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Proceedings of the National Academy of... Dec 2022Studies of spatial population synchrony constitute a central approach for understanding the drivers of ecological dynamics. Recently, identifying the ecological impacts...
Studies of spatial population synchrony constitute a central approach for understanding the drivers of ecological dynamics. Recently, identifying the ecological impacts of climate change has emerged as a new important focus in population synchrony studies. However, while it is well known that climatic seasonality and sequential density dependence influences local population dynamics, the role of season-specific density dependence in shaping large-scale population synchrony has not received attention. Here, we present a widely applicable analytical protocol that allows us to account for both season and geographic context-specific density dependence to better elucidate the relative roles of deterministic and stochastic sources of population synchrony, including the renowned Moran effect. We exemplify our protocol by analyzing time series of seasonal (spring and fall) abundance estimates of cyclic rodent populations, revealing that season-specific density dependence is a major component of population synchrony. By accounting for deterministic sources of synchrony (in particular season-specific density dependence), we are able to identify stochastic components. These stochastic components include mild winter weather events, which are expected to increase in frequency under climate warming in boreal and Arctic ecosystems. Interestingly, these weather effects act both directly and delayed on the vole populations, thus enhancing the Moran effect. Our study demonstrates how different drivers of population synchrony, presently altered by climate warming, can be disentangled based on seasonally sampled population time-series data and adequate population models.
Topics: Animals; Ecosystem; Population Dynamics; Climate Change; Arctic Regions; Weather; Arvicolinae; Population Density
PubMed: 36520669
DOI: 10.1073/pnas.2210144119 -
Heredity Oct 2016
Topics: Animals; Ecology; Evolution, Molecular; Genetics, Population; Linkage Disequilibrium; Models, Genetic; Polymorphism, Single Nucleotide; Population Density
PubMed: 27553454
DOI: 10.1038/hdy.2016.75 -
Philosophical Transactions of the Royal... Jan 2021One prominent feature of human culture is that different populations have different tools, technologies and cultural artefacts, and these unique toolkits can also differ... (Review)
Review
One prominent feature of human culture is that different populations have different tools, technologies and cultural artefacts, and these unique toolkits can also differ in size and complexity. Over the past few decades, researchers in the fields of prehistoric demography and cultural evolution have addressed a number of questions regarding variation in toolkit size and complexity across prehistoric and modern populations. Several factors have been proposed as possible explanations for this variation: in particular, the mobility of a population, the resources it uses, the volatility of its environment and the number of individuals in the population. Using a variety of methods, including empirical and ethnographic research, computational models and laboratory-based experiments, researchers have found disparate results regarding each hypothesis. These discordant findings have led to debate over the factors that most significantly influence toolkit size and composition. For instance, several computational, empirical and laboratory studies of food-producing populations have found a positive correlation between the number of individuals in a population and toolkit size, whereas similar studies of hunter-gatherer populations have found little evidence of such a link. In this paper, we conduct a comprehensive review of the literature in this field of study and propose corollaries and interdisciplinary approaches with the goal of reconciling dissimilar findings into a more comprehensive view of cultural toolkit variation. This article is part of the theme issue 'Cross-disciplinary approaches to prehistoric demography'.
Topics: Anthropology, Cultural; Cultural Evolution; Demography; Humans; Population Density
PubMed: 33250027
DOI: 10.1098/rstb.2019.0713 -
Heredity Jan 2022Linkage disequilibrium (LD) is the non-random association of alleles at different loci. Squared LD coefficients r (for phased genotypes) and [Formula: see text] (for...
