diversity showed general patterns over the world. We did not find clear patterns along latitudinal, altitudinal or environmental gradients, suggesting that stochasticity typical of frequently‐disturbed stream ecosystems may hinder finding clear patterns in stream insect beta diversity.

We evaluated the beta diversity patterns of aquatic macroinvertebrate assemblages at two spatial scales in streams in the Eastern Amazon, as well as tested whether environmental and spatial factors affected these assemblage patterns differently for non-flying (i.e., shrimps) and flying (i.e., insects) macroinvertebrate groups. Fifteen streams were sampled, focusing on two hierarchical spatial levels: sampling units (length: five meters) and stream sites (length: 150 m). We additively partitioned gamma diversity to test the relative importance of each spatial level to regional diversity. The total beta diversity at each spatial level was decomposed into the components of replacement and abundance difference. To test whether there was an effect of spatial distances and environmental variables on the dissimilarity matrices, we used multiple regression on distance matrices (MRM). Our results showed that: (1) In both macroinvertebrate groups, alpha diversity contributed less than beta diversity, and dissimilarity between stream sites presented a greater contribution to gamma diversity; (2) the decomposition of beta diversity showed similar patterns in both groups and between the two spatial levels, with a greater contribution of abundance difference than replacement; and (3) the MRM models showed that only environmental distance was important to explain beta diversity of insects, while for shrimps both environmental and spatial distances were significant. We conclude that different ecological processes and environmental variables were important to explain the distributions of insects and shrimps, which is probably related to the different dispersal modes and environmental niche requirements.

Taxonomic richness is one of the most important measures of biological diversity in ecological studies, including those with stream macroinvertebrates. However, it is impractical to measure the true richness of any site directly by sampling. Our objective was to evaluate the effect of sampling effort on estimates of macroinvertebrate family and Ephemeroptera, Plecoptera, and Trichoptera (EPT) genera richness at two scales: basin and stream site. In addition, we tried to determine which environmental factors at the site scale most influenced the amount of sampling effort needed. We sampled 39 sites in the Cerrado biome (neotropical savanna). In each site, we obtained 11 equidistant samples of the benthic assemblage and multiple physical habitat measurements. The observed basin-scale richness achieved a consistent estimation from Chao 1, Jack 1, and Jack 2 richness estimators. However, at the site scale, there was a constant increase in the observed number of taxa with increased number of samples. Models that best explained the slope of site-scale sampling curves (representing the necessity of greater sampling effort) included metrics that describe habitat heterogeneity, habitat structure, anthropogenic disturbance, and water quality, for both macroinvertebrate family and EPT genera richness. Our results demonstrate the importance of considering basin- and site-scale sampling effort in ecological surveys and that taxa accumulation curves and richness estimators are good tools for assessing sampling efficiency. The physical habitat explained a significant amount of the sampling effort needed. Therefore, future studies should explore the possible implications of physical habitat characteristics when developing sampling objectives, study designs, and calculating the needed sampling effort.

Chalcopteryx rutilans Rambur, 1842 (Polythoridae, Odonata) is a species widely distributed in central Amazonia. Due to its sensitivity to environmental changes, it is a bioindicator species used to evaluate the environmental conditions of streams in federally protected areas. By sequencing C. rutilans mitogenome, we report the first whole mitogenome from the Polythoridae family and the first from an Odonata species endemic to South America. The entire mitogenome has 15,653 bp and contains 13 protein-coding, 22 tRNA, and two rRNA genes. The nucleotide composition of the mitogenome is 42.7%, T: 25.5%, C: 19.4%, and G: 12.4%. The AT and GC skews of the mitogenome sequence were 0.249 and −0.220, respectively. C. rutilans was recovered as a sister to Pseudolestes mirabilis Kirby, 1900 (Pseudolestidae), demonstrating the absence of mitogenomes of species from multiple families in the current literature. Mitogenome data from this study will provide useful information for further studies on the phylogeny and conservation of Polythoridae.

