scholarly journals Does density-induced stress promote density-dependent reproduction in root voles? Two field experiments

2021 ◽  
Author(s):  
guo-zhen shang ◽  
Shouyang Du ◽  
Yanbin yang ◽  
Yan Wu ◽  
Yi-Fan Cao ◽  
...  
Keyword(s):  
Density Dependence ◽  
Field Experiments ◽  
Reproductive Traits ◽  
Founder Population ◽  
Reproductive Condition ◽  
Density Dependent ◽  
Induced Stress ◽  
Live Trapping ◽  
Reproductive Females ◽  
Population Numbers

Density dependence in reproduction plays an important role in stabilising population dynamics via immediate negative feedback from population density to reproductive output. Although previous studies have shown that density dependence is associated with strong spacing behaviour and social interaction between individuals, the proximal mechanism for generating density-dependent reproduction remains unclear. In this study, we investigated the effects of density-induced stress on reproduction in root voles. Founder population enclosures were established by introducing six (low density) and 30 (high density) adults per sex into per enclosure (four enclosures per density in total) during the breeding season from April to July 2012 and from May to August 2015. Faecal corticosterone metabolite (FCM) levels, reproductive traits (recruitment and the proportion of reproductive condition), and founder population numbers were measured following repeated live-trapping in both years. The number of founders was negatively associated with recruitment rates and the proportion of reproductive conditions, displaying a density-dependent reproduction. FCM level was positively associated with the number of founders. The number of founder females indirectly affected the proportion of reproductive females in 2012 and recruitment in 2015 through their FCM levels; the effect of the number of male founders on the proportion of reproductive condition was mediated by their FCM level in 2012, but the effect was not found in 2015. Our results showed that density-induced stress affected density-dependent reproduction and that density-induced stress is one ecological factor generating density-dependent reproduction.

scholarly journals Assessing density-dependent establishment and dispersal: an example using caddisfly larvae

2000 ◽  
Vol 57 (6) ◽  
pp. 1190-1199 ◽  
Author(s):  
B L Kerans ◽  
Peter L Chesson ◽  
Roy A Stein
Keyword(s):  
Density Dependence ◽  
Laboratory Experiments ◽  
Field Experiments ◽  
Laboratory Data ◽  
Population Level ◽  
Model Fit ◽  
Low Flow ◽  
Density Dependent ◽  
Caddisfly Larvae ◽  
Benthic Stream

Density dependence in colonization is poorly understood. We studied colonization by a benthic, stream-dwelling caddisfly, Hydropsyche slossonae, through experiments varying conspecific densities and environmental conditions. A model of larval acceptance or rejection of a locality (dispersal from the locality) was developed and fitted to the data to estimate the relative strengths of density-dependent and density-independent processes underlying dispersal. In spring and fall, we varied density, substrate size, and current velocity in laboratory experiments and varied density in field experiments. In the laboratory, dispersal of fifth instars was always density dependent, but the strength of density dependence was highest in spring when the proportion dispersing was lowest. Dispersal in field experiments was density dependent only in spring. Proportion dispersing was highest under low flow. The model fit to laboratory data suggested that stronger density dependence in spring occurred because of a reduction in density-independent dispersal stimuli with no change in density-dependent stimuli. In contrast, a change in density-dependent stimuli did appear to cause differences between the proportions dispersing under the two flow regimes. The model reveals the potential for density-independent dispersal stimuli to modify the strength of density dependence detectable at the population level.

scholarly journals Conspecific negative density dependence and why its study should not be abandoned

2020 ◽  
Author(s):  
Joseph A. LaManna ◽  
Scott A. Mangan ◽  
Jonathan A. Myers
Keyword(s):  
Density Dependence ◽  
Latitudinal Gradient ◽  
Null Model ◽  
Statistical Bias ◽  
Fitness Components ◽  
Density Dependent ◽  
Statistical Errors ◽  
Negative Density Dependence ◽  
Model Approach

AbstractRecent studies showing bias in the measurement of density dependence have the potential to sow confusion in the field of ecology. We provide clarity by elucidating key conceptual and statistical errors with the null-model approach used in Detto et al. (2019). We show that neither their null model nor a more biologically-appropriate null model reproduces differences in density-dependent recruitment between forests, indicating that the latitudinal gradient in negative density dependence is not an artefact of statistical bias. Finally, we suggest a path forward that combines observational comparisons of density dependence in multiple fitness components across localities with mechanistic and geographically-replicated experiments.

