- Universidade Federal de Goiás, Departamento de Ecologia, Post-DocUniversity of Guelph, Integrative Biology, Department Memberadd
Studies on phylogenetic community ecology usually infer habitat filtering when communities are phylogenetically clustered or competitive exclusion when communities are overdispersed. This logic is based on strong competition and niche... more
Studies on phylogenetic community ecology usually infer habitat filtering when communities are phylogenetically clustered or competitive exclusion when communities are overdispersed. This logic is based on strong competition and niche similarity among closely related species-a less common phenomenon than previously expected. Dragonflies and damselflies are good models for testing predictions based on this logic because they behave aggressively towards related species due to mistaken identification of conspecifics. This behavior may drive communities toward phylogenetic overdispersion if closely related species frequently exclude each other. However, phylogenetically clustered communities could also be observed if habitat filtering and/or competitive asymmetry among distantly related species are major drivers of community assembling. We investigated the phylogenetic structure of odonate assemblages in central Brazil in a watershed characterized by variations in stream width, vegetation cover, aquatic vegetation, and luminosity. We observed general clustering in communities according to two indices of phylogenetic structure. Phylogenetic beta diversity coupled with Mantel tests and RLQ analysis evidenced a correlation between the riverine gradient and phylogenetic structure. Larger rivers with aquatic vegetation were characterized by anisopterans, while most zygopterans stayed in small and shaded streams. These results indicate niche conservatism in Odonata habitat occupancy, and that the environment is a major influence on the phylogenetic structure of these communities. We suggest that this is due to clade-specific ecophysiological requirements, and because closely related species may also have competitive advantages and dominate certain preferred habitats.
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The assumption that traits and phylogenies can be used as proxies of species niche has faced criticisms. Evidence suggested that phylogenic relatedness is a weak proxy of trait similarity. Moreover, different processes can select... more
The assumption that traits and phylogenies can be used as proxies of species niche has faced criticisms. Evidence suggested that phylogenic relatedness is a weak proxy of trait similarity. Moreover, different processes can select different traits, giving opposing signals in null model analyses. To circumvent these criticisms, we separated traits of stream insects based on the concept of α and β niches, which should give clues about assembling pressures expected to act independently of each other. We investigated the congruence between the phylogenetic structure and trait structure of communities using all available traits and all possible combinations of traits (4095 combinations). To account for hierarchical assembling processes, we analyzed patterns on two spatial scales with three pools of genera. Beta niche traits selected a priori - i.e., traits related to environmental variation (e.g., respiration type) - were consistently clustered on the smaller scale, suggesting environmental filtering, while α niche traits - i.e., traits related to resource use (e.g., trophic position) - did not display the expected overdispersion, suggesting a weak role of competition. Using all traits together provided random patterns and the analysis of all possible combinations of traits provided scenarios ranging from strong clustering to overdispersion. Communities were phylogenetically overdispersed, a pattern previously interpreted as phylogenetic limiting similarity. However, our results likely reflect the co-occurrence of ancient clades due to the stability of stream habitats along the evolutionary scale. We advise ecologists to avoid using combinations of all available traits but rather carefully traits based on the objective under consideration. Both trait and phylogenetic approaches should be kept in the ecologist toolbox, but phylogenetic distances should not be used as proxies of traits differences. Although the phylogenetic structure revealed processes operating at the evolutionary scale, only specific traits explained local processes operating in our communities.
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We investigated (1) the variation of both species composition and species relative abundances of aquatic beetles associated with submerged woody debris in a transitional region between Cerrado (Brazilian savannah) and Atlantic Forest... more
We investigated (1) the variation of both species composition and species relative abundances of aquatic beetles associated with submerged woody debris in a transitional region between Cerrado (Brazilian savannah) and Atlantic Forest biomes; and (2) which assembling processes are more associated with the observed patterns, species sorting or mass effects. We hypothesized that the marked differences between Cerrado and Atlantic Forest streams regarding vegetation composition and structure would produce different environmental conditions for stream beetle faunas assembling. We used spatial explicit multivariate techniques to analyze whether metacom-munity patterns were more associated with environmental variables, indicating a major role of species sorting, or with spatial variables, indicating intense dispersal. We found distinct communities within each biome in terms of both changes in taxonomic composition and species relative abundance driven by environmental factors. Biome type, a regional scale variable, and variation in dissolved oxygen levels, a local scale variable, were the best explanatory variables of variation in metacommunity structure. We did not find any evidence of the influence of processes related to the spatial configuration of streams. Altogether our results pointed to species sorting structuring saproxylic beetles assemblages patterns.