Abstract Atypical drought events have increasingly occurred in Brazil over the last years due to global climate changes. However, their consequences on aquatic biota in reservoirs are poorly known. We tested the hypothesis that macroinvertebrate communities are negatively affected by atypical drought events, given the sensitivity of many taxa to environmental changes. We predicted that: (a) there would be changes in limnological and sediment parameters between a regular year and an atypical year, (b) abundance and richness of the genera of Chironomidae and of exotic species would be higher due to the enhanced ability of these organisms to adapt to changes in the physical environment, and (c) community structure metrics (i. richness; ii. % richness; iii. abundance; iv. % abundance) would be affected by disturbance indices (i. Buffer Disturbance Index-BDI; ii. Local Disturbance Index-LDI; iii. Integrated Disturbance Index-IDI) in both years. The study was carried out in the reservoir of the Nova Ponte Hydroelectric Power Plant, state of Minas Gerais, comparing two sampling periods: a regular climatological year (2010) and an atypical drought year (2014). A total of 40 sampling sites were defined along the shore of the reservoir, and types of land use in the surrounding area of each site were measured, as well as physical habitat conditions, sediments, and benthic macroinvertebrate communities. Sampling was performed at these sites in the end of the rainy season in both years. The intensity of anthropogenic modifications was assessed at local scale and in the areas (buffers) surrounding the sampling sites using quantitative disturbance indices. There were striking differences in limnological parameters and sediment characteristics between sampling periods. Taxonomic richness was significantly lower in the drought year. As opposed to our predictions, richness and abundance of Chironomidae and exotic species did not increase with the atypical drought event. Besides, most community structure metrics showed a significant relationship with disturbance indices only during the regular climatological year, thus indicating that the large-scale effects of water stress may override the conditions of local habitats and the surrounding landscape. Therefore, in addition to a correct political-environmental management of water resources at local-scale, which includes maintaining the water quality and the riparian and landscape integrity, addressing large-scale climate issues is required for the maintenance of the ecological integrity of tropical reservoirs. Resumo A ocorrência de episódios atípicos de seca vem crescendo nos últimos anos no Brasil em decorrência de mudanças globais no clima. Entretanto, as consequências disso para a biota aquática são ainda pouco conhecidas. Testamos a hipótese de que comunidades de macroinvertebrados são negativamente afetadas por eventos de seca atípica, dada a sensibilidade de muitos taxa às alterações ambientais. Nossas predições foram que (a) parâmetros limnológicos e características de sedimento seriam alterados em um ano de seca atípica, (b) encontraríamos maior abundância e riqueza de gêneros de Chironomidae e de espécies exóticas dada à alta capacidade destes organismos de adaptarem-se às mudanças no ambiente, (c) métricas de estrutura de comunidade (i. riqueza; ii. % riqueza; iii. abundância e iv. % abundância) seriam afetadas por índices de distúrbio (i. Índice de Distúrbio no Buffer-IDB; ii. Índice de Distúrbio Local-IDL e iii. Índice de Distúrbio Integrado-IDI) em ambos os anos. O estudo foi realizado no reservatório da Usina Hidrelétrica de Nova Ponte, Minas Gerais, comparando dois períodos amostrais: um ano climatológico normal (2010) e um ano de seca atípica (2014). Foram definidos 40 sítios amostrais na região litorânea do reservatório onde foram mensurados os tipos de usos do solo no entorno, condições de habitats físicos, características limnológicas na coluna d'água, sedimento e comunidades de macroinvertebrados bentônicos. A intensidade de alterações antrópicas foi avaliada em escala local e no entorno dos pontos amostrais (buffers) por meio de índices de distúrbio. Observamos diferenças expressivas nos parâmetros limnológicos e nas características dos sedimentos entre os dois períodos amostrais. A riqueza taxonômica foi significativamente menor no ano de seca. Ao contrário do esperado, os valores de riqueza e abundância de Chironomidae e de espécies exóticas não aumentaram com o evento extremo de seca. Paralelamente, a maioria das métricas de estrutura de comunidade apresentou relação significativa com os índices de distúrbio somente durante o ano climatológico normal, indicando que os efeitos de estresse hídrico em larga escala podem se sobrepor às condições locais de habitat e de paisagem circundante. Portanto, deve ser considerada não só a correta gestão político-ambiental de recursos hídricos em escala local, que inclui a manutenção da qualidade da água e da integridade da região ripária e uso do solo da região de entorno, mas também abordar questões climáticas em larga escala faz-se necessário para a manutenção da integridade ecológica em reservatórios tropicais.

Hyphessobrycon heterorhabdus (Ulrey, 1894), popularly known as ‘Flag Tetra’ in English speaking countries, belongs to the genus Hyphessobrycon of the family Characidae, and is widely present in the eastern Amazon basin. Here, using Illumina sequencing, we report the complete mitogenome sequence of H. heterorhabdus. Overall, the mitogenome has 17,021 bp, containing 13 protein-coding, 22 tRNA, and 2 rRNA genes. Non-ambiguous nucleotide compositions of the H. heterorhabdus mitogenome are A: 29.2%, T: 29.4%, G: 15.6%, and C: 25.8%. As recently indicated, the phylogenetic analyses did not support four separate genera (Hemigrammus, Hyphessobrycon, Moenkhausia, and Psalidodon) of Characidae. Understanding the H. heterorhabdus mitogenome is important for taxonomic purposes as well as for the molecular characterization of environmental pollutants. Thus, the mitogenome described here will be a valuable resource for studies on environmental changes, evolutionary genetics, species delimitation, and phylogenetic analyses in Characidae.

