Aquatic Insect Communities Research Articles

Fluvial geomorphology and aquatic‐to‐terrestrial Hg export are weakly coupled in small urban streams of Columbus, Ohio

AbstractAlthough mercury (Hg) contamination is common in stream ecosystems, mechanisms governing bioavailability and bioaccumulation in fluvial systems remain poorly resolved as compared to lentic systems. In particular, streams in urbanized catchments are subject to fluvial geomorphic alterations that may contribute to Hg distribution, bioaccumulation, and export across the aquatic‐to‐terrestrial boundary. In 12 streams of urban Columbus, Ohio, we investigated the influence of fluvial geomorphic characteristics related to channel geometry, streamflow, and sediment size and distribution on (1) Hg concentrations in sediment and body burdens in benthic larval and adult emergent aquatic insects and (2) aquatic‐to‐terrestrial contaminant transfer to common riparian spiders of the families Pisauridae and Tetragnathidae via changes in aquatic insect Hg body burdens as well as in aquatic insect density and community composition. Hydrogeomorphic characteristics were weakly related to Hg body burdens in emergent insects (channel geometry) and tetragnathid spiders (streamflow), but not to Hg concentrations in sediment or benthic insects. Streamflow characteristics were also related to emergent insect density, while wider channels were associated with benthic insect community shifts toward smaller‐bodied and more tolerant taxa (e.g., Chironomidae). Thus, our results provide initial evidence that fluvial geomorphology may influence aquatic‐to‐terrestrial contaminant Hg transfer through the collective effects on emergent insect body burdens as well as on aquatic insect community composition and abundance.

Phylogenies and traits provide distinct insights about the historical and contemporary assembly of aquatic insect communities.

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.

Functional Process Zones Characterizing Aquatic Insect Communities in Streams of the Brazilian Cerrado.

Stream ecology studies see to understand ecological dynamics in lotic systems. The characterization of streams into Functional Process Zones (FPZ) has been currently debated in stream ecology because aquatic communities respond to functional processes of river segments. Therefore, we tested if different functional process zones have different number of genera and trophic structure using the aquatic insect community of Neotropical streams. We also assessed whether using physical and chemical variables may complement the approach of using FPZ to model communities of aquatic insects in Cerrado streams. This study was conducted in 101 streams or rivers from the central region of the state of Goiás, Brazil. We grouped the streams into six FPZ associated to size of the river system, presence of riparian forest, and riverbed heterogeneity. We used Bayesian models to compare number of genera and relative frequency of the feeding groups between FPZs. Streams classified in different FPZs had a different number of genera, and the largest and best preserved rivers had an average of four additional genera. Trophic structure exhibited low variability among FPZs, with little difference both in the number of genera and in abundance. Using functional process zones in Cerrado streams yielded good results for Ephemeroptera, Plecoptera, and Trichoptera communities. Thus, species distribution and community structure in the river basin account for functional processes and not necessarily for the position of the community along a longitudinal dimension of the lotic system.

Eco-hydrobiology with Special Reference to Entamofauna and Avifaunal Diversity of Sothuparai Reservoir, Periyakulam, Theni District, Tamilnadu, India

Sothuparai reservoir is located at the foothills of the Western Ghats. The water quality parameters such as water temperature, PH, turbidity, total dissolved solids, total hardness, electrical conductivity, magnesium, calcium and chloride were analyzed and are within the permissible limits and can be used for irrigation and domestic purpose. A total of 2,670 individuals of aquatic entamofauna were represented by 43 genera categorized under 32 families and 9 orders during the study period. The diversity, evenness and the Ephemeroptera, Plecoptera and Trichoptera families were higher in upperstream than in downstream. Ephemeropteran was most diverse and its presence is an indicative of good water quality. The abundance of organic pollution tolerant Baetis species was found in downstream. To compare with the upperstream has the better water quality than the downstream of the reservoir. This may be due to the interruptions by anthropogenic activities in the downstream. The diversity and structure of bird communities is essential to delineate the importance of regional or local landscapes for avian conservation. Total count method was used and a total of 1,348 individuals belonging to 38 species of 25 families were observed in Sothuparai reservoir. Out of 25 Families, Muscicapidae dominated with 4 species and Culicidae with 3 species. Thus the present investigation depicts that the Sothuparai reservoir supports variety of bird’s population and aquatic insect communities. Regular monitoring of the reservoir using aquatic insects and birds as indicators will facilitate better conservation and management.

