Exploitation Of Food Resources Research Articles

Mechanical and Fracture Properties Evolution of Gnathostome Dental Enamel and Orthodentine

During gnathostome diversification modifications to dental form and mineralized tissues (enamel, dentines, and cementum) facilitated the exploitation of novel food resources, leading to the occupation of an unprecedented variety of ecological trophic niches. Generally, it has been assumed that the intra‐tissue biomechanics of these constituents had little bearing on whole‐tooth functionality, aside from mammalian enamel in occluding dentitions. Many mammals, for example, possess teeth that self‐wear to a functional topography with a diversity of derived tissues—some which possess unique mechanical attributes to resist wear and fracture. Here we formally test the hypothesis that gnathostome dental tissue material properties were static prior to the cladogenesis of Mammalia. Hardness (a proxy for wear resistance) and elastic modulus (proxy for structural rigidity and relevant to whole tooth rigidity) were tested using two standardized material science techniques, microindentation and nanoindentation, as well as a novel approach for quantifying fracture propagation patterns from indentation cracks. These data were analyzed in an ecological context using modern phylogenetic comparative methods. The results show these material properties to be highly variable within and between major groups of gnathostomes, with enamel and orthodentine hardnesses ranging from ~2.1 gigapascals (GPa) to ~6.1 GPa and ~0.5 GPa to ~1.5 Gpa, respectively. Elastic modulus values measured spanned ~34.6 GPa to ~112.5 Gpa in enamel, and from ~15.6 GPa to ~33.4 GPa in orthodentine. Lissamphibia display the lowest hardness and elastic modulus values of both enamel and orthodentine while the higher hardness and elastic modulus values are found in specific taxa from chondrichthyans, mammals, and some squamates. Aside from enamel hardness, there is no significant relationship between most material properties and assigned dietary classes. An ancillary goal of this work is also to glean initial insights about how dental attributes for non‐mammalian and mammalian taxa more generally may contribute to whole‐tooth form, function, performance, and diet. Clade‐specific complex fracture patterns in the enamels of mammals and chondrichthyans, for example, show that gnathostome lineages independently evolved traits that function to control fracture and minimize damage associated with catastrophic failure. Overall, this study suggests that selection operated at the tissue level primarily in enamel to bring about shifts in whole‐tooth functionality across Gnathostomata.Support or Funding InformationNSF EAR 0959029 awarded to Gregory M EricksonSigma Xi GIAR awarded to David Ian KayThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Environmental heterogeneity influences plant resource use – A case study in a rural community of NE Brazil

In regions of high environmental heterogeneity, it is important to observe if different landscape units are used differently by human populations, which can have consequences for the conservation of these units. Thus, the present study seeks to answer the following questions: (1) are different native vegetation units used for different purposes by the local population? (2) is there a difference between the conservation status of native vegetation units according to the local perception? The study was implemented in the rural community of Morrão de Cima, in the municipality of São Desidério (Northeast Brazil). Data were collected through semi-structured interviews and participatory workshops. The main native vegetation units recognized by the interviewees were Brejo, Mata Seca, Serra and Chapada. The community uses the different units of native vegetation for different purposes. The extraction of medicinal resources was important in the Chapada, while the exploitation of food resources was important in the Brejo, and the collection of wood resources was more substantial in Mata Seca and in Serra. We also found differences in the perceived conservation status of the native vegetation units. Our findings indicate the need of caution when proposing conservation strategies in heterogeneous environments, since each landscape unit may be undergoing specific processes, requiring different strategies.

Putrescible Waste Landfills as Bird Habitats in Urban Cities: A case from an Urban Landfill in the Colombo District of Sri Lanka

As putrescible waste landfills are reliable and rich sources of food, these man-made habitats can support large populations of avifauna composed of different feeding guilds. Unusually high population inflations of few opportunistic species of birds could impose a severe impact on the overall ecological balance. We studied the bird community in an open waste dump located in a highly urbanised area in the Colombo District, Sri Lanka. Bird census were performed using block counts in two contrasting sites of the landfill i.e., active dumping area and inactive dumping area between April 2015 and March 2016. Abundance and density of birds were significantly higher in the active dumping area than in the inactive area. The inactive dumping area accounted for the highest avifaunal richness, diversity and evenness. Bubulcus ibis and Corvussplendens were the dominant species at the active dump, and their foraging and social behaviors probably discouraged other bird species from exploiting food resources in the dump despite belonging to different feeding guilds. The forging bird community at the landfill exhibited seasonal variations in abundance and other interspecific interactions. Since the influx of large numbers of birds to landfills can potentially cause numerous environmental issues in urban areas, the current study highlights the importance of study of the seasonal patterns of bird communities in relation to location and management of landfills.

