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Proceedings. Biological Sciences Nov 2023Following severe environmental change that reduces mean population fitness below replacement, populations must adapt to avoid eventual extinction, a process called...
Following severe environmental change that reduces mean population fitness below replacement, populations must adapt to avoid eventual extinction, a process called evolutionary rescue. Models of evolutionary rescue demonstrate that initial size, genetic variation and degree of maladaptation influence population fates. However, many models feature populations that grow without negative density dependence or with constant genetic diversity despite precipitous population decline, assumptions likely to be violated in conservation settings. We examined the simultaneous influences of density-dependent growth and erosion of genetic diversity on populations adapting to novel environmental change using stochastic, individual-based simulations. Density dependence decreased the probability of rescue and increased the probability of extinction, especially in large and initially well-adapted populations that previously have been predicted to be at low risk. Increased extinction occurred shortly following environmental change, as populations under density dependence experienced more rapid decline and reached smaller sizes. Populations that experienced evolutionary rescue lost genetic diversity through drift and adaptation, particularly under density dependence. Populations that declined to extinction entered an extinction vortex, where small size increased drift, loss of genetic diversity and the fixation of maladaptive alleles, hindered adaptation and kept populations at small densities where they were vulnerable to extinction via demographic stochasticity.
Topics: Animals; Biological Evolution; Population Dynamics; Population Density; Probability; Extinction, Biological
PubMed: 37989246
DOI: 10.1098/rspb.2023.1228 -
American Journal of Public Health Sep 2017
Topics: Adult; Humans; Population Density; Sampling Studies; Sexual Behavior; Transgender Persons; Transsexualism
PubMed: 28787216
DOI: 10.2105/AJPH.2017.303964 -
Biology Letters Feb 2023Most small rodent species display cyclic fluctuations in their population density. The mechanisms behind these cyclical variations are not yet clearly understood....
Most small rodent species display cyclic fluctuations in their population density. The mechanisms behind these cyclical variations are not yet clearly understood. Density-dependent effects on reproductive function could affect these population variations. The fossorial water vole ecotype, , exhibits multi-year cyclical dynamics with outbreak peaks. Here, we monitored different water vole populations over 3 years, in spring and autumn, to evaluate whether population density is related to male reproductive physiology. Our results show an effect of season and inter-annual factors on testis mass, plasmatic testosterone level, and androgen-dependent seminal vesicle mass. By contrast, population density does not affect any of these parameters, suggesting a lack of modulation of population dynamics by population density.
Topics: Animals; Male; Population Density; Seasons; Population Dynamics; Arvicolinae
PubMed: 36815586
DOI: 10.1098/rsbl.2022.0441 -
American Journal of Public Health Nov 1974
Topics: Behavior; Disease; Humans; Personality; Population Density; Social Conditions; Social Environment; Social Mobility; Stress, Psychological
PubMed: 4415129
DOI: 10.2105/ajph.64.11.1052 -
Mathematical Biosciences and... Jan 2024Epidemiologists have used the timing of the peak of an epidemic to guide public health interventions. By determining the expected peak time, they can allocate resources...
Epidemiologists have used the timing of the peak of an epidemic to guide public health interventions. By determining the expected peak time, they can allocate resources effectively and implement measures such as quarantine, vaccination, and treatment at the right time to mitigate the spread of the disease. The peak time also provides valuable information for those modeling the spread of the epidemic and making predictions about its future trajectory. In this study, we analyze the time needed for an epidemic to reach its peak by presenting a straightforward analytical expression. Utilizing two epidemiological models, the first is a generalized $ SEIR $ model with two classes of latent individuals, while the second incorporates a continuous age structure for latent infections. We confirm the conjecture that the peak occurs at approximately $ T\sim(\ln N)/\lambda $, where $ N $ is the population size and $ \lambda $ is the largest eigenvalue of the linearized system in the first model or the unique positive root of the characteristic equation in the second model. Our analytical results are compared to numerical solutions and shown to be in good agreement.
Topics: Humans; Epidemics; Quarantine; Public Health; Population Density
PubMed: 38454709
DOI: 10.3934/mbe.2024126 -
Scientific Reports Jun 2022Thriving under high population density is considered a major feature of urban exploiter species. Nevertheless, population density appears to be a surprisingly overlooked...
Thriving under high population density is considered a major feature of urban exploiter species. Nevertheless, population density appears to be a surprisingly overlooked factor in urban ecology studies. High population numbers observed in urban species might promote pathogen transmission and negatively affect health or condition, thus requiring investments in immunocompetence. The feral pigeon Columba livia domestica is an example of a successful city-dweller, found in great abundance in large cities across the globe. We investigated the effects of population density on induced immune response (phytohaemagglutinin skin test) and body condition (blood haemoglobin concentration and size-corrected body mass) in 120 feral pigeons, captured along population density gradient in Łódź (central Poland). We found that stronger immune response was associated with higher population density, but was not related to physiological condition and physiological stress (heterophil/lymphocyte ratio). Moreover, condition indices were not associated with population density. However, since pigeon population density was highly correlated with the level of habitat urbanization, we cannot exclude that any density-dependent effects may be mediated by habitat variation. Our results indicate that urban environment, via population density, might exert different selective pressures on immunocompetence and body condition in this successful urban exploiter.