A comparative study of the aquatic insect diversity of two ponds locatedin Cachar District, Assam, India

Ponds play a vital role in the conservation of aquatic biodiversity at the local level apart from other lakes and rivers. A comparative study was carried out on the aquatic insect diversity of two different ponds, one in an urban area (urban pond, UP) and another in a rural area (Jalinga pond, JP). Two seasonal collections (postmonsoon and winter) were made to check the pollution status of the two ponds based on the aquatic insect community and physicochemical properties of water. Consequently, 29 species, 17 families, and 5 orders of aquatic insects from UP and 17 species, 8 families, and 3 orders from JP were recorded. Aphelonecta sp., Cloeon sp., and Micronecta sp. were the eudominant species recorded. According to the Shannon (H') index, UP was more diverse than JP. Family level biotic indices and scores further proved the better water quality of UP than of JP. Hence, it can be said that urban ponds have an important role to play in biodiversity conservation.

Diversity, distribution and habitat requirements of aquatic insect communities in tropical mountain streams (South-eastern Guinea, West Africa)

Considering that knowledge of the biodiversity of a region is the first step toward its conservation and given the paucity of studies on aquatic insects from the Simandou streams, the diversity of these communities was assessed. Aquatic insects were sampled with a hand-net (mesh size: 250 μm) on four occasions between March 2011 and September 2012 at 27 sites. Environmental variables were also recorded. Overall, 129 taxa belonging to 51 families and eight orders were recorded. Multivariate analyses gathered sites into three clusters in regard to aquatic insect composition. The rarefied taxonomic richness showed decreases in association with increasing levels of human impact. Cluster 1 that contained most disturbed sites displayed low taxonomic richness compared with the two others. The highest taxonomic richness was registered in cluster 2 that contained a mixture of upland and lowland sites; the latter remained minimally disturbed. These sites could be considered as reference sites in studies for assessing water quality. Generalised additive models calculated for the most frequent taxa showed that water temperature, dissolved oxygen, conductivity and pH were the incorporated explanatory variables. Therefore, further anthropogenic activities should preserve the surrounding forest in order to preserve the quality of Simandou streams and consequently aquatic biodiversity.

Aquatic insect β‐diversity is not dependent on elevation in Southern Rocky Mountain streams

Summary Relatively high β‐diversity among aquatic insect communities inhabiting high‐elevation streams is most commonly presumed to result from increased dispersal limitation between isolated mountaintop ‘islands’. However, these elevational patterns of β‐diversity have been predominately drawn from observed changes in community composition along single‐thread channels, where the downstream increase in habitat size and hydrologic connectivity provides potential alternative explanations. In this study, we applied an alternative conceptual ‘tributary model’ to ask whether patterns of aquatic insect β‐diversity in similar‐sized, hydrologically disconnected streams showed a similar elevational gradient in diversity patterns as previously reported for conceptual ‘mainstem model’ studies. Aquatic insects were sampled from 24 low‐order, montane streams that are tributaries to larger rivers in three adjacent catchments spanning c. 2000–3500 m in elevation. We used relative abundance data to quantify two types of β‐diversity: (i) community turnover‐β, or the change in local diversity among adjacent streams along the elevational gradient within each catchment, and (ii) community variation‐β, or the change in local diversity among all streams within three elevation zones combined across catchments. Our results provided evidence of no relationship between β‐diversity and elevation in aquatic insect communities in small montane streams. Community turnover‐β was found to be consistently high among sites within catchments and displayed no significant trend across the elevational gradient for any catchment. Community variation‐β showed a nonlinear response to elevation, with sites in the high‐elevation and low‐elevation zones having similarly high community variation‐β compared to sites in the mid‐elevation zone. Our ‘tributary model’ results provide the first evidence that β‐diversity among small, isolated streams can have similar turnover rates across broad elevational gradients. Our results also show similar patterns of β‐diversity among low‐ and high‐elevation tributaries, suggesting that dispersal limitation is not restricted to high‐elevation streams.