Diet of Hemigrammus marginatus (Characiformes: Characidae) in the Upper Contas River, Diamantina Plateau (Bahia, Brazil)

ABSTRACT Studies on the composition of fish diet and on how species exploit food resources are especially relevant in tropical freshwater systems, where dietary plasticity is a commonly used strategy. In this study, we analysed the food spectrum and the environmental, seasonal and ontogenetic variations in the diet of a characid species [Hemigrammus marginatus Ellis, 1911 (Characidae)] in the region of the Upper Contas River, in the Diamantina Plateau, Brazil. We verified an omnivorous/invertivorous and opportunistic food habit, with predominance of insects and microcrustaceans, followed by filamentous algae. Seasonality did not alter the food resources used by the species. However, differences were detected in the dominant categories when comparing the two sampled rivers, as well as in the food consumption throughout the development of the species. These data increase the knowledge about the biology of H. marginatus and allow understanding the influence of the characteristics of the rivers and their surroundings in the trophic ecology of the species, as our findings have shown that, although insects have been expressive in both studied localities, microcrustaceans exhibit a greater relative importance in the more lentic environment, which is probably related to the variation in the availability of these resources in the environment.

Home sweet home? Adjustments in the ecology, behaviour and vocalisations of Amazonian squirrel monkeys inhabiting an Atlantic forest fragment

Inadvertent or intentional introductions of species in non-native habitats are forcing them to adapt quickly, resulting in evolutionarily significant changes in their ecology and social organisation. Understanding how these species are adapting in non-native areas will elucidate evolutionary aspects of migration and adaptation skills of exotic species in general. Thus, we investigated how Amazonian squirrel monkeys (Saimiri sciureus) have adjusted their behavioural ecology and call propagation in an Atlantic forest fragment in north-eastern Brazil. Behavioural ecology data were obtained via instantaneous scan and ad libitum sampling methods. Call propagation data were obtained through playback experiments conducted in the Atlantic and Amazon forests. Atlantic forest squirrel monkey diet was found to be composed, primarily, of fruits considered “exotic” to the region. There was no variation between dry and wet months in food-resource exploitation except for flowers. Squirrel monkeys spent most of their time engaged in locomotion and foraging activities and had a preference for the Atlantic forest mid-strata. Nevertheless, resting, locomotion and social activities were most frequently demonstrated in the dry months, whereas foraging behaviours were mostly performed in the wet months. We found no variation between dry and wet months in the vertical use of the stratum, daily path length or home range size. The propagation of squirrel monkey isolation calls was more efficient in the Amazon compared with the Atlantic forest, with call acoustic parameters degrading faster in the Atlantic forest. Our results indicate that exotic squirrel monkeys have adjusted their activity pattern and diet in the Atlantic forest, resulting in behavioural variations consistent with the existing resources. Vocalisations, however, despite not being fully adapted for propagation in the Atlantic forest, do not appear to interfere in the occupation success of the species in the Atlantic forest.

ZooMS identification of bone tools from the North African Later Stone Age

This study applies peptide mass fingerprinting (also known as ‘ZooMS’) to bone tools from the North African Palaeolithic, as the first stage in a research programme aimed at understanding distinct phases within a bone tool chaîne opératoire. We report on the largest collection of bone tools from the North African Later Stone Age (LSA), from the cave site of Taforalt (Grotte des Pigeons) in eastern Morocco. Their appearance at this site from c. 15,000 cal BP appears to coincide with other changes in human behaviour which led to increased sedentism, cemetery use, and intensive exploitation of certain food resources. As such, bone tools can provide insights into how such broad-scale cultural renegotiations may have been brokered technologically, independent of the lithic record. Here, we explore initial raw material selection and manufacture strategies through use of ZooMS, a technique that permits identification of specific animals from very small bone samples. We found that ZooMS is highly suitable for use on the Taforalt material, and that bone tool morphology and construction tracks closely with the original animal from which a tool was made. Our results indicate that the Iberomaurusian occupants of Taforalt embedded bone tools within culturally-mediated technological strategies, potentially involving other perishable materials.

