Trophic Niche Breadth Research Articles

Trophic Interactions between Two Cichlid Species in Shatt Al-Arab River, Iraq

The diet composition and trophic relationships of the blue tilapia, Oreochromis aureus and redbelly tilapia, Coptodon zillii were investigated in the Shatt Al-Arab river from November 2015 to October 2016. Fishes were collected by gill nets, cast net and electro-fishing. The index of relative importance (IRI%) of food items was determined by combining the frequency of occurrence and points methods. There were monthly variations in feeding activity and intensity of both species, which decreased in the colder months. Both species were classified as herbivores. The main food items of O. aureus were macrophytes (44.3%), algae (31.4%), diatoms (9.3%), aquatic insects (6.6%) and detritus (6.3%). The diet of C. zillii is composed mainly of macrophytes (60.8%), algae (23.0%), detritus (8.6%) and diatoms (6.4). The trophic niche breadth values varied between 0.217 for C. zillii and 0.360 for O. aureus. The results demonstrated a high degree of dietary overlap between O. aureus and C. zillii, as both species fed on the same food sources

Macrophyte diversity alters invertebrate community and fish diet

The diversity of aquatic macrophytes can offer different local conditions required to support an increased number of microhabitats, therefore resulting in diverse biotic communities. This study assessed the influence of macrophyte diversity on the ecological attributes of the associated invertebrates (diversity, richness and abundance), as well as the diet composition of a small fish, Moenkhausia forestii, that inhabits the Upper Parana River floodplain in abundance, and present great contributions of invertebrates in its diet. The richness and diversity of invertebrates increased with increasing macrophyte diversity, while the abundance of invertebrates didn’t show a significant relationship. The diet of M. forestii differed among stands and the consumption of invertebrates increased with increasing macrophyte diversity, while the consumption of aquatic plants decreased. Moreover, the trophic niche breadth of M. forestii expanded, a probable result of the increase in the ecological opportunity promoted by higher macrophyte diversity. Our study emphasizes the importance of the diversity of these plants as they structure the environment and the associated communities, and changes in the attributes of these plants could be reflected on other trophic levels and even on a local scale.

Interactions between a planktivorous fish and planktonic microcrustaceans mediated by the biomass of aquatic macrophytes

AbstractHabitat complexity is recognized to mediate predator–prey relationships by offering refuge or not. We investigated the availability of planktonic microcrustaceans and the diet of a planktivorous fish (Hyphessobrycon eques) at different levels (low, intermediate and high) of aquatic macrophyte biomass. Sampling was carried out in a river with low flow speed, located in a Neotropical floodplain. We collected fish and microcrustaceans in macrophyte stands with variations in biomass. There were no differences in microcrustacean density in the water among the levels of macrophyte biomass, but microcrustacean richness and diet composition of H. eques differed. Microcrustacean richness and trophic niche breadth of the planktivorous fish were higher in high biomass stands. There was high consumption of a small cladoceran species in low macrophyte biomass, which was replaced by larger species, such as copepods, in intermediate and high biomass. Thus, the selection of some species was different among the biomass levels. These results suggest that plant biomass plays an important role in the interaction between fish and microcrustaceans, and prey characteristics such as size, escape ability and energy value make them more or less subject to predation by fish according to habitat structuring.

Seasonal feeding habits and ontogenetic diet shift of black bullhead (Ameiurus melas) in Lake Sava (Serbia)

The black bullhead is an invasive species that forms dense populations and has a negative impact on the native ichthyofauna. Recent studies indicate that it is one of the most dominant invasive fish species in Serbian waters. Feeding habits based on stomach contents of individuals caught in Lake Sava were analyzed as a first step towards evaluating its possible negative impact on the native fish fauna of the lake. The following indices for diet analysis were applied: vacuity index, frequency of occurrence, numerical abundance and prominence value. Trophic niche breadth and seasonal trophic diversity were calculated using the Shannon?s index. The diet spectrum comprised 16 different prey categories from five groups: Mollusca, Crustacea, Insecta, Teleostei and plants. Fish were the main prey in all seasons, followed by aquatic invertebrates. Plant material and terrestrial insects were used as food in relatively small quantities. Predation on fish eggs was also detected. Our research confirmed that this species is an opportunistic generalist. An ontogenetic diet shift was also detected. The lowest value of trophic diversity was found in age 1+ individuals (H=1.39), while the highest was found in age 3+ individuals (H=2.00). The widest niche breadth was recorded in spring 2011 (H=2.12).

