Niche Breadth Research Papers - Academia.edu (original) (raw)

BACKGROUND & OBJECTIVES The predatory potential of the larvivorous fishes can be affected by the presence of alternative preys. In the present study the predation pattern of the sewage dwelling Poecilia reticulata (Peters 1872) on the... more

BACKGROUND & OBJECTIVES The predatory potential of the larvivorous fishes can be affected by the presence of alternative preys. In the present study the predation pattern of the sewage dwelling Poecilia reticulata (Peters 1872) on the larvae of Culex quinquefasciatus Say 1823 (Diptera: Culicidae) was evaluated in the presence of alternative preys. METHODS The predation of Cx. quinquefasciatus larvae by different size groups of R. reticulata fishes was evaluated. In addition to this, the niche breadth (N) and diet breadth (B) were measured following Manly's selectivity index (Si) as an indicator of variation of such predation pattern in the presence of alternative prey types, like chironomid larvae and tubificid worms. RESULTS The consumption of IV instar Cx. quinquefasciatus larvae by individual P. reticulata ranged between 65 and 84 in a 3 h feeding period and varied with the size of fish (F2,33 = 34.91; p < 0.001). The selectivity coefficient revealed a significantly low pr...

The ability to make a priori assessments of a species' response to fragmentation, based on its distribution in the landscape, would serve as a valuable conservation and management tool. During 1997-1999, we monitored 717 scent stations to... more

The ability to make a priori assessments of a species' response to fragmentation, based on its distribution in the landscape, would serve as a valuable conservation and management tool. During 1997-1999, we monitored 717 scent stations to examine seasonal use of forest patches, corridors, and crop fields by coyotes (Canis latrans), domestic cats (Felis catus), foxes (Vulpes vulpes and Urocyon cinereoargenteus), raccoons (Procyon lotor), striped skunks (Mephitis mephitis), opossums (Didelphis virginiana), and long-tailed weasels (Mustela frenata). For each species we developed landscape-based ecologically scaled landscape indices (ELSI), and we modeled species spatial distribution across three spatial scales (landscape-level, element-level, and local habitat-level). Our results suggest that these predators view landscape fragmentation at different spatial scales and demonstrate strong interspecific differences in their response to elements of the landscape. All species except coyotes and domestic cats avoided agricultural fields. In general, predator species that were more mobile (i.e. high ESLI for landscape connectivity; coyotes) were characterized by landscape-and element-based logistic models. In contrast, models including local habitat features generally were most appropriate for less mobile or more stenophagous predators (e.g. long-tailed weasels). Our analysis extends the application of the ESLI concept to species assemblages that do not appear to function as metapopulations, and it highlights the importance of examining spatial scale and species-specific responses to habitat fragmentation. We discuss the relevance of these findings for defining ecological landscapes, understanding predator-prey interactions at multiple spatial scales, and conserving predator and prey populations in fragmented landscapes. #

... 1997]). Additionally, patch occupancy patterns of spiders relate to life-history traits, such as dispersal capacity, competition ability, and phenology ([Bonte et al., 2004], [Draney and Crossley, 1999] and [Le Viol et al., 2008]). In... more

... 1997]). Additionally, patch occupancy patterns of spiders relate to life-history traits, such as dispersal capacity, competition ability, and phenology ([Bonte et al., 2004], [Draney and Crossley, 1999] and [Le Viol et al., 2008]). In ...

Spotted hyaenas Crocuta crocuta were once considered mere scavengers; however, detailed research revealed that they are very efficient predators. Information on what spotted hyaenas actually prefer to prey on and what they avoid is... more

Spotted hyaenas Crocuta crocuta were once considered mere scavengers; however, detailed research revealed that they are very efficient predators. Information on what spotted hyaenas actually prefer to prey on and what they avoid is lacking, as well as the factors that influence prey selection. Data from 14 published and one unpublished study from six countries throughout the distribution of the spotted hyaena were used to determine which prey species were preferred and which were avoided using Jacobs' index. The mean of these values for each species was used as the dependent variable in multiple regression, with prey abundance and prey body mass as predictive variables. In stark contrast to the rest of Africa's large predator guild, spotted hyaenas do not preferentially prey on any species. Also surprisingly, only buffalo, giraffe and plains zebra are significantly avoided. Spotted hyaena most prefer prey within a body mass range of 56-182 kg, with a mode of 102 kg. The dietary niche breadth of the spotted hyaena is similar to that of the lion Panthera leo, and the two species have a 58.6% actual prey species overlap and a 68.8% preferred prey species overlap. These results highlight the flexible and unselective nature of spotted hyaena predation and are probably a reason for the species' success throughout its range, despite a large degree of dietary overlap with lions. a Three hundred and fifty-five kills were observed during the 7-year study period. b Data presented as percentages.

Identifying the factors that influence the extinction risk of animals is essential in conservation biology because they help identify endangered species and provide the basis for their preservation. We present a comparative study that... more

Identifying the factors that influence the extinction risk of animals is essential in conservation biology because they help identify endangered species and provide the basis for their preservation. We present a comparative study that uses data from the literature on the diet and morphological specialization of European and North American bat species to investigate the effect of specialization on extinction risk. We focused on bats because many species are endangered and their high ecological diversity makes them a good model system for our purpose. After correcting for phylogenetic inertia, we compared the influence of dietary niche breadth as a measure of food specialization and of wing morphology as a measure of foraging strategy, habitat adaptation, and migratory ability on the vulnerability of 35 insectivorous bat species. Our results do not support the hypothesis that a narrow dietary niche breadth is related to high extinction risk. Instead they suggest that habitat specialization, which is reflected in wing morphology, influences the extinction risk of bats. Our study shows that an initial risk assessment in temperate-zone bats could be based on data of wing morphology but not on dietary data obtained from fecal analyses.

The diet composition of otters in the upper catchment of the River Agri (southern Italy) was investigated by spraint analysis (N = 555) between May 2001 and January 2003. Once a season, spraints were collected along four riverine... more

The diet composition of otters in the upper catchment of the River Agri (southern Italy) was investigated by spraint analysis (N = 555) between May 2001 and January 2003. Once a season, spraints were collected along four riverine stretches, two with swift-waters and two with slow-waters. Overall, fish represented the dominant food (percent mean volume, Vm% = 57.30), followed by amphibians (Vm% = 18.90) and crayfish (Vm% = 15.60). The food composition of otters feeding along swift-water sections differed significantly from that recorded along slow-water sections. The trophic niche was larger for slow-water sections, because of the presence of more fish species. In both sampled habitats (swift-and slow-waters) the importance of fish decreased in winter when flooding increasing water speeds and turbidity and thus reduced the hunting efficiency of the otters. Hibernating amphibians represented a primary alternative resource. As expected, insects and reptiles were eaten more frequently in summer, while birds predominated during their breeding season. Seasonal variation in fish consumption could have been related to changes in fish activity and to environmental conditions, which influenced the availability of prey to the otters. For both habitats, trophic niche breadth showed a minimum value in autumn, when fish were dominant in the otters' diet, whilst a peak was reached in summer for slowwater sections and in spring for swift-water sections. time-lag of about 13 years seemed to have occurred between the introduction of centrarchids, mainly the largemouth bass (Micropterus salmoides), and their predation by otters. This relatively long lag phase could have been related to the pattern of alien fish invasion rather than to the inability of the otters to readily prey on newly available resources. Our results confirm the opportunistic feeding behaviour of the otter in Mediterranean habitats, the species diet tending to match the seasonal and spatial variation in the relative abundance of different prey items. key words: Lutra lutra, diet, alien fish, swift-and slow-waters, southern Italy.