Increased climate seasonality during the late glacial in the Gebel Akhdar, Libya

Oxygen isotope analysis (δ18O) of caprine and bovine tooth enamel carbonates from the Haua Fteah cave (Gebel Akhdar massif, northeast Libya) reveals significant differences in palaeoseasonality during the last c. 70 ka. Data indicate different phases of human occupation of the region occurred under notably different climatic conditions. During the last glacial period, prior to the Last Glacial Maximum, a gradual increase in climate aridity occurred. This was followed in the late glacial (c. 16.6–14.7 ka) by considerably more arid conditions and much greater climate seasonality, which was likely produced by changing winter precipitation amounts and a strengthening of arid summer air masses. The high seasonality in the late glacial coincides with a period when human activity at the Haua Fteah greatly intensified. Significant changes in subsistence strategies and the seasonal exploitation of food resources also occurred at this time. The results presented here suggest that changes in the seasonal climate may have affected the seasonal supply of floral and faunal resources available to local human populations at the time, which resulted in changing subsistence practices.

Becoming sedentary? The seasonality of food resource exploitation in the Mesolithic-Neolithic Danube Gorges

Becoming sedentary? The seasonality of food resource exploitation in the Mesolithic-Neolithic Danube Gorges

Testing MacArthur's minimisation principle: do communities minimise energy wastage during succession?

Robert MacArthur developed a theory of community assembly based on competition. By incorporating energy flow, MacArthur's theory allows for predictions of community function. A key prediction is that communities minimise energy wastage over time, but this minimisation is a trade-off between two conflicting processes: exploiting food resources, and maintaining low metabolism and mortality. Despite its simplicity and elegance, MacArthur's principle has not been tested empirically despite having long fascinated theoreticians. We used a combination of field chronosequence experiments and laboratory assays to estimate how the energy wastage of a community changes during succession. We found that older successional stages wasted more energy in maintenance, but there was no clear pattern in how communities of different age exploited food resources. We identify several reasons for why MacArthur's original theory may need modification and new avenues to further explore community efficiency, an understudied component of ecosystem functioning.

Climate change alters fish community size‐structure, requiring adaptive policy targets

AbstractSize‐based indicators are used worldwide in research that supports the management of commercially exploited wild fish populations, because of their responsiveness to fishing pressure. Observational and experimental data, however, have highlighted the deeply rooted links between fish size and environmental conditions that can drive additional, interannual changes in these indicators. Here, we have used biogeochemical and mechanistic niche modelling of commercially exploited demersal fish species to project time series to the end of the 21st century for one such indicator, the large fish indicator (LFI), under global CO2 emissions scenarios. Our modelling results, validated against survey data, suggest that the LFI's previously proposed policy target may be unachievable under future climate change. In turn, our results help to identify what may be achievable policy targets for demersal fish communities experiencing climate change. While fisheries modelling has grown as a science, climate change modelling is seldom used specifically to address policy aims. Studies such as this one can, however, enable a more sustainable exploitation of marine food resources under changes unmanageable by fisheries control. Indeed, such studies can be used to aid resilient policy target setting by taking into account climate‐driven effects on fish community size‐structure.

Acute exposure to methylmercury chloride induces fast changes in swimming performance, cognitive processes and oxidative stress of zebrafish (Danio rerio) as reference model for fish community

Fishes are the first group of vertebrates that respond when the environment is contaminated with pollutants resulted from anthropogenic activities. The development of the toxicity tests is bringing new evidence about the toxicological effects of the pollutants upon the life forms. Behavioural abnormalities in the swimming performance and cognitive processes were well associated with the response of organisms to pollutants from environment. The aim of the paper was to study the behavioural changes of zebrafish (memory, swimming performances and aggression) and oxidative stress (superoxide dismutase and malondialdehyde) during 32 h of acute exposure with methylmercury (II) chloride to measure its neurotoxicity effects upon fish community. The experiments from this study tested and measured the fish community response to methylmercury concentrations (1 μg L−1 and 15 μg L−1) in the first hours after it contamination based on zebrafish model. The changes of the behaviour in the case of a fish species may lead in the end to their population reduction based on less reproductive success, lower food resource exploitation and problems in the predator avoidance. The behavioural tests described in the present study can be applied to measure the neurotoxicity of other metals compounds, to do plans and protocols for avoiding future ecological disasters. The behavioural changes of zebrafish exposed to methylmercury (II) chloride were similar to mammal models and they will have applications in future research.

Attraction of Male Nymphs to Adult Male Volatiles in the Bronze Bug Thaumastocoris peregrinus Carpintero & Dellape (Heteroptera: Thaumastocoridae).