Impacts of deep-water spills on mesopelagic communities and implications for the wider pelagic food web

Mesopelagic fishes link lower trophic levels and higher predators, as well as production at the surface to the deep sea. Mesopelagic fish may be vulnerable to deep entrained oil plumes of the type seen in the 2010 Deepwater Horizon spill; even at low concentrations, exposure to polycyclic aromatic hydrocarbons (PAHs) may cause lethal and sublethal effects, such as endocrine disruption, growth inhibition, and genetic damage. A reduction in the abundance of mesopelagic fish could potentially shift predation pressure by large pelagics to epipelagic forage or other species, with potential fisheries consequences. We explored this hypothesis on the West Florida Shelf using an Atlantis model for the Gulf of Mexico. Atlantis is a 3-dimensional, spatially explicit marine and coastal modeling framework that incorporates multiple submodels integrating biophysical, chemical, ecological, and fisheries dynamics. We found that biomass, trophic niche width, and predation mortality exerted by mesopelagic predators showed small but varied responses across different contributions of mesopelagics to predator fish diet under oil impacts. We observed shifts in the diet of pelagic predators with increasing availability of mesopelagic fish prey, suggesting that pelagic fish predator populations are more vulnerable to oil exposure if they are tightly coupled to the mesopelagic food web. These results suggest that when measured at the population level, oil-spill impacts may be harder to detect due to the response of individual fish species.

Little interannual variability in gray seal (Halichoerus grypus) trophic niches during pregnancy despite variable environmental conditions

The successful recruitment of juveniles into a population is often dependent on receiving sufficient nutrition pre- and post-parturition. Thus, variation in maternal foraging ecology during pregnancy, whether due to prey choice, prey availability or fluctuations in environmental conditions, can impact offspring fitness in the subsequent breeding season. As many pinnipeds spend the majority of the gestation period at sea, past studies have used the biogeochemical analysis of pup tissues to infer female diets during this critical period. The objective of our study was to examine the trophic niches of a population of pregnant female gray sealsHalichoerus grypusover a 4 yr period in coastal Massachusetts, USA by analyzing the stable carbon (δ13C) and nitrogen (δ15N) values of pup lanugo. In addition, we sought to determine if individual and inter-annual variation in pup body condition could be explained by differences in female trophic niches, prey availability, or environmental conditions. Stable isotope-based metrics of trophic niche position, width, and overlap indicated little to no interannual variability in female foraging ecology at the population level despite variation in environmental conditions and prey availability in the fall on Georges Bank. Model selection indicated a positive relationship between pup body condition and δ13C values, which is indicative of pregnant females foraging on benthic, demersal, or nearshore prey species during the fall prior to parturition. This indicates that individual variation in female foraging ecology during pregnancy has a carry-over effect on offspring condition with possible implications for first-year survival, and ultimately recruitment to the adult population.

Trophic interactions between native and exotic cichlids in a shallow tropical estuary (Lake Vembanad, India)

Feeding ecology and seasonal diet variation between a non-native (Oreochromis mossambicus) and two native cichlids (Etroplus suratensis and Pseudetroplus maculatus) in a tropical estuary was studied. E. suratensis and O. mossambicus fed predominately on blue green algae, whereas P. maculatus preferred aquatic insects. Trophic niche breadth analysis showed that P. maculatus had a broader diet spectrum than did E. suratensis and O. mossambicus. Feeding strategy analysis through dominant prey items showed that E. suratensis and O. mossambicus preferred blue green algae, whereas P. maculatus relied mostly on animal diet (mainly insects), highlighting food segregation shown by this species compared with the other two large-growing cichlids. The highest diet overlap index value was recorded between E. suratensis and O. mossambicus (0.83), compared with P. maculatus and O. mossambicus (0.69), and E. suratensis and P. maculatus (0.64). Intensity of trophic interdependence among the three cichlids showed that the two, large growing species share available food resources, whereas the smaller species considerably alters its food preference.

