Variation In Habitat Structure Research Articles

Conserving biodiversity in coffee agroecosystems: Insights from a herpetofauna study in the Colombian Andes with sustainable management proposal

Amphibians and reptiles are important indicators of ecosystem health, yet their populations are declining worldwide due to habitat loss and climate change. Agroecosystems, such as coffee plantations, can provide important habitat for these species. We conducted field surveys in the Sumapaz region of Colombia to identify the habitat structural variables that influence the diversity and abundance of herpetofauna in coffee crops. The canonical correspondence analysis revealed that abundance of leaf litter, leaf litter moisture, shade percentage, plantation area, and plantation age category were the most important variables for determining herpetofauna diversity. Our findings suggest that shaded coffee plantations can sustain herpetofauna diversity, and maintaining a thick layer of leaf litter is critical for establishing complex and structured animal communities. This study proposes a set of sustainable agricultural management principles to promote the existence of amphibians and reptiles in coffee crops. By adopting these practices, it is possible to prevent the decline in the population of amphibians and reptiles due to the expansion of the agricultural frontier, as seen in other coffee-growing regions. The findings of this study contribute to a better understanding of how to balance agricultural production and biodiversity conservation in the context of agroecosystems.

Do reptile responses to habitat structure and time since fire depend on landscape structure?

Land use changes, such as the development of agriculture and plantation forestry, and altered fire regimes, are major drivers of biodiversity loss worldwide, influencing the availability of suitable habitat for species. Reptiles are sensitive to both these processes as they are influenced by native vegetation extent and habitat structure. While much is known about the independent effects of fire and land use change on species distributions, few studies have investigated potential interactive effects; specifically, whether the influence of site-scale variables on reptiles depends on the properties of the surrounding landscape. We sampled reptiles at 107 sites in fire-prone heathy woodland, interspersed with plantation forestry and agriculture in south-west Victoria, Australia. We investigated the responses of seven reptile species to both site-scale variables (time since fire and several measures of habitat structure) and landscape-scale variables (extent of native vegetation and plantations and the presence of pasture within a 3.14 square km area) to 1) identify whether species’ responses to fire and habitat depended on landscape structure, and 2) examine the relative influence of time since fire, habitat structure and landscape structure on reptile abundance. We predicted that responses to site-scale variables would vary with a key landscape structure variable: the amount of native vegetation cover. Further, we predicted that site-scale variables would be stronger predictors of species abundance than landscape-scale variables. Generalised linear models, accounting for imperfect detection, were used to estimate species responses to site and landscape-scale predictors. For two species (Amphibolurus muricatus and Liopholis whitii) there was evidence that their responses to site-scale variables depended on landscape structure. However, contrary to our first prediction, native vegetation cover was not the only landscape structure variable that influenced species’ responses to site-scale variables. Three species (Acritoscincus duperreyi, A. muricatus, and Lerista bougainvillii) responded to both habitat structure and landscape structure variables, though the relative influence of the variables at the different scales was varied among the species. One species (Lampropholis guichenoti) responded to fire and habitat structure variables at the site-scale but did not respond to landscape structure. One species (Aprasia striolata) responded to landscape structure variables but not to site-scale variables. Our second prediction, that site-scale variables would be the strongest predictors of abundance, was true for two species, but overall, our results were varied, with species responding at both scales. Examining species' responses to drivers at multiple spatial scales is essential for conservation management, as even species with low dispersal capacity such as reptiles can respond to processes occurring at large spatial scales.