The bronze bug, Thaumastocoris peregrinus Carpintero & Dellape (Heteroptera: Thaumastocoridae), is an exotic emerging pest in Eucalyptus commercial forests in South America, Africa and southern Europe. Information on the chemical communication system and reproductive ecology of this insect is scant, and it may be relevant for designing management strategies for eucalypt plantations. Adults and nymphs usually aggregate in the field, possibly by means of chemical signals. Males emit large amounts of 3-methyl-2-butenyl butyrate, which attracts conspecific adult males but not females. The ecological role of this putative male aggregation pheromone remains unknown. Here, we report olfactometer bioassays showing that late-instar male nymphs are also attracted to synthetic 3-methyl-2-butenyl butyrate and to adult male volatile extracts, which contain this compound as the major component. As previously shown for adult females, nymphs that moulted into females were not attracted to either volatile stimulus. The intra-gender attraction of nymphs and adults may be related to the exploitation of food resources, or as a reproductive strategy for newly emerged males. Further studies on the reproductive behaviour and mating system of T. peregrinus will contribute to understanding the ecological significance of male-male, adult-nymph attraction, as well as the practical applications that may result from these findings.

Arctic Climate Change, Economy and Society (ACCESS): Integrated perspectives

This introduction to the special issue presents an overview of the wide range of results produced during the European Union project Arctic Climate Change, Economy and Society (ACCESS). This project assessed the main impacts of climate change on Arctic Ocean’s geophysical variables and how these impending changes could be expected to impact directly and indirectly on socio-economic activities like transportation, marine sea food production and resource exploitation. Related governance issues were examined. These results were used to develop several management tools that can live on beyond ACCESS. In this article, we synthesize most of the project results in the form of tentative responses to questions raised during the project. By doing so, we put the findings of the project in a broader perspective and introduce the contributions made in the different articles published in this special issue.

A framework for testing assumptions about foraging scales, body mass, and niche separation using telemetry data.

Ecological theory predicts that if animals with very similar dietary requirements inhabit the same landscape, then they should avoid niche overlap by either exploiting food resources at different times or foraging at different spatial scales. Similarly, it is often assumed that animals that fall in different body mass modes and share the same body plan will use landscapes at different spatial scales. We developed a new methodological framework for understanding the scaling of foraging (i.e. the range and distribution of scales at which animals use their landscapes) by applying a combination of three well‐established methods to satellite telemetry data to quantify foraging patch size distributions: (1) first‐passage time analysis; (2) a movement‐based kernel density estimator; and (3) statistical comparison of resulting histograms and tests for multimodality. We demonstrate our approach using two sympatric, ecologically similar species of African ducks with quite different body masses: Egyptian Geese (actually a shelduck), and Red‐billed Teal. Contrary to theoretical predictions, the two species, which are sympatric throughout the year, foraged at almost identical spatial scales. Our results show how ecologists can use GPS tracking data to explicitly quantify and compare the scales of foraging by different organisms within an animal community. Our analysis demonstrates both a novel approach to foraging data analysis and the need for caution when making assumptions about the relationships among niche separation, diet, and foraging scale.

Altered epiphyte community and sea urchin diet in Posidonia oceanica meadows in the vicinity of volcanic CO2 vents

Ocean acidification (OA) predicted for 2100 is expected to shift seagrass epiphyte communities towards the dominance of more tolerant non-calcifying taxa. However, little is known about the indirect effects of such changes on food provision to key seagrass consumers. We found that epiphyte communities of the seagrass Posidonia oceanica in two naturally acidified sites (i.e. north and south sides of a volcanic CO2 vent) and in a control site away from the vent at the Ischia Island (NW Mediterranean Sea) significantly differed in composition and abundance. Such differences involved a higher abundance of non-calcareous crustose brown algae and a decline of calcifying polychaetes in both acidified sites. A lower epiphytic abundance of crustose coralline algae occurred only in the south side of the vents, thus suggesting that OA may alter epiphyte assemblages in different ways due to interaction with local factors such as differential fish herbivory or hydrodynamics. The OA effects on food items (seagrass, epiphytes, and algae) indirectly propagated into food provision to the sea urchin Paracentrotus lividus, as reflected by a reduced P. oceanica exploitation (i.e. less seagrass and calcareous epiphytes in the diet) in favour of non-calcareous green algae in both vent sites. In contrast, we detected no difference close and outside the vents neither in the composition of sea urchin diet nor in the total abundance of calcareous versus non-calcareous taxa. More research, under realistic scenarios of predicted pH reduction (i.e. ≤ 0.32 units of pH by 2100), is still necessary to better understand cascading effects of this altered urchin exploitation of food resources under acidified conditions on ecosystem diversity and function.