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Inter-specific competition is considered one of the main selective pressures affecting species distribution and coexistence. Different species vary in the way they forage in order to minimize encounters with their competitors and with... more
Inter-specific competition is considered one of the main selective pressures affecting species distribution and coexistence. Different species vary in the way they forage in order to minimize encounters with their competitors and with their predators. However, it is still poorly known whether and how native species change their foraging behavior in the presence of exotic species, particularly in South America. Here we compare diet overlap of fruits and foraging activity period of two sympatric native ungulates (the white-lipped peccary, Tayassu pecari, and the collared peccary, Pecari tajacu) with the invasive feral pig (Sus scrofa) in the Brazilian Pantanal. We found high diet overlap between white-lipped pecca-ries and feral pigs, but low overlap between collared peccaries and feral pigs. Furthermore, we found that feral pigs may influence the foraging period of both native peccaries, but in different ways. In the absence of feral pigs, collared peccary activity peaks in the early evening , possibly allowing them to avoid white-lipped peccary activity peaks, which occur in the morning. In the presence of feral pigs, collared peccaries forage mostly in early morning, while white-lipped peccaries forage throughout the day. Our results indicate that collared peccaries may avoid foraging at the same time as white-lipped peccaries. However, they forage during the same periods as feral pigs, with whom they have lower diet overlap. Our study highlights how an exotic species may alter interactions between native species by interfering in their foraging periods.
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Background/Question/Methods The metacommunity concept has been increasingly applied when studying the regulation of biodiversity. A metacommunity refers to a set of local communities connected by the dispersal of multiple interacting... more
Background/Question/Methods The metacommunity concept has been increasingly applied when studying the regulation of biodiversity. A metacommunity refers to a set of local communities connected by the dispersal of multiple interacting species. Within a metacommunity, variation in local community structure is affected by variation in local environmental characteristics and the spatial arrangement of the sites. Organisms with contrasting dispersal modes are likely to respond differently to these factors. Poorly dispersing organisms are expected to be constrained by the spatial distances between sites. Conversely, the effectively dispersing organisms (as being better able to track environmental heterogeneity) should be relatively more affected by the local environmental characteristics. We studied how dispersal mode affect the relative effects of local environmental conditions and spatial location on the structure of stream macroinvertebrate metacommunities. We sampled macroinvertebrate...
SUMMARY 1. The correspondence between physical classification schemes and the structure of biological assemblages has been intensively investigated in recent years for the implementation of bioassessment, biomonitoring and conservation... more
SUMMARY 1. The correspondence between physical classification schemes and the structure of biological assemblages has been intensively investigated in recent years for the implementation of bioassessment, biomonitoring and conservation programs. 2. We evaluated the effect of temporal variability on the classification strengths of geographically and limnologically delimited regions and types of environments (ie, isolated and connected lakes) for biological assemblages in a Neotropical floodplain. 3. We sampled data for ...
Predicting how anthropogenic activities may influence the various components of biodiversity is essential for finding ways to reduce diversity loss. This challenge involves: a) understanding how environmental factors influence diversity... more
Predicting how anthropogenic activities may influence the various components of biodiversity is essential for finding ways to reduce diversity loss. This challenge involves: a) understanding how environmental factors influence diversity across different spatial scales, and b) developing ways to measure these relationships in a way that is fast, economical, and easy to communicate. In this study, we investigate whether landscape and bioclimatic variables could explain variation in biodiversity indices in macroinvertebrate communities from 39 Atlantic Forest streams. In addition to traditional diversity measures, i.e., species richness, abundance and Shannon index, we used a taxonomic distinctness index that measures the degree of phylogenetic relationship among taxa. The amount of variation in the diversity measures that was explained by environmental and spatial variables was estimated using variation partitioning based on multiple regression. Our study demonstrates that taxonomic d...
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ABSTRACT In this study, patterns of body size of Phanocerus clavicornis Sharp, 1882 (Coleoptera: Elmidae: Larainae) were investigated along a gradient of change in speed of flow conditions in streams of low order in the Atlantic... more
ABSTRACT In this study, patterns of body size of Phanocerus clavicornis Sharp, 1882 (Coleoptera: Elmidae: Larainae) were investigated along a gradient of change in speed of flow conditions in streams of low order in the Atlantic Rainforest in southeastern Brazil. Specifically, the hypothesis that the distribution of P. clavicornis larvae vary in size in response to variations in the speed of flow in streams was tested. A Surber sampler was used to collect larvae from the streambed during two sampling periods, defined by the rain regime: August in the dry season and February in the rainy season. Possible differences in mean measured body size were tested by analysis of variance (ANOVA). The ANOVA result indicated for all measurements on the larvae collected in first-order streams (head width, prothoracic width and total body length), there were significant differences indicating a morphometric variation due to changing hydraulic conditions, the smallest larvae being associated with the period of greater rainfall. However, the larger streams (3rd order), where the rain events had less impact on the larval size, varied widely. The results of this study suggest that the interstitial space is important for the protection of the larvae from water flow, and that populations of P. clavicornis have high plasticity, a key feature for the occupation of unstable environments for this species. These results are important for an understanding of the life history and behavioural characteristics of the species, which allow them to persist in streams along a gradient of flow disturbance.
