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Scientific American Jul 2016
Topics: Animals; Behavior, Animal; Conservation of Natural Resources; Photography; Population Density; Predatory Behavior; Tigers
PubMed: 27348380
DOI: 10.1038/scientificamerican0716-54 -
Journal of Insect Physiology 2022The density-dependent prophylaxis hypothesis predicts that risk of pathogen transmission increases with increase in population density, and in response to this,...
The density-dependent prophylaxis hypothesis predicts that risk of pathogen transmission increases with increase in population density, and in response to this, organisms mount a prophylactic immune response when exposed to high density. This prophylactic response is expected to help organisms improve their chances of survival when exposed to pathogens. Alternatively, organisms living at high densities can exhibit compromised defense against pathogens due to lack of resources and density associated physiological stress; the crowding stress hypothesis. We housed adult Drosophila melanogaster flies at different densities and measured the effect this has on their post-infection survival and resistance to starvation. We find that flies housed at higher densities show greater mortality after being infected with bacterial pathogens, while also exhibiting increased resistance to starvation. Our results are more in line with the crowding stress hypothesis that postulates a compromised immune system when hosts are subjected to high densities.
Topics: Animals; Bacterial Infections; Drosophila melanogaster; Population Density; Starvation; Stress, Physiological
PubMed: 35753428
DOI: 10.1016/j.jinsphys.2022.104415 -
The Journal of Animal Ecology Jan 2016Habitats have substantial influence on the distribution and abundance of animals. Animals' selective movement yields their habitat use. Animals generally are more... (Review)
Review
Habitats have substantial influence on the distribution and abundance of animals. Animals' selective movement yields their habitat use. Animals generally are more abundant in habitats that are selected most strongly. Models of habitat selection can be used to distribute animals on the landscape or their distribution can be modelled based on data of habitat use, occupancy, intensity of use or counts of animals. When the population is at carrying capacity or in an ideal-free distribution, habitat selection and related metrics of habitat use can be used to estimate abundance. If the population is not at equilibrium, models have the flexibility to incorporate density into models of habitat selection; but abundance might be influenced by factors influencing fitness that are not directly related to habitat thereby compromising the use of habitat-based models for predicting population size. Scale and domain of the sampling frame, both in time and space, are crucial considerations limiting application of these models. Ultimately, identifying reliable models for predicting abundance from habitat data requires an understanding of the mechanisms underlying population regulation and limitation.
Topics: Animal Distribution; Animals; Ecosystem; Models, Biological; Movement; Population Density
PubMed: 25786026
DOI: 10.1111/1365-2656.12359 -
Scandinavian Journal of Medicine &... Nov 2018Inconsistencies in community size effects found between and within countries (Baker et al Eur J Sport Sci. 2009;9:329-339; Bruner et al J Sports Sci....
Inconsistencies in community size effects found between and within countries (Baker et al Eur J Sport Sci. 2009;9:329-339; Bruner et al J Sports Sci. 2011;29:1337-1344; Wattie et al J Sports Sci. 2018;36:436-444) suggest population size may not be an accurate predictor of athlete development and that other proxies of early environmental characteristics are needed. Researchers have begun to explore the influence of population density and proximity to local sport clubs on athlete development in European countries; however, similar analysis remains to be conducted in Canadian ice hockey. The current study focused on National Hockey League (NHL) draftees and explored whether population density and proximity to Canadian Hockey League teams were associated with the number of draftees produced. Linear regression analyses showed a significant positive relationship between population density and the development of draftees in all provincial regions; however, a significant negative relationship between proximity to CHL teams and NHL draftee development was observed in four out of six provincial regions (British Columbia, Ontario, Quebec, and the Atlantic Provinces). Moreover, population density appeared to be a better predictor of NHL talent development than proximity to CHL teams. Future research may benefit from exploring the effects of these two variables within population size categories, as well as between different regions within provinces.
Topics: Aptitude; Canada; Geography; Hockey; Humans; Linear Models; Population Density
PubMed: 29938850
DOI: 10.1111/sms.13247 -
The Journal of Animal Ecology Feb 2020Territoriality is an important process shaping population dynamics, and the defence of a territory is crucial for individuals to increase the duration of territory...
