Why does the hare population fluctuation

There was a two-fold increase in lipid peroxidation on days 4 to 8 post-inoculation. Conclusions Contrary to all expectations, the present study demonstrates that the European brown hare shows relatively low susceptibility to tularemia. Therefore, the circumstances of tularemia in hares under natural conditions should be further studied.

Physiological responses in air traffic control personnel : O' Hare Tower. Physiological and biochemical measurements were made on 22 air traffic controllers at O' Hare tower during five days of the heavy traffic evening shift and five days of the light traffic morning shift The purpose of this survey was to identify equipment currently installed to aid in providing visual guidance to pilo Aircraft wake vortex takeoff tests at O' Hare International Airport.

Three wake vortex measurement systems anemometer, acoustic doppler, and laser : doppler were used to collect wake vortex data from aircraft departing Runway 22L at : Chicago's O' Hare airport for nine months in The data were analyzed to determ Bottom-up processes drive reproductive success in an apex predator. One of the central goals of the field of population ecology is to identify the drivers of population dynamics , particularly in the context of predator-prey relationships.

Understanding the relative role of top-down versus bottom-up drivers is of particular interest in understanding ecosystem dynamics. Our goal was to explore predator-prey relationships in a boreal ecosystem in interior Alaska through the use of multispecies long-term monitoring data. We used 29 years of field data and a dynamic multistate site occupancy modeling approach to explore the trophic relationships between an apex predator, the golden eagle, and cyclic populations of the two primary prey species available to eagles early in the breeding season, snowshoe hare and willow ptarmigan.

We found that golden eagle reproductive success was reliant on prey numbers, but also responded prior to changes in the phase of the snowshoe hare population cycle and failed to respond to variation in hare cycle amplitude. There was no lagged response to ptarmigan populations , and ptarmigan populations recovered quickly from the low phase.

Together, these results suggested that eagle reproduction is largely driven by bottom-up processes, with little evidence of top-down control of either ptarmigan or hare populations. Although the relationship between golden eagle reproductive success and prey abundance had been previously established, here we established prey populations are likely driving eagle dynamics through bottom-up processes. The key to this insight was our focus on golden eagle reproductive parameters rather than overall abundance.

Although our inference is limited to the golden eagle- hare -ptarmigan relationships we studied, our results suggest caution in interpreting predator-prey abundance patterns among other species as strong evidence for top-down control. Mycosporine-like amino acids are multifunctional molecules in sea hares and their marine community. Molecules of keystone significance are relatively rare, yet mediate a variety of interactions between organisms.

They influence the distribution and abundance of species, the transfer of energy across multiple trophic levels, and thus they play significant roles in structuring ecosystems. Despite their potential importance in facilitating our understanding of ecological systems, only three molecules thus far have been proposed as molecules of keystone significance: saxitoxin and dimethyl sulfide in marine communities and tetrodotoxin in riparian communities. These alarm cues are released in the ink secretion of sea hares and cause avoidance behaviors in neighboring conspecifics.

Further, we show that these three bioactive MAAs, two [aplysiapalythine A APA and -B APB ] being previously unknown molecules, are present in the algal diet of sea hares and are concentrated in their defensive secretion as well as in their skin. MAAs are known to be produced by algae, fungi, and cyanobacteria and are acquired by many aquatic animals through trophic interactions. MAAs are widely used as sunscreens, among other uses, but sea hares modify their function to serve a previously undocumented role, as intraspecific chemical cues.

Our findings highlight the multifunctionality of MAAs and their role in ecological connectivity, suggesting that they may function as molecules of keystone significance in marine ecosystems. The transcriptional landscape of seasonal coat colour moult in the snowshoe hare.

Seasonal coat colour change is an important adaptation to seasonally changing environments but the evolution of this and other circannual traits remains poorly understood.

In this study, we use gene expression to understand seasonal coat colour moulting in wild snowshoe hares Lepus americanus. We used hair colour to follow the progression of the moult, simultaneously sampling skin from three moulting stages in hares collected during the peak of the spring moult from white winter to brown summer pelage. Using RNA sequencing, we tested whether patterns of expression were consistent with predictions based on the established phases of the hair growth cycle.

