Elements of metacommunity structure in Amazonian Zygoptera among streams under different spatial scales and environmental conditions

An important aspect of conservation is to understand the founding elements and characteristics of metacommunities in natural environments, and the consequences of anthropogenic disturbance on these patterns. In natural Amazonian environments, the interfluves of the major rivers play an important role in the formation of areas of endemism through the historical isolation of species and the speciation process. We evaluated elements of metacommunity structure for Zygoptera (Insecta: Odonata) sampled in 93 Amazonian streams distributed in two distinct biogeographic regions (areas of endemism). Of sampled streams, 43 were considered to have experienced negligible anthropogenic impacts, and 50 were considered impacted by anthropogenic activities. Our hypothesis was that preserved (“negligible impact”) streams would present a Clementsian pattern, forming clusters of distinct species, reflecting the biogeographic pattern of the two regions, and that anthropogenic streams would present random patterns of metacommunity, due to the loss of more sensitive species and dominance of more tolerant species, which have higher dispersal ability and environmental tolerance. In negligible impact streams, the Clementsian pattern reflected a strong biogeographic pattern, which we discuss considering the areas of endemism of Amazonian rivers. As for communities in human‐impacted streams, a biotic homogenization was evident, in which rare species were suppressed and the most common species had become hyper‐dominant. Understanding the mechanisms that trigger changes in metacommunities is an important issue for conservation, because they can help create mitigation measures for the impacts of anthropogenic activities on biological communities, and so should be expanded to studies using other taxonomic groups in both tropical and temperate systems, and, wherever possible, at multiple spatial scales.     

Carotenoids of dragonflies,from the perspective of comparative biochemical and chemical ecological studies

Carotenoids of 20 species of dragonflies (including 14 species of Anisoptera and six species of Zygoptera) were investigated from the viewpoints of comparative biochemistry and chemical ecology. In larvae, β-carotene, β-cryptoxanthin, lutein, and fucoxanthin were found to be major carotenoids in both Anisoptera and Zygoptera. These carotenoids were assumed to have originated from aquatic insects, water fleas, tadpoles, and small fish, which dragonfly larvae feed on. Furthermore, β-caroten-2-ol and echinenone were also found in all species of larvae investigated. In adult dragonflies, β-carotene was found to be a major carotenoid along with lutein, zeaxanthin, β-caroten-2-ol, and echinenone in both Anisoptera and Zygoptera. On the other hand, unique carotenoids, β-zeacarotene, β,ψ-carotene (γ-carotene), torulene, β,γ-carotene, and γ,γ-carotene, were present in both Anisoptera and Zygoptera dragonflies. These carotenoids were not found in larvae. Food chain studies of dragonflies suggested that these carotenoids originated from aphids, and/or possibly from aphidophagous ladybird beetles and spiders, which dragonflies feed on. Lutein and zeaxanthin in adult dragonflies were also assumed to have originated from flying insects they feed on, such as flies, mosquitoes, butterflies, moths, and planthoppers, as well as spiders. β-Caroten-2-ol and echinenone were found in both dragonfly adults and larvae. They were assumed to be metabolites of β-carotene in dragonflies themselves. Carotenoids of dragonflies well reflect the food chain during their lifecycle.     

Neotropical dragonflies (Insecta: Odonata) as indicators of ecological condition of small streams in the eastern Amazon

Sensitive and cost‐effective indicators of aquatic ecosystem condition in Amazon streams are necessary to assess the effects of anthropogenic disturbances on those systems in a viable and ecologically meaningful manner. We conducted the present study in the municipality of Paragominas, state of Pará, northern Brazil, where we sampled adult dragonflies in 50 100‐m‐long wadeable stream sites in 2011. We collected 1769 specimens represented by 11 families, 41 genera and 97 species. The suborder Zygoptera contributed 961 individuals and Anisoptera 808. Among the 97 recorded species, nine were classified as useful indicators of ecological condition, with four species being associated with more degraded streams (three Anisoptera, one Zygoptera) and five with more preserved streams (all were Zygoptera). Anisoptera (dragonflies) tend to provide more useful indicators of more degraded environments because they have more efficient homeostatic mechanisms and are more mobile, enabling them to tolerate a wider range of environmental conditions. By contrast, Zygoptera (damselflies) tend to provide a more useful role as indicators of more preserved environments and high levels of environmental heterogeneity because of their smaller body sizes and home ranges and greater ecophysiological restrictions. We conclude from our assessment of this low‐order Amazonian stream system that (i) the occurrence of specific odonate species is strongly associated with the configuration of riparian vegetation, (ii) agricultural activities appear to be the main factor determining changes in the composition of odonate assemblages and (iii) these insects can act as useful indicators of the ecological consequences of riparian habitat loss and disturbance. Because generalist species invade moderately degraded areas, those areas may have high species richness but host few species of Zygoptera. Therefore, preserving dense riparian vegetation is necessary to maintain aquatic ecological condition, and that condition can be rehabilitated by planting new trees. Both require enforcing existing environmental regulations, various types of incentives and educating local communities.     

