Trophic Preferences Research Articles

An Entomological Investigation during a Recent Rift Valley Fever Epizootic/Epidemic Reveals New Aspects of the Vectorial Transmission of the Virus in Madagascar.

A Rift Valley fever (RVF) outbreak occurred in at least five regions of Madagascar in 2021. The aim of this study was to provide an overview of the richness, abundance, ecology, and trophic preferences of mosquitoes in the Mananjary district and to investigate the distribution of mosquitoes that were RT-PCR-positive for RVFV. Three localities were prospected from 26 April to 4 May 2021, using light traps, BG-Sentinel traps baited with an artificial human odor, Muirhead-Thomson pit traps, and indoor pyrethroid spray catches. A total of 2806 mosquitoes belonging to at least 26 species were collected. Of 512 monospecific pools of mosquitoes tested with real-time RT-PCR, RVFV was detected in 37 pools representing 10 mosquito species. The RVFV-positive species were as follows: Aedes albopictus, Ae. argenteopunctatus, Anopheles coustani, An. gambiae s.l., An. mascarensis, An. squamosus/cydippis, Culex antennatus, Cx. decens, Cx. Tritaeniorhynchus, and Uranotaenia spp. Of the 450 tested engorged females, 78.7% had taken a blood meal on humans, 92.9% on cattle, and 71.6% had taken mixed (human-cattle) blood meals. This investigation suggests the potential role of mosquitoes in RVFV transmission within this epizootic/epidemic context and that the human populations at the three study sites were highly exposed to mosquitoes. Therefore, the use of impregnated mosquito nets as an appropriate prevention method is recommended.

Microplastics ingestion and endocrine disrupting chemicals (EDCs) by breeding seabirds in the east tropical Atlantic: Associations with trophic and foraging proxies (δ15N and δ13C)

In this study we found that endocrine disrupting chemicals (EDCs) were omnipresent in a tropical seabird community comprising diverse ecological guilds and distinct foraging and trophic preferences. Because EDCs tend to bioaccumulate within the food web and microplastics can absorb and release harmful chemical compounds, our findings draw attention to the potential threats to wildlife. Thus, the goal of this study was to investigate the role of plastic ingestion, trophic and foraging patterns (δ15N and δ13C) of five tropical seabird species breeding in sympatry, on the exposure to EDCs, namely Polybrominated diphenyl ethers (PBDEs), methoxylated polybrominated diphenyl ethers (MeO-PBDEs) and personal care products (PCPs, e.g., musk fragrances and UV-filters). Results indicated that microplastics occurrence and EDCs detection frequency varied among species. Microplastics occurrence was higher in species with dual and coastal foraging strategies. Preen oil had higher levels of MeO-PBDEs and PCPs, while serum had higher levels of PBDEs. In brown boobies, the correlation between microplastics and ∑PBDEs levels was significant, suggesting that microplastics ingestion is a key PBDEs route. Trophic position (δ15N) plays a key role in PBDEs accumulation, particularly in Bulwer's petrel, which occupies a high trophic position and had more specialized feeding ecology than the other species. MeO-PBDEs were linked to foraging habitat (δ13C), although the link to foraging locations deserves further investigation. Overall, our findings not only fill key gaps in our understanding of seabirds' exposure to microplastics and EDCs, but also provide an essential baseline for future research and monitoring efforts. These findings have broader implications for the marine wildlife conservation and pollution management in sensitive environments, such as the tropical regions off West Africa.