Three years after a river restoration scheme in the Syr Valley (Luxembourg) we investigated habitat development and habitat use of Galloway cattle deployed in a low-intensity grazing system on a permanent floodplain pasture. Habitats were... more

Three years after a river restoration scheme in the Syr Valley (Luxembourg) we investigated habitat development and habitat use of Galloway cattle deployed in a low-intensity grazing system on a permanent floodplain pasture. Habitats were delimited with a mobile GPS/GIS mapping system and their spatial development was assessed over three consecutive years. During these three years, the patches of the six habitats decreased to 40% of mean initial size, and a rapid net area expansion of wetland habitats (large sedge swamps: +100%, marsh and tall forb grasslands: + 43%) was observed. The behavioural patterns and grazing preferences of the cattle were observed directly during the vegetation period in June, August and November. These observations were complemented by a transect analysis of cattle impact indicators in June and November. The cattle grazed the different habitats very selectively, as they preferred the mesophilic, and ruderal grasslands 1.6, and 5.6 times more than expected respectively. During the growing season, the grazing niche breadth declined (3.92 in June to 2.68 in November), and less preferred forage habitats like large sedge swamps were grazed primarily in the autumn. We used bite and step rates to investigate grazing intensity by habitat type. During summer, grazing intensity correlated with forage quality in the different habitat patches, whereas in autumn it was obviously influenced by the effort required to access the desired forage plants in a given habitat. The impact indicators revealed a matter transfer from riparian areas to the valley edge. Here, we give a first insight into habitat development and habitat use of Galloway cattle in a recently restored floodplain area and derive recommendations for the adaptive management of future projects.

In fragmented landscapes, the likelihood that a species occupies a particular habitat patch is thought to be a function of both patch area and patch isolation. Ecologically scaled landscape indices (ESLIs) combine a species' ecological... more

In fragmented landscapes, the likelihood that a species occupies a particular habitat patch is thought to be a function of both patch area and patch isolation. Ecologically scaled landscape indices (ESLIs) combine a species' ecological profile, i.e., area requirements and dispersal ability, with indices of patch area and connectivity. Since their introduction, ESLIs for area have been modified to incorporate patch quality. ESLIs for connectivity have been modified to incorporate niche breadth, which may influence a species' ease in crossing the non-habitat matrix between patches. We evaluated the ability of 4 ESLIs, the original and modified indices of area and connectivity, to explain patterns in patch occupancy of 5 forest rodents. Occupancy of eastern gray squirrels (Sciurus carolinensis), North American red squirrels (Tamiasciurus hudsconicus), fox squirrels (Sciurus niger), white-footed mice (Peromyscus leucopus), and eastern chipmunks (Tamias striatus) was modeled at 471 sites in 35 landscapes sampled from the upper Wabash River basin in Indiana. Models containing ESLIs received support for gray squirrels, red squirrels, and chipmunks. Modified ESLIs were important in models for red squirrels. However, none of the models demonstrated high predictive ability. Incorporating habitat quality and using surrogate measures of dispersal can have important effects on model results. Additionally, different responses of species to area, isolation, and habitat quality suggest that generalizing patterns of metapopulation dynamics was not justified, even across closely related species.

In spite of the worldwide occurrence of domestic cats and dogs, and their close relationship with humans, the number of published papers on free-ranging cats Felis catus and dogs Canis familiaris, is small. The diet of both species was... more

In spite of the worldwide occurrence of domestic cats and dogs, and their close relationship with humans, the number of published papers on free-ranging cats Felis catus and dogs Canis familiaris, is small. The diet of both species was estimated in a suburban and rural environment in July 2002 and January 2003. Visual observations and scat collection of both species were accomplished along a 10 km transect line in the Campus 'Luiz de Queiroz', University of Sa˜o Paulo, Piracicaba, south-eastern Brazil. The diet of both species was determined by analysis of sterilized, washed, dried and sorted scats. Estimated abundances of free-ranging cats and dogs in the sampled area were 81 ( AE 4.32) and 42 ( AE 2.96), respectively. Cats and dogs were more abundant in the suburban than in the rural environment (t= 3.78, Po0.001, N = 55; t= 8.38, Po0.001, N = 55, respectively) and cats were more abundant than dogs in the suburban environment (t= 6.76, Po0.001, N = 55), even though there was no significant difference between the abundance of both species in the rural environment (t = 0.82, P= 0.46, N= 55). Invertebrates were the most commonly consumed item by both species, followed by mammals (cats: 63.24 and 20.51%; dogs: 57.05 and 25.15%, respectively). Niche breadth was 0.4892 for cats and 0.4463 for dogs. Niche overlap was almost complete (0.97108). The consumption of mammals was estimated to be between 16.76 and 25.42 kg individual À1 year À1 for dogs and between 2.01 and 2.9 kg individual À1 year À1 for cats. These data might be useful to establish a management program to minimize the predation pressure of free-ranging cats and dogs on wildlife.

An ability to predict species' sensitivities to habitat loss and fragmentation has important conservation implications, and numerous hypotheses have been proposed to explain interspecific differences observed in human-dominated... more

An ability to predict species' sensitivities to habitat loss and fragmentation has important conservation implications, and numerous hypotheses have been proposed to explain interspecific differences observed in human-dominated landscapes. We used occupancy data collected on

The puma (Felis concolor) has the most extensive range of any terrestrial mammal in the Western Hemisphere, covering over 100 ~ latitude. Food habits of different puma subspecies vary with latitude. Subspecies from temperate habitats... more

The puma (Felis concolor) has the most extensive range of any terrestrial mammal in the Western Hemisphere, covering over 100 ~ latitude. Food habits of different puma subspecies vary with latitude. Subspecies from temperate habitats generally eat larger prey and specialize on a smaller number of prey taxa, whereas, in tropical habitats, they prey on smaller, more varied prey. In North America, ungulates (primarily deer) represented 68% of the puma's diet by frequency of occurrence. Mean weight of vertebrate prey (MWVP) was positively correlated (r = 0.875) with puma body weight and inversely correlated (r=-0.836) with food niche breadth in all America. In general, MWVP was lower in areas closer to the Equator. Patterns of puma prey selection are probably influenced by prey availability and vulnerability, habitat characteristics, and potential competition from the jaguar (Panthera onca).