The Amazon forests are under threat from multiple human land uses, but the effect of the different types of land uses on environmental heterogeneity and the α- and β-diversity of aquatic insects remains unclear. We studied how habitat features of streams and aquatic insect diversity in the orders Ephemeroptera, Plecoptera, and Trichoptera (hereafter, EPT) responded to different land uses in the Brazilian Amazon. By sampling and analyzing EPT community data from 83 streams distributed in multiple land uses and land covers, we found that the impact of forest conversion was mixed. Despite contiguous and fragmented forest streams presenting similar environmental conditions, they differed in insect diversity metrics. α-diversity was highest in contiguous forest streams and EPT β-diversity was higher in streams surrounded by livestock farming and primary oil palm plantations. The association between land use and habitat degradation may not be so direct, mainly when streams are inserted into or surrounded by forest fragments. This has important implications because politicians and policymakers often regard forest fragments as degraded landscapes, to justify their conversion to other land uses. Our study shows that forest fragments must be protected and restored to reduce the risks of degrading the ecological condition of Amazonian streams.

Identifying the hierarchical spatial levels that show the greatest dissimilarities between communities and how these patterns are generated is essential to provide insights into the monitoring and protection of biodiversity. In this study, we additively partitioned diversity of macroinvertebrates into alpha, beta, and gamma diversity across multiple scales in typical and semi-arid tropical estuaries. We also determined which components of the total beta diversity, in terms of species replacement or richness difference (presence-absence data) and abundance difference (relative abundance data), had the greatest relative importance in structuring the composition of benthic macrofauna. In typical and semi-arid tropical estuaries, a non-random spatial pattern was observed in additive partitioning of diversity, with higher values of beta diversity obtained at the largest scales analyzed. When considering the presence-absence data, in general there was no clear trend which components of beta diversity had greater relative importance in typical estuaries. In the semi-arid tropical estuaries, the richness difference component showed greater relative importance in the rainy season, whereas the species replacement presented greater proportions in the dry season. When considering abundance data, in general the abundance difference component showed greater relative importance in typical and semi-arid tropical estuaries in the two seasonal periods. Therefore, approaches based on the presence/absence and on the relative abundance of species provided complementary answers about the distribution patterns of benthic macroinvertebrate communities. We demonstrated that environmental filtering and dispersal limitation may affect the patterns of distribution of benthic macrofauna in estuaries located in regions with different climatic conditions.

This study investigated the effects of activities carried out by traditional populations on aquatic ecosystems using the assemblages of Ephemeroptera, Plecoptera, and Trichoptera insect orders, and identified fluvial habitat characteristics modified by the disturbances. We surveyed two groups of streams—17 streams representing control conditions (CON) and 17 streams influenced by traditional population settlements (TPO). Genera richness and abundance of individuals did not vary between groups. With regard to physical habitat metrics, the percentage of leaf litter, amount of woody debris in the channel, proximity to farming, percentage of slow water in the channel, and the mean riparian vegetation cover all influenced benthic macroinvertebrate assemblages. Considerable differences were found in genera composition between the two groups. The genera Ulmeritoides , Miroculis , and Brasilocaenis were associated with the CON group, and Macronema and Campsurus with the TPO group. We conclude that even small-scale impacts, such as those performed by traditional Amazonian populations, can have major effects on aquatic biota, which reiterates the fragile nature of these ecosystems and emphasizes the need for adequate management of these activities.

The organisms of the infraorder Nepomorpha (Heteroptera) present complex habitat requirements in headwater streams, usually being related to local substrate conditions. Therefore, in this study, we evaluated how the diversity of Nepomorpha responded to a wide gradient of habitat and ecological conditions. We tested two hypotheses: (1) local substrate composition is the most important factor determining the diversity of Nepomorpha compared to other physical habitat metrics, (2) Nepomorpha assemblage diversity respond more readily to anthropogenic disturbances at local scale. Our results did not corroborate the first hypothesis, and showed that the assemblage diversity was mostly related to water quality and geomorphology, indicating that substrate requirements are not the only important driver. Our second hypothesis was partially corroborated, as all diversity metrics presented significant correlation with human disturbances at both local and catchment spatial scales. These results show that Nepomorpha assemblages have high potential use as ecological indicators, which should be better explored in future biomonitoring studies of anthropogenic changes.