scholarly journals Competition and feeding ecology in two sympatric Xenopus species (Anura: Pipidae)

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3130 ◽  
Author(s):  
Solveig Vogt ◽  
F. André de Villiers ◽  
Flora Ihlow ◽  
Dennis Rödder ◽  
John Measey
Keyword(s):  
Food Preferences ◽  
Stomach Contents ◽  
Niche Overlap ◽  
Niche Differentiation ◽  
Shannon Index ◽  
Trophic Niche ◽  
Western Cape ◽  
The South ◽  
Amphibian Species ◽  
Study Sites

The widespread African clawed frog (Xenopus laevis) occurs in sympatry with the IUCN Endangered Cape platanna (Xenopus gilli) throughout its entire range in the south-western Cape, South Africa. In order to investigate aspects of the interspecific competition between populations of X. laevis and X. gilli, an assessment of their niche differentiation was conducted through a comprehensive study on food composition and trophic niche structure at two study sites: the Cape of Good Hope (CoGH) and Kleinmond. A total of 399 stomach contents of X. laevis (n = 183) and X. gilli (n = 216) were obtained together with samples of available prey to determine food preferences using the Electivity index (E*), the Simpson’s index of diversity (1 − D), the Shannon index (H′), and the Pianka index (Ojk). Xenopus gilli diet was more diverse than X. laevis, particularly in Kleimond where the Shannon index was nearly double. Both species were found to consume large amounts of tadpoles belonging to different amphibian species, including congeners, with an overall higher incidence of anurophagy than previously recorded. However, X. laevis also feeds on adult X. gilli, thus representing a direct threat for the latter. While trophic niche overlap was 0.5 for the CoGH, it was almost 1 in Kleinmond, suggesting both species utilise highly congruent trophic niches. Further, subdividing the dataset into three size classes revealed overlap to be higher in small frogs in both study sites. Our study underlines the importance of actively controlling X. laevis at sites with X. gilli in order to limit competition and predation, which is vital for conservation of the south-western Cape endemic.

scholarly journals Feeding aspects of Knodus heteresthes (Eigenmann, 1908) and Moenkhausia lepidura (Kner, 1858) (Characiformes, Characidae) in the Teles Pires and Juruena Rivers, southern Amazon

2020 ◽  
Author(s):  
E. Oliveira ◽  
A. R. A. Ignácio ◽  
W. L. Lázaro ◽  
C. C. Muniz ◽  
D. V. S. Campos ◽  
...  
Keyword(s):  
Stomach Contents ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Frequency Of Occurrence ◽  
Dietary Preference ◽  
Importance Index

Abstract The composition of the diet of two species of characids (Knodus heteresthes and Moenkhausia lepidura) was evaluated in the Teles Pires and Juruena Rivers, sampled in September and October 2016. We analyzed 226 stomachs of K. heteresthes and 425 of M. lepidura. The analysis of the stomach contents was based on volumetric and frequency of occurrence methods, applying the food importance index. For the similarity of the diets between the species we calculated the niche overlap with Pianka’s index. Both species in the Juruena River have a dietary preference for arthropods (IAi > 0.95). In the Teles Pires River the diet is concentrated in three sources for both species: arthropods (IAi > 0.52), vegetables (IAi > 0.33) and fish (IAi > 0.12). The diet was dissimilar when compared to environments (ANOSIM, R ≥ 0.57, p < 0.001) with high trophic niche overlap (α > 0.97), regardless of the sampled environment. In the Teles Pires River, both species were classified as omnivorous with an insectivorous tendency and in the Juruena River the insectivorous behaviour occurs.

Niche differentiation of tallgrass prairie plants species along soil hydrological gradients

Botany ◽  
2019 ◽  
Vol 97 (9) ◽  
pp. 487-494
Author(s):  
John Markham
Keyword(s):  
Tallgrass Prairie ◽  
Niche Overlap ◽  
Niche Differentiation ◽  
Vegetation Survey ◽  
Soil Hydrology ◽  
Hydrological Conditions ◽  
Species Analysis ◽  
Species Pairs ◽  
Tallgrass Prairies ◽  
Study Sites

This study addressed whether the distribution of species in frequently burned lowland tallgrass prairies is driven by gradients in soil hydrology. On three study sites, the hydrological conditions in 1 m2 vegetation survey plots where quantified as the number of days the soil was anaerobic less than 15 cm below the surface, and the surface of the soil was drier than 0.4 m3·m−3. On each site, the centroid of each species hydrological niche was defined as the hydrological conditions in plots where it occurred, weighted by its abundance. Species found on all sites maintained a consistent ranking between sites along the soil drying gradient, but not the anaerobic gradient. The levels of niche overlap between species pairs along both hydrological gradients were significantly less than the overlap from randomly assigning species to the hydrological gradients. Indicator species analysis suggested that on each site the communities were best described as consisting of two subgroups. The hydrological niches of the species in these subgroups were significantly different from one another, suggesting that these subgroups are associated with wet or dry habitats. Overall, these analyses suggest that hydrology plays a major role in determining the structure of these frequently disturbed communities.