Feeding habits of young predatory fishes in marsh creeks situated along the salinity gradient of the Schelde estuary, Abstract Fish and macrobenthos were sampled in four different marshes along the salinity gradient of the Schelde... more

Feeding habits of young predatory fishes in marsh creeks situated along the salinity gradient of the Schelde estuary, Abstract Fish and macrobenthos were sampled in four different marshes along the salinity gradient of the Schelde estuary, Belgium/Netherlands, to investigate the importance of marsh creeks as foraging grounds for the dominant, larger fish species. The total density and biomass of all the main macrobenthic taxa (Corophium volutator, Nereis diversicolor, Oligochaeta, Macoma baltica and Heteromastus fliliformis) were measured. The feeding habits of the larger predatory fishes (Platichthys flesus, Dicentrarchus labrax) were investigated. Qualitative and quantitative stomach analyses included the calculation of different indices, showing the niche breadth (as diet diversity) and the niche overlap (as similarity between the predators' diet) for this habitat. These analyses showed that the two most important benthic prey species for P. flesus were C. volutator and N. diversicolor. D. labrax preyed upon a wider range of species, including C. volutator, N. diversicolor, Crangon crangon, Carcinus maenas and Orchestia spp. The stomach diversity of D. labrax and P. flesus showed differences between the marshes although there was no consistent pattern in diet composition, reflecting the opportunistic nature of feeding by these large predators. The fullness indices of both flounder and sea bass did not differ significantly along the salinity gradient and the estimated minimum consumption by these predators did not indicate a top-down control of the macrobenthic community. The salt marsh creeks seem to provide excess food for the visiting fish species. The benthic prey was present in very high abundances, which may suggest that the typical nursery species such as C. crangon and C. maenas, and early juveniles of P. flesus, D. labrax and Pomatoschistus microps were not preyed upon significantly. This supports the hypothesis that salt marsh creeks provide good refuge areas for nursery species against predation by larger fish.

The arrival of large masses of drifting Sargassum since 2011 has caused changes in the natural dynamics of Caribbean coastal ecosystems. In the summer of 2015, unprecedented and massive mats of S. fluitans and S. natans have been observed... more

The arrival of large masses of drifting Sargassum since 2011 has caused changes in the natural dynamics of Caribbean coastal ecosystems. In the summer of 2015, unprecedented and massive mats of S. fluitans and S. natans have been observed throughout the Mexican Caribbean including exceptional accumulations ashore. This study uses stable isotopes to assess the impact of Sargassum blooms on the trophic dynamics of the Diadema antillarum sea urchin, a keystone herbivore on many Caribbean reefs. Bayesian models were used to estimate the variations in the relative proportions of carbon and nitrogen of assimilated algal resources. At three lagoon reef sites, the niche breadth of D. antillarum was analysed and compared under massive influx of drifting Sargassum spp. vs. no influx of Sargassum blooms. The effects of the leachates generated by the decomposition of Sargassum led to hypoxic conditions on these reefs and reduced the taxonomic diversity of macroalgal food sources available to D. antillarum. Our trophic data support the hypothesis that processes of assimilation of carbon and nitrogen were modified under Sargassum effect. Isotopic signatures of macroalgae associated with the reef sites exhibited significantly lower values of δ 15 N altering the natural herbivory of D. antillarum. The Stable Isotopes Analysis in R (SIAR) indicated that, under the influence of Sargassum blooms, certain algal resources (Dictyota, Halimeda and Udotea) were more assimilated due to a reduction in available algal resources. Despite being an abundant available resource, pelagic Sargassum was a negligible contributor to sea urchin diet. The Stable Isotope Bayesian Ellipses in R (SIBER) analysis displayed differences between sites, and suggests a reduction in trophic niche breadth, particularly in a protected reef lagoon. Our findings reveal that Sargassum blooms caused changes in trophic characteristics of D. antillarum with a negative impact by hypoxic conditions. These dynamics, coupled with the increase in organic matter in an oligotrophic system could lead to reduce coral reef ecosystem function.

The relationship between herbivore diet quality, and diet composition (the range of food plants consumed) and body mass on resource partitioning of herbivores remains the subject of an ongoing scientific debate. In this study we... more

The relationship between herbivore diet quality, and diet composition (the range of food plants consumed) and body mass on resource partitioning of herbivores remains the subject of an ongoing scientific debate. In this study we investigated the importance of diet composition and diet quality on resource partitioning among eight species of savanna herbivore in north Cameroon, with different body mass. Dung samples of four to seven wild herbivore and one domesticated species were collected in the field during the dry and wet period. Diet composition was based on microhistological examination of herbivore droppings, epidermis fragments were identified to genus or family level. In addition, the quality of the faecal droppings was determined in terms of phosphorus, nitrogen and fibre concentrations. The results showed that there was no significant correlation between body mass and (differences in) diet composition for wet and dry season. When all species are considered, only significant relationships are found by the Spearman rank correlation analyses during the wet season between body mass and phosphorus and nitrogen, but this relationship did not exist during the dry season. When the analyses focuses on ruminants only (thus leaving out hippo), none of the relationships between body mass and diet quality was significant in either season. During the dry season the proportion of graminoids ranged between 10% (small unidentified herbivore species) to 90% (hippopotamus), during the wet season this proportion ranged from 60% (zebu) to 90% (hippopotamus). All species but zebu had more graminoids in their dung during wet season compared with dry season. However all species but hartebeest had more graminoids old stems in their dung during the dry season, compared with the wet season. The niche breadth for food categories consumed by kob (0.300), hippo (0.090), hartebeest (0.350), roan (0.510) and zebu (0.300) was much greater in the dry season than in the wet season for kob (0.120), hippo (0.020), hartebeest (0.190), roan (0.090) and zebu (0.200). When looking at grass taxa consumed, the niche breadth of kob (0.220), hartebeest (0.140), and roan (0.250) was also greater in the dry season when compared with the wet season for kob (0.050), hartebeest (0.120) and roan (0.120). The opposite was found for zebu and hippo. Comparison of the species' diet compositions with randomized data showed that dietary overlap between different herbivore species was much higher than what would be expected on the basis of chance, demonstrating surprisingly limited niche separation between species. This offers potential for competition, but it is more likely that the high niche overlap indicates absence of competition, due to low herbivore densities and abundant food resources, permitting species to share non-limiting resources. With increasing herbivore densities and subsequent increasing scarcity of resources, the relationship between diet quality and body mass in combination with increased niche separation is expected to become more visible.

Resource partitioning in a community of diurnal arboreal mammals consisting of the lion-tailed macaque Macaca silenus, bonnet macaque (BM) Macaca radiata, Nilgiri langur Semnopithecus johnii, and the Indian giant squirrel Ratufa indica of... more

Resource partitioning in a community of diurnal arboreal mammals consisting of the lion-tailed macaque Macaca silenus, bonnet macaque (BM) Macaca radiata, Nilgiri langur Semnopithecus johnii, and the Indian giant squirrel Ratufa indica of the Western Ghats, southern India, was studied. Differences in their diet, vertical stratification, food resource niche breadth, niche overlap, and behavioral interactions were examined. Resource partitioning was through differential habitat use, resource use, and vertical stratification. Of the four species, the BM was not a resident species and made frequent forays into evergreen forest from the adjacent deciduous forest during the flowering season of Cullenia exarillata and fruiting season of Ficus microcarpa. The macaques had narrower niches, and the langur and the squirrel had wider niches. Niche overlap was highest between the two macaques. Overlap among the study species was particularly pronounced during the flowering of C. exarillata. There was significant correlation between niche overlap and intolerance among the study species. Certain species pairs showed little or no mutual intolerance despite high overlap. Cooperative interactions such as alarm calls occurred more frequently among the resident species. Interaction matrices revealed an underlying pattern of interspecific dominance hierarchy, with the BM dominating over the other three species. Our study suggests that the BM do not coexist with the other three because of high overlap with its congener and low occurrence of cooperative interactions.