Topics: Adaptation, Physiological; Animals; Columbidae; Immunity; Population Density; Urbanization
PubMed: 35650222
DOI: 10.1038/s41598-022-12910-1 -
Proceedings. Biological Sciences Dec 2020Animals living at high population densities commonly experience greater exposure to disease, leading to increased parasite burdens. However, social animals can benefit...
Animals living at high population densities commonly experience greater exposure to disease, leading to increased parasite burdens. However, social animals can benefit immunologically and hygienically from cooperation, and individuals may alter their socio-spatial behaviour in response to infection, both of which could counteract density-related increases in exposure. Consequently, the costs and benefits of sociality for disease are often uncertain. Here, we use a long-term study of a wild European badger population () to investigate how within-population variation in host density determines infection with multiple parasites. Four out of five parasite taxa exhibited consistent spatial hotspots of infection, which peaked among badgers living in areas of low local population density. Combined movement, survival, spatial and social network analyses revealed that parasite avoidance was the likely cause of this negative density dependence, with possible roles for localized mortality, encounter-dilution effects, and micronutrient-enhanced immunity. These findings demonstrate that animals can organize their societies in space to minimize parasite infection, with important implications for badger behavioural ecology and for the control of badger-associated diseases.
Topics: Animals; Movement; Mustelidae; Population Density; Symbiosis
PubMed: 33323092
DOI: 10.1098/rspb.2020.2655 -
Theoretical Population Biology Dec 2022This study deals with the problem of the population shrinking in habitats affected by aging and excessive migration outflows. First, a control-oriented population...
This study deals with the problem of the population shrinking in habitats affected by aging and excessive migration outflows. First, a control-oriented population dynamics model was proposed that catches the effect of depopulation. The model also includes the effect of spatial interaction-driven migration flows on population size. The resulting model is a non-homogeneous ordinary differential equation. It includes such phenomena that are important from the control point of view, such as the influence of migration costs on population dynamics, the impact of aging on population size, or the effect of the habitats' carrying capacity on migration flows. Based on the model, controllability conditions are formulated and a control strategy was developed that is meant to avoid the depopulation of the habitat. The control method acts on the migration costs to achieve the control goal and requires only population size measurements. Simulation measurements are presented in the paper to show the effectiveness of the proposed modeling and control methods.
Topics: Population Dynamics; Population Density; Computer Simulation; Ecosystem; Conservation of Natural Resources
PubMed: 36379299
DOI: 10.1016/j.tpb.2022.11.002 -
Plant Disease Aug 2020The soybean cyst nematode (SCN), , is the most damaging pathogen of soybean. Use of resistant cultivars is an effective strategy to manage SCN, but it also selects for...
The soybean cyst nematode (SCN), , is the most damaging pathogen of soybean. Use of resistant cultivars is an effective strategy to manage SCN, but it also selects for virulent populations over time. A 12-year field experiment was initiated in 2003 to study how tillage and 11 different sequences of four cultivars impact SCN population dynamics and virulence. An SCN-susceptible cultivar and three resistant cultivars (R1, R2, and R3 derived from cultivars PI 88788, Peking, and PI 437654, respectively) were used. Tillage had minimal effect on SCN population density. Compared with no till, conventional tillage resulted in a faster increase of SCN virulence to Peking when the SCN was selected by R2 and virulence to PI 88788 by R3. Among the three SCN-resistant cultivars, R1 supported the greatest population density, R2 supported intermediate population density, and R3 supported the least SCN population density. The SCN populations selected by R1 overcame the resistance in PI 88788 but not in Peking and PI 437654. R2 selected SCN populations that overcame the resistance in Peking but not in PI 88788 and PI 437654. In contrast, R3 selected SCN populations that overcame both PI 88788 and Peking sources of resistance. There was no increase of virulence to PI 437654 in any cultivar sequence. R1 in rotation with R2 or R3 had a negative effect on female index on Peking. Susceptible soybean reduced SCN virulence to Peking, indicating that there was fitness cost of the Peking virulent SCN type. These results suggest that rotation of Peking with PI 88788 is a good strategy for managing the SCN, and susceptible cultivar and no till may reduce SCN virulence selection pressure in some rotations.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
Topics: Animals; Cysts; Phenotype; Plant Diseases; Population Density; Glycine max; Virulence
PubMed: 32539592
DOI: 10.1094/PDIS-09-19-1916-RE -
Brazilian Journal of Biology = Revista... 2021Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) is a predatory arthropod with potential for conservation biological control. In addition to being considered a...
Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) is a predatory arthropod with potential for conservation biological control. In addition to being considered a bioindicator of environmental quality, this arthropod provides an important service for agriculture by reducing insect-pest populations. In this work we seek to understand how the plants Andropogon bicornis L., Saccharum angustifolium Nees and Eustachys retusa Lag (Poales: Poaceae) and their different clump sizes affect the population density, spatial distribution and determination of the minimum number of samples to estimate its population density during the winter. Among the evaluated host plants, S. angustifolium and A. bicornis presented higher population density than E. retusa, but we observed that the clump diameter significantly influences the population density and the minimum number of samples. We observed a gregarious behavior in plants of A. bicornis and E. retusa. For S. angustifolium, a uniform distribution was observed.
Topics: Agriculture; Animals; Population Density; Predatory Behavior; Sample Size; Spiders
PubMed: 33053133
DOI: 10.1590/1519-6984.232607