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Genome Biology and Evolution Jul 2022We discuss the genetic, demographic, and selective forces that are likely to be at play in restricting observed levels of DNA sequence variation in natural populations...
We discuss the genetic, demographic, and selective forces that are likely to be at play in restricting observed levels of DNA sequence variation in natural populations to a much smaller range of values than would be expected from the distribution of census population sizes alone-Lewontin's Paradox. While several processes that have previously been strongly emphasized must be involved, including the effects of direct selection and genetic hitchhiking, it seems unlikely that they are sufficient to explain this observation without contributions from other factors. We highlight a potentially important role for the less-appreciated contribution of population size change; specifically, the likelihood that many species and populations may be quite far from reaching the relatively high equilibrium diversity values that would be expected given their current census sizes.
Topics: Genetic Variation; Genetics, Population; Models, Genetic; Population Density; Selection, Genetic
PubMed: 35738021
DOI: 10.1093/gbe/evac096 -
Environmental Entomology Apr 2021Larval density is an important factor modulating larval resource-acquisition, influencing development of insects. This study aimed to evaluate the effect of larval...
Larval density is an important factor modulating larval resource-acquisition, influencing development of insects. This study aimed to evaluate the effect of larval density and substrate content on some life-history parameters of Musca domestica Linnaeus, 1758 (Diptera: Muscidae). This research was carried out from March 2019 through September 2019 at Animal Physiology Laboratory of Ondokuz Mayıs University, Samsun, Turkey. Groups of 25, 100, 200, and 400 newly hatched M. domestica larvae were transferred to a polyethylene cup filled with different substrates (i.e., wheat bran, poultry meal, soybean meal) and kept at 25°C, 62% RH with a photoperiod of 12:12 (L:D) h. A two-way analysis of variance (Two way ANOVA) was used to analyze the data on the percentage of pupal and larval survival development time, pupal, and adult weight to evaluate the effect of density and rearing substrate. In this study, increasing larval density and nutrient content of food led to changes in the larval and pupal development time of M. domestica. The results also indicated that the weight of pupae and adult survival was negatively affected by increasing larval density. The wheat bran diet was superior to the other diets for all parameters tested. Our study indicated that life history parameters of Musca domestica are affected by the rearing conditions.
Topics: Animals; Houseflies; Larva; Muscidae; Population Density; Turkey
PubMed: 33377158
DOI: 10.1093/ee/nvaa165 -
Health & Place May 2023Population density is an indicator in many studies, but often with only a cursory explanation of why. Unfortunately, elected officials and the media draw misleading...
Population density is an indicator in many studies, but often with only a cursory explanation of why. Unfortunately, elected officials and the media draw misleading conclusions about population density and public health. After providing three reasons why population density is linked to human health outcomes, using state, county, municipal and neighborhood scale data, we show that population density serves as a surrogate for explaining the geographical distribution of life expectancy and broadband access. However, population density loses its unique contribution when other factors influencing health are included. We urge authors to explain why they include population density in their studies.
Topics: Humans; Population Density; Life Expectancy; Residence Characteristics
PubMed: 36947902
DOI: 10.1016/j.healthplace.2023.103001 -
Genetics May 2023Population bottlenecks are commonplace in experimental evolution, specifically in serial passaging experiments where microbial populations alternate between growth and...
Population bottlenecks are commonplace in experimental evolution, specifically in serial passaging experiments where microbial populations alternate between growth and dilution. Natural populations also experience such fluctuations caused by seasonality, resource limitation, or host-to-host transmission for pathogens. Yet, how unlimited growth with periodic bottlenecks influence the adaptation of populations is not fully understood. Here, we study theoretically the effects of bottlenecks on the accessibility of evolutionary paths and on the rate of evolution. We model an asexual population evolving on a minimal fitness landscape consisting of two types of beneficial mutations with the empirically supported trade-off between mutation rate and fitness advantage, in the regime where multiple beneficial mutations may segregate simultaneously. In the limit of large population sizes and small mutation rates, we show the existence of a unique most likely evolutionary scenario, determined by the size of the wild-type population at the beginning and at the end of each cycle. These two key demographic parameters determine which adaptive paths may be taken by the evolving population by controlling the supply of mutants during growth and the loss of mutants at the bottleneck. We do not only show that bottlenecks act as a deterministic control of evolutionary paths but also that each possible evolutionary scenario can be forced to occur by tuning demographic parameters. This work unveils the effects of demography on adaptation of periodically bottlenecked populations and can guide the design of evolution experiments.