Competitive and predatory interactions between invasive mosquitofish and native larval newts

Invasive fish have a high disruptive potential in aquatic ecosystems, in which amphibians may be highly impacted due to intense competition and/or predation on their eggs and larvae. Most studies have focused on the effect of large invasive fishes such as salmonids, whereas the effect of smaller fish on amphibians has been seldom investigated. We experimentally studied effects of the invasive Eastern mosquitofish (Gambusia holbrooki) on pygmy newts (Triturus pygmaeus), a species endemic to the Iberian Peninsula. We set up outdoor mesocosms in Donana National Park with native aquatic flora and invertebrate fauna, and containing larval newts at two experimental densities. Density of larval newts was also crossed with presence or absence of mosquitofish, either free-swimming or caged, in order to distinguish consumptive and non-consumptive effects. Increased density of coexisting larval newts did not reduce their survival, but reduced their growth and development. Newt survival and size at metamorphosis were dramatically reduced in the presence of free-swimming mosquitofish, whether at low or high fish densities. Caged mosquitofish, however, had no effect on larval newts. In laboratory trials, mosquitofish preyed more efficiently on insect larvae than did larval pygmy newts, highlighting the high competitive potential of mosquitofish. This was confirmed by the depletion of zooplankton that free fish caused in the experimental outdoor mesocosms. Our study suggests that invasive mosquitofish exert a high negative impact on coexisting newt populations. Such effects can be explained by a combination of direct predation, injuries caused by predation attempts, and intense competitive exploitation of common food resources.

Effects of Waterfowl Hunting on Raccoon Movements

Nontarget wildlife may react to hunters with avoidance, ambivalence, or attraction, depending upon the frequency of contact and the consequences of past contacts. We studied raccoons (Procyon lotor) located within the Bear River Migratory Bird Refuge, Utah, before and during waterfowl hunting seasons to assess changes in the size of their distributions, locations, and travel distances. Raccoon distribution size did not change with the onset of hunting. Once hunting began, raccoons were located more frequently in areas with lower densities of hunters and less frequently in areas with higher densities of hunters. Raccoons also responded to the presence of waterfowl hunters by traveling shorter distances at dawn, when hunters were active, and longer distances at dusk. This shift in movement to dusk may have allowed raccoons to exploit food resources provided by hunters, such as litter and wounded ducks, when few waterfowl hunters were in the marsh.

Food resource partitioning between two sympatric temperate wrasses

The present study analysed two sympatric wrasses, Thalassoma pavo and Coris julis, with similar sizes and morphologies, that are widespread in the reef habitats of the Mediterranean and the eastern Atlantic coast. Ocean warming has induced the northward movement of T. pavo, whereas C. julis has been moving to deeper habitats. In addition, under conditions of high slope of the sea bottom, T. pavo occupies shallow habitats and C. julis is in greater abundance in deeper habitats. By investigating stomach contents and prey availability in the benthos, we assessed whether the two wrasses exploit food resources by choosing different prey within the same habitat both under co-existence and segregation conditions. The results showed that T. pavo mainly feeds on gammarids and sipunculids, whereas C. julis mainly feeds on Alvania spp. and Paguroidea. The two wrasses also showed an intrinsic partitioning of food resources, independently of the condition of co-existence or segregation and benthic prey availability in the environment. The two wrasses fall in the ‘over dispersion of resource use’ model, in which species share numerous niche dimensions in a variable manner. Our findings may contribute to exclude a greater trophic competition between these labrid species in a projected warming scenario.

Becoming sedentary? The seasonality of food resource exploitation in the Mesolithic-Neolithic Danube Gorges

In this paper, we investigate whether the Mesolithic-Neolithic sites in the Danube Gorges were occupied seasonally or all year round by looking at animal skeletal remains. The hunting seasons of most important game animals have been determined on the basis of antler and teeth growth, supplemented by looking into the presence of migratory fish and birds. The patterns of food resource exploitation seem to indicate year-round occupation of the settlements, and suggest that a significant degree of sedentism existed in the Danube Gorges prior to, and independently of, the adoption of animal and plant husbandry.

Highly segregated trophic niche of two congeneric fish species in Neotropical floodplain lakes.

The diets of two sympatric, morphologically similar species of Moenkhausia were studied to investigate whether the manner in which they exploit food resources can help to explain their coexistence. Fish diets were evaluated during the low-water season in six lakes of the upper Paraná River floodplain (Brazil). The results indicate that these two species segregate in relation to food resources and that the differential use of resources is probably a strategy that reduces competition during periods of a potential food shortage (the low-water season).