The relative role of rivers,environmental heterogeneity and species traits in driving compositional changes in southeastern Amazonian bird assemblages

Amazonian rivers have been proposed to act as geographic barriers to species dispersal, either driving allopatric speciation or defining current distribution limits. The strength of the barrier varies according to the species’ ecological characteristics and the river's physical properties. Environmental heterogeneity may also drive compositional changes but has not been well assessed in Amazonia. Aiming to understand the contributions of riverine barriers and environmental heterogeneity in shaping compositional changes in Amazonian forest bird assemblages, we focus on the Tapajós River. We investigate how spatial variation in species composition is related to physical barriers (Tapajós and Jamanxim rivers), species’ ecological characteristics (distinct guilds), and environmental heterogeneity (canopy reflectance, soils, and elevation). We sampled birds through point-counts and mist nets on both banks of the Tapajós and Jamanxim rivers. To test for relationships between bird composition and environmental data, we used Mantel and partial Mantel tests, NMDS, and ANOVA + Tukey HSD. The Mantel tests showed that the clearest compositional changes occurred across the Tapajós River, which seems to act unequally as a significant barrier to the bird guilds. The Jamanxim River was not associated with differences in bird communities. Our results reinforce that the Tapajós River is a biogeographical boundary for birds, while environmental heterogeneity influences compositional variation within interfluves. We discuss the combined influence of geographical barriers, environmental heterogeneity, and ecological characteristics of species in shaping species distributions and community composition and the complexity of extrapolating the patterns found for birds to other Amazonian organisms. Abstract in Portuguese is available with online material.     

The distribution patterns of dragonflies (Insecta: Odonata) along the Kiewa River,Australia, and their relevance in conservation assessment

Sampling of larval and adult Odonata from 16 sites along the Kiewa River, Victoria, yielded 34 species: 10 Zygoptera, 24 Anisoptera. Patterns of larval and adult incidence were appraised, and showed that most species were restricted in incidence to several consecutive sites along the river, and that there is clear distinction also between the faunas of the potamon, rhithron and eucrenon regions. Different species of some genera of Anisoptera displayed different zonational distributions, and patterns of incidence and relative abundance of larvae and adults confirmed zonational occupancy. For larvae, these distribution patterns transcended the mode of collection, although many species were found most abundantly in one microhabitat or by one of several sampling methods employed at each site. Sampling of the two stages separately showed considerable concurrence of distributional patterns, so that either stage alone may provide data of value in faunal and conservation assessment. This revised version was published online in July 2006 with corrections to the Cover Date.     

Host community similarity and geography shape the diversity and distribution of haemosporidian parasites in Amazonian birds

Identifying the mechanisms driving the distribution and diversity of parasitic organisms and characterizing the structure of parasite assemblages are critical to understanding host–parasite evolution, community dynamics, and disease transmission risk. Haemosporidian parasites of the genera Plasmodium and Haemoproteus are a diverse and cosmopolitan group of bird pathogens. Despite their global distribution, the ecological and historical factors shaping the diversity and distribution of these protozoan parasites across avian communities and geographic regions remain unclear. Here we used a region of the mitochondrial cytochrome b gene to characterize the diversity, biogeographical patterns, and phylogenetic relationships of Plasmodium and Haemoproteus infecting Amazonian birds. Specifically, we asked whether, and how, host community similarity and geography (latitude and area of endemism) structure parasite assemblages across 15 avian communities in the Amazon Basin. We identified 265 lineages of haemosporidians recovered from 2661 sampled birds from 330 species. Infection prevalence varied widely among host species, avian communities, areas of endemism, and latitude. Composition analysis demonstrated that both malarial parasites and host communities differed across areas of endemism and as a function of latitude. Thus, areas with similar avian community composition were similar in their parasite communities. Our analyses, within a regional biogeographic context, imply that host switching is the main event promoting diversification in malarial parasites. Although dispersal of haemosporidian parasites was constrained across six areas of endemism, these pathogens are not dispersal‐limited among communities within the same area of endemism. Our findings indicate that the distribution of malarial parasites in Amazonian birds is largely dependent on local ecological conditions and host evolutionary relationships.     