We found functionally consistent clustering across skin types, with genes differentially expressed between moult stages. Skin samples from transitional "intermediate" and "brown" pelage were transcriptionally similar and resembled the regressive transition to catagen regressive stage. We also detected differential expression of several key circadian clock and pigmentation genes, providing important means to dissect the bases of alternate seasonal colour morphs. Our results reveal that pelage colour is a useful biomarker for seasonal change but that there is a consistent lag between the main gene expression waves and change in visible coat colour.

These experiments establish that developmental sampling from natural populations of nonmodel organisms can provide a crucial resource to dissect the genetic basis and evolution of complex seasonally changing traits.

Volume I. Technical Description,. In our article J. Hare , with psychopathy itself. In their response, R. Hare and C. Neumann seemed to agree with key points that the PCL-R should not be confused with psychopathy and that criminal behavior is not…. Using the system performance specifications, an estimate has been made of the ASDE-2's tolerance to power loss and deg The interrater reliability and internal consistency coefficients were high, and similar to those obtained in other countries.

This data provides support for the homogeneity and unidimensionality of the psychopathy construct in Spanish male prison samples. The analysis of factor structure also replicated the two factor solution of previous studies.

The two factors showed different patterns of intercorrelations with several self-report measures of personality, demographic, and criminal history variables, which confirmed the construct validity of PCL-R. The results confirm the psychometric properties of the PCL-R as a measure of psychopathy in Spanish male inmates, and suggest that psychopathy is a construct also observed in Southern European countries.

Tularaemia in a brown hare Lepus europaeus in first case in the Netherlands in 60 years. Tularaemia has not been reported in Dutch wildlife since To enhance detection, as of July , brown hares Lepus europaeus submitted for postmortem examination in the context of non-targeted wildlife disease surveillance, were routinely tested for tularaemia by polymerase chain reaction PCR.

Francisella tularensis subspecies holarctica infection was confirmed in a hare submitted in May The case occurred in Limburg, near the site of the case. Further surveillance should clarify the significance of this finding. Effect of age and gender on carcass traits and meat quality of farmed brown hares. A total of 48 sub-adult hares and adult reproducing farmed hares were used to characterize carcass and meat traits according to the age and gender of animals. With respect to carcass traits, when age increased, the carcass weight significantly increased to g; P hares compared with the sub-adult ones.

Meat water and protein contents decreased in the hind leg and LL of the adult hares compared with the sub-adult ones, whereas ether extract increased in a restricted range in LL only 0.

Acidity enhances the effectiveness of active chemical defensive secretions of sea hares , Aplysia californica, against spiny lobsters, Panulirus interruptus. Sea hares such as Aplysia californica, gastropod molluscs lacking a protective shell, can release a purple cloud of chemicals when vigorously attacked by predators. This active chemical defense is composed of two glandular secretions, ink and opaline, both of which contain an array of compounds.

This secretion defends sea hares against predators such as California spiny lobsters Panulirus interruptus via multiple mechanisms, one of which is phagomimicry, in which secretions containing feeding chemicals attract and distract predators toward the secretion and away from the sea hare.

We show here that ink and opaline are highly acidic, both having a pH of approximately 5. We examined if the acidity of ink and opaline affects their phagomimetic properties. We tested behavioral and electrophysiological responses of chemoreceptor neurons in the olfactory and gustatory organs of P. Both behavioral and electrophysiological responses to ink and opaline were enhanced at low pH, and low pH alone accounted for most of this effect.

Our data suggest that acidity enhances the phagomimetic chemical defense of sea hares. Food and feed traceability has become a priority for governments due to consumer demand for comprehensive and integrated safety policies. In the present work, a TaqMan real-time PCR assay targeting the mitochondrial 12S rRNA gene was developed for specific detection of rabbit and hare material in animal feeds and pet foods. Successful detection of highly degraded rabbit and hare material was achieved at the lowest target concentration assayed 0.