Anadromous Sturgeons: Habitats, Threats, and Management

2007 ◽  
Keyword(s):  
Density Dependence ◽  
Simulation Study ◽  
White Sturgeon ◽  
Acipenser Transmontanus ◽  
Snake River ◽  
Spawning Habitat ◽  
Density Dependent ◽  
Hydrologic Conditions ◽  
Genetic Results ◽  
New Alleles

<em>Abstract.</em>— This paper describes a simulation study of reconnection options for white sturgeon <em>Acipenser transmontanus</em> subpopulations in adjacent river segments above and below CJ Strike Dam on the Snake River, Idaho, USA. In contrast to the downstream river segment, the upstream river segment is long and has areas that are suitable for spawning during normal and wet hydrologic conditions. We evaluated demographic and genetic consequences of upstream and downstream passage using different model assumptions about trashrack spacing and density-dependent effects on the spawning interval. Our genetic results predict that, although reconnection would introduce new alleles to the upstream subpopulation, it would also preserve alleles from the downstream subpopulation by propagating them in the larger subpopulation above the dam. Our demographic results predict that halving the space between trashracks would have large and unequivocal benefits, whereas the predicted effects of reconnection were smaller and more sensitive to model assumptions. Simulated upstream passage tended to benefit both subpopulations only in the absence of density-dependent limitation. In the presence of density dependence, the combination of halved trashrack spacing and upstream and downstream passage produced the best results. Narrower trashracks kept spawning adults in the upstream segment with spawning habitat, while allowing their progeny to migrate downstream. Screening appears to be the best option for such a species in this configuration of a long river segment acting as a demographic source above a short one acting as a demographic sink.

Density-Dependent Population Growth

2020 ◽  
pp. 29-46
Author(s):  
Michael J. Fogarty ◽  
Jeremy S. Collie
Keyword(s):  
Population Density ◽  
Population Growth ◽  
Density Dependence ◽  
Multiple Equilibria ◽  
Dynamical Behavior ◽  
Logistic Growth ◽  
Density Dependent ◽  
Per Capita ◽  
Discrete Time Models ◽  
Complex Dynamical Behavior

The observation that no population can grow indefinitely and that most populations persist on ecological timescales implies that mechanisms of population regulation exist. Feedback mechanisms include competition for limited resources, cannibalism, and predation rates that vary with density. Density dependence occurs when per capita birth or death rates depend on population density. Density dependence is compensatory when the population growth rate decreases with population density and depensatory when it increases. The logistic model incorporates density dependence as a simple linear function. A population exhibiting logistic growth will reach a stable population size. Non-linear density-dependent terms can give rise to multiple equilibria. With discrete time models or time delays in density-dependent regulation, the approach to equilibrium may not be smooth—complex dynamical behavior is possible. Density-dependent feedback processes can compensate, up to a point, for natural and anthropogenic disturbances; beyond this point a population will collapse.

scholarly journals Territorial landscapes: incorporating density-dependence into wolf habitat selection studies

2019 ◽  
Vol 6 (11) ◽  
pp. 190282 ◽  
Author(s):  
Shawn T. O'Neil ◽  
Dean E. Beyer ◽  
Joseph K. Bump
Keyword(s):  
Habitat Selection ◽  
Density Dependence ◽  
Temporal Dynamics ◽  
Wildlife Habitat ◽  
Population Increase ◽  
Habitat Availability ◽  
Functional Responses ◽  
Model Framework ◽  
Selection Probability ◽  
Density Dependent