Positive long-term effects of year-round horse grazing in orchid-rich dry calcareous grasslands–Results of a 12-year study

IntroductionDry calcareous grasslands are among the most species-rich habitats worldwide but strongly endangered by abandonment causing a severe decline of characteristic species such as orchids. To counteract further degradation, economically sustainable restoration tools such as megaherbivore grazing, that aim to substitute extinct wild grazers, should be considered. However, the long-term effects on target species of dry grasslands, and in particular for orchid populations, is still unclear.MethodsTo contribute to this knowledge gap, we applied vegetation surveys (5 m × 5 m), as well as large-scale census-based orchid observation and mapping of habitat structures (50 m × 50 m) in a year-round grazing scheme of a Natura 2000 site in Central Germany over 12 years. The horses and their grazing activity were observed via GPS telemetry. We fitted linear mixed models to evaluate whether Ophrys apifera density was affected by horse feeding frequency, habitat structure variables (bare soil patches, woody plant cover), grassland type or years.ResultsA The main results were that the target dry calcareous grassland vegetation significantly increased in species numbers and cover. The total abundance of O. apifera increased from 1,237 (2013) and 1,893 (2018), to 4,652 (2021) individuals. Ophrys apifera density was positively affected by horse feeding frequency as well as grazing-induced enhanced bare soil patches but underlying mechanisms varied between the three classified grassland types.DiscussionOur results indicate that low-intensity year-round horse grazing as a relatively new restoration tool in dry calcareous grasslands has the potential to enhance floristic biodiversity in general, and particularly O. apifera density in the long run. Furthermore, we showed that highvalue xeric grasslands with outstanding orchid abundances can be integrated into the year-round grazing system and that there is no need of fencing off such sections.

Benthic Macroinvertebrates Associated with Riparian Habitat Structural Diversity in an Eastern Amazon Stream Urbanization Gradient

Benthic Macroinvertebrates Associated with Riparian Habitat Structural Diversity in an Eastern Amazon Stream Urbanization Gradient

Amphibian Taxonomic and Functional Diversity in a Heterogeneous Landscape of West-Central Mexico

Land use in Mexico has dramatically changed in recent decades since deforested lands have been repurposed for agriculture. We evaluated the amphibian taxonomic and functional diversity of a heterogeneous landscape with ten land cover/use types in west-central Mexico. Taxonomic diversity was evaluated with q-order indices, and functional diversity was calculated with three multivariate functional diversity indices by land cover/use. The relationship between amphibian diversity, habitat structure, and environmental variables was analyzed using multidimensional distance-based analyses. Our results showed that most native land cover types exhibited a similar species richness (low values) among the studied crops, except for the riparian habitat surrounded by tropical dry forest (high richness) and secondary vegetation (intermediate richness). Regarding functional diversity, the riparian habitat surrounded by tropical dry forest, sugar cane field, and secondary vegetation had the highest values. The secondary vegetation had more functional groups than other land cover/use types. Despite the lack of a clear spatial pattern of amphibian taxonomic and functional diversity, we determined that attributes such as herbaceous cover and water availability are essential to maintain both facets with high amphibian diversity in the land cover/use types (e.g., secondary vegetation and sugar cane).

The use of remotely sensed data to model habitat selections of pileated woodpeckers (Dryocopus pileatus) in fragmented landscapes

Light detection and ranging (LiDAR) and four-channel red, green, blue, and near-infrared (RGBI) remote sensed imageries allow an accurate quantification and contiguous measurement of vegetation characteristics and forest structures. This information facilitates the generation of habitat structure variables for forest species distribution modelling. However, applications of remote sensing data, especially the combination of structural and spectral information, to support evidence-based decisions in forest managements and conservation practices at local scale are not widely adopted. In this study, we examined the habitat requirements of pileated woodpecker (Dryocopus pileatus) (PW) in Hamilton County, Ohio, using ecologically relevant forest structural and vegetation characteristics derived from LiDAR and RGBI data. We hypothesized that the habitat of PW is shaped by vegetation characteristics that are directly associated with the availability of food, hiding and nesting resources, the spatial arrangement of habitat patches within home range, as well as proximity to water sources. We used 186 PW presence or absence locations to model their presence and absence in generalized additive model (GAM) at two scales, representing foraging and home range size, respectively. The results confirm PW’s preference for tall and large mature stands with structural complexity, typical of late-successional or old-growth forests. Besides, the crown size of dead trees shows a positive relationship with PW occurrence, therefore indicating the importance of declining living trees or early-stage dead trees within PW home range. These locations are preferred by PW for nest cavity excavation as it attempts to balance the ease of excavation and tree security. In addition, we found that PW can adjust its travel distance to the nearest water resource, suggesting that habitat fragmentation can have certain impacts on PW. Based on our findings, we recommend that forest managers should use different priorities to manage nesting, roosting, and feeding habitats. Particularly, when devising forest management and hazard tree removal plans, one needs to consider retaining enough cavity trees within high-quality PW habitat. By mapping PW habitat suitability for the study area, we highlight the importance of riparian corridor in facilitating PW to adjust to the fragmented urban landscape. Indeed, habitat improvement for PW in the study area could be achieved by conserving riparian corridors and promoting riparian forest succession along major rivers in Hamilton County. (The acronyms used in this paper are listed in Table A1 of the Appendix.)