ABSTRACT Aquatic insects are used extensively in freshwater bioassessment because they are good indicators of human impact. The most successful bioassessment initiatives have focused mainly on comparing insect communities from potential... more
ABSTRACT Aquatic insects are used extensively in freshwater bioassessment because they are good indicators of human impact. The most successful bioassessment initiatives have focused mainly on comparing insect communities from potential impacted sites to those predicted by empirical correlative models that occur in pristine sites. The theoretical scope that underpins the use of these models is derived from a deterministic view of ecology, particularly based on niche theory – i.e., predicting taxa occurrence from environmental conditions. In recent years, however, the development of new concepts (e.g., the metacommunity concept), use of new techniques (e.g., artificial neural networks) and availability of better datasets (e.g., geographic information system layers) could change this scenario. In this chapter, we explore the use of metacommunity models, the geometry of riverine networks and organism dispersal conceptually with a simulation exercise to discuss the challenges of modelling metacommunities in biomonitoring aquatic networks.
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In order to evaluate the potential risks of human visitation on macroinvertebrate communities in streams, we investigated the effect of trampling using two short-term experiments conducted in a Brazilian ecotourism karst region. We asked... more
In order to evaluate the potential risks of human visitation on macroinvertebrate communities in streams, we investigated the effect of trampling using two short-term experiments conducted in a Brazilian ecotourism karst region. We asked three questions: (a) Does trampling increase the drift rate of aquatic macroinvertebrates and organic matter? (b) Does trampling change the macroinvertebrate community organization? (c) If trampling alters the community structure, is a short time (5 days, a between weekends interval - peaks of tourism activities) sufficient for community restructuring? Analysis of variance of richness, total abundance, abundance of the most abundant genus (e.g., Simothraulopsis and Callibaetis), and community composition showed that trampling immediately affects macroinvertebrate community and that the intervals between the peaks of visitation (5 days) are not sufficient to complete community restructuring. Considering that bathing areas receive thousands of visitors every year and that intervals of time without visitation are nearly nonexistent, we suspect that the negative effects on the macroinvertebrate community occur in a cumulative way. Finally, we discuss some simple procedures that could potentially be used for reducing trampling impacts in lotic environments.
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1Faculdade de Ciências Biológicas e Ambientais, Universidade Federal da Grande Dourados UFGD, Unidade II, Rodovia Dourados Ithaum, Km 12, Caixa Postal. 533, CEP 79804-970, Dourados, MS, Brasil. Email: roque.eco@gmail.com.br 2Programa de... more
1Faculdade de Ciências Biológicas e Ambientais, Universidade Federal da Grande Dourados UFGD, Unidade II, Rodovia Dourados Ithaum, Km 12, Caixa Postal. 533, CEP 79804-970, Dourados, MS, Brasil. Email: roque.eco@gmail.com.br 2Programa de Pós-Graduação em ...
Estimamos a diversidade ea riqueza de Chironomidae (Diptera) em dois diferentes córregos através da análise de exúvias de pupa. As coletas realizadas no período de estiagem (agosto/2001) foram feitas com auxílio de redes de deriva e de... more
Estimamos a diversidade ea riqueza de Chironomidae (Diptera) em dois diferentes córregos através da análise de exúvias de pupa. As coletas realizadas no período de estiagem (agosto/2001) foram feitas com auxílio de redes de deriva e de mão, em trechos de 100 ...
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The Atlantic Forest domain, one of the 25 world's hotspots for biodiversity, has experienced dramatic changes in its landscape. While the loss of species diversity is well documented, functional diversity has not received the same amount... more
The Atlantic Forest domain, one of the 25 world's hotspots for biodiversity, has experienced dramatic changes in its landscape. While the loss of species diversity is well documented, functional diversity has not received the same amount of attention. In this study, we evaluated functional diversity of insects in streams utilizing three indices: functional diversity (FD), functional dispersion (FDis), and functional divergence (FDiv), seeking to understand the roles of three predictor sets in explaining functional patterns: (1) bioclimatic and landscape variables; (2) spatial variables; and (3) local environmental variables. We determined the amount of variation in different measures of functional diversity that was explained by each predictor set and their interplays using variation partitioning. Our study showed that variation in functional diversity is better explained by a set of variables linked to different scales dependent on spatial structures, indicating the importance of landscape and mainly environmental variables in the functional organization of aquatic insect communities, and that the relative importance of predictor sets depends on the indices considered. Variation in FD was better explained by the interplay among the three predictor sets and by local environmental variables, whereas variation in FDis was better explained by spatial variables and by the interplay between environmental and spatial variables. Variation in FDiv was not significantly explained by any predictors. Our study adds more evidence on the harmful effects caused by landscape changes on biodiversity in the Atlantic Forest, suggesting that these effects also influence the functional organization of stream insect communities.