Unexpected diversity in the catfish Pseudancistrus brevispinis reveals dispersal routes in a Neotropical center of endemism: the Guyanas Region

Neotropical freshwater fishes have reached an unrivalled diversity, organized into several areas of endemism, yet the underlying processes are still largely unknown. The topographical and ecological characteristics of the Guyanas Region make it an ideal area of endemism in which to investigate the forces that have shaped this great diversity. This region is thought to be inhabited by species descending from Amazonian ancestors, which would have used two documented routes that, however, hardly explain the entrance of species adapted to running waters. Here, we investigate the evolutionary history of Pseudancistrus brevispinis , a catfish endemic to this region and exclusively found in running waters, thus making it an ideal model for investigating colonization routes and dispersal in such habitats. Our analyses, based on mitochondrial and nuclear markers, revealed an unexpected diversity consisting of six monophyletic lineages within P. brevispinis , showing a disjoint distribution pattern. The lineages endemic to Guyanas coastal rivers form a monophyletic group that originated via an ancestral colonization event from the Amazon basin. Evidence given favours a colonization pathway through river capture between an Amazonian tributary and the Upper Maroni River. Population genetic analyses of the most widespread species indicate that subsequent dispersal among Guyanas coastal rivers occurred principally by temporary connections between adjacent rivers during periods of lower sea level, yet instances of dispersal via interbasin river captures are not excluded. During high sea level intervals, the isolated populations would have diverged leading to the observed allopatric species. This evolutionary process is named the sea level fluctuation (SLF) hypothesis of diversification.     

Patterns of sexual dimorphism in flight agility in territorial and non-territorial Odonata

Journal of Ethology - Adult dragonflies (Anisoptera) and damselflies (Zygoptera) are amongst the most accomplished flying insects on the planet. The main functions of spatial displacement by flight...     

Climate and geographic distance are more influential than rivers on the beta diversity of passerine birds in Amazonia

Variation in the spatial structure of communities in terms of species composition (beta diversity) is affected by different ecological processes, such as environmental filtering and dispersal limitation. Large rivers are known as barriers for species dispersal (riverine hypothesis) in tropical regions. However, when organisms are not dispersal limited by geographic barriers, other factors, such as climatic conditions and geographic distance per se, may affect species distribution. In order to investigate the relative contribution of major rivers, climate and geographic distance on Passeriformes beta diversity, we divided Amazonia into 549 grid cells (1° of latitude and longitude) and obtained data of species occurrence, climate and geographic position for each cell. Beta diversity was measured using taxonomic, phylogenetic and functional metrics of composition. The influence of climatic variables, geographic distance and rivers on these metrics was tested using regression analyses. Passerine beta diversity is characterized mainly by the change in species taxonomic identity and in phylogenetic lineages across climatic gradients and over geographic distance. However, species with similar traits are found throughout the entire Amazonia. The size of rivers was proportional to their effect on species composition. However, climate and geographic distance are relatively more important than rivers for Amazonian taxonomic and phylogenetic species composition.     

The impacts of habitat disturbance on adult and larval dragonflies (Odonata) in rainforest streams in Sabah,Malaysian Borneo

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Net primary productivity and seasonality of temperature and precipitation are predictors of the species richness of the Damselflies in the Amazon

Several hypotheses have been proposed to explain the mechanisms that generate temporal and spatial species richness patterns. We tested four common hypotheses (water, energy, climatic heterogeneity and net primary productivity) to evaluate which factors best explain patterns of Zygoptera species richness. Of these, we predicted that climatic heterogeneity would be the most important predictor for Zygoptera richness patterns. We sampled communities of adult Zygoptera in 100 small Amazonian streams. Based on generalized linear mixed models (GLMM), we found that net primary productivity and climatic heterogeneity comprised the best model of Zygoptera species richness in Amazonian streams, with an pseudo r² of 39.5%. Results indicate that species richness increases by one species per 1 kg of biomass per square meter in NPP, or with an increase of 2 °C in air temperature variability. Our work corroborates a recent study with other taxa in Brazilian Bioms. This suggests that temporal variation in climate and net primary productivity are important predictors of the macroecological patterns of richness for aquatic organisms in tropical regions.     