Furthermore, the method was applied to 96 processed commercial pet food products to determine whether correct labelling had been used at the market level. The reported real-time PCR technique detected the presence of rabbit tissues in 80 of the 96 samples analysed The real-time PCR method reported may be a useful tool for traceability purposes within the framework of feed control.

A cluster of tularaemia after contact with a dead hare in the Netherlands. Tularemia is thought to be rare in the Netherlands. Here we describe a cluster of two patients who contracted tularaemia after field dressing of a hare found dead. Additionally, infection from the same source is suggested in three animals. The generalizability of the psychopathy construct to Eastern European cultures has not been well-studied, and no prior studies have evaluated psychopathy in non-offender samples from this population.

The current validation study examines the factor structure, internal consistency, and external validity of the Bulgarian translation of the Hare Psychopathy Checklist: Screening Version. Two hundred sixty-two Bulgarian adults from the general community were assessed, of which had a history of substance dependence.

Confirmatory factor analysis indicated good fit for the two-, three-, and four-factor models of psychopathy. Zero-order and partial correlation analyses were conducted between the two factors of psychopathy and criterion measures of antisocial behavior, internalizing and externalizing psychopathology, personality traits, addictive disorders and demographic characteristics.

Relationships to external variables provided evidence for the convergent and discriminant validity of the psychopathy construct in a Bulgarian community sample. In evolutionary computing EC , population size is one of the critical parameters that a researcher has to deal with. Hence, it was no surprise that the pioneers of EC, such as De Jong and Holland , had already studied the population sizing from the very beginning of EC.

What is perhaps surprising is that more than three decades later, we still largely depend on the experience or ad-hoc trial-and-error approach to set the population size. For example, in a recent monograph, Eiben and Smith indicated: "In almost all EC applications, the population size is constant and does not change during the evolutionary search.

In this paper, I propose to develop a population dynamics theory forEC with the inspiration from the population dynamics theory of biological populations in nature. Essentially, the EC population is considered as a dynamic system over time generations and space search space or fitness landscape , similar to the spatial and temporal dynamics of biological populations in nature. With this conceptual mapping, I propose to 'transplant' the biological population dynamics theory to EC via three steps: i experimentally test the feasibility—whether or not emulating natural population dynamics improves the EC performance; ii comparatively study the underlying mechanisms—why there are improvements, primarily via statistical modeling analysis; iii conduct theoretical analysis with theoretical models such as percolation theory and extended evolutionary game theory that are generally applicable to both EC and natural populations.

This article is a summary of a series of studies we have performed to achieve the general goal [27][30]-[32]. In Sections 4 to 6, I briefly discuss three. The ligand-binding profile of HARE : hyaluronan and chondroitin sulfates A, C, and D bind to overlapping sites distinct from the sites for heparin, acetylated low-density lipoprotein, dermatan sulfate, and CS-E.

J Biol Chem. Our goal was to map the binding sites of eight different ligands within HARE. Hep and HA binding or endocytosis is mutually inclusive; binding of these two GAGs occurs with functionally separate, noncompetitive, and apparently noninteracting domains. These results enable us to outline, for the first time, a binding activity map for multiple ligands of HARE.

The vortices from over 21, aircraft were tracked using the propeller anemometer Ground-Wi Relationship between heavy metal accumulation and morphometric parameters in European hare Lepus europaeus inhabiting various types of landscapes in southern Poland.

To evaluate the influence of hazardous substances in the environment, studies of pollutant accumulation in wild living animals are needed.

Studies dealing with heavy metal contamination in mammals usually focus on a single organ. Hares were captured during the hunting season.

We tested metal accumulation in 14 organs and tissues using 35 individuals with known body weight and sex inhabiting agricultural, industrial and other types of landscapes. To obtain deeper insight into contamination patterns, we used accumulation data from the liver since it is the most frequently investigated organ and prone to pollution accumulation. Based on the data obtained for the liver, we tested the impact of metal pollution on hare morphology, including body length and several skull cranimetric parameters.

Metals content differed between organs. Moreover, individuals from industrial areas had higher Cd content in their body. We distinguished two groups of elements: the first group, Cd, Fe and Zn, revealed the highest toxic effect in the liver and kidneys; the second group, Cr, Ni, and Pb, accumulated primarily in the brain.