Parasites of juvenile Salminus brasiliensis and Brycon orbignyanus (Characiformes, Bryconidae) in the middle Paraná River, Argentina

Piscivorous Salminus brasiliensis and herbivorous/omnivorous Brycon orbignyanus often form mixed schools in the same habitats. The aims of this study were: (a) to analyze and compare ecto- and endoparasite communities in juvenile S. brasiliensis and B. orbignyanus in the Middle Paraná River, Argentina; and (b) to evaluate the possible relationships between degree of parasitic infestation and body condition (Kn) of the fish. Fish necropsy was performed in search of endo- and ectoparasites, which were mounted in permanent or semi-permanent preparations for taxonomic study using helminthological techniques. A total 24 macroparasite taxa were recorded from the two host species. The parasitic infracommunities of both hosts were competitively structured. Ectoparasite communities were more similar than endoparasite communities. The abundance of parasitic species was not correlated with the standard length, weight and Kn of host individuals, except for the abundance of the copepod E. lacusauratus in the host S. brasiliensis, which was positively related to fish condition. New records of parasites were observed for native hosts, extending the geographic range of several species already known in the Upper Paraná River. The general structure of parasite communities can be determined by several factors, such as parasite-host relationship, host trophic level, and environment. In concordance with the similarity in habitat preferences, and the strong differences in trophic preferences, ectoparasite communities were found to be more similar than endoparasite communities between the two host species.

Host feeding preferences of malaria vectors in an area of low malaria transmission

Studying the behaviour and trophic preferences of mosquitoes is an important step in understanding the exposure of vertebrate hosts to vector-borne diseases. In the case of human malaria, transmission increases when mosquitoes feed more on humans than on other animals. Therefore, understanding the spatio-temporal dynamics of vectors and their feeding preferences is essential for improving vector control measures. In this study, we investigated the feeding behaviour of Anopheles mosquitoes at two sites in the Sudanian areas of Senegal where transmission is low following the implementation of vector control measures. Blood-fed mosquitoes were collected monthly from July to November 2022 by pyrethrum spray catches in sleeping rooms of almost all houses in Dielmo and Ndiop villages, and blood meals were identified as from human, bovine, ovine, equine and chicken by ELISA. Species from the An. gambiae complex were identified by PCR. The types and numbers of potential domestic animal hosts were recorded in each village. The Human Blood Index (HBI) and the Manly Selection Ratio (MSR) were calculated to determine whether hosts were selected in proportion to their abundance. Spatio-temporal variation in HBI was examined using the Moran’s index. A total of 1251 endophilic Anopheles females were collected in 115 bedrooms, including 864 blood fed females of 6 species. An. arabiensis and An. funestus were predominant in Dielmo and Ndiop, respectively. Of the 864 blood meals tested, 853 gave a single host positive result mainly on bovine, equine, human, ovine and chicken in decreasing order in both villages. Overall, these hosts were not selected in proportion to their abundance. The human host was under-selected, highlighting a marked zoophily for the vectors. Over time and space, the HBI were low with no obvious trend, with higher and lower values observed in each of the five months at different points in each village. These results highlight the zoophilic and exophagic behaviour of malaria vectors. This behaviour is likely to be a consequence of the distribution and use of LLINs in both villages and may increase risk of residual outdoor transmission. This underlines the need to study the feeding host profile of outdoor resting populations and how domestic animals may influence malaria epidemiology in order to tailor effective malaria vector control strategies in the two villages.

Trait-independent habitat associations explain low co-occurrence in native and exotic birds on a tropical volcanic island.

On oceanic islands, strong human impacts on habitats, combined with introductions of exotic species, modify the composition of terrestrial bird assemblages and threaten their ecological functions. In La Réunion, an oceanic island located in the Madagascan region, a national park was established in 2007 to counter the ecosystem-level effects of three centuries of habitat conversion, native species destruction and exotic species introductions. Here, we investigated how bird assemblages were structured in these human-modified landscapes, 10 years before the national park set out its first conservation measures. We used a combination of multivariate statistics and generalized additive models to describe variations in the taxonomic and functional composition and diversity of 372 local bird assemblages, encompassing 20 species, along gradients of habitat composition and configuration. We found that native species were tied to native habitats while exotic species were associated with urban areas and man-modified landscape mosaics, with some overlap at mid-elevations. Species' trophic preferences were segregated along habitat gradients, but ecological traits had an overall weak role in explaining the composition of species assemblages. Hence, at the time of the survey, native and exotic species in La Réunion formed two spatially distinct species assemblages with contrasting ecological trait suites that benefited from antagonistic habitat compositions and dynamics. We conclude that our results support the analysis of historical data sets to establish reference points to monitor human impacts on insular ecosystems.