Rocky escarpment versus savanna woodlands: comparing diet and body condition as indicators of habitat quality for the endangered northern quoll (

Abstract Context Understanding what constitutes high-quality habitat for threatened species is critical for conservation management planning. The endangered northern quoll (Dasyurus hallucatus) has experienced an uneven range contraction among habitat types. Once common across multiple habitats of northern mainland Australia, declining populations have now contracted to rocky escarpments. Aim The island refuge of Groote Eylandt, Northern Territory, Australia, has not experienced the declines as seen on mainland Australia. Here, northern quolls persist in both rocky escarpment and savanna woodland, which provides a rare opportunity to investigate the habitat quality of rocky escarpments and savanna woodland for the northern quoll. Methods Northern quolls (n = 111) were trapped in both rocky escarpment (n = 61) and savanna woodland (n = 50) habitats before the breeding season (May). We conducted body condition assessment, scat analysis, and measured trophic niche breadth of individuals occupying each habitat type. Key results Female quolls occupying rocky escarpments exhibited a lower body condition than did quolls occupying savanna woodland. Quolls from rocky escarpments consumed a significantly higher proportion of mammals and fed within a narrower dietary niche than did those occupying savanna woodland. Conclusions Quolls had adapted to the dietary resources available within each habitat type, suggesting that the lack of quolls in savanna woodland on the mainland is due to factors other than availability of dietary resources. Implications Groote Eylandt is of critical conservation significance, where high numbers of northern quolls exist in both rocky escarpment and savanna woodland habitats. For population viability on the mainland, managing threats such as feral predators and inappropriate fire regimes in savanna woodland, particularly those surrounding rocky escarpment, should be prioritised.

Evaluation of the trophic status of Sillago sihama and Sillago arabica at the south of Shatt Al-Arab River, Iraq

The present study is investigated the diet composition, feeding activity and intensity, and trophic niche breadth of two Sillaginid fish, Sillago sihama and Sillago arabica at the south of the Shatt Al-Arab River, Iraq from May 2019 to April 2020. A total of 511 specimens of fish comprised of 239 S. sihama and 272 S. arabica were used for the study. Fish length ranged from 11.7-23.7 and 13.0- 31.2 cm of the previous species, respectively. The results showed that the feeding activity and intensity influenced by months since the lowest stomach fullness occurred during the winter months. The analysis of diet for both species using the index of relative importance (IRI %) of prey items showed that the species were carnivores. The prey items of S. sihama were crabs (80.8%), shrimp (14.6%) and fish (4.6%), while the diet of S. arabica composed mainly on crabs (54.3%), shrimp (32.7%) and fish (13.0%). The overall values of feeding and vacuity indices were 40.4% and 9.5%, respectively for S. sihama, whereas 52.0% and 18.2%, respectively for S. arabica. Based on the results of trophic niche breadth indicate that S. schema is a high specialist feeder (Bi= 0.23), while S. arabica was considered a non-specialized feeder (Bi= 0.71). The study concludes that both species were carnivorous feeders, feeding mainly on crabs, shrimp and fish. S. sihama was a low specialized feeder, while S. arabica was not specialized.