Effects of Environmental Changes on Gerromorpha (Heteroptera: Hemiptera) Communities from Amazonian Streams

The presence of environmental conditions that are suitable for the development of agricultural and cattle-raising activities has favored the expansion of land use in the Brazilian Amazon. This expansion changes the environmental conditions of aquatic ecosystems by altering the structure of the streambeds and the physicochemical conditions of the water. Therefore, this manuscript aimed to assess the effect of changes in environmental conditions along a gradient of different land uses on the richness and species composition of Gerromorpha (Heteroptera: Hemiptera) communities in streams from the Brazilian Amazon. We sampled Gerromorpha communities and environmental variables (physical structure of the habitat and physicochemical characteristics of the water) in 45 streams in the municipality of Paragominas in the state of Pará, Brazil. We then performed variation partitioning analyses to assess the relative contribution of habitat structure and water physicochemical variables on the richness and species composition. The Habitat Integrity Index (HII), which measures the habitat physical structure, was the best predictor of species richness. The HII and physicochemical variables were jointly the best predictors of species composition. Our results show that Gerromorpha communities respond to gradients of environmental anthropization in the Amazon region, which reinforces the importance of habitat integrity and water quality for the maintenance of Gerromorpha communities.

Forest-dependent bird communities of West African cocoa agroforests are influenced by landscape context and local habitat management

We undertook nearly 300 point counts of birds in cocoa plantations around Gola Rainforest National Park, eastern Sierra Leone, to assess how their vegetation structure, management and landscape context influence bird communities and the distribution of four globally threatened or forest-restricted species. Forest bird species richness, and the occurrence of Yellow-casqued Hornbill (Ceratogymna elata), were higher in abandoned than in actively managed cocoa farms. Yellow-casqued Hornbill presence was also associated with higher canopy volume and Brown-cheeked Hornbill (Bycanistes cylindricus) was associated with greater forest cover in the surrounding landscape. Overall forest bird species richness was associated with the interaction between canopy volume and proportion of forest in the surrounding landscape. Our results indicate that where forest cover is low in the landscape, low-intensity cocoa agroforestry can provide compensatory habitat for forest bird species, but when forest cover is high, cocoa that is more forest-like in structure may not lead to increased bird species richness, although it may benefit certain species. Most habitat structure variables, other than canopy volume and openness of understorey, were poor predictors of most of the variables analysed, suggesting that within the narrow range of observed production intensity, management has little impact on bird communities once productivity increases above zero by rehabilitating abandoned farms. However, over 60% of the species recorded and over half of all recorded detections were of biome-restricted species, suggesting that low-intensity cocoa plantations hold considerable conservation value. Changes in cocoa management may therefore impact those species.