scholarly journals Changes in trophic characteristics of two fish species of Astyanax (Teleostei: Characidae) in response to aquatic pollution

2019 ◽  
Vol 36 ◽  
pp. 1-12 ◽  
Author(s):  
Mirella B. Alonso ◽  
Débora R. de Carvalho ◽  
Carlos B. M. Alves ◽  
Marcelo Z. Moreira ◽  
Paulo S. Pompeu
Keyword(s):  
Isotopic Composition ◽  
Fish Species ◽  
Environmental Changes ◽  
Stomach Contents ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Metropolitan Region ◽  
Trophic Plasticity ◽  
Polluted Sites ◽  
Belo Horizonte

The trophic plasticity of most fish species of Astyanax Baird &amp; Girard, 1854 in response to environmental changes and resource availability is high. This work evaluates the differences in the trophic characteristics of two congeneric species, Astyanaxtaeniatus (Jenyns, 1842) and Astyanaxlacustris (Lütken, 1875), in Rio das Velhas Basin, which is highly impacted by the discharge of sewage from the Metropolitan Region of Belo Horizonte (MRBH). Eight sites were sampled and grouped into three regions: upper course (two sites upstream of the MRBH); middle course (three sites located in the middle portion of the Rio das Velhas, region with greater influence of the MRBH), and lower course (three sites downstream of the MRBH). Samples of fish and food resources were collected from all sites to obtain the isotopic composition of nitrogen (δ15N) and carbon (δ13C), and the stomach contents of the two species was analized. The most common items in the stomach of A.lacustris and A.taeniatus, respectively, were from plants and insects, followed by algae/periphyton (especially at the low course of Rio das Velhas). In contrast, stable isotope analyses indicated that algae (in polluted sites) and periphyton (in least-disturbed sites) were best assimilated both species. Both analyses indicated that the trophic niches of the two species overlap more in more polluted sites relative to less polluted sites. Astyanaxtaeniatus and A.lacustris only presented different isotopic composition of carbon and nitrogen in the upper course of the Rio das Velhas, probably in response to the greater diversity of food items consumed by each species. In the other regions, the species presented similar isotopic signatures, with δ15N and δ13C notably enriched in the most polluted regions (middle and low course). Our results suggest that pollution acts by increasing trophic niche overlap of these species, altering the type of resources most assimilated, and promoting a greater enrichment of δ15N in fish and resources.

A historical perspective of niche differentiation between two top predators in the Uruguayan coastal area

2019 ◽  
Vol 46 (2) ◽  
pp. 136 ◽  
Author(s):  
Florencia Artecona ◽  
Maite De María ◽  
Leandro Bergamino ◽  
Diana Szteren
Keyword(s):  
Marine Mammals ◽  
Species Abundance ◽  
Niche Differentiation ◽  
Trophic Niche ◽  
Trophic Levels ◽  
Isotopic Niche ◽  
Recent Period ◽  
The South ◽  
Coastal Habitat ◽  
Top Predators

Context As top predators, marine mammals play a key role consuming in different trophic levels and the trophic niche characterization may help to understand how species utilize and share resources . On the coast of the Río de la Plata and the South-west Atlantic, the South American sea lion (Otaria flavescens) and the franciscana dolphin (Pontoporia blainvillei) are two important predators. Aims The present study investigated potential trophic overlap of both species by measuring stable carbon (δ13C) and nitrogen (δ15N) isotopes over two periods: historical (1959–79) and recent (2002–15) on the Uruguayan coast. Methods Bone samples of P. blainvillei and O. flavescens were used to determine the isotopic niche using the Stable Isotope Bayesian Ellipses in R (SIBER) analysis. Key results The isotopic niche did not overlap between species in any period. δ15N was higher in O. flavescens in both periods (20.29‰±0.73 in the historical and 19.95‰±1.0 in the recent period), indicating that it feeds at a higher trophic level than P. blainvillei. The δ13C was also significantly higher in O. flavescens than in P. blainvillei during the two periods (O. flavescens: –11.43±0.6‰ historic, –12.72±0.4‰ recent, and P. blainvillei: –12.69±1.1‰ historic, –13.84±1.3‰ recent). The isotopic niche areas of P. blainvillei in recent and historic periods confirmed they forage in 2 distinct environments, marine and estuarine, with low isotopic overlap. This overlap was higher in the recent period. Conclusions and Implications O. flavescens and both P. blainvillei groups were segregated in both periods, with a higher overlap in the recent. These species appear to reduce competition by using different resources in the same coastal habitat. O. flavescens preferentially feeds on benthic fish and showed wider trophic amplitude in both periods, whereas P. blainvillei has a more coastal–pelagic diet and included a greater variability of resources in its diet. The differences between species trophic niches can still be detected after both marine mammals species abundance has declined and after the development of fisheries.