Aquatic pollution increases use of terrestrial prey subsidies by stream fish

Summary Stream food webs are connected with their riparian zones through cross‐ecosystem movements of energy and nutrients. The use and impact of terrestrial subsidies on aquatic consumers is determined in part by in situ biomass of aquatic prey. Thus, stressors such as aquatic pollutants that greatly reduce aquatic secondary production could increase the need for and reliance of stream consumers on terrestrial resource subsidies. To test this hypothesis, we surveyed stream fish, their diets and resource availability in 16 subalpine streams over a regional gradient of trace metals known to strongly impact aquatic insect communities (i.e. fish prey) in the Colorado Rocky Mountains, USA. Fish increased their reliance on terrestrial insect prey as stream metals increased. Relative biomass of terrestrial insects in stomach contents of Brook and Brown Trout increased with respect to aquatic insect biomass and total stomach contents. Drifting insect biomass showed a declining trend for aquatic, but not terrestrial insects, over the metal gradient. Trout densities were unrelated to metal concentrations in streams where we found fish. Synthesis and applications. Our results indicate that diets of aquatic consumers can become more terrestrial as aquatic stressors that limit in situ food production increase and that these subsidies may compensate for loss of aquatic resources. This work implies an important connection between preserving aquatic–terrestrial linkages and management of fish populations in stressed watersheds. Specifically, intact riparian zones and aquatic–terrestrial linkages are likely to be important for maintaining trout production in streams with moderate metal contamination.

How does the management of rice in natural ponds alter aquatic insect community functional structure?

Changes to biodiversity have mainly been assessed using taxonomic diversity indices. Although these approaches contribute to our scientific understanding of species richness and composition patterns, trait-based metrics may be more useful for detecting responses to land-use change. We compared functional diversity of aquatic insect communities along a gradient of agricultural intensification. Our goal was to compare functional redundancy, functional richness, functional evenness and functional divergence among natural ponds, and organic and conventional rice fields. We recorded 15606 aquatic insects distributed across 61 genera. The highest functional redundancy and richness were observed in the natural ponds, followed by organic rice fields and conventional ones. The functional composition varied among natural ponds and rice fields, and differed between organic and conventional rice fields. Organic management favoured the establishment of some pond insect traits, such as predatory taxa, in rice agroecosystems. Our analysis suggests that the conversion of ponds to rice fields results in a shift to less specialised aquatic insect communities with altered functional composition groups. Nevertheless, this result should not be seen as a negative reflection on organic rice fields, because organic rice production affords a better compromise between agricultural production and ecosystem function than conventional agriculture.

Dispersal traits drive the phylogenetic distance decay of similarity in Neotropical stream metacommunities

AbstractAimThe drivers of phylogenetic beta diversity include both local processes (e.g. environmental filtering) and regional processes (e.g. dispersal limitation). The role of environmental filtering can be investigated more directly by analysing community–environment associations, but dispersal limitation is one of the most challenging processes to examine. We investigated the role of traits related to dispersal – flight capacity, body size and voltinism – as drivers of phylogenetic distance decay relationships in Neotropical stream insect communities.LocationHeadwater streams spread over 600 km in south‐eastern Brazil.MethodsWe compiled a data set of aquatic insect communities inhabiting streams across the State of São Paulo (Brazil). Then, we investigated environmental and spatial signals on phylobetadiversity patterns of aquatic insects using Mantel tests, multiple regressions on distance matrices and variation partitioning. We employed null models to investigate whether phylogenetic distance decay differed from pure compositional distance decay. We deconstructed the data set based on dispersal‐related traits; we then ran distance decay analyses for these subsets separately.ResultsGeographical distance, rather than environmental distance, better explained the patterns of phylobetadiversity. We found that the phylogenetic decay relationship differed from the relationship expected for the null models only for univoltine, large‐bodied genera with a high‐flight capacity.Main conclusionsDispersal limitation, rather than species sorting, was the main driver for phylogenetic beta diversity in the metacommunity that we studied. We suggest that life‐history strategies and mainly voltinism drive the distance decay of similarity in the insect communities examined. We additionally discuss the role of dispersal events over time to explain differences in distance decay patterns among tropical and other regions.