Historical biogeography of South American freshwater fishes

Aim To investigate biogeographical patterns of the obligate freshwater fish order Characiformes. Location South America. Methods Parsimony analysis of endemicity, likelihood analysis of congruent geographical distribution, and partition Bremer support were used. Results Areas of endemism are deduced from parsimony analysis of endemicity, and putative dispersal routes from a separate analysis of discordant patterns of distribution. Main conclusions Our results demonstrate the occurrence of 11 major areas of endemism and support a preferential eastern–western differentiation of the characiforms in the Amazonian region, contrasting with the southern–northern differentiation of terrestrial organisms. The areas of endemism identified seem to be deeply influenced by the distribution of the emerged land during the 100‐m marine highstand that occurred during the late Miocene and allow us to hypothesize the existence of eight aquatic freshwater refuges at that time. The raw distribution of non‐endemic species supports nine patterns of species distribution across the 11 areas of endemism, two of which support a southern–northern differentiation in the eastern part of the Amazon. This result shows that the main channel of the Amazon limited dispersal between tributaries from each bank of the river. The levels of endemism further demonstrate that the aquatic freshwater refuges promoted allopatric speciation and later allowed the colonization of the lowlands. By contrast, the biogeographical pattern found in the western part of the Amazon is identified as a result of the Miocene Andean foreland dynamic and the uplift of the palaeoarches that promoted allopatric divergence across several sedimentary basins by the establishment of disconnected floodplains. The assessment of conflicting species distributions also shows the presence of seven putative dispersal routes between the Amazon, Orinoco and Paraná rivers. Our findings suggest that, rather than there being a single predominant process, the establishment of the modern South American freshwater fish biotas is the result of an interaction between marine incursions, uplift of the palaeoarches, and historical connections allowing cross‐drainage dispersal.     

Biogeography of the freshwater fishes of the Guianas using a partitioned parsimony analysis of endemicity with reappraisal of ecoregional boundaries

The Guianas are one of the most diverse regions of the Neotropics, hosting a particularly high rate of freshwater fish endemism. The present distributional patterns of freshwater fish species in the major catchments of the Guianas (comprising Guyana, Suriname and French Guiana) were analysed to reveal the faunal relationships between rivers, evaluate different hypotheses concerning biogeographical units, and redefine the boundaries of the Guianese freshwater ecoregions. A parsimony analysis of endemicity was performed using a data partitioning strategy to alleviate some drawbacks inherent to the method (e.g. long branch attraction artefact, heterotachy), and take into account alternative parsimony models assigning different constraints on state changes for the different species. A strong spatial element was present in the data with a structuring of species along a west–east gradient. Two main biogeographical units were highlighted: one to the west, ranging from the Essequibo to the Commewijne rivers and including the Proto Berbice and Surinamese regions, and one to the east ranging from the Maroni to the Oyapock rivers and including the Western, Central and Eastern French Guiana regions. Each ecoregion possessed distinctive fish assemblages, and three to four potential zones of faunal exchanges between Amazonian and Guianese rivers have been confirmed.     

Are all Mexican odonate species documented? An assessment of species richness

With the aim of protecting Mexican diversity, one current governmental task is to complete national biological inventories. In the case of odonate insects, several researchers have hypothesized that species richness is complete (205 dragonflies and 151 damselflies), but there has not been any formal exercise to test this. Thus, we have investigated whether odonate species richness (for Mexican endemics, dragonflies (suborder Anisoptera), damselflies (suborder Zygoptera) and total species) is complete using sample-based and coverage-based rarefaction curves. Along with this, we also showed how good distribution data are in the country. The rarefaction curves have indicated 100% completeness for all groups suggesting that the inventory is complete. However, species' distribution data is highly patchy regarding areas either well (e.g. central Mexico) or badly (e.g. coast of Guerrero and Oaxaca) collected. We encourage researchers to continue odonate sampling in order to support at least three conservation actions: (i) conservation assessment of endangered species; (ii) knowledge of range shifts given rising global temperatures; and (iii) increase public interest and awareness in protected, touristic areas.     

