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276 results for “Small population”
Capturing the dynamics of small populations: A retrospective assessment using long-term data for an island reintroduction
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Data from: Strong population genetic structure and contrasting demographic histories for the small-spotted catshark (Scyliorhinus canicula) in the Mediterranean Sea
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Data from: Small N e of the isolated and unmanaged horse population on Sable Island
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Data from: Wind farms affect the occurrence, abundance and population trends of small passerine birds: the case of the Dupont's lark
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Reduced pollinator service in small populations of Arabidopsis lyrata at its southern range limit
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Data from: Drift load in populations of small size and low density
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Data from: Spatial patterns of immunogenetic and neutral variation underscore the conservation value of small, isolated American badger populations
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Data from: Small population size and low genomic diversity have no effect on fitness in experimental translocations of a wild fish
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Data from: Senescence or selective disappearance? Age trajectories of body mass in wild and captive populations of a small-bodied primate
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Unburnt habitat patches are critical for survival and in situ population recovery in a small mammal after fire
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Data from: Hidden founder effects: small-scale spatial genetic structure in recently established populations of the grassland specialist plant Anthyllis vulneraria
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Individual genotypes of 1 416 brook trout genotyped at 14 779 high-quality SNPs for studying local adaptation and maladaptation in small populations
<p><span><span><span><span><span><span><span><span><span><span><span>Investigating the relative importance of neutral <i>versus</i> selective processes governing the accumulation of genetic variants is a key goal in both evolutionary and conservation biology. This is particularly true in the context of small populations, where genetic drift can counteract the effect of selection. Using Brook Charr (<i>Salvelinus fontinalis</i>) from Québec, Canada as a case study, we investigated the importance of demographic <i>versus</i> selective processes governing the accumulation of both adaptive and maladaptive mutations in closed <i>versus</i> open and connected populations to assess gene flow effect. This was achieved by using 14 779 high-quality filtered SNPs genotyped among 1 416 fish representing 50 populations from three life history types: lacustrine (closed populations), riverine and anadromous (connected populations). Using the Provean algorithm, we observed a considerable accumulation of putative deleterious mutations across populations. The absence of correlation between the occurrence of putatively beneficial or deleterious mutations and local recombination rate supports the hypothesis that genetic drift might be the main driver of the accumulation of such variants. However, despite a lower genetic diversity observed in lacustrine than in riverine or anadromous populations, lacustrine populations do not exhibit more deleterious mutations than the two other history types, suggesting that the negative effect of genetic drift in lacustrine populations may be mitigated by that of relaxed purifying selection. Moreover, we also identified genomic regions associated with anadromy, as well as an overrepresentation of transposable elements associated with variation in environmental variables, thus supporting the importance of transposable elements in adaptation. </span></span></span></span></span></span></span></span></span></span></span></p>
Productivity loss associated with physical impairment in a contemporary small-scale subsistence population
<p>Humans experience unique physical impairments with potentially severe economic consequences. Quantifying the burden of impairment in subsistence populations is critical for understanding selection pressures underlying strategies that minimize risk of production deficits. We examine among forager-horticulturalists whether compromised bone strength (indicated by vertebral fracture and lower bone mineral density, BMD) is associated with diminished subsistence involvement. We estimate the magnitude of productivity losses associated with compromised bone strength. Fracture is associated with cessation of hunting, tree chopping and walking long distances, but not tool manufacture. Age-specific productivity losses from hunting cessation related to fracture and lower BMD are substantial. Productivity loss is thus substantial for high strength and endurance tasks. Determining the extent to which impairment obstructs productivity in contemporary subsistence populations improves the ability to infer consequences of impairment over human evolution.</p>
Data from: Interactions between demography, genetics, and landscape connectivity increase extinction probability for a small population of large carnivores in a major metropolitan area
The extinction vortex is a theoretical model describing the process by which extinction risk is elevated in small, isolated populations owing to interactions between environmental, demographic, and genetic factors. However, empirical demonstrations of these interactions have been elusive. We modelled the dynamics of a small mountain lion population isolated by anthropogenic barriers in greater Los Angeles, California, to evaluate the influence of demographic, genetic, and landscape factors on extinction probability. The population exhibited strong survival and reproduction, and the model predicted stable median population growth and a 15% probability of extinction over 50 years in the absence of inbreeding depression. However, our model also predicted the population will lose 40–57% of its heterozygosity in 50 years. When we reduced demographic parameters proportional to reductions documented in another wild population of mountain lions that experienced inbreeding depression, extinction probability rose to 99.7%. Simulating greater landscape connectivity by increasing immigration to greater than or equal to one migrant per generation appears sufficient to largely maintain genetic diversity and reduce extinction probability. We provide empirical support for the central tenet of the extinction vortex as interactions between genetics and demography greatly increased extinction probability relative to the risk from demographic and environmental stochasticity alone. Our modelling approach realistically integrates demographic and genetic data to provide a comprehensive assessment of factors threatening small populations.