Flood pulses drive the temporal dynamics of assemblages of aquatic insects (Heteroptera and Coleoptera) in a temperate floodplain

SummaryLowland riverine floodplains are among the most dynamic and heterogeneous of ecosystems, but many have been extensively modified. Their provision of important habitats provides a key motivation for restoring natural flow regimes (in terms of magnitude, frequency, duration, timing and rate of change of hydrological conditions). Despite general recognition that aquatic insects respond to changes in water availability, there is little agreement about the influence of flow regime components on community structure in floodplains.We analysed a 6‐year (2005 and 2007–2011) data set of aquatic insects (Heteroptera and Coleoptera) in a large Danubian floodplain characterised by pronounced hydrological variability. We hypothesised that abundance and assemblage structure would depend on flow regime components. In particular, we predicted that high‐flow events in the mainstream and concurrent high‐magnitude floods of prolonged duration would have a positive effect on diversity and abundance and that insect assemblages would differ between phases of hydrological connectivity. In addition, we assessed whether the survival of two threatened aquatic insects,Graphoderus bilineatusandBerosus geminus, depends on hydrological connectivity.Abundance and species richness of Heteroptera and Coleoptera increased during years with frequent extremely high flood pulses and prolonged flooding. Multivariate ordination showed subtle relationships between hydrological conditions, hydrological connectivity and insect assemblages with number of days in flood providing the best fit. Spring floods had a more pronounced effect on the assemblages than autumn floods. The time lag between flood occurrence and its apparent effect on aquatic insects was 17–31 days, reflecting insect life cycles.The abundance ofG. bilineatus(Coleoptera: Dytiscidae) was affected by mean water level during the month preceding sampling, whereas the abundance ofB. geminus(Coleoptera: Hydrophilidae) was related to the occurrence of prolonged high‐magnitude floods.The current water regime of the Danube River favours generalist species with high dispersal capacities and broad niches and food resources. Changes in flow management practices could remove the positive influence of floods on aquatic insect communities and lead to losses of threatened species that depend on these river–floodplain habitats. Our results contribute to the understanding necessary for appropriate evaluation and prioritisation of international floodplain conservation efforts.

The Aquatic Insect Communities of Universiti Malaysia Sabah (UMS), Sabah, Malaysia

A s tudy was conducted to investigate the aquatic insect communities in Universiti Malaysia Sabah (UMS), Sabah, Malaysia. Two sampling sites were selected: lakes at School of Science and Technology (SST), and another near College E (CE) (student accommodation). Each lake consisted of four sampling stations. Aquatic insects were sampled using dip net from November 2013 to January 2014. Four water quality parameters were measured at each station. Shannon-Weiner’s diversity index and biotic indices (BMWP) were used in this study. Student’s t-test was used for testing the significant difference of water quality parameters, Shannon-Weiner’s diversity index and BMWP between these lakes. Pearson’s correlation was used to investigate relationships between aquatic insect assemblage and water quality parameters. A total of 1987 individuals composed of five orders that representing eleven families were recorded in this study. Baetidae (56.67%) was the dominant family in UMS, where Diptera order had least abundant with only 0.4% of overall sample. Aquatic insect abundance were significantly higher (P<0.05) in CE Lake. Bray-Curtis Similarity index showed 53.75% similarity between these two lakes. Pearson’s correlation showed that aquatic insect abundance and richness had significant relationships with water temperature, dissolved oxygen, salinity and pH (P<0.05 or 0.01), except for salinity with taxa richness. Based on Malaysia’s INWQS, water quality parameters of these two lakes were categorized as Class I, but with dissolved oxygen the CE and SST lakes were classified as Class IIA and III respectively. The BMWP index showed similar results as dissolved oxygen, where SST Lake (score=40) had poor water quality.

The rainy season increases the abundance and richness of the aquatic insect community in a Neotropical reservoir.

Alterations in aquatic systems and changes in water levels, whether due to rains or dam-mediated control can cause changes in community structure, forcing the community to readjust to the new environment. This study tested the hypothesis that there is an increase in the richness and abundance of aquatic insects during the rainy season in the Serra da Mesa Reservoir, with the premise that increasing the reservoir level provides greater external material input and habitat diversity, and, therefore, conditions that promote colonization by more species. We used the paired t test to test the differences in richness, beta diversity, and abundance, and a Non-metric Multidimensional Scaling (NMDS) was performed to identify patterns in the community under study. Additionally, Pearson correlations were analyzed between the richness, abundance, and beta diversity and the level of the reservoir. We collected 35,028 aquatic insect larvae (9,513 in dry period and 25,515 in the rainy season), predominantly of the Chironomidae family, followed by orders Ephemeroptera, Trichoptera, and Odonata. Among the 33 families collected, only 12 occurred in the dry season, while all occurred in the rainy season. These families are common in lentic environments, and the dominance of Chironomidae was associated with its fast colonization, their behavior of living at high densities and the great tolerance to low levels of oxygen in the environment. The hypothesis was confirmed, as the richness, beta diversity, and abundance were positively affected by the increase in water levels due to the rainy season, which most likely led to greater external material input, greater heterogeneity of habitat, and better conditions for colonization by several families.