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Because of inadequate knowledge and funding, the use of biodiversity indicators is often suggested as a way to support management decisions. Consequently, many studies have analyzed the performance of certain groups as indicator taxa.... more
Because of inadequate knowledge and funding, the use of biodiversity indicators is often suggested as a way to support management decisions. Consequently, many studies have analyzed the performance of certain groups as indicator taxa. However, in addition to knowing whether certain groups can adequately represent the biodiversity as a whole, we must also know whether they show similar responses to the main structuring processes affecting biodiversity. Here we present an application of the metacommunity framework for evaluating the effectiveness of biodiversity indicators. Although the metacommunity framework has contributed to a better understanding of biodiversity patterns, there is still limited discussion about its implications for conservation and biomonitoring. We evaluated the effectiveness of indicator taxa in representing spatial variation in macroinvertebrate community composition in Atlantic Forest streams, and the processes that drive this variation. We focused on analyzing whether some groups conform to environmental processes and other groups are more influenced by spatial processes, and on how this can help in deciding which indicator group or groups should be used. We showed that a relatively small subset of taxa from the metacommunity would represent 80% of the variation in community composition shown by the entire metacommunity. Moreover, this subset does not have to be composed of predetermined taxonomic groups, but rather can be defined based on random subsets. We also found that some random subsets composed of a small number of genera performed better in responding to major environmental gradients. There were also random subsets that seemed to be affected by spatial processes, which could indicate important historical processes. We were able to integrate in the same theoretical and practical framework, the selection of biodiversity surrogates, indicators of environmental conditions, and more importantly, an explicit integration of environmental and spatial processes into the selection approach.
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One of the most popular approaches for investigating the roles of niche and neutral processes driving metacommunity patterns consists of partitioning variation in species data into environmental and spatial components. The logic is that... more
One of the most popular approaches for investigating the roles of niche and neutral processes driving metacommunity patterns consists of partitioning variation in species data into environmental and spatial components. The logic is that the distance decay of similarity in communities is expected under neutral models. However, because environmental variation is often spatially structured, the decay could also be attributed to environmental factors that are missing from the analysis. Here, we use a spatial autocorrelation analysis protocol, previously developed to detect isolation-by-distance in allele frequencies, to evaluate patterns of species abundances under neutral dynamics. We show that this protocol can be linked with variation partitioning analyses. Moreover, in an attempt to test the neutral model, we derive three predictions to be applied both to original species abundances and to abundances predicted by a pure spatial model species abundances will be uncorrelated; Moran's I correlograms will reveal similar short-distance autocorrelation patterns; an increasing degree of non-neutrality will tend to generate patterns of correlation among abundances within groups of species with similar correlograms (i.e. within species with neutral and non-neutral dynamics). We illustrate our protocol by analyzing spatial patterns in abundance of 28 terrestrially breeding anuran species from Central Amazonia. We recommend that researchers should investigate spatial autocorrelation patterns of abundances predicted by pure spatial models to identify similar patterns of spatial autocorrelation at short distances and lack of correlation between species abundances. Therefore, the hypothesis that spatial patterns in abundances are primarily due to pure neutral dynamics (rather than to missing spatiallystructured environmental factors) can be confirmed after taking environmental variables into account.
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Ecologists have long investigated why communities are composed of a few common species and many rare species. Most studies relate rarity to either niche differentiation among species or spatial processes. There is a parallel between these... more
Ecologists have long investigated why communities are composed of a few common species and many rare species. Most studies relate rarity to either niche differentiation among species or spatial processes. There is a parallel between these processes and the processes proposed to explain the structure of metacommunities. Based on a metacommunity perspective and on data on stream macroinvertebrates from different regions of Brazil, we answer two questions. i: Are sets of common and rare species affected by similar niche and spatial processes? ii: How does the community composition of common and of rare species differ? The main hypothesis we test is that common species are mainly affected by environmental factors, whereas rare species are mostly influenced by dispersal limitation. We used variation partitioning to determine the proportion of variation explained by the environment and space in common and rare species matrices. Contrary to our expectations, evidence supported the idea that both common and rare species are affected mainly by environmental factors, even after controlling for the differing information content between common and rare species matrices. Moreover, the abundance of some common species is also a good predictor of variation in rare species matrices. Niche differences are unlikely to be the sole cause of patterns of rarity in these metacommunities. We suggest that sets of common and rare species react to similar major environmental gradients and that rare species also respond to processes that operate at a more fine-grained spatial scale, particularly biotic interactions. We extend the view that species sorting is the dominant process structuring metacommunities and argue that future studies focusing on rarity would benefit from a metacommunity perspective.