Combined effects of urbanization and longitudinal disruptions in riparian and in-stream habitat on water quality of a prairie stream

Local habitat and riparian modifications imposed by surrounding land use drastically impact the water quality of streams. However, whether these effects could still be discernible when the watercourse also receives urbanization effluents has not been fully explored. We evaluated the water quality of a Neotropical prairie stream exposed to urbanization and explored the role of downstream patches of different surrounding land uses (cropland and livestock) in further regulating water quality. Forty-two variables of water quality, habitat structure and riparian condition were measured at four reaches of the Langueyú stream. Significant differences in water quality were observed. Water conductivity, dissolved oxygen, salinity, dissolved solids, chloride, inorganic nitrogen and bacteriological loads displayed a continuum of recovery from the urban reach. Indeed, almost 24 percent of the total variation in water quality was explained by the longitudinal arrangement of sites. Alternatively, pH, phosphorous, suspended solids and chemical oxygen demand showed a disruption in this continuum of recovery and were highly related with local aspects of habitat structure and riparian conditions imposed by cropland and livestock. Key aspects of effluent treatment, riparian integrity and in-stream habitat must be addressed within a comprehensive social context in order to design sustainable management of fluvial urbanised ecosystems.

Vulture Abundance and Habitat Association Following Major Hurricane Disturbance in the Tropical Dry Forest of Western Mexico

Scavenger birds are common species frequently associated with open habitats, but sympatric vulture species have differing natural history traits that may influence seasonal habitat relationships and responses to natural disturbances, such as hurricanes. We evaluated seasonality and habitat relationships of Black Vultures (Coragyps atratus) and Turkey Vultures (Cathartes aura) at sites within and outside the path of maximum winds of Hurricane Patricia in western Mexico. We used 1.5-km line transects to survey vultures during dry and rainy seasons in four habitats of the tropical dry forest biome over a 2-yr period after hurricane landfall. We measured habitat structure along each transect using the point-centered quarter method, and determined landscape composition within a 3000-ha circular plot centered around the midpoint of each transect. Vulture abundance was influenced by habitat structure variables of open areas, but at sites affected by hurricane disturbance vulture abundance was positively associated with increased cover of wetlands and agricultural land. Both species of vultures had low abundance in forests, and Black Vultures had significantly higher abundance in agricultural land and wetlands. Season significantly influenced vulture abundance by habitat: agricultural land and wetlands had higher vulture abundance in the rainy season, but forests had higher abundance in the dry season. Disturbance by a major hurricane induced species-specific changes in spatial-temporal abundance of vultures: the Black Vulture in particular had higher abundance in all habitats except wetlands during the dry season, and greater abundance in the first months after hurricane landfall. Hence, although vultures occur predominantly in open areas, they show species-specific habitat associations and responses to hurricane disturbance.

Ecological drivers of intraspecific variation in seed dispersal services of a common neotropical palm

AbstractThrough frugivory and seed dispersal, vertebrates influence plant demography and forest regeneration. Variation in local habitat surrounding fruiting plants can influence frugivore foraging decisions, thereby creating intraspecific variation in seed dispersal services. However, we have little knowledge of drivers of local variation in frugivory. Here, we investigate factors that may influence frugivore diversity and fruit removal at the level of individual plants. We focus on a common understory palm within a continuous Chocó forest with mixed land‐use histories in Ecuador. The density of pioneer tree species in the genus Cecropia around focal palms was negatively related to fruit removal and the diversity of frugivores visiting palms. This may relate to the fact that the presence and abundance of Cecropia species often indicate the existence and severity of past disturbances. Local Cecropia density was also related to an overall shift in the frugivore community that corresponded with an increase in fruit removal by lower‐quality seed dispersers (rodents). We also found that the local density of fruiting conspecifics was positively related to frugivore diversity, but not fruit removal. Our results provide information on drivers of intraspecific inequalities in plant populations across tropical forest landscapes. The reduction in fruit removal and frugivore diversity associated with local Cecropia abundance suggests that seed dispersal services can be sensitive to fine‐scale variation in habitat structure. Furthermore, because Cecropia are often indicative of past disturbances, this indicates that even small‐scale habitat degradation by humans can have lasting effects by creating localized pockets of forest unfavored by frugivores.Abstract in Spanish is available with online material.