Closely Related Tree Species Differentially Influence the Transfer of Carbon and Nitrogen from Leaf Litter Up the Aquatic Food Web

Decomposing leaf litter in streams provides habitat and nutrition for aquatic insects. Despite large differences in the nutritional qualities of litter among different plant species, their effects on aquatic insects are often difficult to detect. We evaluated how leaf litter of two dominant riparian species (Populus fremontii and P. angustifolia) influenced carbon and nitrogen assimilation by aquatic insect communities, quantifying assimilation rates using stable isotope tracers (13C, 15N). We tested the hypothesis that element fluxes from litter of different plant species better define aquatic insect community structure than insect relative abundances, which often fail. We found that (1) functional communities (defined by fluxes of carbon and nitrogen from leaf litter to insects) were different between leaf litter species, whereas more traditional insect communities (defined by relativized taxa abundances) were not different between leaf litter species, (2) insects assimilated N, but not C, at a higher rate from P. angustifolia litter compared to P. fremontii, even though P. angustifolia decomposes more slowly, and (3) the C:N ratio of material assimilated by aquatic insects was lower for P. angustifolia compared to P. fremontii, indicating higher nutritional quality, despite similar initial litter C:N ratios. These findings provide new evidence for the effects of terrestrial plant species on aquatic ecosystems via their direct influence on the transfer of elements up the food web. We demonstrate how isotopically labeled leaf litter can be used to assess the functioning of insect communities, uncovering patterns undetected by traditional approaches and improving our understanding of the association between food web structure and element cycling.

Linkages between benthic microbial and freshwater insect communities in degraded peatland ditches

Many wetlands are heavily modified and identifying the environmental drivers of indicator groups like aquatic insects is complicated by multiple stressors and co-varying environmental factors. Yet, incorporating data from other biological groups, such as microbial communities, potentially reveals which environmental factors are underpinning insect community composition. In the present study we investigated the application of benthic microbial community composition, as determined by phospholipid fatty acid (PLFA) analysis, alongside aquatic insect data in 25 peatland ditches in the province of North Holland, The Netherlands. We applied clustering and principal component analysis to a matrix of 26 PLFAs to group ditches by the microbial community. Generalized linear models were used to examine correlations between microbial PLFAs, insects, vegetation (emergent and submerged) and abiotic factors. The ratio of heterotrophic (e.g. sulphate reducing bacteria) to autotrophic (e.g. algae and cyanobacteria) derived PLFAs could be estimated as the ratio between saturated and branched to monounsaturated and polyunsaturated fatty acids (SB/MP). SB/MP was correlated with insect community composition, differences in water chemistry (in particular bicarbonate, sulphate and nutrients) and vegetation cover in the ditches. Moreover, ditches distinguished by their microbial communities differed in the number of insects they supported with differences most pronounced for Odonata, Trichoptera and Chironomus larvae. This study demonstrates that integrating microbial and aquatic insect community data provides insight into key environmental drivers in modified aquatic ecosystems and may facilitate the development of remediation strategies for degraded wetlands.

Diversity and ecological aspects of aquatic insect communities from montane streams in southern Brazil

AIMS: In this study, the diversity of Ephemeroptera, Plecoptera, Trichoptera and Coleoptera communities was surveyed in the Toropi River basin, a watershed localized in a slope region, in southernmost Brazil. The influence of some local abiotic factors on the most common genera was also analyzed. METHODS: Samplings were conducted at 40 sites in 1st-4th order streams, along a short elevation gradient (70-500 m), with a Surber sampler. Water physico-chemical factors, as well as substrate type, were obtained at each site. RESULTS: At all, 5,320 specimens were collected, belonging to 18 families and 52 genera. The caddisflies Austrotinodes and Celaenotrichia, and an undescribed Elmidae, Genus M, are new records for the region. The caddisfly Smicridea was the most frequent genus in the study area. The mayflies Camelobaetidius, Paracloeodes and Americabaetis were influenced by stream order. Smicridea was related to air temperature, while the mayfly Thraulodes was influenced by high levels of electrical conductivity. CONCLUSIONS: The high diversity found in the study area, compared to other Brazilian regions, reflects the environmental heterogeneity in the region. These data show that hydrographic basins in slope areas from extreme Southern Brazil sustain high levels of diversity of aquatic insect communities.