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"Podonomus Philippi was recently found in Brazilian inselbergs. In this study, we used sequences from the barcode region of cytochrome c oxidase I (COI) to assess Podonomus molecular diversity from mountains in Southeastern Brazil. Our... more
"Podonomus Philippi was recently found in Brazilian inselbergs. In this study, we used sequences from the barcode region of cytochrome c oxidase I (COI) to assess Podonomus molecular diversity from mountains in Southeastern Brazil. Our results revealed the adult female and the larvae of Podonomus pepinellii
Roque and Trivinho-Strixino, 2004 and extended the known geographical distribution of the species. Moreover, we found high molecular divergence in two populations located in the Serra da Mantiqueira and Serra do Espinhac¸o mountain range when compared with the only species recorded to Brazil, indicating the possibility of two more species to be described."
Roque and Trivinho-Strixino, 2004 and extended the known geographical distribution of the species. Moreover, we found high molecular divergence in two populations located in the Serra da Mantiqueira and Serra do Espinhac¸o mountain range when compared with the only species recorded to Brazil, indicating the possibility of two more species to be described."
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In this study we investigated whether there is correspondence between aquatic macroinvertebrate communities and the typological classification of white and clean-water streams in western Amazonia lowlands. We worked within two distinct... more
In this study we investigated whether there is correspondence between aquatic macroinvertebrate communities and the typological classification of white and clean-water streams in western Amazonia lowlands. We worked within two distinct hydrographic basins Moa River catchment (clear-water streams) and Azul River catchment (white-water streams) in the Serra do Divisor National Park, Acre State, Brazil, sampling ten streams in each basin. A total of 2,952 individuals were collected, distributed among 134 taxa. Our results show that macroinvertebrate communities, at genus as well as family level, are in concordance to a priori classifications that distinguish between white and clear water streams. The main implication of our results for biomonitoring is that biotic variation between white and clear streams can be partitioned regionally, which would improve the bioassessment accuracy of the Amazonian streams.
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Ecologists usually estimate means, but devote much less attention to variation. The study of variation is a key aspect to understand natural systems and to make predictions regarding them. In community ecology, most studies focus on local... more
Ecologists usually estimate means, but devote much less attention to variation. The study of variation is a key aspect to understand natural systems and to make predictions regarding them. In community ecology, most studies focus on local species diversity (alpha diversity), but only in recent decades have ecologists devoted proper attention to variation in community composition among sites (beta diversity). This is in spite of the fact that the first attempts to estimate beta diversity date back to the pioneering work by Koch and Whittaker in the 1950s. Progress in the last decade has been made in the development both of methods and of hypotheses about the origin and maintenance of variation in community composition. For instance, methods are available to partition total diversity in a region (gamma diversity), in a local component (alpha), and several beta diversities, each corresponding to one scale in a hierarchy. The popularization of the so-called raw-data approach (based on partial constrained ordination techniques) and the distance-based approach (based on correlation of dissimilarity/distance matrices) have allowed many ecologists to address current hypotheses about beta diversity patterns. Overall, these hypotheses are based on niche and neutral theory, accounting for the relative roles of environmental and spatial processes (or a combination of them) in shaping metacommunities. Recent studies have addressed these issues on a variety of spatial and temporal scales, habitats and taxonomic groups. Moreover, life history and functional traits of species such as dispersal abilities and rarity have begun to be considered in studies of beta diversity. In this article we briefly review some of these new tools and approaches developed in recent years, and illustrate them by using case studies in aquatic ecosystems.
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"1. Analyses of species association have major implications for selecting indicators for freshwater biomonitoring and conservation because they allow for the elimination of redundant information and focus on taxa that can be easily... more
"1. Analyses of species association have major implications for selecting indicators for freshwater biomonitoring and conservation because they allow for the elimination of redundant information and focus on taxa that can be easily handled and identified. These analyses are particularly relevant in the debate about using speciose groups (such as the Chironomidae) as indicators in the tropics, because they require difficult and time-consuming analysis and their responses to environmental gradients, including anthropogenic stressors, are poorly known.
2. Our objective was to show whether chironomid assemblages in Neotropical streams have clear taxon associations and, if so, how well these associations could be explained by a set of models containing information from different spatial scales. For this, we formulated a priori models that allowed for the influence of local, landscape and spatial factors on chironomid taxon associations (CTA). These models represented biological hypotheses capable of explaining associations between chironomid taxa. For instance, CTA could be best explained by local variables (e.g., pH, conductivity and water temperature) or by processes acting at wider landscape scales (e.g., percentage of forest cover).
3. Biological data were taken from 61 streams in southeastern Brazil, 47 of which were in well-preserved regions, and 14 of which drained areas severely affected by anthropogenic activities. We adopted a model selection procedure using Akaike’s information criterion to determine the most parsimonious models for explaining chironomid taxon associations.