The Pantepuí region of the Guyana Shield of Northern South America harbors a unique biota. It is characterized by high local species endemism, especially applicable to its table mountain-like outcrops, the tepuís. For this region, also... more

The Pantepuí region of the Guyana Shield of Northern South America harbors a unique biota. It is characterized by high local species endemism, especially applicable to its table mountain-like outcrops, the tepuís. For this region, also known as the 'Lost World', different hypotheses have been proposed to explain its Biogeography. We suggest that the amphibian and reptile communities' suit well as target group to study the hypotheses since these vertebrates are relatively well documented through comprehensive species lists and are less mobile than other terrestrial vertebrates. However, records for the majority of endemic amphibian and reptile species naturally numbered only a few. We hence used extant dimensions of the vegetation zones associated to amphibians and reptiles. By running maximum entropy-based Climate Envelope Distribution Models (CEDM), these were projected to climatic scenarios as suggested for the Last Glacial Maximum (LGM, 21,000 years BP). Our results promote the Cool Climate hypothesis for diversity and distribution of amphibians and reptile communities in the Pantepuí region, in which species' geographic ranges were displaced followed by speciation along with the climate change during glacial-interglacial Quaternary cycles. Moreover, we studied the impact of expected future anthropogenic global warming on these vegetation zones. Climate change scenarios used, consider demographic, politicoeconomic, social and technological futures at different degrees with either more or less environmentally conscious, regionalized solutions to economic, social and environmental sustainability. For the 'Lost World', our CEDM results demonstrated

This paper investigates the trophic niche of a poorly studied cave salamander, Speleomantes italicus. We examined Central Appennine hypogean populations that inhabit seven caves situated in three limestone areas in Umbria Region (Italy).... more

This paper investigates the trophic niche of a poorly studied cave salamander, Speleomantes italicus. We examined Central Appennine hypogean populations that inhabit seven caves situated in three limestone areas in Umbria Region (Italy). Adults displayed feeding activity from May to December and the Vacuity Index analysis revealed a discontinuous trophic activity pattern throughout the year related to prey phenology. According to the qualitative analysis of the trophic spectrum, the populations in question can be defined as euryphagous, while the quantitative analysis (in terms of number and volume of preyed taxa) revealed a specialist strategy with a clear preference towards Diptera Limnobiidae. Both sexes presented similar trophic niche breadth and a high diet overlap, showing no intersexual differences. The hypogean populations of S. italicus, similarly to S. strinatii, showed a narrower trophic niche than epigeans of the same species, probably due to the limited food availability in the cave habitat.

To cite this Article Capula, Massimo, Luiselli, Luca and Rugiero, Lorenzo(1993) 'Comparative ecology in sympatric Podarcis muralis and P. sicula (Reptilia: Lacertidae) from the historical centre of Rome: What about competition and niche... more

To cite this Article Capula, Massimo, Luiselli, Luca and Rugiero, Lorenzo(1993) 'Comparative ecology in sympatric Podarcis muralis and P. sicula (Reptilia: Lacertidae) from the historical centre of Rome: What about competition and niche segregation in an urban habitat?'

In spite of its wide distribution, Geoffroy's cat (Oncifelis geoffroyi) has been recently upgraded from Least Concern IUCN category to Near Threatened because of lack of knowledge. In this study, we examine at the Mar Chiquita Biosphere... more

In spite of its wide distribution, Geoffroy's cat (Oncifelis geoffroyi) has been recently upgraded from Least Concern IUCN category to Near Threatened because of lack of knowledge. In this study, we examine at the Mar Chiquita Biosphere Reserve (371 46'S, 571 27'W; Argentina) their seasonal diet, and their feeding preference in relation to waterbird abundance, size, and distance of waterbird prey before attack. The diet, evaluated by feces analysis, was comprised of 42% waterbirds and 40% small mammals. The relative importance of waterbirds in the diet changed throughout the year associated with seasonal fluctuations in their availability. Predation on waterbirds increased from autumn to summer, while predation on small mammals decreased during this period. Trophic-niche breadth for prey occurrence was higher in autumn and lower in spring. We found that abundance, distance of waterbird prey before attack, and prey size were significant predictors of waterbird consumption by the Geoffroy's cat. This small cat appears to change its kill rate in relation to waterbird abundance changes. The overconsumption of prey close to vegetation and big prey indicates selective predatory behavior by this cat.

Understanding the ultimate causes of population declines and extinction is vital in our quest to stop the currently rampant biodiversity loss. Comparison of ecological characteristics between threatened and nonthreatened species may... more

Understanding the ultimate causes of population declines and extinction is vital in our quest to stop the currently rampant biodiversity loss. Comparison of ecological characteristics between threatened and nonthreatened species may reveal these ultimate causes. Here, we report an analysis of ecological characteristics of 23 threatened and 72 nonthreatened butterfly species. Our analysis reveals that threatened butterflies are characterized by narrow niche breadth, restricted resource distribution, poor dispersal ability, and short flight period. Based on the characteristics, we constructed an ecological extinction risk rank and predicted which of the currently nonthreatened species are at the highest risk of extinction. Our analysis reveals that two species currently classified as nonthreatened are, in fact, at high risk of extinction, and that the status of a further five species should be reconsidered.

The diet of feral cats in the main habitats of the Canary Islands is composed of introduced mammals, birds, reptiles and insects. However, introduced mammals constitute the main source of biomass consumed, followed in importance by... more

The diet of feral cats in the main habitats of the Canary Islands is composed of introduced mammals, birds, reptiles and insects. However, introduced mammals constitute the main source of biomass consumed, followed in importance by reptiles and birds. PCA analysis of biomass revealed the ordination of three different groups, corresponding to the diet in the laurel forest (La Gomera), thermophilous forest (El Hierro) and one large group that include the rest of habitat types. A similar pattern was observed when these habitats were analyzed in a single island (La Palma). Oryctolagus cuniculus was an important prey in practically all habitats, while Rattus rattus was frequently captured in the laurel forest, Mus musculus domesticus in the open shrubs (both xeric and high mountain), reptiles (mainly lizards genus Gallotia) in the open habitats of Tenerife, birds play a relative role in forest habitats, and large invertebrates (basically Orthoptera and Coleoptera) in the three forest habitats and in the xerophytic shrub of Fuerteventura. Morisita's index of similarity of diet showed maximum differences between the forest habitats (pine and thermophilous vs. laurel forest), indicating an important heterogeneity in the diet of feral cats in these environments. Shrub habitats showed smaller values of Levin's niche breadth than those from the forest habitats, showing a broader diet in the latter. Lastly, the diet of feral cats on the Canary Islands follows the general pattern of other islands located at similar latitude and mainly composed by rabbits and mice. However, specific preys such as lizards, rats or birds, play an important role in particular habitats in which they are abundant.