Three‐dimensional mapping reveals scale‐dependent dynamics in biogenic reef habitat structure

AbstractHabitat structure influences a broad range of ecological interactions and ecosystem functions across biomes. To understand and effectively manage dynamic ecosystems, we need detailed information about habitat properties and how they vary across spatial and temporal scales. Measuring and monitoring variation in three‐dimensional (3D) habitat structure has traditionally been challenging, despite recognition of its importance to ecological processes. Modern 3D mapping technologies present opportunities to characterize spatial and temporal variation in habitat structure at a range of ecologically relevant scales. Biogenic reefs are structurally complex and dynamic habitats, in which structure has a pivotal influence on ecosystem biodiversity, function and resilience. For the first time, we characterized spatial and temporal dynamics in the 3D structure of intertidal Sabellaria alveolata biogenic reef across scales. We used drone‐derived structure‐from‐motion photogrammetry and terrestrial laser scanning to characterize reef structural variation at mm‐to‐cm resolutions at a habitat scale (~35 000 m2) over 1 year, and at a plot scale (2500 m2) over 5 years (2014–2019, 6‐month intervals). We found that most of the variation in reef emergence above the substrate, accretion rate and erosion rate was explained by a combination of systematic trends with shore height and positive spatial autocorrelation up to the scale of colonies (1.5 m) or small patches (up to 4 m). We identified previously undocumented temporal patterns in intertidal S. alveolata reef accretion and erosion, specifically groups of rapidly accreting, short‐lived colonies and slow‐accreting, long‐lived colonies. We showed that these highly dynamic colony‐scale structural changes compensate for each other, resulting in seemingly stable reef habitat structure over larger spatial and temporal scales. These patterns could only be detected with the use of modern 3D mapping technologies, demonstrating their potential to enhance our understanding of ecosystem dynamics across scales.

Drivers of coral bleaching in a Marine Protected Area of the Southern Gulf of Mexico during the 2015 event

Here we report the bleached coral cover and its drivers observed at Alacranes Reef in 2015. Our results show that 2015 was an unprecedented heat stress event. However, we observed low coral bleaching, with the most substantial impact on sites with a 10–20% of coral cover with bleaching. Depth was the most relevant variable related to coral bleaching and the bleaching severity index, with deeper reefs being most affected. Further, our results show that reefs with higher structural complexity based on species composition were among the most affected. We identified that accumulated heat stress and thermal variation in the last 28 days were relevant drivers of coral bleaching. This work highlights the importance of multidimensional frameworks in assessing the spatial variation of coral bleaching, demonstrating the importance of structural habitat variables such as depth in high heat stress events and at a reef scale.

Determinants of fish distribution pattern and habitat preference in protected Karaj River, Iran

Lack of information about ichthyofauna makes it difficult to predict human effects on the communities. In this study, the effects of the environmental and human factors were examined on altitudinal patterns of fish habitat selection, faunal changes, species richness and fish abundance from upstream to downstream in the southern part of the central Alborz Protected Area during 2016 and 2017. 366 fish individuals of five species in three families were identified and brown trout was the dominant species. The river was divided into three zones based on habitat structure, species composition and influence of physical and chemical variables. The results indicate that, in some situations, including small changes in habitat structure indices, physical and chemical variables along the altitudinal gradient are more effective in habitat preference, describing the composition, and abundance. Chemical variables can help to have a better understanding of the conventional patterns, shaped by the habitat structure and physical variables. Habitat suitability index model for brown trout in three zones is completely different over the two years and this species could overcome these conditions. However, upstream areas were more appropriate. Dam, with decreases of outlet water temperature, also creates homogeneous and simple habitats leading to changes in expected fish distribution patterns with decreasing altitude. These conditions may have increased habitat suitability index for the brown trout in downstream, while despite favorable ecological conditions in the middle zone, habitat suitability index and alternative habitats available in this zone are likely to decline due to density and interspecific competition. The natural pattern of fish distribution and habitat selection varies along the altitudinal gradient due to various factors and human disturbances. Optimal management of protected areas can control the effects of some of these factors at least temporarily.