Spatial and trophic niche overlap between Diplodus bellottii and Diplodus vulgaris in the Tagus estuary, Portugal

2004 ◽  
Vol 84 (4) ◽  
pp. 837-842 ◽  
Author(s):  
Manuel Horta ◽  
Maria José Costa ◽  
Henrique Cabral
Keyword(s):  
Feeding Habits ◽  
Stomach Contents ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Sea Bream ◽  
Tagus Estuary ◽  
Otter Trawl ◽  
Limiting Factor ◽  
Species Competition ◽  
Competition For Space

To evaluate the consequences of the coexistence of the Senegal sea bream Diplodus bellottii with one other species of Diplodus, Diplodus vulgaris, in the Tagus estuary (Portugal), the distribution and feeding habits of juveniles and adults of both species were studied. Sampling took place between May 2001 and March 2002, in five zones, including the estuary and adjacent coastal area, using an otter trawl. Both species were abundant in the estuary and their distribution overlapped. The stomach contents analysis showed that the diet of both species was mainly composed of algae, bivalves and crustaceans. Diphodus bellottii and D. vulgaris showed a generalist feeding behaviour and were clearly omnivorous, being detected in a high trophic niche overlap between the two species. Competition for space and food may occur when densities are high and food became a limiting factor.

Isotopic niche of two coastal dolphins in a tropical marine area: specific and age class comparisons

2015 ◽  
Vol 96 (4) ◽  
pp. 853-858 ◽  
Author(s):  
Ana Paula Madeira Di Beneditto ◽  
Leandro Rabello Monteiro
Keyword(s):  
Stomach Contents ◽  
Niche Overlap ◽  
Niche Differentiation ◽  
Trophic Levels ◽  
Food Sources ◽  
Isotopic Niche ◽  
Marine Area ◽  
Age Class ◽  
Niche Metrics ◽  
Pontoporia Blainvillei

Niche differentiation is the process by which species evolve different forms of resource use, and is used to explain the co-occurrence in a variety of habitats. The Bayesian framework of isotopic niche through quantitative niche metrics was applied to estimate and compare the niche breadth of two sympatric coastal dolphinsPontoporia blainvilleiandSotalia guianensisin a tropical marine area. The standard ellipse areas (SEAs) based on species were quite similar, but the SEAs based on age class showed that the matures’ niche space is larger than the immatures’ for both dolphins. A probabilistic comparison of SEAs indicated that specific differences are negligible compared with age class differences. Trophic level measures (δ15N range) indicated that the dolphins are comparable as top predators, and that immature specimens have a lower range of trophic levels than mature ones. In terms of variability of food sources (δ13C range),S. guianensisshowed a larger value thanP. blainvilleiand mature specimens had larger δ13C range than immatures for both species. In general,P. blainvilleiandS. guianensiswere similar in the niche metrics, with SEAs overlap of 52.1 and 39.7%. The immature specimens showed reduced isotopic niche overlap between species (<3%). In conclusion,Pontoporia blainvilleiandS. guianensisspecimens have similar isotopic niches, but pronounced differences between immature and mature specimens, both intraspecific and interspecific. Isotopic niche and quantitative metrics along with previous data on stomach contents provide a strong representation of species niche and their relationships.

scholarly journals Trophic niche overlap among scavengers in Patagonia supports the condor-vulture competition hypothesis

2017 ◽  
Vol 28 (3) ◽  
pp. 390-402 ◽  
Author(s):  
FERNANDO BALLEJO ◽  
SERGIO A. LAMBERTUCCI ◽  
ANA TREJO ◽  
LUCIANO J. M. DE SANTIS
Keyword(s):  
Human Activities ◽  
Food Resource ◽  
Niche Overlap ◽  
Shannon Index ◽  
Trophic Niche ◽  
Foraging Strategies ◽  
Cathartes Aura ◽  
Turkey Vulture ◽  
Black Vulture ◽  
Andean Condor