High-Resolution Lacustrine Records of the Late Holocene Hydroclimate of the Sikhote-Alin Mountains, Russian Far East.

There is little information about moisture changes in different altitudinal belts in mountainous regions of the southern Russian Far East. We present ecological and taxonomic compositions of the diatom flora and identify the botanical composition of peat in small mountain lake/mire complexes located in the Central Sikhote-Alin Mountains, within large landslides on the paleovolcanic slopes. Frequent changes in diatom assemblages and peat-forming plants indicate unstable hydroclimatic conditions with varying degrees of wet and dry conditions up to the overgrowth of the lakes. Frequent change in sphagnum mosses with different trophic preferences was identified. The chronology is based on 11 radiocarbon dates. Accumulation rates reached 1.7-1.9 mm/year, and the temporal resolution for the reconstructions was up to 30-40 yr. The tendencies of lake evolution depended on different scale hydroclimatic changes over the last 4400 yr. The most detailed data for the last 2600 yr were obtained from the Nizhnee Lake sequence, which is more sensitive to climatic changes. The main reason for the change in the hydrological regime of the lakes was variations in precipitation during short-term climatic changes. The sediment record of moisture fluctuations is relatively well correlated with regional patterns reflecting summer monsoon intensity and cyclogenesis activity.

Insights into the metabolic specificities of pathogenic strains from the Ralstonia solanacearum species complex.

All the strains grouped under the species Ralstonia solanacearum represent a species complex responsible for many diseases on agricultural crops throughout the world. The strains have different lifestyles and host range. Here, we investigated whether specific metabolic pathways contribute to strain diversification. To this end, we carried out systematic comparisons on 11 strains representing the diversity of the species complex. We reconstructed the metabolic network of each strain from its genome sequence and looked for the metabolic pathways differentiating the different reconstructed networks and, by extension, the different strains. Finally, we conducted an experimental validation by determining the metabolic profile of each strain with the Biolog technology. Results revealed that the metabolism is conserved between strains, with a core metabolism composed of 82% of the pan-reactome. The three species composing the species complex could be distinguished according to the presence/absence of some metabolic pathways, in particular, one involving salicylic acid degradation. Phenotypic assays revealed that the trophic preferences on organic acids and several amino acids such as glutamine, glutamate, aspartate, and asparagine are conserved between strains. Finally, we generated mutants lacking the quorum-sensing-dependent regulator PhcA in four diverse strains, and we showed that the phcA-dependent trade-off between growth and production of virulence factors is conserved across the R. solanacearum species complex. IMPORTANCE Ralstonia solanacearum is one of the most important threats to plant health worldwide, causing disease on a very large range of agricultural crops such as tomato or potato. Behind the R. solanacearum name are hundreds of strains with different host range and lifestyle, classified into three species. Studying the differences between strains allows to better apprehend the biology of the pathogens and the specificity of some strains. None of the published genomic comparative studies have focused on the metabolism of the strains so far. We developed a new bioinformatic pipeline to build high-quality metabolic networks and used a combination of metabolic modeling and high-throughput phenotypic Biolog microplates to look for the metabolic differences between 11 strains across the three species. Our study revealed that genes encoding enzymes are overall conserved, with few variations between strains. However, more variations were observed when considering substrate usage. These variations probably result from regulation rather than the presence or absence of enzymes in the genome.