4. Applying Kendall’s coefficient of concordance, seven genera (Tanytarsus/Caladomyia, Ablabesmyia, Parametriocnemus, Pentaneura, Nanocladius, Polypedilum and Rheotanytarsus) were identified as associated taxa. The best-supported model explained 42.6% of the total variance in the abundance of associated taxa. This model combined local and landscape environmental filters, and spatial variables (which were derived from eigenfunction analysis). However, the model with local filters and spatial variables also had a good chance of being selected as the best model.
5. Standardized partial regression coefficients of local and landscape filters, including spatial variables, derived from model averaging allowed an estimation of which variables were best correlated with the abundance of associated taxa. In general, the abundance of the associated genera tended to be lower in streams characterized by a high percentage of forest cover (landscape scale), lower proportion of muddy substrata and high values of pH and conductivity (local scale).
6. Overall, our main result adds to the increasing number of studies that have indicated the importance of local and landscape variables, as well as the spatial relationships among sampling sites, for explaining aquatic insect community patterns in streams. Furthermore, our findings open new possibilities for the elimination of redundant data in the assessment of anthropogenic impacts on tropical streams."
2. Our objective was to show whether chironomid assemblages in Neotropical streams have clear taxon associations and, if so, how well these associations could be explained by a set of models containing information from different spatial scales. For this, we formulated a priori models that allowed for the influence of local, landscape and spatial factors on chironomid taxon associations (CTA). These models represented biological hypotheses capable of explaining associations between chironomid taxa. For instance, CTA could be best explained by local variables (e.g., pH, conductivity and water temperature) or by processes acting at wider landscape scales (e.g., percentage of forest cover).
3. Biological data were taken from 61 streams in southeastern Brazil, 47 of which were in well-preserved regions, and 14 of which drained areas severely affected by anthropogenic activities. We adopted a model selection procedure using Akaike’s information criterion to determine the most parsimonious models for explaining chironomid taxon associations.
4. Applying Kendall’s coefficient of concordance, seven genera (Tanytarsus/Caladomyia, Ablabesmyia, Parametriocnemus, Pentaneura, Nanocladius, Polypedilum and Rheotanytarsus) were identified as associated taxa. The best-supported model explained 42.6% of the total variance in the abundance of associated taxa. This model combined local and landscape environmental filters, and spatial variables (which were derived from eigenfunction analysis). However, the model with local filters and spatial variables also had a good chance of being selected as the best model.
5. Standardized partial regression coefficients of local and landscape filters, including spatial variables, derived from model averaging allowed an estimation of which variables were best correlated with the abundance of associated taxa. In general, the abundance of the associated genera tended to be lower in streams characterized by a high percentage of forest cover (landscape scale), lower proportion of muddy substrata and high values of pH and conductivity (local scale).
6. Overall, our main result adds to the increasing number of studies that have indicated the importance of local and landscape variables, as well as the spatial relationships among sampling sites, for explaining aquatic insect community patterns in streams. Furthermore, our findings open new possibilities for the elimination of redundant data in the assessment of anthropogenic impacts on tropical streams."
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Citation frequency has been considered a biased surrogate of publication merit. However, previous studies on this subject were based on small sample sizes and were entirely based on null-hypothesis significance testing. Here we evaluated... more
Citation frequency has been considered a biased surrogate of publication merit. However, previous studies on this subject were based on small sample sizes and were entirely based on null-hypothesis significance testing. Here we evaluated the relative effects of different predictors on citation frequency of ecological articles using an information theory framework designed to evaluate multiple competing hypotheses. Supposed predictors of citation frequency (e.g., number of authors, length of articles) accounted for a low fraction of the total variation. We argue that biases concerning citation are minor in ecology and further studies that attempt to quantify the scientific relevance of an article, aiming to make further relationships with citation, are needed to advance our understanding of why an article is cited.
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The relative importance of local and regional processes in shaping natural communities within a metacommunity context has been a focus of intense debate in recent years. Floodplain lakes provide a good system for testing this theoretical... more
The relative importance of local and regional processes in shaping natural communities within a metacommunity context has been a focus of intense debate in recent years. Floodplain lakes provide a good system for testing this theoretical approach, as they undergo seasonal variations in physical, chemical and biological factors, as well as in their degree of connectivity. Here, we investigated how local phytoplankton communities in lakes of a tropical river-floodplain system (Araguaia River floodplain–Central Brazil) were affected by environmental and spatial (dispersal) predictors in two rainy and two dry seasons (two consecutive years). Partial redundancy analysis indicated that during the periods analyzed the effects of neither predictor were significant. Although we cannot exclude the possibility that these tropical phytoplankton communities could be regulated by stochastic events, we suggested that further studies will have greater explanatory power if they include other variables related to biotic interactions (e.g., abundance of grazers) and fine-scale environmental variation.