Distribution pattern, endemism, threat status and conservation measures of fishes in the Tunga and Bhadra rivers of Western Ghats, India

This study documents the distribution patterns, endemism and uniqueness (species richness) of fishes in the Tunga and Bhadra rivers of Western Ghats, India. We recorded 77 species represented by 7 orders, 16 families and 44 genera, of which 36 species are endemic to Western Ghats, 12 species endemic to India and 26 species endemic to the Indian Subcontinent. Based on our analysis on the distribution patterns, the Tunga River is richer in diversity and higher in endemism than the Bhadra. We calculated the similarity of the species composition among sites within these two rivers using the Jacquard index. The similarity index between the sampling sites of these rivers revealed that the similarity decreases with increasing distance between the sampling sites. Of the 77 fish species we collected, 8 species (11.1%) are in the Critical category, 10 species (13.8%) are in the High Risk category, 36 species (50%) are in the Moderate category and the remaining 18 species (25%) are at lower risk. The threat status of fishes found in the Tunga and Bhadra rivers strongly suggests the need for effective conservation measures to conserve the fish species richness of these rivers.     

Artificial ponds increase local dragonfly diversity in a global biodiversity hotspot

Human demands have led to an increased number of artificial ponds for irrigation of crops year-round. Certain insect species have established in these ponds, including dragonflies (Insecta: Odonata). There has been discussion around the value of artificial ponds for encouraging dragonfly diversity, with little work in biodiversity hotspots rich in rare and endemic species. We focus here on the Cape Floristic Region (CFR) global biodiversity hotspot, which has many endemic dragonfly species but has few natural ponds. Yet it has many artificial ponds mostly used for irrigation on local farms. This leads to an interesting question: to what extent do these artificial ponds provide habitats for dragonflies in this biologically rich, agriculturally fragmented landscape? To answer this, we recorded dragonfly species richness and abundances from 17 artificial ponds and 13 natural stream deposition pools as reference, in an area of the CFR where there are no local, natural, perennial ponds. Thirteen environmental and physical variables were recorded at the ponds and pools. We found that although ponds attracted no rare or threatened dragonfly species, they increased the area of occupancy and population sizes of many generalist species. These came from nearby natural deposition pools or from unknown sources elsewhere in the region, so providing refuges which otherwise would not be there. Interestingly, some CFR endemic species were also recorded at our artificial ponds. Overall dragonfly assemblages and those of true dragonflies (Anisoptera) and damselflies (Zygoptera) differed between artificial ponds and deposition pools, suggesting that artificial ponds are to some extent a novel ecosystem. Habitat type, elevation and temperature were significant drivers in structuring overall species assemblages. For the Anisoptera, riparian vegetation and level of landscape connectivity was important, while temperature was not. In contrast, Zygoptera species were most affected by river catchment, habitat type and temperature. In sum, these artificial ponds are stepping stone habitats across an increasingly fragmented landscape. Managing these ponds with perennial water, constant water levels, and maximum complexity and heterogeneity of habitats in terms of vegetation will conserve a wide range of generalists and some specialists.     

A palaeobiogeographic model for biotic diversification within Amazonia over the past three million years

Many hypotheses have been proposed to explain high species diversity in Amazonia, but few generalizations have emerged. In part, this has arisen from the scarcity of rigorous tests for mechanisms promoting speciation, and from major uncertainties about palaeogeographic events and their spatial and temporal associations with diversification. Here, we investigate the environmental history of Amazonia using a phylogenetic and biogeographic analysis of trumpeters (Aves: Psophia), which are represented by species in each of the vertebrate areas of endemism. Their relationships reveal an unforeseen 'complete' time-slice of Amazonian diversification over the past 3.0 Myr. We employ this temporally calibrated phylogeny to test competing palaeogeographic hypotheses. Our results are consistent with the establishment of the current Amazonian drainage system at approximately 3.0-2.0 Ma and predict the temporal pattern of major river formation over Plio-Pleistocene times. We propose a palaeobiogeographic model for the last 3.0 Myr of Amazonian history that has implications for understanding patterns of endemism, the temporal history of Amazonian diversification and mechanisms promoting speciation. The history of Psophia, in combination with new geological evidence, provides the strongest direct evidence supporting a role for river dynamics in Amazonian diversification, and the absence of such a role for glacial climate cycles and refugia.     