To litter or not to litter that is the question, or the impact of tourist litter pollution on the macrofauna

Discarded bottles abandoned by tourists in forests pose a considerable threat to invertebrates that has not been adequately researched to date. In order to investigate this matter, empty PET bottles and aluminium cans containing small amounts of 5 qualitatively different beverages they were originally filled with were placed simultaneously in forests. They were subsequently collected, 3 bottles/cans of each type, during three site inspections to analyze mortality of the macrofauna inside them. The composition of macrofauna may be affected by the presence of Anoplotrupes stercorosus, which occasionally feeds on dead animal matter. Therefore, the study consisted of 2 stages, the aim being to identify patterns of invertebrate mortality in bottles when A. Stercorosus presence was limited (stage 1) and not limited (stage 2). The effect of certain beverages on macrofauna mortality was also studied. Stage 2 additionally involved 4 variants of habitat fertility. The most marked differences compared with invertebrate mortality in mineral water bottles (control) were noted for beer cans, which was attributed to the dark insides of the latter. The sequence of appearance of isopods, predators and different developmental stages of dipterans inside the cans indicated the presence of an operational detritus mini ecosystem. Invertebrate mortality in empty bottles originally containing caffeine and a high amount of sugar was also different from the patterns identified in the control bottles (mineral water). This was thought to be related to the luring „power” of sugar. The highest mortality of the macrofauna was recorded in a moderately fertile forest habitat, followed by the most fertile habitat. This was believed to be related to the well-developed vertical structure of the moderately fertile habitat. Altogether, this study shows that litter collecting campaigns in forest and other valuable natural habitats is an aesthetic procedure that also protects the macrofauna of the litter and soil representing a range of diversified trophic preferences.

Mosquito community composition in two major stopover aquatic ecosystems used by migratory birds in northern Spain.

Mosquitoes (Diptera: Culicidae) are common bloodsucking Diptera frequently found in aquatic environments, which are valuable ecosystems for many animal species, particularly migrating birds. Therefore, interactions between these animal species and mosquitoes may play a critical role in pathogen transmission. During 2018-2019, mosquitoes were collected from two aquatic ecosystems in northern Spain using different methodologies and identified using classical morphology and molecular tools. A total of 1529 males and females of 22 native mosquito species (including eight new records for the region) were trapped using CO2 -baited Centers for Disease Control and Prevention (CDC) traps and sweep netting. Among the blood-fed female mosquitoes, 11 vertebrate host species-six mammals and five birds-were identified using DNA barcoding. The developmental sites of eight mosquito species were determined across nine microhabitats, and 11 mosquito species were caught landing on humans. The flight period varied among mosquito species, with some peaking in the spring and others in the summer. Our study highlights the advantages of mosquito sampling using various techniques to comprehensively characterise species composition and abundance. Information on the trophic preferences, biting behaviour and influence of climatic variables on the ecology of mosquitoes is also provided.

Not all dung beetles feed on dung: Scarabaeinae (Coleoptera: Scarabaeidae) attracted to different carrion types in contrasting habitats at Brazilian Amazon

AbstractBy understanding how assemblages segregate according to food types, it is possible to depict and understand species distribution and exploitation of similar food resources. Although it is well known that dung beetles may feed on carrion, but the attractiveness of different carrion types for these beetles is still poorly understood. In this study, we compared the dung beetle (Coleoptera: Scarabaeidae: Scarabaeinae) diversity attracted to two carrion types in different habitats in an Amazonian landscape. Dung beetles were captured by using pitfall traps baited with decaying cattle beef and cattle liver in native forest, peach palm plantation, teak plantation and exotic pasture. Overall, we captured 582 dung beetles of 43 species, where Canthidium aff. lentum was classified as a specialist of cattle beef, Deltochilum sp. One was considered specialist of liver carrion, 11 were considered generalists and for the 30 remaining species, it was not possible to determine their carrion preference due to the low number. Abundance, but not species richness, was affected by carrion type, and a higher number of beetles was recorded in beef‐baited traps compared to liver‐baited traps. According to functional groups, endocoprid beetles were more abundant in traps baited with decaying beef, while paracoprid and telecoprid beetles did not show preference for any carrion type. This study suggests a novel scenario of intra‐resource segregation, where species vary their preferences depending to the part of the dead corpse being exploited. The amount of food resource, the maintenance of stable populations and trophic preference mediated by chemical cues are some mechanisms that may explain the segregation of dung beetles among carrion types.