Dieta y amplitud del nicho trófico del cormorán neotropical [Nannopterum brasilianus (Gmelin, 1789)] en el Santuario de Flora y Fauna Ciénaga Grande de Santa Marta, Caribe de Colombia

El cormorán neotropical (Nannopterum brasilianus) es un ave piscívora con reproducción colonial. Se distribuye desde el sur de Norteamérica hasta Argentina. La colonia más grande en Colombia se encuentra en la localidad de Punta Blanca, localizada en el Santuario de Flora y Fauna Ciénaga Grande de Santa Marta (SFF CGSM), en el complejo lagunar del mismo nombre (CL CGSM). En el presente estudio se analizó la dieta y la amplitud de nicho de N. brasilianus a partir de egagrópilas recolectadas en el borde occidental de la colonia de anidación de Punta Blanca durante la época reproductiva de 2017. La identificación de presas se basó principalmente en la morfología de los otolitos de peces encontrados en las egagrópilas (n = 64). Se identificaron ocho especies de peces en la dieta de N. brasilianus, de las cuales tres fueron nuevos registros para la dieta de la población del complejo lagunar (Mugil liza, M. curema y M. cephalus). Se destacó la representatividad de Cathorops mapale como principal presa consumida durante el estudio (89,5 % en número y 91,8 % en frecuencia de ocurrencia). Se observó una amplitud de nicho trófico estrecha (Levin’s de 0,002) y una dieta con baja equitatividad (q2 = 2,1), lo que corresponde a una respuesta adaptativa modelada por la disponibilidad de presas.

Raptors, doves and fragmented landscapes: Overabundance of native birds elicit numerical and functional responses of avian top predators

The replacement of natural habitats by fields destined for agricultural-livestock production causes changes in species composition. Some species benefitting from these changes can become more abundant. Increased populations can alter trophic webs. In the center of Argentina, populations of the native eared dove (Zenaida auriculata) have increased significantly in several provinces to such an extent that the species has been declared a pest. In 2014, 20 transects were sampled monthly to determine spatial and temporal abundance fluctuations of two raptor species, the crested caracara (Caracara plancus) and the black-chested buzzard eagle (Geranoaetus melanoleucus) to increases in the population of eared doves. The diet of these birds of prey was determined over 10 years, between 2003-2007 and 2010-2015. The monthly average (± SD) of crested caracaras and black-chested buzzard eagles was 97.75 (± 33.6) individuals and 3.91 (± 3.0) individuals, respectively. The monthly average of eared doves during surveys was 63,460 (± 113,497) individuals. Although both raptor species strongly rely on eared doves as their main prey, only black-chested buzzard eagle's trophic niche breadth was determined by the presence of this prey by having a potential functional response. The crested caracara, by contrast, could show a numerical response to increase of eared dove abundance that was not evident with the black-chested buzzard eagle. Anthropogenic disturbances and habitat fragmentation are the main drivers of eared dove overabundance, whose populations can cause changes in the composition and structure of these two raptor communities and consequently disturb ecosystem processes.

Association of Success in Interspecific Rearing of Nestlings with the Width of Trophic Niche of the Recipient Species in Hollow-Nesting Birds

The structure of the diet of passerine bird nestlings was analyzed in order to identify possible ways to reduce food competition between these species during the breeding period. We assumed that analysis of the effects of obtaining diets of heterospecific birds by nestlings in nature can help better understand their species-specific adaptations to living conditions, and we considered the case of joint nesting of the coal tit (Periparus ater (L. 1758)) (CT) and pied flycatcher (Ficedula hypoleuca (Pallas 1764)) (PF) in Moscow oblast as a key link. A PF male attracted a female to an artificial nest box, which has been already occupied by a CT pair. The females of both species incubated a mixed clutch sitting side by side. The CT nestlings hatched earlier than the PF nestlings, and the parents of both species began to feed them. The CT nestlings started to die one by one on the 4th day of joint feeding, and the last nestling died on the 11th day. This case encouraged us to compare the diets of nestlings from 22 broods of CTs and PFs in the same region. To compare the ratios of nestlings, we collected the portions of food that were delivered to nestlings by their parents and analyzed video recordings from the nests. The diet of PF nestlings was significantly more diverse than in CT nestlings (Berger–Parker reverse indices (1/d) were 3.01 and 2.11, respectively). Caterpillars and spiders (objects with a high content of carotenoids and taurine important for the development of nestlings) dominated in the CT diet. In PF feed, these objects occupied a much smaller portion. In addition to the above, compared with coal tits, PFs brought the following to nestlings: a significant number of objects with rough, highly chitinized covers (Coleoptera, Homoptera, etc.); objects with a sharp taste, such as true bugs (Heteroptera), ladybirds (Coleoptera, Coccinellidae), and millipedes (Diplopoda, Julidae); insects containing cantharidin toxin (soldier beetles, Coleoptera, Cantharidae). The nestlings developed successfully in PF nests to which parents brought such feed objects. The dimensional ranges of objects in the CT and PF diets completely overlapped. According to our opinion, the rougher, highly chitinized food and some poisonous insects (Cantharidae) in the PF diet make fundamentally important differences in the nutrition of PFs and CTs. Most likely, PFs have resistance to cantharidin and some other toxins that are contained in insects and therefore have a wider trophic niche.