A field survey was conducted in a highly degraded barren environment in Sicily in order to investigate herpetofaunal community composition and structure, habitat use (niche breadth and overlap) and relative abundance of a snake predator... more

A field survey was conducted in a highly degraded barren environment in Sicily in order to investigate herpetofaunal community composition and structure, habitat use (niche breadth and overlap) and relative abundance of a snake predator and two species of lizard prey. The site was chosen because it has a simple community structure and thus there is potentially less ecological complexity to cloud any patterns observed. We found an unexpectedly high overlap in habitat use between the two closely related lizards that might be explained either by a high competition for space or through predator-mediated co-existence i.e. the prevention of the competitive exclusion of one lizard over the other. We also found a strong positive correlation between predator density and tail damage in lizards and we suggest that tail damage is a direct consequence of snake activity (because no other natural predators occur in the area).

On islands, one of the greatest risks to native wildlife is the establishment of alien species. In Ireland, the Irish hare (Lepus timidus hibernicus ), the only native lagomorph, may be at risk from competitive exclusion and hybridisation... more

On islands, one of the greatest risks to native wildlife is the establishment of alien species. In Ireland, the Irish hare (Lepus timidus hibernicus ), the only native lagomorph, may be at risk from competitive exclusion and hybridisation with naturalised brown hares (L. europaeus) that were introduced during the late nineteenth century. Pre-and post-breeding spotlight surveys during 2005 in the north of Ireland determined that brown hare populations are established in mid-Ulster and west Tyrone. In mid-Ulster, brown hares comprised 53% Á 62% of the hare population, with an estimated abundance of 700 Á 2000 individuals between pre-and post-breeding periods. Comparison of habitat niches suggest that Irish and brown hares have comparable niche breadths that at times completely overlap, suggesting the potential for strong competition between the species. Anecdotal evidence suggests that both species may hybridise. Further research is urgently required to assess the degree of risk that naturalised brown hares pose to the Irish hare population and what action, if any, is needed to ensure the future ecological security and genetic integrity of the native species.

We studied the diet of 15 montane frog species of the genus Pristimantis (Craugastoridae) from the Andes of Western Colombia to determine the diet range, breadth of niche and overlap among species. We identified 499 prey items from... more

We studied the diet of 15 montane frog species of the genus Pristimantis (Craugastoridae) from the Andes of Western Colombia to
determine the diet range, breadth of niche and overlap among species. We identified 499 prey items from stomach and intestinal
contents of 154 specimens. Prey items were included in 74 different categories. The most common 15 prey categories accounted
for 65 % of all frogs’ diet. The invertebrate families Isotomidae, Chironomidae, Formicidae, and Tipulidae were the most abundant
categories and accounted for 32 % of the frogs’ diet. Ten of the 15 frog species were found with at least one item of Araneae.
Coleoptera and Tipulidae were found in nine frog species, and Acari and Carabidae in eight frog species. In general, beetles were found
in gastrointestinal tracts of all species examined, except for P. quantus, but interpretation needs caution because only one individual
of this species was caught. Pristimantis hectus showed a specialized diet, consuming mainly dipterans of the family Chironomidae,
while the remaining species showed a generalist diet. Pristimantis palmeri showed niche overlap with P. erythropleura (Фjk = 0.69), P.
myops (Фjk = 0.64), and P. orpacobates (Фjk = 0.64). Our results suggest that most of the frogs species studied are generalist, foraging
opportunistically on dipterans, arachnids, collembolans, coleopterans, and hymenopterans. Here, we report the diet of montane
Pristimantis species and discuss the results in comparison with data on related species in montane and lowland regions.
Keywords: Colombia, diet, niche breadth, niche overlap, Pristimantis, Western Cordillera.

In dry-summer seasonal climates, the beginning of the rainy season can prompt germination under different temperatures, depending on altitude. Understanding germination responses to temperature with altitude is important in fire-prone... more

In dry-summer seasonal climates, the beginning of the rainy season can prompt germination under different temperatures, depending on altitude. Understanding germination responses to temperature with altitude is important in fire-prone environments for species regenerating after fire from seeds (seeders), particularly under changing climate. Here we investigated the role of temperature in four Mediterranean seeder shrubs from Central Spain. Seeds from 17 sites (285-1,253 m altitude), of two hard-seeded nanophanerophytes (Cistus ladanifer and C. salviifolius) and two soft-seeded chamaephytes (Lavandula pedunculata and Thymus mastichina) were investigated. Intact and heat shock treated seeds were set to germinate under four temperature regimes, including a treatment simulating future warming. GLM with binomial or gamma functions were used to test treatment effects using altitude as a covariate. Altitude was a significant covariate only in L. pedunculata. Temperature did not affect final germination in either Cistus, but it significantly affected T. mastichina, and interacted with altitude in L. pedunculata, whereby the higher the altitude the less it germinated with decreasing temperature. Germination speed (T 50 ) was lower at colder temperatures in all but C. salviifolius that was insensitive to our treatments. Heat shock significantly increased final germination in both Cistus and T. mastichina, but did not interact with temperature or altitude. We conclude that germination response to temperature, including varying sensitivity with altitude, differed among these species; thus, changes in the timing of the onset of the rainy season will diversely affect populations at various altitudes. We discuss our results in a context of changing climate and fire.

The feeding ecology of eight demersal elasmobranchs, three sharks (Etmopterus spinax, Scyliorhinus canicula and Galeus melastomus) and five batoids (Myliobatis aquila, Leucoraja naevus, Raja polystigma, R. miraletus and R. clavata), from... more

The feeding ecology of eight demersal elasmobranchs, three sharks (Etmopterus spinax, Scyliorhinus canicula and Galeus melastomus) and five batoids (Myliobatis aquila, Leucoraja naevus, Raja polystigma, R. miraletus and R. clavata), from the Balearic Sea (western Mediterranean) was analyzed. For each species, the diet and feeding habits were characterized by depth strata using quantitative indices such as diet overlap, diet breadth and prey diversity. Diet variation with size and depth were also tested for the most abundant species. For shelf-living species, natantian and reptantian crustaceans together with teleosts were the most important preys. On slope bottoms, euphausiids were the preferential prey for S. canicula and G. melastomus, while E. spinax fed mainly on cephalopods. The most specialist and generalist diet corresponded to G. melastomus living on the upper slope and S. canicula from the continental shelf, respectively. High overlap was found between all the skates on the continental shelf and the sympatric sharks S. canicula and G. melastomus on the slope. Significant overlap was also found between S. canicula and R. clavata on the continental shelf. Size was found to significantly affect the diet of S. canicula, G. melastomus and R. clavata, whereas depth affected exclusively S. canicula.