Hares inhabiting industrial areas had higher concentration of Cd and Pb, and lower levels of Cr and Fe in their liver in comparison with those from agricultural and forest habitats. Heavy metals had an effect on body length that was negatively associated with Cr levels.

Skull diastema length was associated positively with accumulation of Cd and Pb. We showed that hare organs and tissues could be used as bioindicators of environmental pollution by heavy metals. Fire drives transcontinental variation in tree birch defense against browsing by snowshoe hares. John P. Bryant; Thomas P. Clausen; Robert K. Swihart; Simon M. Stevens; Christopher D.

Kirilenko; Alasdair M. Veitch; Richard A. Popko; David T. Cleland; Joseph H. Williams; Walter J. Jakubas; Michael R. Paragi; Peter M. Picone; Jeffery E.

Moore; Edmond C. Packee; Thomas Malone. Fire has been the dominant disturbance in boreal America since the Pleistocene, resulting in a spatial mosaic in which the most fire occurs in the continental northwest. Spatial variation in snowshoe hare Lepus americanus density reflects the fire mosaic. Because fire initiates secondary forest succession, a fire mosaic creates Population Dynamics of Genetic Regulatory Networks.

Unlike common objects in physics, a biological cell processes information. The cell interprets its genome and transforms the genomic information content, through the action of genetic regulatory networks, into proteins which in turn dictate its metabolism, functionality and morphology.

Understanding the dynamics of a population of biological cells presents a unique challenge. It requires to link the intracellular dynamics of gene regulation, through the mechanism of cell division, to the level of the population.

We present experiments studying adaptive dynamics of populations of genetically homogeneous microorganisms yeast , grown for long durations under steady conditions.

We focus on population dynamics that do not involve random genetic mutations. Our experiments follow the long-term dynamics of the population distributions and allow to quantify the correlations among generations. We focus on three interconnected issues: adaptation of genetically homogeneous populations following environmental changes, selection processes on the population and population variability and expression distributions.

We show that while the population exhibits specific short-term responses to environmental inputs, it eventually adapts to a robust steady-state, largely independent of external conditions. Cycles of medium-switch show that the adapted state is imprinted in the population and that this memory is maintained for many generations. To further study population adaptation, we utilize the process of gene recruitment whereby a gene naturally regulated by a specific promoter is placed under a different regulatory system.

This naturally occurring process has been recognized as a major driving force in evolution. We have recruited an essential gene to a foreign regulatory network and followed the population long-term dynamics. Rewiring of the regulatory network allows us to expose their complex dynamics and phase space structure.

Regional Population Dynamics. The population dynamics of the southern pine beetle SPB exhibit characteristic fluctuations between relatively long endemic and shorter outbreak periods. Populations exhibit complex and hierarchical spatial structure with beetles and larvae aggregating within individual trees, infestations with multiple infested trees, and regional outbreaks that comprise a large Alpine glacial relict species losing out to climate change: The case of the fragmented mountain hare population Lepus timidus in the Alps.

Alpine and Arctic species are considered to be particularly vulnerable to climate change, which is expected to cause habitat loss, fragmentation and-ultimately-extinction of cold-adapted species. However, the impact of climate change on glacial relict populations is not well understood, and specific recommendations for adaptive conservation management are lacking. We focused on the mountain hare Lepus timidus as a model species and modelled species distribution in combination with patch and landscape-based connectivity metrics.

They were derived from graph-theory models to quantify changes in species distribution and to estimate the current and future importance of habitat patches for overall population connectivity. Models were calibrated based on 1, locations of species presence distributed across three biogeographic regions in the Swiss Alps and extrapolated according to two IPCC scenarios of climate change RCP 4.

However, the predicted changes in habitat availability and connectivity varied considerably between biogeographic regions: Whereas the greatest habitat losses with an increase in inter-patch distance were predicted at the southern and northern edges of the species' Alpine distribution, the greatest increase in patch number and decrease in patch size is expected in the central Swiss Alps.