Diet of deep-sea holothurians in theVolcanologists Massif, Bering sea, as inferred from stable isotope and fatty acid analyses

Holothurians are one of the key components of the deep-sea megabenthos, often forming significant aggregations with high abundance and biomass. The crucial factors determining the pattern of their spatial distribution might be their food strategies, as well as the quantity and quality of available food. Using the set of trophic markers (analysis of fatty acid (FA) composition and stable nitrogen and carbon isotope signatures), we studied the trophic preferences of four common species of deep-sea holothurians (Paelopatides sp., Pannychia henrici, Psolidium sp., and Scotoplanes kurilensis) inhabiting the Volcanologists Massif, Bering Sea, at depths from 984 m to 3395 m. The δ13С values in tissues of all four species varied slightly (from −16.2 to −16.6‰) and were significantly higher than those in sediment organic matter (SOM) (on average, −21.5‰), which indicates the use of organic matter of the same origin by all species. The δ15N values (10.1–12.9‰) were also significantly higher than in SOM (on average, 4.4‰). The lowest average δ15N value was recorded for the deepest-dwelling species (Scotoplanes kurilensis), and the highest value from the shallowest-dwelling ones (Psolidium sp.). All the species differed significantly in FA composition. Psolidium sp. was distinguished by the highest saturated FA content (45.5%) and the lowest polyunsaturated FA (PUFA) content (18.7%). In the rest of the species, PUFAs dominated (>35%). The ratios of major PUFAs varied among the four species studied but all holothurians species were rich in phytoplankton derived FA suggesting tight trophic coupling to phytodetritus. However, for Psolidium sp., bacteria could constitute a substantial portion in the diet. The high level of 20:4n-6 might indicate a significant contribution of protozoans to the diet of Pannychia henrici. Paelopatides sp. and Scotoplanes kurilensis were characterized by a high level of 20:5n-3 and a high value of the 20:5n-3/20:4n-6 ratio, which indicates the predominance of fresh phytodetritus in their diet. The high level of primary production in the upper layers of the Bering Sea provides the high quality of the sedimentary OM and food supply of deposit feeders even at the greatest depths.

Differences in the structure of bat assemblages among habitats in the Caatinga dry forest

Abstract The Caatinga is the largest seasonal tropical dry forest with extreme environmental and meteorological conditions. It harbours many phytophysiognomies and vegetational units, but bat fauna is poorly known in many regions. We analysed the structure of bat assemblages by mist-netting during 99 nights in seven habitats throughout six sites in the northeasternmost region of the Caatinga in Rio Grande do Norte State, in the Brazilian northeast. With a sampling effort of 239 665 m2h, we captured 1575 individuals of 31 species of bats. Bat assemblages’ structure and species distribution changed according to the habitat type, and differences in richness, abundance, species composition, and trophic guild representation were found. The frugivore A. planirostris was widespread, and its superabundance hold for all habitats. The distinct array of the most abundant species with several exclusive species in each habitat suggests species- and trophic guild-specific preferences to particular habitats. Differences in the structure of bat assemblages may be driven by each habitat’s vegetational structure and plant composition (e.g., semi-open habitats vs. tall forest stands) that offers distinct exploitable resources (e.g., food and roosts). Finally, we discuss the importance of foraging habitats for the conservation of these unique bat assemblages in the northeasternmost region of the Caatinga dry forest.