Habitat selection is a process that spans space, time and individual life histories. Ecological analyses of animal distributions and preferences are most accurate when they account for inherent dynamics of the habitat selection process. Strong territoriality can constrain perception of habitat availability by individual animals or groups attempting to colonize or establish new territory. Because habitat selection is a function of habitat availability, broad-scale changes in habitat availability or occupancy can drive density-dependent habitat functional responses. We investigated density-dependent habitat selection over a 19-year period of grey wolf ( Canis lupus ) recovery in Michigan, USA, using a generalized linear mixed model framework to develop a resource selection probability function (RSPF) with habitat coefficients conditioned on random effects for wolf packs and random year intercepts. In addition, we allowed habitat coefficients to vary as interactions with increasing wolf density over space and time. Results indicated that pack presence was driven by factors representing topography, human development, winter prey availability, forest structure, roads, streams and snow. Importantly, responses to many of these predictors were density-dependent. Spatio-temporal dynamics and population changes can cause considerable variation in wildlife–habitat relationships, possibly confounding interpretation of conventional habitat selection models. By incorporating territoriality into an RSPF analysis, we determined that wolves' habitat use in Michigan shifted over time, for example, exhibiting declining responses to winter prey indices and switching from positive to negative responses with respect to stream densities. We consider this an important example of a habitat functional response in wolves, driven by colonization, density-dependence and changes in occupancy during a time period of range expansion and population increase.

Ecological correlates of pneumonia epizootics in bighorn sheep herds

2001 ◽  
Vol 79 (8) ◽  
pp. 1423-1432 ◽  
Author(s):  
Ryan J Monello ◽  
Dennis L Murray ◽  
E Frances Cassirer
Keyword(s):  
Horizontal Transmission ◽  
Bighorn Sheep ◽  
Ovis Canadensis ◽  
Domestic Sheep ◽  
Population Declines ◽  
Density Dependent ◽  
Temperature Regimes ◽  
Reservoir Hosts ◽  
The Relationship ◽  
Population Numbers

Bighorn sheep (Ovis canadensis) populations commonly experience pneumonia outbreaks caused by Pasteurella spp. that result in a partial or complete dieoff. Although several factors can contribute to Pasteurella spp. transmission or infectivity in bighorn sheep, to date the importance of such factors in population declines has not been rigorously examined. We evaluated the relationship between pneumonia-induced dieoffs in bighorn sheep and environmental and biological factors by analyzing demographic information for 99 herds across the species' geographic range. Our analysis revealed that 88% of pneumonia-induced dieoffs occurred at or within 3 years of peak population numbers, which implies that density-dependent forces such as food shortage or stress contribute to bighorns' susceptibility to pneumonia. There were few differences in the growth rates of dieoff and non-dieoff populations, suggesting that pneumonia did not manifest itself demographically prior to an outbreak. On average, abundance of lambs was most dramatically reduced post outbreak (–66%) relative to that of either rams (–35%) or ewes (–42%). Deviations in normal precipitation and temperature regimes were not associated with the onset of pneumonia outbreaks, but herds found in proximity to domestic sheep tended to be more susceptible to dieoff. Our results suggest that bighorn sheep herds are rendered vulnerable to pneumonia principally through density-dependent factors, as well as through horizontal transmission of Pasteurella spp. from domestic sheep serving as reservoir hosts.

Stability and Hopf Bifurcation of a Delayed Density-Dependent Predator–Prey System with Beddington–DeAngelis Functional Response

2016 ◽  
Vol 26 (10) ◽  
pp. 1650165 ◽  
Author(s):  
Haiyin Li ◽  
Gang Meng ◽  
Zhikun She
Keyword(s):  
Hopf Bifurcation ◽  
Density Dependence ◽  
Functional Response ◽  
Positive Equilibrium ◽  
Stability Switches ◽  
Predator Prey ◽  
Geometric Criterion ◽  
Density Dependent ◽  
Prey System ◽  
The Stability

In this paper, we investigate the stability and Hopf bifurcation of a delayed density-dependent predator–prey system with Beddington–DeAngelis functional response, where not only the prey density dependence but also the predator density dependence are considered such that the studied predator–prey system conforms to the realistically biological environment. We start with the geometric criterion introduced by Beretta and Kuang [2002] and then investigate the stability of the positive equilibrium and the stability switches of the system with respect to the delay parameter [Formula: see text]. Especially, we generalize the geometric criterion in [Beretta & Kuang, 2002] by introducing the condition [Formula: see text] which can be assured by the condition [Formula: see text], and adopting the technique of lifting to define the function [Formula: see text] for alternatively determining stability switches at the zeroes of [Formula: see text]s. Afterwards, by the Poincaré normal form for Hopf bifurcation in [Kuznetsov, 1998] and the bifurcation formulae in [Hassard et al., 1981], we qualitatively analyze the properties for the occurring Hopf bifurcations of the system (3). Finally, an example with numerical simulations is given to illustrate the obtained results.