Finally, both the number of isolated habitat patches and the number of patches crucial for maintaining the habitat network increased under the different variants of climate change.

Focusing conservation action on the central Swiss Alps may help mitigate the predicted effects of. Effects of protective fencing on birds, lizards, and black-tailed hares in the Western Mojave Desert. Effects of protective fencing on birds, lizards, black-tailed hares Lepus californicus , perennial plant cover, and structural diversity of perennial plants were evaluated from spring through winter at the Desert Tortoise Research Natural Area DTNA , in the Mojave Desert, California.

Abundance and species richness of birds were higher inside than outside the DTNA, and effects were larger during breeding than wintering seasons and during a high than a low rainfall year. Ash-throated flycatchers Myiarchus cinerascens , cactus wrens Campylorhynchus brunneicapillus , LeConte's thrashers Toxostoma lecontei , loggerhead shrikes Lanius ludovicianus , sage sparrows Amphispiza belli , and verdins Auriparus flaviceps were more abundant inside than outside the DTNA.

Nesting activity was also more frequent inside. Total abundance and species richness of lizards and individual abundances of western whiptail lizards Cnemidophorous tigris and desert spiny lizards Sceloporus magister were higher inside than outside. In contrast, abundance of black-tailed hares was lower inside.

Black-tailed hares generally prefer areas of low perennial plant cover, which may explain why they were more abundant outside than inside the DTNA. Habitat structure may not affect bird and lizard communities as much as availability of food at this desert site, and the greater abundance and species richness of vertebrates inside than outside the DTNA may correlate with abundances of seeds and invertebrate prey.

The operations environments for the periods selected for detailed analysis of the ASDE films and controller communications recording are described.

The report describes the approach followed and the analysis techniques employed in the performance of the operations analysis of the current ASTC system for the baseline airport, O' Hare International Airport, Chicago, Illinois. It also describes the Comparing models of Red Knot population dynamics. Predictive population modeling contributes to our basic scientific understanding of population dynamics , but can also inform management decisions by evaluating alternative actions in virtual environments.

Quantitative models mathematically reflect scientific hypotheses about how a system functions. In Delaware Bay, mid-Atlantic Coast, USA, to more effectively manage horseshoe crab Limulus polyphemus harvests and protect Red Knot Calidris canutus rufa populations , models are used to compare harvest actions and predict the impacts on crab and knot populations. Management has been chiefly driven by the core hypothesis that horseshoe crab egg abundance governs the survival and reproduction of migrating Red Knots that stopover in the Bay during spring migration.

However, recently, hypotheses proposing that knot dynamics are governed by cyclical lemming dynamics garnered some support in data analyses. In this paper, I present alternative models of Red Knot population dynamics to reflect alternative hypotheses. Using 2 models with different lemming population cycle lengths and 2 models with different horseshoe crab effects, I project the knot population into the future under environmental stochasticity and parametric uncertainty with each model.

I then compare each model's predictions to 10 yr of population monitoring from Delaware Bay. Using Bayes' theorem and model weight updating, models can accrue weight or support for one or another hypothesis of population dynamics.

With 4 models of Red Knot population dynamics and only 10 yr of data, no hypothesis clearly predicted population count data better than another. The models that predicted no decline or stable populations i. Inhibition of snowshoe hare succinate dehydrogenase activity as a mechanism of deterrence for papyriferic acid in birch.

The plant secondary metabolite papyriferic acid PA deters browsing by snowshoe hares Lepus americanus on the juvenile developmental stage of the Alaska paper birch Betula neoalaskana. However, the physiological mechanism that reduces browsing remains unknown. We used pharmacological assays and molecular modeling to test the Multi-scale habitat relationships of snowshoe hares Lepus americanus in the mixed conifer landscape of the Northern Rockies, USA: Cross-scale effects of horizontal cover with implications for forest management.

Snowshoe hares Lepus americanus are an ecologically important herbivore because they modify vegetation through browsing and serve as a prey resource for multiple predators. We implemented a multiscale approach to characterize habitat relationships for snowshoe hares across the mixed conifer landscape of the northern Rocky Mountains, USA.