The effects of morphology, phylogeny and prey availability on trophic resource partitioning in an anuran community

Several factors influence the partitioning of trophic resources in ecological communities, such as morphology, evolutionary history, and resource availability. Although the effects of morphology, phylogeny, and resource availability on trophic ecology have long been explored by theoretical studies, little has been done to empirically test these relationships. Here, we tested whether phylogenetic and morphological distances correlate with trophic niche overlap using a path analysis of multiple partial regression of distance matrices. Also, we tested whether niche breadth is influenced by body size using Phylogenetic Generalized Least Squares analysis. Trophic niche overlap was better explained by morphology per se than by the phylogenetic distance. We also found that predator's body size influences niche breadth calculated considering prey traits and availability, but not when we do not include these availability data. Additionally, trophic niche breadth was usually smaller when we considered prey traits and availability, differently from niche overlap, whose values increased when we did not consider these data. Our findings show that the interpretation of trophic niche in communities changes if we consider availability data, affecting inferences about coexistence and trophic specialization. Our study contributes to understanding trophic specialization and emphasizes the importance of incorporating prey availability and their traits into diet analysis.

Trophic ecology of detritivorous fish along a reservoir cascade in a tropical semi‐arid region

AbstractThe objectives of this study were to investigate the food resources consumed by two species of detritivorous fishes along the Apodi‐Mossoró River reservoir cascade system, located in the tropical semi‐arid region of Brazil. The hypotheses tested were as follows: (a) the diet, niche breadth and niche overlap of the species in the reservoirs downstream of the cascade are different due to the blockage of food resources upstream, and (b) the two species coexist in the reservoir cascade system due to resource partitioning. The diets of the species were analysed based on the volumetric data of the food resources using NMDS ordination, and possible differences in diet were tested with PERMANOVA. The contribution of each food resource was analysed by SIMPER analysis. Trophic niche breadth was evaluated by PERMDISP analysis, and the trophic niche overlap was calculated by the Pianka index. The difference in niche overlap between the reservoirs was evaluated by Welch's t test. Plant material, detritus and sediment were the most important food resources in the diets of the two species, but they differed along the reservoir cascade. Plant material, detritus and sediments were the predominant resources in their diets, which showed differences in feeding, a narrow trophic niche and high dietary overlap. The differences in diet observed along the cascade did not follow the expected pattern, and the narrow trophic niche and high trophic overlap indicate that the sharing of food resources was not the main cause of the coexistence of these species in the reservoirs.

Seasonality and interspecific competition shape individual niche variation in co‐occurring tetra fish in Neotropical streams

AbstractThe drivers of intraspecific niche variation and its effects on species interactions are still unclear, especially in species‐rich Neotropical environments. Here, we investigated how ecological opportunity and interspecific competition affect the degree of individual trophic specialization and the population niche breadth in tetra fish. We studied the four ecologically similar species (Psalidodon aff. gymnodontus, P. aff. paranae, P. bifasciatus, and Bryconamericus ikaa) in subtropical headwater streams (three sites with two co‐occurring species and three sites with only one species). We sampled fish in two contrasting seasons (winter/dry and summer/wet) and quantified their trophic niches using gut content analysis. Psalidodon bifasciatus was the only species distributed over all the sampled streams. We observed seasonal differences in population trophic niche breadth of P. bifasciatus just when this species co‐occurred with P. aff. gymnodontus. These findings confirm the complex nature of the effects of interspecific competition, depending, for instance, on the identity of the competitor. The degree of individual specialization of P. bifasciatus was higher in the winter, and it was not influenced by the presence of another species. Conversely, the other two Psalidodon species studied presented greater individual specialization in the summer, when fish consumed a higher proportion of allochthonous items (terrestrial insects and seeds), and there were no effects only for B. ikaa. Herein, our results suggest that seasonality in food‐resource availability is a major driver of niche variation and it has the potential to play an important role in how these similar tetra species interact and coexist.Abstract in Portuguese is available with online material.