Linkage disequilibrium (LD) is the non-random association of alleles at different loci. Squared LD coefficients r (for phased genotypes) and [Formula: see text] (for unphased genotypes) will converge to constants that are determined by the sample size, the recombination frequency, the effective population size and the mating system. LD can therefore be used for gene mapping and the estimation of effective population size. However, current methods work only with diploids. To resolve this problem, we here extend the linkage disequilibrium measures to include polysomic inheritance. We derive the values of r and [Formula: see text] at equilibrium state for various mating systems and different ploidy levels. For unlinked loci, [Formula: see text] for monoecious and dioecious (with random pairing) mating systems or [Formula: see text] for dioecious mating systems (with lifetime pairing), where f is the number of females in a half-sib family and η is a constant related to the ploidy level. We simulate the application of estimating N using unphased genotypes. We find that estimating N in polyploids requires similar sample sizes and numbers of loci as in diploids, with the main source of bias due to using 0.5 as the recombination frequency.
Topics: Genetics, Population; Genotype; Linkage Disequilibrium; Models, Genetic; Population Density
PubMed: 34983965
DOI: 10.1038/s41437-021-00482-1 -
Microbiology Spectrum Dec 2016Fungal plant pathogens are ubiquitous and highly diverse. Key to their success is high host density, which notably is the case in agroecosystems. Several hypotheses... (Review)
Review
Fungal plant pathogens are ubiquitous and highly diverse. Key to their success is high host density, which notably is the case in agroecosystems. Several hypotheses related to the effects of plant pathogens on plant diversity (the Janzen-Connell hypothesis, the dilution effect hypothesis) and the phenomenon of higher biomass in plant mixtures (i.e., overyielding) can all be explained by the quantitative interplay between host and pathogen density. In many agroecosystems, fungal plant pathogens cause great losses, since in monocultures diseased plants cannot be replaced by healthy plants. On the other hand, in natural ecosystems fungal plant pathogens shape the succession of vegetation and enhance the biodiversity of forests and grasslands. When pathogens are introduced into areas outside their natural range, they may behave differently, causing severe damage. Once introduced, changes may occur such as hybridization with other closely related pathogens or host shifts, host jumps, or horizontal gene transfer. Such changes can be hazardous for both agricultural and natural ecosystems.
Topics: Ecosystem; Fungi; Plant Diseases; Population Density
PubMed: 28087933
DOI: 10.1128/microbiolspec.FUNK-0013-2016 -
Biological Reviews of the Cambridge... Apr 2022Dispersal is a key demographic process involving three stages: emigration, transience and settlement; each of which is influenced by individual, social and environmental... (Review)
Review
Dispersal is a key demographic process involving three stages: emigration, transience and settlement; each of which is influenced by individual, social and environmental determinants. An integrated understanding of species dispersal is essential for demographic modelling and conservation planning. Here, we review the dispersal patterns and determinants documented in the scientific literature for the grey wolf (Canis lupus) across its distribution range. We showed a surprisingly high variability within and among study areas on all dispersal parameters - dispersal rate, direction, distance, duration and success. We found that such large variability is due to multiple individual, social and environmental determinants, but also due to previously overlooked methodological research issues. We revealed a potential non-linear relationship between dispersal rate and population density, with dispersal rate higher at both ends of the gradient of population density. We found that human-caused mortality reduces distance, duration and success of dispersal events. Furthermore, dispersers avoid interaction with humans, and highly exposed areas like agricultural lands hamper population connectivity in many cases. We identified numerous methodological research problems that make it difficult to obtain robust estimates of dispersal parameters and robust inferences on dispersal patterns and their determinants. In particular, analyses where confounding factors were not accounted for led to substantial knowledge gaps on all aspects of dispersal in an otherwise much-studied species. Our understanding of wolf biology and management would significantly benefit if wolf dispersal studies reported the results and possible factors affecting wolf dispersal more transparently.
Topics: Animals; Population Density; Wolves
PubMed: 34664396
DOI: 10.1111/brv.12807 -
ELife Sep 2020Natural populations can contain multiple types of coexisting individuals. How does natural selection maintain such diversity within and across populations? A popular...