Our objectives were to Structural stability of nonlinear population dynamics. In population dynamics , the concept of structural stability has been used to quantify the tolerance of a system to environmental perturbations. Yet, measuring the structural stability of nonlinear dynamical systems remains a challenging task. Focusing on the classic Lotka-Volterra dynamics , because of the linearity of the functional response, it has been possible to measure the conditions compatible with a structurally stable system.

However, the functional response of biological communities is not always well approximated by deterministic linear functions. Thus, it is unclear the extent to which this linear approach can be generalized to other population dynamics models. Here, we show that the same approach used to investigate the classic Lotka-Volterra dynamics , which is called the structural approach, can be applied to a much larger class of nonlinear models.

This class covers a large number of nonlinear functional responses that have been intensively investigated both theoretically and experimentally. We also investigate the applicability of the structural approach to stochastic dynamical systems and we provide a measure of structural stability for finite populations. Overall, we show that the structural approach can provide reliable and tractable information about the qualitative behavior of many nonlinear dynamical systems.

Brasilenyne and cis-dihydrorhodophytin: Antifeedant medium-ring haloethers from a sea hare Aplysia brasiliana. Kinnel, R. Two straight-chain C15 fish antifeedants have been isolated from the sea hare Aplysia brasiliana. Chemical, spectral, and x-ray diffraction studies led to the characterization of these medium-ring ethers as brasilenyne 2 and cis-dihydrorhodophytin 3. The oxonin ring system of 2 is novel in nature. Biosynthetic considerations permit the postulation that a third compound, a noncrystalline congener of these compounds, is cis-isodihydrohodophytin 4.

Population dynamics on heterogeneous bacterial substrates. How species invade new territories and how these range expansions influence the population 's genotypes are important questions in the field of population genetics. The majority of work addressing these questions focuses on homogeneous environments. Much less is known about the population dynamics and population genetics when the environmental conditions are heterogeneous in space.

To better understand range expansions in two-dimensional heterogeneous environments, we employ a system of bacteria and bacteriophage, the viruses of bacteria. Thereby, the bacteria constitute the environment in which a population of bacteriophages expands.

The spread of phage constitutes itself in lysis of bacteria and thus formation of clear regions on bacterial lawns, called plaques. We study the population dynamics and genetics of the expanding page for various patterns of environments. Federal Register , , , , An individual-based model of zebrafish population dynamics accounting for energy dynamics.

Developing population dynamics models for zebrafish is crucial in order to extrapolate from toxicity data measured at the organism level to biological levels relevant to support and enhance ecological risk assessment.

To achieve this, a dynamic energy budget for individual zebrafish DEB model was coupled to an individual based model of zebrafish population dynamics IBM model. Next, we fitted the DEB model to new experimental data on zebrafish growth and reproduction thus improving existing models.

Finally, the predictions of the DEB-IBM were compared to existing observations on natural zebrafish populations and the predicted population dynamics are realistic. While our zebrafish DEB-IBM model can still be improved by acquiring new experimental data on the most uncertain processes e. Hubble Catches a Galaxy Duo by the " Hare ". This particular object stands out from the crowd by actually being composed of two separate galaxies rushing past each other at about 2 million kilometers 1,, miles per hour.

This speed is most likely too fast for them to merge and form a single galaxy. However, because of their small separation of only about 20, light-years, the galaxies will distort one another through the force of gravity while passing each other, changing their structures on a grand scale. Such galactic interactions are a common sight for Hubble, and have long been a field of study for astronomers. The intriguing behaviors of interacting galaxies take many forms; galactic cannibalism, galaxy harassment and even galaxy collisions.

The Milky Way itself will eventually fall victim to the latter, merging with the Andromeda Galaxy in about 4. Harvest and dynamics of duck populations. The role of harvest in the dynamics of waterfowl populations continues to be debated among scientists and managers. Our perception is that interested members of the public and some managers believe that harvest influences North American duck populations based on calls for more conservative harvest regulations.