Metrics for macroscale invasion and dispersal patterns

Aim The ability to quantitatively measure the continuum of macroscale patterns of species invasion is a first step toward deeper understanding of their causal factors. We took advantage of two centuries worth of herbarium data, to evaluate a set of metrics to measure macroscale patterns, allowing cross-species comparisons of invasive expansion across large geographic areas.Methods We used herbarium specimens to reconstruct county-level invasion histories for two non-native plants (Alliaria petiolata and Lonicera japonica), with distinct spatiotemporal distribution patterns over the past two centuries. Using county centroids from species' initial occurrences, we quantified point pattern metrics from multiple disciplines (e.g. urban crime analysis, landscape ecology etc.) that are historically used at smaller spatial scales, to evaluate their ability to detect macroscale spatial diffusion and amount of directional expansion. Metrics were further assessed for their ease of use, data requirements, independence from other metrics and intuitiveness of interpretation.Important findings We identified four suitable metrics for distinguishing differences in spatial patterns: (i) standard distance, (ii) number of patches, (iii) Euclidean nearest neighbor summary class statistic coefficient of variation and (iv) mean center that when applied to county-level presence data allowed us to determine the directions by which distributions expanded and if distributions increased via outward expansion, infilling and/or jump dispersal events. These metrics when compared during the same invasion phase are capable of quantifying macroscale variability among species in their distributional and dispersal patterns. Being able to quantify differences among species in these patterns is important in understanding the drivers of species dispersal patterns. These metrics therefore represent a simple yet thorough toolset for achieving this goal.     

Concordance among stream assemblages and spatial autocorrelation along a fragmented gradient

Patterns of spatial autocorrelation of biota and distributional similarity (concordance) between assemblages of different organism groups have important implications in both theoretical ecology and biodiversity conservation. Here we report environmental gradients and spatial distribution patterns of taxonomic composition among stream fish, benthic macroinvertebrate, and diatom assemblages along a fragmented stream in south‐western France. We quantified spatial patterns of lotic assemblage structure along this stream, and we tested for concordance in distribution patterns among the three taxonomic groups. Our results showed that both environmental characteristics and stream assemblages were spatially autocorrelated. For stream fish and diatom assemblages, these patterns reflected assemblage changes along the longitudinal stream gradient, whereas environmental variables and benthic macroinvertebrates exhibited a more patchy spatial pattern. Cross‐taxa concordance was significant between stream fish and diatoms, and between stream fish and benthic macroinvertebrates. The assemblage concordance between stream fish and diatoms could be attributed to similar responses along the longitudinal gradient, whereas those between stream fish and benthic macroinvertebrates may result from biotic interactions. Based on potential dispersal capacities of taxa, our results validated the hypotheses that weakly dispersing taxa exhibit greater concordance than highly dispersing ones and that dispersal capacities affect how taxonomic groups respond to their local environment. Both diatoms and highly dispersing stream fish were affected by stream fragmentation (i.e. the number of dams between sites), while the effect of fragmentation was not significant for invertebrates that fly well in their adult stage, thus emphasizing the importance of the way of dispersal. These results suggest that addressing the effects of dispersal capacity on stream assemblage patterns is crucial to identifying mechanisms behind patterns and to better understanding the determinants of stream biodiversity.     

Isolation by distance,not rivers,control the distribution of termite species in the Amazonian rain forest

The spatial distribution of species is affected by dispersal barriers, local environmental conditions and climate. However, the effect of species dispersal and their adaptation to the environment across geographic scales is poorly understood. To investigate the distribution of species from local to broad geographic scales, we sampled termites in 198 transects distributed in 13 sampling grids in the Brazilian Amazonian forest. The sampling grids encompassed an area of 271 500 km² and included the five major biogeographic regions delimited by Amazonian rivers. Environmental data for each transect were obtained from local measurements and remote sensing. Similar to previous studies, termite species composition at the local scale was mostly associated with measures of soil texture and chemistry. In contrast, termite species composition at broad geographic scales was associated with soil nutrients, and the geographic position of the transects. Between 17 and 30% of the variance in termite species composition could be attributed exclusively to the geographic position of the transects, but could not be attributed to measured environmental variables or the presence of major rivers. Isolation by distance may have strong effects on termite species composition due to historic processes and the spatially structured environments along distinct geological formations of Amazonia. However, in contrast to many taxa in Amazonia, there is no evidence that major rivers are important barriers to termite dispersal.