Feeding ecology of Crossodactylus schmidti (Anura: Hylodidae) in southern Brazil. Zoological Studies 51(4): 484-493. The diet of the frog Crossodactylus schmidti was studied from Sept. 2009 to Mar. 2010 in the Turvo State Park, a locality... more

Feeding ecology of Crossodactylus schmidti (Anura: Hylodidae) in southern Brazil. Zoological Studies 51(4): 484-493. The diet of the frog Crossodactylus schmidti was studied from Sept. 2009 to Mar. 2010 in the Turvo State Park, a locality of mesophytic semideciduous forest in southern Brazil, based on 93 stomach contents obtained by stomach-flushing (n = 80) and analysis of preserved specimens (n = 13). In addition to describing the diet, we determined the niche breadth on the basis of prey categories, and calculated electivities to evaluate the relation between the diet and prey availability in the environment. We also tested for differences in diets between sexes and between adults and juveniles. Crossodactylus schmidti consumed 19 categories of prey, of which ants, beetles, and dipterans had the highest importance values. Despite the varied diet, the niche breadth was narrow, with only a few prey categories being consumed predominantly. Ants, dipterans, and spiders were consumed in proportions similar to those estimated in the environment. There was no relationship between mouth width and length/volume of prey consumed, but there were significant sexual and age differences in the diet composition. Males consumed 18 prey categories, and females consumed 15; juveniles consumed 13 prey categories, and adults consumed 19. Despite differences in diet compositions between the sex and age groups, ants were the most important prey for all of them. Considering the varied diet and relationships between some of the most important items in the diet with their availability in the environment, C. schmidti can be characterized as an opportunistic feeder with feeding habits similar to those of other Crossodactylus species. Similarities in the importance of prey items such as ants, beetles, dipterans, and insect larvae in the diet of C. schmidti and other Hylodidae species are discussed. http://zoolstud.sinica.edu.tw/Journals/51.4/484.pdf

In this work, the concepts of niche breadth and redundancy were used to analyse the use of fuelwood species in rural populations in Patagonia, Argentina. We conducted semi-structured interviews to estimate the fuel niche breadth (FNB).... more

In this work, the concepts of niche breadth and redundancy were used to analyse the use of fuelwood species in rural populations in Patagonia, Argentina. We conducted semi-structured interviews to estimate the fuel niche breadth (FNB). For this, the variables used were as follows: use consensus of native species, use consensus of preferred species and use consensus of pruning species. Moreover, two indices were created to compare socio-environmental fuel redundancy and economic dependence between populations. The most isolated population presented the highest values for FNB, considering principally the use consensus of native species and high environmental redundancy, while the community with most access to urban centres showed the highest FNB value for use consensus of pruning species. The
third community presented intermediate values for FNB and low levels of redundancy, showing notable vulnerability. The FNB measured through fuelwood use contributes to the description of socio-ecological factors. Evaluation of redundancy in terms of a resource and its different functional varieties, while not focusing in particular on the functionality of the species, allows the evaluation of the current situation of the resource under study. The indices created in this work can also be used for other variables related to subsistence lifestyles.

The crustacean zooplankton communities of seven, small, eutrophic West Virginian impoundments were examined during midsummer. The more eutrophic lakes had as dominants, 2 cyclopoid, i calanoid, and 2 cladoceran species . Cluster analysis... more

The crustacean zooplankton communities of seven, small, eutrophic West Virginian impoundments were examined during midsummer. The more eutrophic lakes had as dominants, 2 cyclopoid, i calanoid, and 2 cladoceran species . Cluster analysis showed that the 4 more eutrophic lakes clustered together, further cluster analysis showed there was a very similar group of 5 species which characterized the most eutrophic lakes . Principal components analysis showed that the more eutrophic lakes were characterized by having more cyclopoids and cladocerans than calanoids . Niche breadth showed that the most often dominant species had much higher 6 values than the species which could be considered secondary dominants.

Co-existence among potentially competing species can be favoured by niche specialisation and/or by reducing the overall intensity of competition via aggregated utilisation of fragmented resources. We investigated the respective roles of... more

Co-existence among potentially competing species can be favoured by niche specialisation and/or by reducing the overall intensity of competition via aggregated utilisation of fragmented resources. We investigated the respective roles of niche specialisation and aggregation in the case of nine congeneric monogenean parasites on the gills of Roach (Rutilus rutilus L.) belonging to the genus Dactylogyrus. The position of each individual parasite of the nine Dactylogyrus species was recorded. Niche breadth and niche overlap of parasite species were estimated. Comparative methods, which take into account phylogenetic information of the analysed species, were used. We reconstructed a phylogeny of the nine Dactylogyrus species based on morphological characters. We used the`aggregation model of co-existence' in the model to test if species co-existence is facilitated when intraspeci®c aggregation exceeds interspeci®c aggregation. We observed a lack of negative correlation in abundance between pairs of parasites, and a negative correlation between niche size and parasite aggregation, for both intraspeci®c and interspeci®c aggregation. Our comparative analysis showed that parasite abundance is positively correlated with niche breadth. Then parasite abundance, and not interactions between Dactylogyrus species, seems to be the most important factor determining niche size This result gives some support to niche segregation by specialisation. Niche size was negatively correlated with both intraspeci®c and interspeci®c aggregation. No relationship was found between an increase of interspeci®c aggregation with an increase of niche overlapping, which suggests that competition may play little role. A lack of competition could be also con®rmed by the lack of negative correlation in abundance between species pairs. A parsimony analysis of the evolution of gill distribution indicates a change in one parameter of the niche (arch, segment and/or area) at each branching event. q

In Mexico, both native and exotic fruit fly parasitoids exhibit spatial and temporal overlaps in distribution. To better characterize the spatial component of foraging in the braconid portion of this guild, and to examine the effects of... more

In Mexico, both native and exotic fruit fly parasitoids exhibit spatial and temporal overlaps in distribution. To better characterize the spatial component of foraging in the braconid portion of this guild, and to examine the effects of intra-and interspecific competition on resource partitioning, we conducted two field-cage experiments aimed at: (1) assessing the host-finding ability of parasitoids when singleor multiple-species cohorts were confronted with very low host-densities only at canopy level; (2) determining the height level preference (canopy vs. ground) for parasitoid foraging activity when single-or multiple-species cohorts were present and host density was high; (3) identifying candidate species for biological control programs using multiple-species releases. We studied two species exotic to Mexico, Diachasmimorpha longicaudata and D. tryoni, and four species native to Mexico, Doryctobracon areolatus, D. crawfordi, Opius hirtus, and Utetes anastrephae (all Braconidae, Opiinae). Parasitoids were allowed to forage for 8-h as single-or multiple-species cohorts in a room-sized cage containing potted trees with guavas artificially infested with Anastrepha ludens larvae and attached to the branches. When parasitoids were released as single-species cohorts into low host-density environments (fruit only at canopy level), D. longicaudata, D. tryoni and O. hirtus clearly distinguished uninfested from infested fruit and exerted the highest rates of parasitism with a significantly female-biased offspring sex ratio. When multiple-species cohorts were released, the same pattern was observed but, D. crawfordi and D. areolatus did not parasitize any larvae. In the case of the high host-density condition and with fruit at canopy and ground levels, when parasitoids were released in single-species cohorts, only D. crawfordi and D. longicaudata parasitized larvae at ground level. At canopy level, D. longicaudata, D. tryoni and D. crawfordi achieved the highest parasitism rates. When parasitoids were released as multiple-species cohorts, individuals of none of the species foraged at ground level, and in the canopy foraging activity and parasitism rates dropped dramatically in all species, except O. hirtus. Given the performance of O. hirtus, it should be considered a potential candidate to complement D. longicaudata in low-host density prevalence areas.