Because of the importance of this issue, we reviewed the evidence for an impact of harvest on duck populations. Our understanding of the effects of harvest is limited because harvest effects are typically confounded with those of population density; regulations are typically most liberal when populations are greatest. Consequently, even where harvest appears additive to other mortality, this may be an artifact of ignoring effects of population density.

Overall, we found no compelling evidence for strong additive effects of harvest on survival in duck populations that could not be explained by other factors. Evolutionary dynamics of cooperation in neutral populations. Cooperation is a difficult proposition in the face of Darwinian selection. Those that defect have an evolutionary advantage over cooperators who should therefore die out.

However, spatial structure enables cooperators to survive through the formation of homogeneous clusters, which is the hallmark of network reciprocity. Here we go beyond this traditional setup and study the spatiotemporal dynamics of cooperation in a population of populations. We use the prisoner's dilemma game as the mathematical model and show that considering several populations simultaneously gives rise to fascinating spatiotemporal dynamics and pattern formation.

Even the simplest assumption that strategies between different populations are payoff-neutral with one another results in the spontaneous emergence of cyclic dominance, where defectors of one population become prey of cooperators in the other population , and vice versa. Moreover, if social interactions within different populations are characterized by significantly different temptations to defect, we observe that defectors in the population with the largest temptation counterintuitively vanish the fastest, while cooperators that hang on eventually take over the whole available space.

Our results reveal that considering the simultaneous presence of different populations significantly expands the complexity of evolutionary dynamics in structured populations , and it allows us to understand the stability of cooperation under adverse conditions that could never be bridged by network reciprocity alone. The evolutionary spread of cheater strategies can destabilize populations engaging in social cooperative behaviors, thus demonstrating that evolutionary changes can have profound implications for population dynamics.

At the same time, the relative fitness of cooperative traits often depends upon population density, thus leading to the potential for bi-directional coupling between population density and the evolution of a cooperative trait. Despite the potential importance of these eco-evolutionary feedback loops in social species, they have not yet been demonstrated experimentally and their ecological implications are poorly understood.

Here, we demonstrate the presence of a strong feedback loop between population dynamics and the evolutionary dynamics of a social microbial gene, SUC2, in laboratory yeast populations whose cooperative growth is mediated by the SUC2 gene. We directly visualize eco-evolutionary trajectories of hundreds of populations over 50— generations, allowing us to characterize the phase space describing the interplay of evolution and ecology in this system.

The presence of cheaters does not significantly affect the equilibrium population density, but it does reduce the resilience of the population as well as its ability to adapt to a rapidly deteriorating environment. Our results demonstrate the potential ecological importance of coupling between evolutionary dynamics and the population dynamics of cooperatively growing organisms, particularly in microbes.

Our study suggests that this interaction may need to be considered in order to explain intraspecific variability in cooperative behaviors, and also that this feedback between evolution and ecology can critically affect the demographic fate. Counterintuitive effects of large-scale predator removal on a midlatitude rodent community. Historically, small mammals have been focal organisms for studying predator-prey dynamics , principally because of interest in explaining the drivers of the cyclical dynamics exhibited by northern vole, lemming, and hare populations.

However, many small-mammal species occur at relatively low and fairly stable densities at temperate latitudes, and our understanding of Evolution of specialization under non-equilibrium population dynamics. We analyze the evolution of specialization in resource utilization in a mechanistically underpinned discrete-time model using the adaptive dynamics approach.

Malnourishment has the most significant effect upon lynx reproduction and population levels. When females are in poor condition, fewer breed and not all of those bred produce litters. Litters are smaller, and most, if not all, of the few kittens born die soon after birth. This means that for a period of three to five years, few or no kittens survive to adulthood. Studies have shown the level of kittens in a lynx population may be zero at the population low and as high as 60 percent when their numbers increase.

Low lynx population levels last for three or four years. When hares become plentiful again, the lynx population begins to increase as well. The highs and lows of the lynx population cycle do not occur at the same time across the NWT. For example, in the early s, lynx numbers peaked two years later in northwestern NWT than in the southwestern NWT.

Enter the terms you wish to search for. Menu Search Enter the terms you wish to search for. Lynx-Snowshoe Hare Cycle. We cannot easily determine the extent to which each of these controls drives population cycles in the Swedish boreal forest, because this system is not amenable to caging experiments, but studies show that food and predation work together to regulate population sizes.