Qualitative Screening of Yeast Biodiversity for Hydrolytic Enzymes Isolated from the Gastrointestinal Tract of a Coprophage “Gymnopleurus sturmi” and Dung of Ruminants

In this study, thirty yeast strains isolated from the gut of coprophagous “Gymnopleurus sturmi” and twenty-four from the dung of ruminants were shown to be producers of cellulases. Cellulolytic yeast isolates could also produce other hydrolytic enzymes such as pectinase, lipase, β-glucosidase, catalase, inulinase, urease, gelatinase, and protease. The oroduction of amylase was present in only one isolate of dung of ruminants. On the other hand, the production of tannase was absent in these isolates. All the yeasts isolated from two sources could utilize various carbon sources, including sorbitol, sucrose, and raffinose, and withstand high concentrations of glucose (300 g/L), salt (100 g/L), and exogenous ethanol. They could grow in a wide pH range of 3 to 11. The growth was stable up to a temperature of 40 °C for isolates from the gut of coprophage and 37 °C for the yeast from the dung of ruminants. These activities and growing conditions were similar to the diet of coprophagous insects and the composition of ruminant manure, likely because the adaptation and distribution of these microorganisms depend on the phenology and trophic preferences of these insects.

Developmental changes of opsin gene expression in ray-finned fishes (Actinopterygii).

Fish often change their habitat and trophic preferences during development. Dramatic functional differences between embryos, larvae, juveniles and adults also concern sensory systems, including vision. Here, we focus on the photoreceptors (rod and cone cells) in the retina and their gene expression profiles during development. Using comparative transcriptomics on 63 species, belonging to 23 actinopterygian orders, we report general developmental patterns of opsin expression, mostly suggesting an increased importance of the rod opsin (RH1) gene and the long-wavelength-sensitive cone opsin, and a decreasing importance of the shorter wavelength-sensitive cone opsin throughout development. Furthermore, we investigate in detail ontogenetic changes in 14 selected species (from Polypteriformes, Acipenseriformes, Cypriniformes, Aulopiformes and Cichliformes), and we report examples of expanded cone opsin repertoires, cone opsin switches (mostly within RH2) and increasing rod : cone ratio as evidenced by the opsin and phototransduction cascade genes. Our findings provide molecular support for developmental stage-specific visual palettes of ray-finned fishes and shifts between, which most likely arose in response to ecological, behavioural and physiological factors.

Mechanical properties, degree of sclerotisation and elemental composition of the gastric mill in the red swamp crayfish Procambarus clarkii (Decapoda, Crustacea)

The gastric mill of Decapoda is a unique feature, which comprises teeth, stabilizing ossicles, and particle sorting setae. Involved in the fragmentation and sorting of the food, this structure serves as interface between the organism and its environment. As material properties complement morphology and hold information about function and trophic preferences, we here provide a basis for more comparative research on gastric mills. For gastric mill components of the adult red swamp crayfish Procambarus clarkii, we studied (a) the micro-structure via scanning electron microscopy, (b) the elemental composition by energy-dispersive X-ray spectroscopy, (c) the heterogeneities in material properties and degree of tanning (autofluorescence) by confocal laser scanning microscopy, and (d) the mechanical properties hardness and elasticity by nanoindentation technique. The morphology and micro-structure were previously described for this species, but the mechanical properties and the autofluorescence were not studied before. As epicuticle and exocuticle could be analyzed individually, material property gradients, with values decreasing from the interacting surface towards interior, could be determined. Finally, we were able to relate the mechanical property data with the elemental composition and the degree of tanning. We found that the epicuticle of the teeth is among the hardest and stiffest biological materials in invertebrates due to the incorporations of high proportions of silicon.

Links Between Feeding Preferences and Electroantennogram Response Profiles in Dung Beetles: The Importance of Dung Odor Bouquets