Environmental influence on the distribution of polychaete families and feeding guilds in benthic communities of the Grand Banks and Flemish Cap (NW Atlantic)

Many biodiversity patterns across the globe can be partially explained by energetics and habitat structure, including in the deep sea. Because of difficulties in logistics, studies focusing on deep-sea benthic systems often have limited sample sets that may be far apart in space. Here, we present analyses based on a well-sampled region, the northwest Atlantic, allowing us to relate patterns of polychaete community structure (using taxonomic families and feeding guilds) against well-resolved environmental gradients. We show that community structure is heterogenous in this area. We observe three major groups within polychaete communities which also show differences in feeding guilds. Several environmental gradients, including long-term variables, explained the differences between the groups. Both energetics and habitat structure variables were important, while past fishing intensity had a weak effect, although there was support for a difference in community composition for communities above and below the historical fishing limit of 1200 m. The effect of long-term environmental factors may indicate that the deep sea is not immune to climate change, and these effects must continue to be considered in future management of exploitation of this ecosystem.

Effects of habitat structure on the mollusc assemblage in Mussismilia corals: evaluation of the influence of different coral growth morphology

AbstractHabitat structure increases richness and abundance of species in many environments by providing easy access to resources and refuge from predators. In coral reefs, corals are habitat for many organisms and differences in their morphologies may act as variation in habitat structure for associated fauna. In the present study, we investigate whether there are differences in the richness and abundance of molluscs associated with three species of Mussismilia corals exhibiting different growth morphologies, in two different reef areas of the Bahia state. Mussismilia harttii has a meandroid pattern, M. hispida is a massive coral, M. braziliensis also has a massive growth pattern with crevices at the corallum base. Coral characteristics were measured in the laboratory. Significant differences were identified for richness among coral species – higher values were reported in colonies of M. harttii and no significant statistical differences were observed between M. braziliensis and M. hispida. Considering the density of associated molluscs, the same pattern was found. The results are in accordance with previous studies and indicate the importance of M. harttii as a key habitat to maintain a richer and more abundant associated fauna. The internal volume of interpolypal space is an important factor influencing the richness and density of associated species.

Reed bed vegetation structure and plant species diversity depend on management type and the time period since last management

AbstractQuestionReed beds, dominated by common reed (Phragmites australis), have high ecological value. Several studies have examined the differences between managed and unmanaged reed beds without taking into account the time passed since the last management. In this paper, we seek to answer the question: how does the time passed since last management and the management method itself affect the plant community and the habitat structure of reed beds?Location“De Østlige Vejler,” Northern Jutland, Denmark.MethodsWe examined four reed bed treatments — beds either cut or harvested during the year of the study (0‐year‐old reed beds) and reed beds harvested 3 and 25 years ago, respectively. The reed bed plant communities and the reed bed habitat structure were determined in May and August. We tested the data for overall between‐treatment differences (multivariate analysis of variance [MANOVA] and principal components analysis [PCA]) and specific differences in the plant community and habitat structure (Kruskal–Wallis).ResultsThe plant community differed significantly between the four reed beds according to treatment, and each reed bed exhibited unique species. Species richness was significantly higher in the recently harvested reed beds (0 and 3 years since harvest) compared with the 25‐year‐old reed beds. Harvest sparked reed rejuvenation and increased the growth of new reeds. The 3‐year‐old reed bed had a habitat structure that equally resembled that of the newly harvested (e.g., similar green reed shoot density) and the 25‐year‐old reed beds (e.g., similar height). Cutting, as opposed to harvesting, created a plant community adapted to less light availability.ConclusionsTo secure most plant species and most variation in habitat structure, reed beds should contain a mosaic of differently aged and differently managed patches. Previous studies have disagreed on the effect of management on plant species diversity, which could be explained either by different reed bed age or different sampling periods.