scholarly journals Increased natural mortality at low abundance can generate an Allee effect in a marine fish

2014 ◽  
Vol 1 (2) ◽  
pp. 140075 ◽  
Author(s):  
Anna Kuparinen ◽  
Jeffrey A. Hutchings
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Density Dependence ◽  
Gadus Morhua ◽  
Allee Effect ◽  
Population Regulation ◽  
Atlantic Cod ◽  
Adult Mortality ◽  
Natural Mortality ◽  
Density Dependent

Negative density-dependent regulation of population dynamics promotes population growth at low abundance and is therefore vital for recovery following depletion. Inversely, any process that reduces the compensatory density-dependence of population growth can negatively affect recovery. Here, we show that increased adult mortality at low abundance can reverse compensatory population dynamics into its opposite—a demographic Allee effect. Northwest Atlantic cod ( Gadus morhua ) stocks collapsed dramatically in the early 1990s and have since shown little sign of recovery. Many experienced dramatic increases in natural mortality, ostensibly attributable in some populations to increased predation by seals. Our findings show that increased natural mortality of a magnitude observed for overfished cod stocks has been more than sufficient to fundamentally alter the dynamics of density-dependent population regulation. The demographic Allee effect generated by these changes can slow down or even impede the recovery of depleted populations even in the absence of fishing.

Density-Dependence at Sea for Coho Salmon (Oncorhynchus kisutch)

1990 ◽  
Vol 47 (9) ◽  
pp. 1765-1772 ◽  
Author(s):  
J. M. Emlen ◽  
R. R. Reisenbichler ◽  
A. M. McGie ◽  
T. E. Nickelson
Keyword(s):  
Density Dependence ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Density Dependent ◽  
Density Dependent Mortality ◽  
Hatchery Fish ◽  
Statistical Assumptions ◽  
Diminishing Returns ◽  
Salmon Hatchery ◽  
Dependent Mortality

The success of expanded salmon hatchery programs will depend strongly on the degree of density-induced diminishing returns per smolt released. Several authors have addressed the question of density-dependent mortality at sea in coho salmon (Oncorhynchus kisutch), but have come to conflicting conclusions. We believe there are compelling reasons to reinvestigate the data, and have done so for public hatchery fish, using a variety of approaches. The results provide evidence that survival of these public hatchery fish is negatively affected, directly by the number of public hatchery smolts and indirectly by the number of private hatchery smolts. These results are weak, statistically, and should be considered primarily as a caution to those who, on the basis of other published work, believe that density-dependence does not exist. The results reported here also re-emphasize the often overlooked point that inferences drawn from data are strongly biased by investigators' views of how the systems of interest work and by the statistical assumptions they make preparatory to the analysis of those data.

HYPERON DENSITY DEPENDENCE OF HYPERON-NUCLEON INTERACTIONS IN NEUTRON STARS

2008 ◽  
Vol 17 (09) ◽  
pp. 1720-1728
Author(s):  
L. DANG ◽  
P. YUE ◽  
L. LI ◽  
P. Z. NING
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Density Dependence ◽  
Mean Field ◽  
Density Dependent ◽  
Effective Potentials ◽  
Relativistic Mean Field ◽  
Nucleon Interactions ◽  
Dependent Factor ◽  
Rmf Model

The hyperon density dependence (YDD) of hyperon-nucleon interactions are studied in the relativistic mean field (RMF) model and their influences on the properties of neutron stars are studied. The extended RMF considered the interior quarks coordinates of hyperon and bring a hyperon density dependent factor, f(ρY), to the meson-hyperon coupling vertexes. The hyperon density dependence of YN interaction affect the properties of neutron stars only after the corresponding hyperon appears. Then, the influences of the density dependence factors are almost ignored at low densities, which are clear at high densities. The compositions and properties of neutron stars are studied with and without the YDD of YN interactions for the different Σ--nucleus effective potentials, (30, 0, -30)MeV. The calculated results indicated that the YDD of YN interaction soften the equation of state of neutron stars at high densities.

Sign in / Sign up

Export Citation Format

Share Document