Topics: Mutation Rate; Mutation; Adaptation, Physiological; Population Density
PubMed: 36728496
DOI: 10.1093/genetics/iyad001 -
Insect Science Dec 2022Insect fecundity is a quantitative phenotype strongly affected by genotypes and the environment. However, interactions between genotypes and environmental factors in...
Insect fecundity is a quantitative phenotype strongly affected by genotypes and the environment. However, interactions between genotypes and environmental factors in modulating insect fecundity remain largely unknown. This study investigated the impact of population density on the fecundity of Nilaparvata lugens (brown planthopper; BPH) carrying homozygous high- (HFG) or low- (LFG) fecundity homozygous genotypes. Under low population densities, the fecundity and population growth rate of both genotypes showed similar increasing trends across generations, while the trends between HFG and LFG under high population densities were opposite. Through a combination of temporal analysis and weighted gene co-expression network analyses on RNA-seq data of HFG and LFG under low and high population densities in the 1st, 3rd, and 5th generations, we identified 2 gene modules that were associated with these density-dependent progenitive phenotypes. Four pathways related to the neural system were simultaneously enriched by the 2 gene modules. Furthermore, Nlpale, which encodes a tyrosine hydroxylase, was identified as a key gene. The RNA interference of this gene and manipulation of its downstream product dopamine significantly affected the basic and density-dependent progenitive phenotypes of BPH. These findings indicated that dopamine biosynthesis is the key regulatory factor that determines fecundity in response to density changes in different BPH genotypes. Thus, this study provides insights into the interaction of a typical environmental factor and insect genotype during the process of population regulation.
Topics: Animals; Dopamine; Hemiptera; Population Density; RNA Interference
PubMed: 35230747
DOI: 10.1111/1744-7917.13019 -
PloS One 2023Large carnivores face numerous threats, including habitat loss and fragmentation, direct killing, and prey depletion, leading to significant global range and population...
Large carnivores face numerous threats, including habitat loss and fragmentation, direct killing, and prey depletion, leading to significant global range and population declines. Despite such threats, leopards (Panthera pardus) persist outside protected areas throughout most of their range, occupying diverse habitat types and land uses, including peri-urban and rural areas. Understanding of leopard population dynamics in mixed-use landscapes is limited, especially in South Africa, where the majority of leopard research has focused on protected areas. We use spatially explicit capture-recapture models to estimate leopard density across a mixed-use landscape of protected areas, farmland, and urban areas in the Overberg region of the Western Cape, South Africa. Data from 86 paired camera stations provided 221 independent captures of 25 leopards at 50 camera trap stations with a population density estimate of 0.64 leopards per 100 km2 (95% CI: 0.55-0.73). Elevation, terrain ruggedness, and vegetation productivity were important drivers of leopard density in the landscape, being highest on elevated remnants of natural land outside of protected areas. These results are similar to previous research findings in other parts of the Western Cape, where high-lying natural vegetation was shown to serve as both a refuge and a corridor for leopard movement in otherwise transformed landscapes. Given the low leopard density and the prevalence of transformed land intermixed with patches of more suitable leopard habitat, prioritising and preserving connectivity for leopards is vital in this shared landscape. Ecological corridors should be developed in partnership with private landowners through an inclusive and multifaceted conservation strategy which also incorporates monitoring of and rapid mitigation of emerging threats to leopards.
Topics: Animals; Panthera; South Africa; Anthropogenic Effects; Ecosystem; Population Density; Conservation of Natural Resources
PubMed: 37889916
DOI: 10.1371/journal.pone.0293445 -
The Journal of Animal Ecology Jun 2020Identifying the drivers of population fluctuations in spatially distinct populations remains a significant challenge for ecologists. Whereas regional climatic factors...
Identifying the drivers of population fluctuations in spatially distinct populations remains a significant challenge for ecologists. Whereas regional climatic factors may generate population synchrony (i.e. the Moran effect), local factors including the level of density dependence may reduce the level of synchrony. Although divergences in the scaling of population synchrony and spatial environmental variation have been observed, the regulatory factors that underlie such mismatches are poorly understood. Few previous studies have investigated how density-dependent processes and population-specific responses to weather variation influence spatial synchrony at both local and regional scales. We addressed this issue in a pond-breeding amphibian, the great crested newt Triturus cristatus. We used capture-recapture data collected through long-term surveys in five T. cristatus populations in Western Europe. In all populations-and subpopulations within metapopulations-population size, annual survival and recruitment fluctuated over time. Likewise, there was considerable variation in these demographic rates between populations and within metapopulations. These fluctuations and variations appear to be context-dependent and more related to site-specific characteristics than local or regional climatic drivers. We found a low level of demographic synchrony at both local and regional levels. Weather has weak and spatially variable effects on survival, recruitment and population growth rate. In contrast, density dependence was a common phenomenon (at least for population growth) in almost all populations and subpopulations. Our findings support the idea that the Moran effect is low in species where the population dynamics more closely depends on local factors (e.g. population density and habitat characteristics) than on large-scale environmental fluctuation (e.g. regional climatic variation). Such responses may have far-reaching consequences for the long-term viability of spatially structured populations and their ability to respond to large-scale climatic anomalies.