Natural populations can contain multiple types of coexisting individuals. How does natural selection maintain such diversity within and across populations? A popular theoretical basis for the maintenance of diversity is cyclic dominance, illustrated by the rock-paper-scissor game. However, it appears difficult to find cyclic dominance in nature. Why is this the case? Focusing on continuously produced novel mutations, we theoretically addressed the rareness of cyclic dominance. We developed a model of an evolving population and studied the formation of cyclic dominance. Our results showed that the chance for cyclic dominance to emerge is lower when the newly introduced type is similar to existing types compared to the introduction of an unrelated type. This suggests that cyclic dominance is more likely to evolve through the assembly of unrelated types whereas it rarely evolves within a community of similar types.
Topics: Animals; Evolution, Molecular; Female; Male; Models, Genetic; Mutation; Population Density; Population Dynamics; Selection, Genetic
PubMed: 32886604
DOI: 10.7554/eLife.57857 -
Trends in Ecology & Evolution Oct 2023Our ability to assess the threat posed by the genetic load to small and declining populations has been greatly improved by advances in genome sequencing and... (Review)
Review
Our ability to assess the threat posed by the genetic load to small and declining populations has been greatly improved by advances in genome sequencing and computational approaches. Yet, considerable confusion remains around the definitions of the genetic load and its dynamics, and how they impact individual fitness and population viability. We illustrate how both selective purging and drift affect the distribution of deleterious mutations during population size decline and recovery. We show how this impacts the composition of the genetic load, and how this affects the extinction risk and recovery potential of populations. We propose a framework to examine load dynamics and advocate for the introduction of load estimates in the management of endangered populations.
Topics: Genetics, Population; Genetic Load; Population Density; Inbreeding; Genetic Variation
PubMed: 37344276
DOI: 10.1016/j.tree.2023.05.008 -
International Journal of Environmental... Feb 2022Over the last three decades, researchers have investigated population density and health outcomes at differing scale. There has not been a systematic review conducted in... (Review)
Review
Over the last three decades, researchers have investigated population density and health outcomes at differing scale. There has not been a systematic review conducted in order to synthesise this evidence. Following the Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines, we systematically reviewed quantitative evidence published since 1990 on population density and non-communicable disease (NCD) within Westernised countries. Fifty-four studies met the inclusion criteria and were evaluated utilising a quality assessment tool for ecological studies. High population density appears to be associated with higher mortality rates of a range of cancers, cardiovascular disease and COPD, and a higher incidence of a range of cancers, asthma and club foot. In contrast, diabetes incidence was found to be associated with low population density. High and low population density are therefore risk markers for a range of NCDs, indicating that there are unidentified factors and mechanisms underlying aetiology. On closer examination, our synthesis revealed important and complex relationships between population density, the built environment, the nature of greenspace and man-made exposures. In light of increasing rates of morbidity and mortality, future research is required to investigate these associations in order to establish causative agents for each NCD.
Topics: Cardiovascular Diseases; Developed Countries; Humans; Neoplasms; Noncommunicable Diseases; Population Density
PubMed: 35270337
DOI: 10.3390/ijerph19052638 -
Nature Communications May 2020Positive interactions are observed at high frequencies in nearly all living systems, ranging from human and animal societies down to the scale of microbial organisms....
Positive interactions are observed at high frequencies in nearly all living systems, ranging from human and animal societies down to the scale of microbial organisms. However, historically, detailed ecological studies of mutualism have been relatively unrepresented. Moreover, while ecologists have long portrayed competition as a stabilizing process, mutualism is often deemed destabilizing. Recently, several key modelling studies have applied random matrix methods, and have further corroborated the instability of mutualism. Here, I reassess these findings by factoring in species densities into the "community matrix," a practice which has almost always been ignored in random matrix analyses. With this modification, mutualistic interactions are found to boost equilibrium population densities and stabilize communities by increasing their resilience. By taking into account transient dynamics after a strong population perturbation, it is found that mutualists have the ability to pull up communities by their bootstraps when species are dangerously depressed in numbers.
Topics: Ecology; Ecosystem; Models, Biological; Population Density; Population Dynamics; Symbiosis
PubMed: 32461545
DOI: 10.1038/s41467-020-16474-4