Spatial variation of aquatic insect community in fish farms pond in the Southern Côte d’ivoire, West Africa

Spatial variation of aquatic insect community in fish farms pond in the Southern Côte d’ivoire, West Africa

The role of emergent vegetation in structuring aquatic insect communities in peatland drainage ditches

Availability of macrophyte habitat is recognized as an important driver of aquatic insect communities in peatland drainage ditches; however, eutrophication can lead to the decline of submerged vegetation. While emergent vegetation is able to persist in eutrophicated ditches, vegetation removal, carried out during ditch maintenance, can reduce the availability of this habitat. In this study, we applied the landscape filtering approach to determine whether the absence of emergent vegetation is a habitat filter which structures aquatic insect communities in peatland drainage ditches under different trophic conditions. To this end, a field study was carried out in one mesotrophic (Naardermeer) and one eutrophic (Wormer and Jisperveld) peatland in the province of North Holland, The Netherlands. We assigned life history strategies to insect species and applied linear mixed models and redundancy analyses to taxonomic and functional aquatic insect community data. Our results indicate that while differences between peatlands primarily determine the species pool within each wetland, emergent vegetation acted as a secondary filter by structuring functional community composition within ditches. The eutrophic peatland was dominated by insects adapted to abiotic extremes, while species with good dispersal abilities were strongly related to emergent vegetation cover. This study demonstrates the applicability of life history strategies to provide insight into the filtering of species due to availability of emergent macrophyte habitat. To ensure greater diversity of insect communities in ditch habitats, it is recommended that some vegetation be spared during maintenance to leave patches from which insect recolonization can occur.

Intrinsic and extrinsic drivers of succession: effects of habitat age and season on an aquatic insect community

1. Classical studies of succession, largely dominated by plant community studies, focus on intrinsic drivers of change in community composition, such as interspecific competition and changes to the abiotic environment. They often do not consider extrinsic drivers of colonization, such as seasonal phenology, that can affect community change. 2. We investigated both intrinsic and extrinsic drivers of succession for dipteran communities that occupy ephemeral pools, such as those in artificial containers. By initiating communities at different times in the season and following them over time, we compared the relative importance of intrinsic (i.e., habitat age) vs. extrinsic (i.e., seasonal phenology) drivers of succession. 3. We placed water-filled artificial containers in a deciduous forest with 20 containers initiated in each of three months. Containers were sampled weekly to assess community composition. Repeated-measures mixed-effects analysis of community correspondence analysis (CA) scores enabled us to partition intrinsic and extrinsic effects on succession. Covariates of temperature and precipitation were also tested. 4. Community trajectories (as defined by CA) differed significantly with habitat age and season, indicating that both intrinsic and extrinsic effects influence succession patterns. Comparisons of AICcs showed that habitat age was more important than season for species composition. Temperature and precipitation did not explain composition changes beyond those explained by habitat age and season. 5. Quantification of relative strengths of intrinsic and extrinsic effects on succession in dipteran and other ephemeral communities enables us to disentangle processes that must be understood for predicting changes in community composition.

Community Structure of Aquatic Insects in the Karstic Jadro River in Croatia

This study focused on the aquatic insect community in the longitudinal gradient and temporal scales of the Jadro River. The river was sampled for a period of ten years (2000–2010), four times per year through the various seasons, along the river course. Sampling stations were selected in the upper, middle, and downstream parts of the river. A total of 21,852 specimens of aquatic insects belonging to six orders were obtained. The species determination confirmed 27 different species in the river. The data were analyzed by the multivariate methodologies of correspondence analysis and cluster analysis (unweighted pair group method with arithmetic mean) using the similarity index of Morosita for all ten years. Canonical correspondence analysis was applied to the data to check which of the mesured physicochemical variables significantly explained community variation. According to those data, significant variables for the upper station were water temperature and dissolved oxygen, and chlorides was the significant variable for the lower stations.