Topics: Amphibians; Animals; Europe; Population Density; Population Dynamics; Population Growth
PubMed: 32173904
DOI: 10.1111/1365-2656.13208 -
Frontiers in Public Health 2021The impact of social participation (SP) on the health of the elderly has been widely recognized, and urban-rural differences in social participation have attracted...
The Influence of Interpersonal Behaviors and Population Density on Grip Strength of Elderly People: An Analysis of the Direct vs. Indirect Effects via Social Participation.
The impact of social participation (SP) on the health of the elderly has been widely recognized, and urban-rural differences in social participation have attracted attention. However, few studies discussed the impact of social participation on specific health indicators and the further subdivision of urban-rural differences. This research aims to use the dimensions of interpersonal behaviors and population density rather than simple urban-rural distinctions to justify community differences and compare these differences' direct and indirect effects on grip strength. This study used 15,871 respondents aged over 50 years from the China Health and Retirement Longitudinal Study (CHARLS). An SEM (Structural Equation Modeling) analysis was used to explore the joint effect of interpersonal behavior and population density on social participation and the consequent impact on changes in grip strength and compare the differences among different genders, ages, wealth levels, and family relationships. The results indicated that community differences characterized by interpersonal behavior and population density have direct effects on grip strength and indirect effects on it through social participation. The conclusion is that the frequency of social activities, such as mah-jong and dancing in the Metropolitan Fringe and county-level cities is higher than that in Metropolitan centers. The high frequency of these activities has a positive and indirect impact on grip strength, and community differences have a more significant impact on women's social participation than men. However, the direct effect of community differences as defined by interpersonal communication and population density on grip strength is greater than the indirect effect of other factors through social participation.
Topics: Aged; China; Female; Hand Strength; Humans; Longitudinal Studies; Male; Population Density; Social Participation
PubMed: 34957015
DOI: 10.3389/fpubh.2021.755695 -
Philosophical Transactions of the Royal... Jan 2021Radiocarbon summed probability distribution (SPD) methods promise to illuminate the role of demography in shaping prehistoric social processes, but theories linking...
Radiocarbon summed probability distribution (SPD) methods promise to illuminate the role of demography in shaping prehistoric social processes, but theories linking population indices to social organization are still uncommon. Here, we develop Power Theory, a formal model of political centralization that casts population density and size as key variables modulating the interactive capacity of political agents to construct power over others. To evaluate this argument, we generated an SPD from 755 radiocarbon dates for 10 000-1000 BP from Central, North Central and North Coast Peru, a period when Peruvian political form developed from 'quasi-egalitarianism' to state levels of political centralization. These data are congruent with theoretical expectations of the model but also point to an artefactual distortion previously unremarked in SPD research. This article is part of the theme issue 'Cross-disciplinary approaches to prehistoric demography'.
Topics: Archaeology; Demography; Humans; Peru; Politics; Population Density
PubMed: 33250024
DOI: 10.1098/rstb.2019.0725 -
Trends in Ecology & Evolution Jun 2024Measuring and tracking biodiversity from local to global scales is challenging due to its multifaceted nature and the range of metrics used to describe spatial and... (Review)
Review
Measuring and tracking biodiversity from local to global scales is challenging due to its multifaceted nature and the range of metrics used to describe spatial and temporal patterns. Abundance can be used to describe how a population changes across space and time, but it can be measured in different ways, with consequences for the interpretation and communication of spatiotemporal patterns. We differentiate between relative and absolute abundance, and discuss the advantages and disadvantages of each for biodiversity monitoring, conservation, and ecological research. We highlight when absolute abundance can be advantageous and should be prioritized in biodiversity monitoring and research, and conclude by providing avenues for future research directions to better assess the necessity of absolute abundance in biodiversity monitoring.
Topics: Biodiversity; Conservation of Natural Resources; Population Density; Population Dynamics; Animals
PubMed: 38508923
DOI: 10.1016/j.tree.2024.01.012