Diet of the coral hawkfish Cirrhitichthys oxycephalus (Family: Cirrhitidae) in a fringing coral reef of the Eastern Tropical Pacific

Hawkfishes are small demersal reef predators. Although their association with the coral substrate has been widely documented for some species, information regarding their feeding habits is limited, especially in the Eastern Tropical Pacific (ETP). We characterized the diet of the coral hawkfish Cirrhitichthys oxycephalus in Isla Gorgona (ETP) by visually analyzing its gut contents and calculating its trophic niche breadth. Crustaceans were the most important (relative importance: 73%) and frequent prey found in 89% of the stomachs analyzed. Among crustaceans, copepods were the most abundant prey, suggesting that C. oxycephalus in Isla Gorgona has a specialized diet. In terms of biomass, decapods represented the highest contribution to the diet. Other prey items included micromolluscs and fish. This study highlights the strong trophic link between coral-dwelling reef fish and mobile invertebrates that comprise the coral reef cryptic fauna, and therefore, the indirect benefit that live coral cover has for this species.

Human disturbance increases trophic niche overlap in terrestrial carnivore communities

Animal foraging and competition are defined by the partitioning of three primary niche axes: space, time, and resources. Human disturbance is rapidly altering the spatial and temporal niches of animals, but the impact of humans on resource consumption and partitioning-arguably the most important niche axis-is poorly understood. We assessed resource consumption and trophic niche partitioning as a function of human disturbance at the individual, population, and community levels using stable isotope analysis of 684 carnivores from seven communities in North America. We detected significant responses to human disturbance at all three levels of biological organization: individual carnivores consumed more human food subsidies in disturbed landscapes, leading to significant increases in trophic niche width and trophic niche overlap among species ranging from mesocarnivores to apex predators. Trophic niche partitioning is the primary mechanism regulating coexistence in many communities, and our results indicate that humans fundamentally alter resource niches and competitive interactions among terrestrial consumers. Among carnivores, niche overlap can trigger interspecific competition and intraguild predation, while the consumption of human foods significantly increases human-carnivore conflict. Our results suggest that human disturbances, especially in the form of food subsidies, may threaten carnivores by increasing the probability of both interspecific competition and human-carnivore conflict. Ultimately, these findings illustrate a potential decoupling of predator-prey dynamics, with impacts likely cascading to populations, communities, and ecosystems.

Resource use by omnivorous fish: Effects of biotic and abiotic factors on key ecological aspects of individuals

AbstractResource use by organisms is mainly influenced by factors such as the morphology of individuals and the diversity and abundance of resources. For omnivores, the influence of these factors is more complex, as they have a morphology adapted to access different trophic levels, and any change in the environment can affect the quality or availability of resources. The aim of this study was to evaluate the effect of biotic and abiotic factors on the use of resources by omnivorous fish. We analysed the diet of 107 individuals of Astyanax lineatus in headwater streams in the Pantanal plateau, Brazil. We analysed the influence of body size and the characteristics of streams on the dietary composition, proportion of allochthonous items, trophic niche width and trophic position of individuals. These alimentary parameters were mainly influenced by body size and environmental variables, such as stream vegetation cover, flow, dissolved oxygen and conductivity. Allochthonous resources were more important to the diet of our model fish. We observed that larger individuals are more specialists than medium‐sized individuals and the trophic position decreases with increasing body size. Basically, three factors may have contributed to these results: large supply of carbon‐rich resources; morphology adapted for the consumption of larger, harder and carbon‐rich foods; and the interaction of increased body size and the high temperatures in the Neotropical region that can increase the demand for carbon for energy production.