SummaryAnimals that share resources tend to use different foraging strategies in order to decrease potential competition. Scavenging birds using the same nutritional resources can segregate into different space and time scales. However, it has been suggested that when the species do not co-evolve to achieve such segregation competition may result. Our aim was to study the trophic niche overlap between three species of obligate scavengers, the Andean CondorVultur gryphus, Turkey VultureCathartes auraand American Black VultureCoragyps atratus, which are the main avian consumers of carcasses in north-western Patagonia. Black Vultures arrived in the area relatively recently, have expanded their distribution following human activities, and have been suggested to compete with the threatened condor. We collected pellets in communal roosts of the three species to determine their diet, and to estimate the diversity (Shannon Index) and diet similarity (Pianka overlap index). We found that the Turkey Vulture has greater niche breadth and, apart from domestic livestock, it incorporates smaller items such as fish, reptiles and a great number of birds, carnivores and mice. Although the Black Vulture diet includes arthropods, they feed primarily on introduced ungulates, overlapping more with condor diet when roosting far from urban centres. As these latter two species share the same food resource, human activities that positively affect the abundance of the Black Vulture could increase competition among them, with possible implications for the conservation of the Andean Condor.

scholarly journals Changes in prey importance and prey niche overlap of sexes during the alpine newt breeding season

2020 ◽  
Vol 146 (2) ◽  
Author(s):  
Oldřich Kopecký
Keyword(s):  
Breeding Season ◽  
Stomach Contents ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Sexual Differences ◽  
Food Sources ◽  
Quantitative Composition ◽  
Important Prey ◽  
Alpine Newt ◽  
Prey Items

Urodeles, including European newts, are usually sexually dimorphic predators. Among newts, the alpine newt has the most pronounced sexual size dimorphism (in favour of females). Gender is a factor that is often associated with intra-specific diet differences. Despite the significant number of dietary studies on the alpine newt, some topics such as the breadth of the trophic niche and its overlap between sexes, or inter-sexual differences in qualitative and quantitative composition of prey remain unresolved. The present study dealing with these questions was conducted at two localities (ponds at an elevation of about 450 m) in the Czech Republic. Newts were captured from the banks during the entire breeding season using a dip net, and the stomach contents were extracted using a stomach flushing technique. Altogether 190 individuals were sampled, and a total of 1,417 prey items were obtained. The available food sources differed over the course of the breeding season, as newts changed the taxa they preyed on. This reflects the ability of newts to switch between several hunting strategies. The overall food niche overlap between the sexes was relatively large (C = 0.761, resp. C = 0.797). Inter-sexual differences were detected at both localities, mainly in the number of prey items consumed from the most important prey categories such as Rana eggs or Isopoda, which were consumed in higher numbers by females. The findings of this study suggest that females are more sensitive to the trade-off between energy intake and expenditure during the breeding season.

Trophic niche overlap in two syntopic colubrid snakes (Hierophis viridiflavus and Zamenis longissimus) with contrasted lifestyles

2012 ◽  
Vol 33 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Hervé Lelièvre ◽  
Pierre Legagneux ◽  
Gabriel Blouin-Demers ◽  
Xavier Bonnet ◽  
Olivier Lourdais
Keyword(s):  
Diet Composition ◽  
Feeding Rate ◽  
Species Coexistence ◽  
Niche Partitioning ◽  
Stomach Contents ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Temperate Climate ◽  
Feeding Strategies ◽  
Mean Body Temperature

In many organisms, including snakes, trophic niche partitioning is an important mechanism promoting species coexistence. In ectotherms, feeding strategies are also influenced by lifestyle and thermoregulatory requirements: active foragers tend to maintain high body temperatures, expend more energy, and thus necessitate higher energy income. We studied diet composition and trophic niche overlap in two south European snakes (Hierophis viridiflavus and Zamenis longissimus) in the northern part of their range. The two species exhibit contrasted thermal adaptations, one being highly mobile and thermophilic (H. viridiflavus) and the other being elusive with low thermal needs (Z. longissimus). We analyzed feeding rate (proportion of snakes with indication of a recent meal) and examined more than 300 food items (fecal pellets and stomach contents) in 147 Z. longissimus and 167 H. viridiflavus. There was noticeable overlap in diet (overlap of Z. longissimus on H. viridiflavus = 0.62; overlap of H. viridiflavus on Z. longissimus = 0.80), but the similarity analyses showed some divergence in diet composition. Dietary spectrum was wider in H. viridiflavus, which fed on various mammals, birds, reptiles, and arthropods whereas Z. longissimus was more specialized on mammals and birds. The more generalist nature of H. viridiflavus was consistent with its higher energy requirements. In contrast to our expectation, feeding rate was apparently higher in Z. longissimus than in H. viridiflavus, but this could be an artifact of a longer transit time in Z. longissimus, given its lower mean body temperature. These results allow a better understanding of the ability to coexist in snakes belonging to temperate climate colubrid communities.

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