The detection of dung odors is a crucial step in the food-searching behavior of dung beetles (Coleoptera: Scarabaeoidea). Yet, whether certain compounds characteristic of a given dung type contribute to a ‘choosy generalism’ behavior proposed for this taxonomic group is unknown. To address this, we analyzed the chemical composition of three types of dung (cow, horse, and rabbit) and conducted behavioral and electroantennogram (EAG) bioassays on 15 species of dung beetles using 19 volatile organic compounds representing the three dung samples. Chemical analyses revealed substantial qualitative and quantitative differences among dung types. When offered these food options in an olfactometer, 14 species exhibited a feeding preference. Surprisingly, all 19 compounds used in the EAG assays elicited antennal responses, with species displaying different olfactory profiles. The relationship between behavioral preferences and electrophysiological profiles highlighted that species with different food preferences had differences in antennal responses. Moreover, a specific set of EAG-active compounds (nonanal, sabinene, acetophenone, ρ-cresol, 2-heptanone, 1H-indole, and 6-methyl-5-hepten-2-one) were the strongest drivers in the distinct sensory profiles of the trophic preference groups. Our results point to the importance of the whole bouquet of dung-emanating compounds in driving food-searching behavior, but specific volatiles could aid in determining highly marked trophic preferences in certain species.

Elucidating the picocyanobacteria salinity divide through ecogenomics of new freshwater isolates

BackgroundCyanobacteria are the major prokaryotic primary producers occupying a range of aquatic habitats worldwide that differ in levels of salinity, making them a group of interest to study one of the major unresolved conundrums in aquatic microbiology which is what distinguishes a marine microbe from a freshwater one? We address this question using ecogenomics of a group of picocyanobacteria (cluster 5) that have recently evolved to inhabit geographically disparate salinity niches. Our analysis is made possible by the sequencing of 58 new genomes from freshwater representatives of this group that are presented here, representing a 6-fold increase in the available genomic data.ResultsOverall, freshwater strains had larger genomes (≈2.9 Mb) and %GC content (≈64%) compared to brackish (2.69 Mb and 64%) and marine (2.5 Mb and 58.5%) isolates. Genomic novelties/differences across the salinity divide highlighted acidic proteomes and specific salt adaptation pathways in marine isolates (e.g., osmolytes/compatible solutes - glycine betaine/ggp/gpg/gmg clusters and glycerolipids glpK/glpA), while freshwater strains possessed distinct ion/potassium channels, permeases (aquaporin Z), fatty acid desaturases, and more neutral/basic proteomes. Sulfur, nitrogen, phosphorus, carbon (photosynthesis), or stress tolerance metabolism while showing distinct genomic footprints between habitats, e.g., different types of transporters, did not obviously translate into major functionality differences between environments. Brackish microbes show a mixture of marine (salt adaptation pathways) and freshwater features, highlighting their transitional nature.ConclusionsThe plethora of freshwater isolates provided here, in terms of trophic status preference and genetic diversity, exemplifies their ability to colonize ecologically diverse waters across the globe. Moreover, a trend towards larger and more flexible/adaptive genomes in freshwater picocyanobacteria may hint at a wider number of ecological niches in this environment compared to the relatively homogeneous marine system.

Drying niches of aquatic macroinvertebrates identify potential biomonitoring indicators in intermittent and ephemeral streams

Intermittent rivers and ephemeral streams (IRES) compose the majority of draining networks on Earth, supporting a unique fraction of biodiversity. Despite their high ecological value, IRES are increasingly threatened by global change and require appropriate biomonitoring and restoration tools. However, indices and indicators used in routine biomonitoring programs are often confounded by drying effects. This occurs because most pollution-sensitive taxa are lost over drying gradients, limiting the utility of current biomonitoring tools in IRES. To address this challenge, there is a need to evaluate which taxa should be used to calculate biomonitoring metrics and indicators over the different portions of the drying gradient. Here, using high-resolution drying data from 33 unpolluted streams, we explored the drying preferences of macroinvertebrates to identify their potential as biomonitoring indicators in IRES. To do this, we characterized macroinvertebrate drying niches and identified those with drying resistance and sensitivity preferences. Next, we evaluated the capacity of functional traits to predict drying specialization and affinity. Finally, to identify potential biomonitoring metrics and indicators for IRES, we evaluated how drying influenced the density, relative abundance and richness of taxa in drying-sensitive and drying-resistant niches. Our results identified three macroinvertebrate groups with drying-resistant niches (partly tolerant, generalist and specialist taxa) and one group of drying-sensitive taxa. We also found that functional traits had a limited capacity to represent differences in drying niches, with shredding trophic preferences and body size showing the strongest correlations. In addition, we observed that the density, relative abundance and richness of drying-resistant taxa were less influenced by drying intensity than those of drying-sensitive taxa. Finally, we found that some pollution-sensitive taxa with partial (e.g., Lepidostoma), moderate (e.g., Corduliidae) or high drying tolerance (e.g., Nemoura) can serve as potential indicators in IRES. Taken together, our results demonstrate that characterizing drying niches can be a useful strategy for developing biomonitoring tools in IRES and for highlighting the limitations of taxonomic and trait-based approaches.