Trophic structure of pelagic fishery organism assemblage in the central and western South China Sea in spring revealed by carbon and nitrogen stable isotope analysis

Carbon and nitrogen stable isotope analysis was carried out on pelagic fishery organisms caught in light traps and falling nets in the central and western South China Sea in the spring of 2018. The stable isotope values of the sampled individuals were used to elucidate the isotopic variations for the pelagic fishery organisms, to classify species into trophic functional groups, and to compare the differences of trophic structure among the classified trophic functional groups. The results showed that among 23 fishery species the mean δ13C value of Coryphaena hippurus was the lowest (-17.58‰±0.21‰), and that of Grammistes sexlineatus was the highest (-19.86‰±0.33‰). The mean δ15N values ranged from 8.31‰ in Psenes cyanophrys to (12.46±0.74)‰ in Chirocentrus dorab. The continuous trophic spectrum indicated that the trophic level (TL) for the sampled pela-gic fishery organisms ranged from 3.01 to 4.23, of which 19 species (83% of the total) fell between TL 3.0 and 4.0. The 23 species of fishery organisms were classified into three trophic functional groups, i.e., plankton feeding functional group (PFFG), nekton feeding functional group (NFFG), and mixed feeding functional group (MFFG). The analysis of standard ellipse area (SEA) showed that the PFFG occupied the largest trophic niche width (SEA=1.56‰2), followed by the MFFG (SEA=0.99‰2) and NFFG (SEA=0.31‰2). The MFFG overlapped with PFFG and NFFG in the trophic niche, with a relative percentage of 17% and 26%, respectively. There was no overlap between PFFG and NFFG.

Diet analysis of three rodent species sigmodontine in three cocoa production systems and forest in Alto Beni, Bolivia

Alto Beni region in Bolivia, presents a mosaic of non-extensive family crops ranging from monocultures to agroforestry systems immersed in a matrix of secondary forest, while the primary forest remains on the steeper slopes. Very little is known about the biology of the rodent species that inhabit this area. Then, the objective of this work was to determine the diet and its variation among three species of sigmodontine rodents ( Akodon dayi, Euryoryomys nitidus and Oligoryzomys microtis ) from 11 agroforestry systems (SAF) of cacao (four traditional monoculture / simple SAF plots, three intermediate SAF and four complex SAF) and two secondary forests. We analyzed contents of the stomach, cecum and intestine for 41 O. microtis (simple-SAF n = 31, complex-SAF n = 4 and forest n = 6), for 11 E. nitidus (simple-SAF n = 6, intermediate-SAF n = 2, complex-SAF n =3 and forest n = 2) and for 10 A. dayi (simple-SAF n =5 and forest n =5). We calculated trophic niche width (Levin’s Index) and measured the degree of niche overlap (an estimate of competition), using Pianka’s Symmetric Overlaying Index. Significant differences in the diet specialization among species across habitats, were tested using the non-parametric Kruskal-Wallis test. A total of 55 food items were obtained and grouped into nine food categories: dicotyledonous vegetative structures, monocotyledonous vegetative structures, vascular tissue, spikelet, seeds, mycorrhizae, adult arthropods, larval arthropods, and others. The study species feed primarily on plants of the family Poaceae. No significant differences were found in the diet between species or between SAF and the forest ( P > 0.05); in addition, there was no evidence of a noticeable overlay of trophic niches by habit type. In the studied season, we found that: O. microtis and E. nitidus are herbivorous omnivore; “generalist” simple-monoculture-SAF and “less generalist” in complex-SAF; besides, O. microtis is “generalist” in forest and E. nitidus is “specialist” in complex-SAF and in forest; while, A. dayi is herbivore-insectivore; “generalist” in simple-monoculture-SAF and in forest. Our results indicate that there is a strong relationship between, the type of plot where they were found and food availability in each habitat.