Figure 2: Outcome of the snowshoe hare field experiment Average showshoe hare density increased under conditions of supplemental food and predator-removal. Density increased dramatically when both food and predation were modified. Field experiments by Charles J. Krebs and colleagues have experimentally teased apart the influence of food abundance and predation on snowshoe hare Lepus americanus populations in Canada. They established nine 1 km 2 blocks in undisturbed forest.

Three plots served as controls. The researchers used the remaining six to test the effects of resource availability, predation, and the interaction of both factors on snowshoe hare populations. They stocked two blocks with supplemental food for the duration of the experiment to test the effect of resource availability. To test the effect of predation pressure, they enclosed two blocks with electric fences to exclude mammalian predators hawks and owls retained access.

They treated the remaining two blocks with fertilizer to increase plant abundance. Of the two predator-exclusion blocks, one contained supplemental food to examine the influence of both resource availability and predation pressure. The food supplements provided higher-quality nutrients than did plants growing in the forest. On each of these plots, they captured, marked and released the hares twice each year: in March, before the onset of the breeding season, and in October, at the onset of winter.

Krebs and colleagues followed snowshoe hare populations on the nine plots over a course of eight years, through one population cycle in which the population peaked and declined on each study plot. At the end, they averaged the number of hares over the experiment. They found that blocks with supplemental food increased hare density three-fold, whereas fertilizer increased plant biomass on treated plots, but did not correspond to an increase in hares.

These findings suggest that resource quality, rather than resource availability, acts as a bottom-up control on hare populations. The predator exclusion blocks increased the average density of hares two-fold, which supported the idea that hare populations were also controlled from the top-down through predation.

The most striking finding of the study came from the plot that both excluded predators and had supplemental food supplies. This block experienced an fold increase in average hare density relative to the controls Figure 2. The researchers found that the increased density of hares was due to both higher survival and reproduction on the study plots. Figure 3: Graphical view of the Lotka-Volterra model Predator and prey populations cycle through time, as predators decrease numbers of prey.

Lack of food resources in turn decrease predator abundance, and the lack of predation pressure allows prey populations to rebound. To survive and reproduce, individuals must obtain sufficient food resources while simultaneously avoiding becoming food for a predator.

The snowshoe hare study demonstrates the role of both predator avoidance and food availability on population sizes. The trade-off between food intake and predator avoidance is not easily addressed in the field, and ecologists have turned to mathematical models to better understand foraging behavior and predator-prey dynamics, just as economists and atmospheric scientists do. Lotka-Volterra models provide a useful tool to help population ecologists understand the factors that influence population dynamics.

They have been particularly useful in understanding and predicting predator-prey population cycles. Although the models greatly simplify actual conditions, they demonstrate that under certain circumstances, predator and prey populations can oscillate over time Figure 3 in a manner similar to that observed in the populations described above. Berven, K. Carr, M.

Biodiversity, population regulation, and the stability of coral-reef fish communities. Synchronous population fluctuations in voles, small game, owls, and tularemia in northern Sweden. Oecologia 32 , Krebs, C. Impact of food and predation on the showshoe hare cycle. Science , What drives the year cycle of snowshoe hares?

Bioscience 51 , Larsson, T. Vole diet on experimentally managed afforestation areas in northern Sweden. Oikos 28 , Disease reveals the predator: Sarcoptic mange, red fox predation, and prey populations.

Ecology 75 , Utida, S. Cyclic fluctuations of population density intrinsic to the host-parasite system. Ecology 38 , Wood, C. Parasites alter community structure.

Predation, Herbivory, and Parasitism. Characterizing Communities. Species with a Large Impact on Community Structure. Successional Changes in Communities. Effects of Biogeography on Community Diversity. Community Ecology Introduction. Avian Egg Coloration and Visual Ecology. Causes and Consequences of Biodiversity Declines.

Disease Ecology. The Ecology of Avian Brood Parasitism. Elemental Defenses of Plants by Metals.