The predatory potential of the larvivorous fishes can be affected by the presence of alternative preys. In the present study the predation pattern of the sewage dwelling Poecilia reticulata (Peters 1872) on the larvae of Culex... more

The predatory potential of the larvivorous fishes can be affected by the presence of alternative preys. In the present study the predation pattern of the sewage dwelling Poecilia reticulata (Peters 1872) on the larvae of Culex quinquefasciatus Say 1823 (Diptera: Culicidae) was evaluated in the presence of alternative preys.

In order to assess diet composition and niche breadth of this species, we analysed the stomach content of 182 specimens collected monthly along the eastern coast of Sicily (Central Mediterranean Sea). Overall, 50 prey taxa belonging to... more

In order to assess diet composition and niche breadth of this species, we analysed the stomach content of 182 specimens collected monthly along the eastern coast of Sicily (Central Mediterranean Sea). Overall, 50 prey taxa belonging to five major groups (algae, gastropods, crustaceans, polychaetes, fishes) were identified in 102 full stomachs. Benthic or epibenthic crustaceans, such as decapods, amphipods and isopods were the most important prey, whereas algae, gastropods, polychaetes and fishes were only occasionally ingested. In terms of composition by species, the diet of Scorpaena maderensis was characterized by a variety of rare or unimportant prey, which was consumed by few individuals only, although sometimes in large amount. As a result, S. maderensis can be considered a generalized and opportunistic feeder. The feeding intensity followed roughly a seasonal trend, with a minimum food intake in summer. The individual fish size was the most important factor affecting diet. According to the observed ontogenetic shift, smallsized individuals fed primarily on small crustaceans (i.e. amphipods and isopods), whereas large-sized specimens consumed preferably bigger and more vagile prey, such as walking and swimming decapods. No significant differences in diet were observed in relation to sex of predator and sampling season.

In this paper, we analyse the patterns and determinants of cacti invasion in 22 European countries. We compiled a checklist for each country. Cacti were classified for each country according to their invasion status as casuals, locally... more

In this paper, we analyse the patterns and determinants of cacti invasion in 22 European countries. We compiled a checklist for each country. Cacti were classified for each country according to their invasion status as casuals, locally established (1-5 localities of small population size) and widely established (45 localities of considerable population size).

Food habits of 15 species of frugivorous bats were studied at La Selva Biological Station, Costa Rica. Eight hundred and fifty-four (854) fecal samples and 169 samples from fruit parts and seeds discarded by bats beneath feeding roosts... more

Food habits of 15 species of frugivorous bats were studied at La Selva Biological Station, Costa Rica. Eight hundred and fifty-four (854) fecal samples and 169 samples from fruit parts and seeds discarded by bats beneath feeding roosts were analyzed. During eight months of study, 47 fruit species consumed by bats were identified. Five plant genera (Cecropia, Ficus, Piper, Solanum, and Vismia) constituted 85% of all plants found in fecal samples. Feeding niche breadth differed significantly among the six most common species of frugivorous bats (Artibeus jamaicensis, Carollia sowelli, C. castanea, C. perspicillata, Dermanura sp., and Glossophaga commissarisi). All species, except for Dermanura sp., showed a diet dominated by one or two plant species. This suggests a pattern of resource partitioning at a generic level, in which Carollia consumed mainly Piper, Artibeus consumed Ficus and Cecropia, and Glossophaga consumed Vismia. Cluster analysis revealed higher values of food niche overlap in congeneric species than among species of different genera. Results show that if food is a limiting factor, mechanisms other than trophic selection must reduce interspecific interference or competition for food in this frugivorous bat guild. Rev. Biol. Trop. 55 (1): 301-313. Epub 2007 March. 31.

The latitudinal gradient in diversity is widely acknowledged, but the mechanisms contributing to this pattern are still poorly known. Given that the species have environmental optima, a central issue is how species' niche parameters, i.e.... more

The latitudinal gradient in diversity is widely acknowledged, but the mechanisms contributing to this pattern are still poorly known. Given that the species have environmental optima, a central issue is how species' niche parameters, i.e. niche breadth and niche position, vary along the latitudinal gradient. In this study, we examined the determinants of fish distribution and the variability in species' niche breadth and position along latitudinal gradient using a regional data set of boreal lakes. Results of the Outlying Mean Index analysis showed that the fish community structure was jointly controlled by a number of environmental factors, ranging from water chemistry and temperature to local physical factors such as lake area and depth. Corroborating the number of earlier findings, the regional occupancy of species was more strongly governed by the niche position than the niche breadth, although both showed a significant relationship with the regional distribution. When the latitudinal variability in niche parameters of the main taxonomic groups was analysed, both percids and cyprinids, being cool water species, showed significant decrease in niche breadth northwards as we predicted. By contrast, the niche position and latitude were nonsignificantly correlated in percids and salmonids, and negatively correlated in cyprinids, the latter showing the opposite pattern as we predicted. However, even if only a part of our predictions was supported, the results generally implied that the examination of latitudinal variability in the niche properties is potentially highly rewarding, not only in estimation of present community structure in lakes but also for predictions of species' responses to climate change.

Diet composition of newly emerged brown trout fry in natural areas remains poorly known, and foraging abilities at this early stage, although presumably reduced, are still under discussion. We have studied gut content composition of brown... more

Diet composition of newly emerged brown trout fry in natural areas remains poorly known, and foraging abilities at this early stage, although presumably reduced, are still under discussion. We have studied gut content composition of brown trout fry in a temperate area (Galicia, NW Spain) and compared it to the benthic macroinvertebrate community. Small prey such as chironomid larvae and baetid nymphs were the most important food items for newborns, some of them still presenting yolk remnants. However, the positive selection observed for Polycentropodidae and Simuliidae and the rejection of Elmidae and Leuctricidae suggest that other factors apart from size, such as locomotor abilities of fish or accessibility and antipredator behaviour of prey play an important role in feeding behaviour. Additionally, analysis of diet changes on the studied fry suggests a dramatic shift in niche breadth at the moment of complete yolk absorption, which might be related to the improvement of swimming and handling ability of fry for capturing and ingesting prey. The presence of aerial imagoes only in the stomachs of fry with no yolk provides further support to this hypothesis. Planning of restoration works on spawning grounds should then allow enough time for complete recolonization by benthic macroinvertebrates, including first instars, as searching for food in newborns is limited to the nest area due to mobility constraints.