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The positive relationship between species regional distribution and local abundance is one of the most ubiquitous patterns in ecology. Among the hypotheses proposed to explain the relationship, the niche breadth and the niche position (or... more
The positive relationship between species regional distribution and local abundance is one of the most ubiquitous patterns in ecology. Among the hypotheses proposed to explain the relationship, the niche breadth and the niche position (or habitat availability) hypothesis are the most investigated. An unappreciated issue, but that is likely to be important for the understanding of the relationship is the nature of variables used to estimated niche measures. Here we analyzed the form of this relationship in lotic chironomid genera and tested whether niche measures estimated from local and landscape variables explain the observed pattern. Analyses were based in forty-seven forested streams within Southeastern Brazil. From our dataset we randomly partitioned the data in two non-overlapping sets to estimate taxa distribution and abundance (Distribution Data; n = 23 sites) and to generate niche measures (Niche Data; n = 24). We repeated that process 1,000 times, and for each one we generated niche breadth and position measures using in-stream and landscape variables, and estimated abundance and distribution for each taxa. With these, we estimated the relationship between both abundance and distribution and niche measures using ordinary least-squares regressions. We found no relationship between niche position estimated from local variables and local abundance nor regional distribution. There was a negative relationship between niche position estimated from landscape and local abundance, and regional distribution. We found a positive relationship between niche breadth (local and landscape) and both local abundance and regional distribution. When the relationship was significant, both niche position and niche breadth explained less than a half of total variation in abundance and distribution. This suggests that not only niche based processes, but also other mechanisms may be responsible for the abundance-distribution relationship in lotic chironomids. A novel finding of this study was that, although there was much unexplained variability around the relationships, niche breadth was a better predictor of abundance and distribution than niche position. We suggest that future studies should investigate if spatial processes, like dispersal, together with environmental processes affect interspecific abundance-distribution relationships.
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A atividade de pesquisa relacionada com os efeitos das mudanças climáticas sobre a biodiversidade tem aumentado apidamente. Uma análise bibliométrica utilizando uma combinação de palavras-chaves (“clima* change” OR “Global change” e... more
A atividade de pesquisa relacionada com os efeitos das mudanças climáticas sobre a biodiversidade tem aumentado apidamente. Uma análise bibliométrica utilizando uma combinação de palavras-chaves (“clima* change” OR “Global change” e biodiversity OR “bio* diversity”) no banco de dados Web of Science® (Thomson ISI) revelou um total de 1.198 artigos. Aproximadamente 83% dos artigos foram publicados nos últimos sete anos (entre 2000 e 12/10/2007), indicando que a produção científica sobre o tema é recente. Uma elevada porcentagem da produção (73,4%) está concentrada em periódicos categorizados nas áreas de Ecologia e Ciências
Ambientais. A produção científica sobre esse tema também tem sido preponderantemente desenvolvida por autores originários de alguns poucos países (EUA e Canadá e Inglaterra). Apenas 17 artigos (1,4%) foram publicados por autores brasileiros, exemplificando o pequeno número de estudos nas regiões tropicais. A despeito da tendência de aumento da atividade
científica sobre mudanças climáticas e biodiversidade, a porcentagem total de artigos abordando o tema é baixa. Em geral, a maior atenção das pesquisas em biologia da conservação ainda é dada a outras ameaças (conversão de habitat, fragmentação, introdução de espécies exóticas).
Provavelmente, os efeitos das mudanças climáticas sobre a biodiversidade serão estudados com maior frequência utilizando modelos baseados na teoria do nicho. No entanto, diversas
limitações dessa estratégia estão sendo listadas na literatura recente, sugerindo que, embora promissoras, esta estratégia deve ser empregada com cautela.
Ambientais. A produção científica sobre esse tema também tem sido preponderantemente desenvolvida por autores originários de alguns poucos países (EUA e Canadá e Inglaterra). Apenas 17 artigos (1,4%) foram publicados por autores brasileiros, exemplificando o pequeno número de estudos nas regiões tropicais. A despeito da tendência de aumento da atividade
científica sobre mudanças climáticas e biodiversidade, a porcentagem total de artigos abordando o tema é baixa. Em geral, a maior atenção das pesquisas em biologia da conservação ainda é dada a outras ameaças (conversão de habitat, fragmentação, introdução de espécies exóticas).
Provavelmente, os efeitos das mudanças climáticas sobre a biodiversidade serão estudados com maior frequência utilizando modelos baseados na teoria do nicho. No entanto, diversas
limitações dessa estratégia estão sendo listadas na literatura recente, sugerindo que, embora promissoras, esta estratégia deve ser empregada com cautela.