Territoriality is an important process shaping population dynamics, and the defence of a territory is crucial for individuals to increase the duration of territory occupancy and, consequently, reproductive success. However, little is known about how the frequency of territory intrusions and subsequent territorial behaviours and aggression by territory owners are affected by external factors, such as population density. This is important because it can affect mate change (the replacement of one pair member) and dispersal, a key ecological process. The aim of this study was to investigate the behavioural and spatial response of territory owners to intruder pressure as a function of population density in a territorial, monogamous mammal, the Eurasian beaver (Castor fiber). Using a combination of GPS technology, scent experiments, camera trap data and tail scar observations from an individual-based long-term study, we investigated the factors influencing spatial movement patterns by territory owners in response to a simulated intruder and the factors affecting territory intrusions. We found consistent inverse density-dependent patterns in territorial behaviours and evidence of conspecific aggression. At lower densities, territory owners detected more simulated intrusions, showed more territorial reactions and experienced increased conspecific aggression as indicated by tail scars, suggesting increased intruder pressure. Inverse density-dependent territorial behaviour and aggression suggest a potential mechanistic link between inverse density-dependent natal dispersal and mate change. At low population densities, increased dispersal amplifies intruder pressure, leading to the observed increases in territorial behaviours, conspecific aggression and previously observed mate turnover, which in turn might increase natal dispersal. Our study demonstrates how population density can affect the behaviour and space use of individuals, which is important for territory occupancy and fitness.
Topics: Aggression; Animals; Population Density; Population Dynamics; Reproduction; Territoriality
PubMed: 31469174
DOI: 10.1111/1365-2656.13100 -
Plant Disease Jan 2023The effects of sampling depth and crop growth stage on the population density of lesion nematodes were investigated in three commercial fields in Wayne and Fulton...
The effects of sampling depth and crop growth stage on the population density of lesion nematodes were investigated in three commercial fields in Wayne and Fulton Counties, Ohio, during the 2016 and 2017 growing seasons. Soil samples were collected at five growth stages by removing 15 soil cores to a depth of 70 cm from each of 25 plots per field-year. Cores were divided into seven 10-cm sections, and nematodes were extracted from the soil and root fractions of each of them. and were detected in approximately 84 and 78% of the samples collected in Wayne and Fulton Counties, respectively. Depth significantly affected total population density of both species as well as densities in the soil and root factions in all field-years, but the effects of growth stage and its interaction with depth varied with field-year. In most cases, mean population densities were higher from 10 to 40 cm soil depth than at the reference 40 to 50 cm depth and lower from 50 to 70 cm. There were quadratic relationships between population density (on the log link scale) and depth, with the highest peaks in estimated predicted densities generally occurring between 20 and 40 cm, depending on crop growth stage and growing conditions. These findings suggest that the standard practice of sampling between growth stages V3 and V6 to a depth of 45 to 50 cm and using the entire core for extraction and enumeration could lead to underestimation of population densities of and .
Topics: Animals; Zea mays; Population Density; Ohio; Plant Diseases; Tylenchoidea; Soil
PubMed: 35640946
DOI: 10.1094/PDIS-02-22-0403-RE -
Proceedings. Biological Sciences Dec 2020Understanding factors affecting the functional diversity of ecological communities is an important goal for ecologists and conservationists. Previous work has largely...
Understanding factors affecting the functional diversity of ecological communities is an important goal for ecologists and conservationists. Previous work has largely been conducted at the community level; however, recent studies have highlighted the critical importance of considering intraspecific functional diversity (i.e. the functional diversity of phenotypic traits among conspecifics). Further, a major limitation of existing literature on this topic is the lack of empirical studies examining functional diversity of -including animal personalities. This is a major shortcoming because personality traits can affect the fitness of individuals, and the composition of personalities in a population can have important ecological consequences. Our study aims to contribute to filling this knowledge gap by investigating factors affecting the functional diversity of personality traits in wild animal populations. Specifically, we predicted that the richness, divergence and evenness associated with personality traits would be impacted by key components of forest structure and would vary between contrasting forest types. To achieve our objective we conducted a fully replicated large-scale field experiment over a 4 year period using small mammal populations as a model system. We found that greater heterogeneity in the cover of shrubs, coarse woody debris and canopy cover was associated with a greater richness, lower divergence and lower evenness in personality traits. Greater population density was associated with greater functional richness and lower functional divergence and evenness of personality traits. To maintain a behaviourally diverse population and its associated functions, managers may promote heterogeneity in vegetation and increased population density, which we found to be the most important determinants driving functional diversity of personality traits.