The influence of ecological features of the Novosibirsk reservoir on its infection with Metorchis bilis

The West Siberian region is the focus of the spread of opisthorchiasis. The first intermediate hosts of these trematodes are pregill gastropods of the fam. Bithyniidae (Gray, 1857). Mollusks eat the eggs of these parasites, and after a cycle of asexual reproduction, opisthorchid larvae (cercariae) emerge from them, which swim in the water and penetrate into the bodies of fish through the skin. Danger for humans and carnivores is represented by fish of carp species (second intermediate hosts), but most often parasites of this fam. Opisthorchidae (Loose, 1899) occur in the ide (Leuciscus idus (Linnaeus, 1758)). The article presents data on the modern ichthyoparasitological state of the ide from the Novosibirsk reservoir and its abundance in the reservoir, on the places of mass accumulation of fish and mollusks in the reservoir, and describes the feeding habits of the studied fish. The relationship between the trophic preferences of this fish species and the indicators of its infection with opisthorchids is revealed: the ide, which feeds mainly on mollusks, lives in those parts of the reservoir where it can satisfy its needs, being in the zone of maximum risk of infection with trematode cercariae. The article explains the surge in infection of an ide from the reservoir with the trematode Methorchis bilis (Braun, 1890) in 2020. The hydrological regime of the reservoir, which is unfavorable for gastropod mollusks, and the presence of an alien species of gastropods Viviparus viviparus (Linnaeus, 1752) competing with bithyniids, as a rule, restrains the growth in abundance molluscs fam. Bithyniidae, which also affects the distribution of opisthorchiasis in fish, however, favorable conditions in 2020 allowed the population of mollusks to increase their numbers, which caused an increase in invasion rates in ide.

Effects of Habitat and Competition on Niche Partitioning and Community Structure in Neotropical Ants

Competition for limited resources can yield two contrasting outcomes in community structure, namely, either (i) dominance of most competitive species (with functional convergence of the traits conferring this ability), or (ii) niche partitioning of species using distinct resources. In addition, varying resource availability in different environmental contexts is expected to yield varying community dynamics and composition between the contexts (habitat filtering). We addressed resource-based ant community structure in a tropical ecosystem. We expected ant species to display varying trophic preferences and foraging behaviors, allowing habitat selection and niche differentiation in ant assemblages. Furthermore, we expected habitat filtering to occur between open and forested areas in the landscape mosaic, and competition to further influence local species co-occurrence. We assessed resource use in nine ant assemblages distributed in two habitats (i.e., forests and croplands), devising two separate experiments using bait-traps to characterize ant species’ trophic preference (e.g., eating prey, seeds, sugars) and their ability to obtain a same resource in heterogeneous forms (e.g., on vegetation, litter, with variable amounts…). The majority of baits offered were rapidly exploited in the two habitats suggesting important resource limitations. Forest and cropland ant communities differed, however, in the proportions of resources exploited, suggesting different competitive pressures toward specific resources between habitats. Within each habitat, ants preferentially exploited the same resources, suggesting habitat filtering, but locally, interspecific resource partitioning resulted in a reduction of resource overlap compared to habitat scale. Our study provides evidence of the effects of habitat filtering and competition for resource in tropical ant community structure. Our findings also suggest that niche filtering and niche partitioning are co-variant forces determining the identity of the species present in local assemblages.