The diet of the Neotropic cormorant (Phalacrocorax brasilianus) was studied by analysing 289 regurgitated pellets collected from a roosting site at Lagoa dos Patos estuary, southern Brazil, between November 2001 and October 2002 (except... more

The diet of the Neotropic cormorant (Phalacrocorax brasilianus) was studied by analysing 289 regurgitated pellets collected from a roosting site at Lagoa dos Patos estuary, southern Brazil, between November 2001 and October 2002 (except April to June). In total, 5,584 remains of prey items from 20 food types were found. Fish composed the bulk of the diet representing 99.9% by mass and 99.7% by number. The main food items were White croaker (Micropogonias furnieri) (73.7% by frequency of occurrence, 48.9% by mass and 41.2% by number), followed by Catfish (Ariidae) and anchovies (Engraulididae). In Lagoa dos Patos estuary the generalist Neotropic cormorant fed mainly on the two most abundant demersal fishes (White croaker and Catfish), which accounted for the low niche breadth calculated. The total length of all fish preyed varied from 27.2 to 318.3 mm (113.5 ± 48.0 mm), and preyed White croakers' size differed between months. Neotropic cormorants seem to prey on most abundant class sizes of White croaker instead of selecting similar prey size throughout the time. However, temporary changes in diet in terms of food items, abundance and prey size were detected, revealing a high ecological plasticity of the species. Individual daily food intake of Neotropic cormorants estimated by pellets and metabolic equations corresponded to 23.7 and 27.1% of their body mass, falling in the range of other cormorant species. Annual food consumption of the population estimated by both methods was 73.4 and 81.9 tonnes, comprising mainly immature and subadult White croaker and Catfish which are commercially important. Temporal variations in diet composition and fish size preyed by Neotropics cormorants, a widespread and generalist species, suggest shifts according to fluctuations in the abundance of prey. The plasticity of this cormorant is also revealed by their ability to adjust feeding behaviour in response to temporal or local changes in the environment, from a generalist at the species level to a specialist at the individual or local population level.

The geographic range of an invasive species is a key determinant of relative impact in the invaded region. Comparison of invasive species that are widespread or rare in invaded ranges can highlight mechanistic traits that determine the... more

The geographic range of an invasive species is a key determinant of relative impact in the invaded region. Comparison of invasive species that are widespread or rare in invaded ranges can highlight mechanistic traits that determine the risk of impact from invasion. Round Goby (Neogobius melanostomus) is more geographically widespread and abundant than Tubenose Goby (Proterorhinus semilunaris) across invaded ranges of the Laurentian Great Lakes. We used stable isotopes of carbon (δ13C) and nitrogen (δ15N) in liver and muscle to contrast the isotopic niche breadth and niche plasticity of Round Goby and Tubenose Goby near the inflow and outflow of Lake St. Clair and in western Lake Superior. At all sites, Round Goby and Tubenose Goby that matched in size (21 – 53 mm standard length) had distinct isotopic niches with no overlap, driven by higher δ15N in Round Goby. The variation in isotopic niche, and the mean difference in δ13C and δ15N between muscle and liver, was greater for Round Goby, suggesting both greater seasonal shifts in diet and niche plasticity in this more widely established invader. Round Goby that were significantly larger than Tubenose Goby had broader isotopic niches and greater niche plasticity in the majority of cases and this was associated with isotopic niche overlap with smaller Round Goby and Tubenose Goby. Our findings suggest that a broad and plastic isotopic niche provides scope for wider establishment range in invasive fish species.

The range of resources that a species uses (i.e. its niche breadth) might determine the geographical area it can occupy, but consensus on whether a niche breadth-range size relationship generally exists among species has been slow to... more

The range of resources that a species uses (i.e. its niche breadth) might determine the geographical area it can occupy, but consensus on whether a niche breadth-range size relationship generally exists among species has been slow to emerge. The validity of this hypothesis is a key question in ecology in that it proposes a mechanism for commonness and rarity, and if true, may help predict species' vulnerability to extinction. We identified 64 studies that measured niche breadth and range size, and we used a meta-analytic approach to test for the presence of a niche breadth-range size relationship. We found a significant positive relationship between range size and environmental tolerance breadth (z = 0.49), habitat breadth (z = 0.45), and diet breadth (z = 0.28). The overall positive effect persisted even when incorporating sampling effects. Despite significant variability in the strength of the relationship among studies, the general positive relationship suggests that specialist species might be disproportionately vulnerable to habitat loss and climate change due to synergistic effects of a narrow niche and small range size. An understanding of the ecological and evolutionary mechanisms that drive and cause deviations from this niche breadth-range size pattern is an important future research goal.

We investigated patterns of resource partitioning between two brackish crustaceans (1. baltica and G. insensibilis) on trophic mosaics of fungal species colonizing vegetal detritus. Laboratory feeding experiments were carried out to... more

We investigated patterns of resource partitioning between two brackish crustaceans (1. baltica and G. insensibilis) on trophic mosaics of fungal species colonizing vegetal detritus. Laboratory feeding experiments were carried out to assess consumption rates and diet selection of single individuals belonging to five populations. Adults of two co-occurring population of both G. insensibilis and IL baltica and one population of G. insensibilis, occurring alone in another habitat patch, were studied. Each individual were offered both fragments of Cymodocea nodosa conditioned by 8 fungal species and sterilized fragments as sole food source for 7 days. Both species preferred conditioned' detritus but potential resource use was greater in G. insensibilis than in I. baltica. Individual niche breadth increased and phenotypic variability reduced in the allotopic sample. Trophic similarities were lower between individuals of co-occurring populations than between I. baltica and the allotopic G. insensibilis. The results suggest that co-occurrence is an important factor contributing to the enhancement of phenotypic variability and, consequently, to a trophic generalization at population level in G. insensibilis. It emphasizes the role of fungal patchiness on detritus in regulating resource partitioning between the two species .

We compared dietary patterns within a temperate estuarine fish assemblage (Suisun Marsh, CA, U.S.A.) during a period of high mysid shrimp abundance and after a major decline in mysid abundance caused by the invasion of the overbite clam... more

We compared dietary patterns within a temperate estuarine fish assemblage (Suisun Marsh, CA, U.S.A.) during a period of high mysid shrimp abundance and after a major decline in mysid abundance caused by the invasion of the overbite clam Potamocorbula amurensis. Prior to the invasion, high dietary overlap, high stomach fullness, and low niche breadth occurred among the fishes in spring when mysid populations were high. Dietary overlaps decreased and niche breadth increased for all species but the endemic splittail Pogonichthys macrolepidotus in fall when mysid populations were low. Eight native species exhibited lower overall collective overlaps and fuller stomachs than five alien species, suggesting more efficient resource partitioning. After mysid abundance declined, only alien striped bass Morone saxatilis preyed upon mysids in greater than trace amounts. An alien mysid became an important prey for small striped bass, but striped bass also switched to piscivory at a smaller size than when mysids were abundant. Eight of 13 species exhibited significant declines in abundance during the study period, which were concordant with the original importance of mysids in their diets. Our results suggest that altered lower food web dynamics in the San Francisco Estuary caused by the invasion of the overbite clam changed fish diets and have contributed to declines in fish abundance.