Topics: Animals; Behavior, Animal; Biodiversity; Ecosystem; Forestry; Forests; Mammals; Personality; Phenotype; Population Density
PubMed: 33290673
DOI: 10.1098/rspb.2020.1713 -
Advances in Experimental Medicine and... 2022The problem of how to create efficient multi-scale models of large networks of neurons is a pressing one. It requires a balance between computational efficiency and a...
The problem of how to create efficient multi-scale models of large networks of neurons is a pressing one. It requires a balance between computational efficiency and a reduction of the number of parameters involved against biological realism. Simulations of point-model neurons show very realistic features of neural dynamics but are very hard to configure and to analyse. Instead of using hundreds or thousands of point-model neurons, a population can often be modeled by a single density function in a way that accurately reproduces quantities aggregated over the population, such as population firing rate or average membrane potential. These techniques have been widely applied in neuroscience, mainly on populations comprised of one-dimensional point-model neurons, such as leaky-integrate-and-fire neurons. Here, we present very general density methods that can be applied to point-model neurons of higher dimensionality that can represent biological features not present in simpler ones, such as adaptation and bursting. The methods are geometrical in nature and lend themselves to immediate visualisation of the population state. By decoupling the neural dynamics and the stochastic processes that model inter-neuron communication, an efficient GPGPU implementation is possible that makes the study of such high-dimensional models feasible. This decoupling also allows the study of different noise models, such as Poisson, white noise, and gamma-distributed interspike intervals, which broadens the application domain considerably compared to the Fokker-Planck equations that have traditionally dominated this approach. We will present several examples based on high-dimensional neural models. We will use dynamical systems that represent point-model neurons, but inherently there is nothing to restrict the approach presented here to neuroscience. MIIND is an open-source simulator that contains an implementation of these techniques.
Topics: Models, Neurological; Neurons; Neurosciences; Noise; Population Density
PubMed: 35471539
DOI: 10.1007/978-3-030-89439-9_7 -
Proceedings. Biological Sciences Aug 2021Conditional strategies occur when the relative fitness pay-off from expressing a given phenotype is contingent upon environmental circumstances. This conditional...
Conditional strategies occur when the relative fitness pay-off from expressing a given phenotype is contingent upon environmental circumstances. This conditional strategy model underlies cases of alternative reproductive tactics, in which individuals of one sex employ different means to obtain reproduction. How kin structure affects the expression of alternative reproductive tactics remains unexplored. We address this using the mite , in which large males develop into aggressive 'fighters' and small males develop into non-aggressive 'scramblers.' Because only fighters kill their rivals, they should incur a greater indirect fitness cost when competing with their relatives, and thus fighter expression could be reduced in the presence of relatives. We raised mites in full-sibling or mixed-sibship groups and found that fighters were more common at higher body weights in full-sibling groups, not less common as we predicted (small individuals were almost exclusively scramblers in both treatments). This result could be explained if relatedness and cue variability are interpreted signals of population density, since fighters are more common at low densities in this species. Alternatively, our results may indicate that males compete more intensely with relatives in this species. We provide the first evidence of kin-mediated plasticity in the expression of alternative reproductive tactics.
Topics: Acaridae; Animals; Humans; Male; Mites; Phenotype; Population Density; Reproduction; Sexual Behavior, Animal
PubMed: 34344179
DOI: 10.1098/rspb.2021.1069 -
Journal of Mathematical Biology Sep 2023Many populations occupy spatially fragmented landscapes. How dispersal affects the asymptotic total population size is a key question for conservation management and the... (Review)
Review
Many populations occupy spatially fragmented landscapes. How dispersal affects the asymptotic total population size is a key question for conservation management and the design of ecological corridors. Here, we provide a comprehensive overview of two-patch models with symmetric dispersal and two standard density-dependent population growth functions, one in discrete and one in continuous time. A complete analysis of the discrete-time model reveals four response scenarios of the asymptotic total population size to increasing dispersal rate: (1) monotonically beneficial, (2) unimodally beneficial, (3) beneficial turning detrimental, and (4) monotonically detrimental. The same response scenarios exist for the continuous-time model, and we show that the parameter conditions are analogous between the discrete- and continuous-time setting. A detailed biological interpretation offers insight into the mechanisms underlying the response scenarios that thus improve our general understanding how potential conservation efforts affect population size.
Topics: Population Density; Population Growth
PubMed: 37733146
DOI: 10.1007/s00285-023-01984-8