Research Interests:
Tropical streams host intriguing interactions between fruits and fruit-eating insects. However, there is little information on the impacts of deforestation on the aquatic insects associated with fallen-fruits in Neotropical streams. Given... more
Tropical streams host intriguing interactions between fruits and fruit-eating insects. However, there is little information on the impacts of deforestation on the aquatic insects associated with fallen-fruits in Neotropical streams. Given that fallen-fruit dwelling insects may depend on the availability of fruits in streams and consequently on the riparian forest condition, we hypothesized that density of the fallen-fruit dwelling chironomid Endotribelos would differ in streams whose catchments differed in land use, particularly riparian forest conditions. To test this hypothesis we experimentally placed fruits in streams characterized by a gradient of riparian forest degradation. We applied correlation analysis between Endotribelos mean density by fruit, number of colonized fruits, and environmental variables. All results evidenced that fallen-fruit chironomid Endotribelos were affected by riparian degradation.
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We report cases of Simuliidae and Chironomidae living on Lachlania nymphs (Ephemeroptera). This is the first record of these associations in South America. Simulium exiguum (pupae and larvae), Simulium cuasiexiguum (larvae), Cricotopus... more
We report cases of Simuliidae and Chironomidae living on Lachlania nymphs (Ephemeroptera). This is the first record of these associations in South America. Simulium exiguum (pupae and larvae), Simulium cuasiexiguum (larvae), Cricotopus sp. (larva) and Rheotanytarsus sp. (larva) were found associated with Lachlania nymphs. We believe that all of these associations can be classified as opportunistic (or casual) attachment.
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In this paper we analyzed the emergence phenology of a highly diverse chironomid assemblage to test for association between emergence and some environmental variables and for the presence of synchrony in emergence. We used a time series... more
In this paper we analyzed the emergence phenology of a highly diverse chironomid assemblage to test for association between emergence and some environmental variables and for the presence of synchrony in emergence. We used a time series of 48 weekly samples from a tropical low order forested stream (south-eastern Brazil) to describe how this assemblage varied in an intra-annual scale. An eigenvector-based filtering approach was adapted to create temporal variables that could be used in our multiple regression analyses, trying to overcome the problems of temporal autocorrelation. Emergence of the Chironomidae, two subfamilies, concordant species, and of dominant species was not related to rainfall, temperature, moon phase or photoperiod. Taxonomic composition and species richness did not change across time. The number of emerging individuals of the subfamily Orthocladiinae was significantly related to temperature and to temporal filters. The inclusion of the temporal filters into the analyses almost eliminated autocorrelation in the regression residuals. We detected interspecific synchrony in a group of species, but an absence of trends and periodicity in chironomid emergence, which was not related to environmental variables. This suggests that unknown factors, differing from those known to control emergence in temperate regions, operate in the tropics. The erratic behaviour of the analyzed series raises the question of whether chaotic dynamics may generate this variability.
Research Interests:
We investigated two of the most studied relationships in the macroecological research program (species richness vs. body size and abundance vs. body size) of a local chironomid assemblage from southeastern Brazil. Although numerous... more
We investigated two of the most studied relationships in the macroecological research program (species richness vs. body size and abundance vs. body size) of a local chironomid assemblage from southeastern Brazil. Although numerous studies have examined these relationships, few have investigated how they vary at different temporal scales. We used data from a forested stream to document and examine these patterns at monthly intervals. Both the species body size distribution and the abundance–body size relationship varied temporally. In some months the body size distribution was skewed to the right, whereas in others it approached normality. We found both linear relationships (with different values of slopes), and a polygonal pattern in the abundance–body size relationship. This temporal variation was not related to environmental variables. Our results suggest that body size relationships are temporally instable properties of this chironomid assemblage.
Research Interests:
Many biomonitoring programs of aquatic systems are based on knowledge of species’ geographic distributions and on how different groups respond facing different sources of impact. In this study, we asked if plecopteran occurrences at genus... more
Many biomonitoring programs of aquatic systems are based on knowledge of species’ geographic distributions and on how different groups respond facing different sources of impact. In this study, we asked if plecopteran occurrences at genus level can be explained using environmental conditions of low-order Southeastern Brazilian streams. Additionally, we asked if plecopteran nymphs discriminate reference streams from streams under diffuse anthropic impacts. We sampled plecopteran nymphs in 44 first- and second-order reference streams and in 14 test streams representing three of the most common land uses in the State of São Paulo (Eucalyptus, sugar-cane plantation and pasture). Our data set included incidence of Plecoptera genera, and genus richness as response variables, and environmental and spatial variables as predictors. We adopted a variation partitioning technique and estimated the unique and common effects of the two sets of explanatory variables on the response variables using multiple regression and RDA analyses. We found no relation between our response variables and environmental factors. Our results also revealed that only spatial variables significantly explained the variation on distributional patterns of Plecoptera in reference streams. This result seems to characterize differences between mountain areas and the sedimentary basin. Defining regions and reference streams for biomonitoring is an essential step to establish effective biomonitoring in the State of São Paulo, because it may contribute to separate natural variability from anthropogenic influences.