Habitat and sex effects on behaviour in fawn-footed mosaic-tailed rats (Melomys cervinipes)

Habitat complexity reflects resource availability and predation pressure – both factors that influence behaviour. We investigated whether exploratory behaviour and activity varied in fawn-footed mosaic-tailed rats (Melomys cervinipes) from two habitats that were categorised differently based on vegetation. We conducted vegetation surveys to determine structural complexity and vegetation cover, confirming that an abandoned hoop-pine (Araucaria cunninghami) plantation forest was structurally less complex, with lower vegetation cover than a variable secondary rainforest. We then tested mosaic-tailed rats from both sites in four behavioural tests designed to assess exploratory and activity behaviours (open field, novel object, light-dark box, acoustic startle), predicting that rats from the less structurally complex habitat would be less exploratory, and show lower activity. Our results provide some evidence for a context-specific trade-off between exploratory behaviour and predation risk in rats from the abandoned hoop pine plantation, as rats were less active, and showed a freezing strategy in the light-dark box. We also found context-specific sex differences in behaviour in response to a novel object and sound. Our results suggest that small-scale variation in habitat structure and complexity, as well as sex differences, is associated with variation in behaviour, most likely through effects on resource availability and/or predation risk.

Effects of Local Environmental and Landscape Variables on the Taxonomic and Trophic Composition of Aquatic Insects in a Rare Forest Formation of the Brazilian Amazon.

In the present study, we analyzed a unique phytophysiognomy in the Amazon region, which is formed by savanna-like vegetation on iron-rich soil (known locally as canga) located within an iron-ore mining region. We used the habitat template theory to test the hypothesis that changes in the physical-chemical properties of streams and the physical structure of their habitats at in-stream and micro-basin (landscape) levels affect the taxonomic and trophic composition of immature aquatic insects. For this, we used a local environmental matrix composed of nine physical-chemical and structural habitat variables, together with the Habitat Integrity Index. We also calculated landscape metrics based on the area of the micro-basin, such as relief, slope, mean current flow, and vegetation cover. We divided the aquatic insects into five functional feeding groups based on their diet and food sources. Our results indicate that changes in the trophic level of the insects of the orders Ephemeroptera, Plecoptera, and Trichoptera are more easily observed than the taxonomic structure of communities. The loss of environmental integrity and vegetation cover were responsible for 84% of the variation observed in the composition of functional feeding groups (FFGs). Our study shows that aquatic insect communities in the canga and in the Amazon regions dominated by forest require specific in-stream and landscape conditions. These findings reinforce the need for the preservation of areas of canga vegetation, which not only have a unique levels of biological diversity, but are also targeted for the exploitation of their economically valuable natural resources.

Laboratory experiments reveal effects of group size on hunting performance in yellow saddle goatfish, Parupeneus cyclostomus

Group hunting where two or more individuals chase the same prey occurs in various vertebrate clades. Its evolution has typically been attributed to the resulting increased prey capture rate. Indeed, many studies have documented positive correlations between the number of individuals and probability of success, suggesting that joint hunting is cooperative. However, all existing data on vertebrates are based on field observations and hence cannot control for factors that may also influence hunting success, such as variation in habitat structure, hunting motivation or prey state. Therefore, we conducted controlled laboratory experiments to test whether hunting performance is affected by group size in the group-hunting yellow saddle goatfish. We presented invertebrate prey in an artificial coral reef and measured hunting performance as a function of manipulated group size, ranging from one to four individuals. We found that individuals hunting alone failed to catch the prey within the trial time limit significantly more often than groups did. Furthermore, we found that time until capture depended on group size, with singletons being slowest and groups of four fastest. With few exceptions, group members were approximately equally likely to catch prey. Hunting success as a singleton did not predict an individual's prey capture probability when in a group, suggesting that group hunting involves some producer–scrounger dynamics. In conclusion, while the experiment cannot address the question of how group size affects individual net calorie intake, the results show that groups are more successful at hunting than singletons are.