Data from: Slowly switching between environments facilitates reverse evolution in small populations
Natural populations must constantly adapt to ever-changing environmental conditions. A particularly interesting question is whether such adaptations can be reversed by returning the population to an ancestral environment. Such evolutionary reversals have been observed in both natural and laboratory populations. However, the factors that determine the reversibility of evolution are still under debate. The timescales of environmental change vary over a wide range, but little is known about how the rate of environmental change influences the reversibility of evolution. Here we demonstrate computationally that slowly switching between environments increases the reversibility of evolution for small populations, which are subject to only modest clonal interference. For small populations, slow switching reduces the mean number of mutations acquired in a new environment and also increases the probability of reverse evolution at each of these "genetic distances." As the population size increases, slow switching no longer reduces the genetic distance, thus decreasing the evolutionary reversibility. We confirm this effect using both a phenomenological model of clonal interference and also a Wright-Fisher stochastic simulation that incorporates genetic diversity. Our results suggest that the rate of environmental change is a key determinant of the reversibility of evolution, and provides testable hypotheses for experimental evolution.
Data from: Evolution of mutation rates in hypermutable populations of Escherichia coli propagated at very small effective population size
Mutation is the ultimate source of the genetic variation—including variation for mutation rate itself—that fuels evolution. Natural selection can raise or lower the genomic mutation rate of a population by changing the frequencies of mutation rate modifier alleles associated with beneficial and deleterious mutations. Existing theory and observations suggest that where selection is minimized, rapid systematic evolution of mutation rate either up or down is unlikely. Here, we report systematic evolution of higher and lower mutation rates in replicate hypermutable Escherichia coli populations experimentally propagated at very small effective size—a circumstance under which selection is greatly reduced. Several populations went extinct during this experiment, and these populations tended to evolve elevated mutation rates. In contrast, populations that survived to the end of the experiment tended to evolve decreased mutation rates. We discuss the relevance of our results to current ideas about the evolution, maintenance and consequences of high mutation rates.
Data from: Reduced lifespan and increased ageing driven by genetic drift in small populations
Explaining the strong variation in lifespan among organisms remains a major challenge in evolutionary biology. Whereas previous work has concentrated mainly on differences in selection regimes and selection pressures, we hypothesize that differences in genetic drift may explain some of this variation. We develop a model to formalize this idea and show that the strong positive relationship between lifespan and genetic diversity predicted by this model indeed exists among populations of Daphnia magna, and that ageing is accelerated in small populations. Additional results suggest that this is due to increased drift in small populations rather than adaptation to environments favoring faster life histories: First, the correlation between genetic diversity and lifespan remains significant after statistical correction for potential environmental covariates. Second, no trade-offs are observed; rather, all investigated traits show clear signs of increased genetic load in the small populations. Third, hybrid vigor with respect to lifespan is observed in crosses between small but not between large populations. Together, these results suggest that the evolution of lifespan and ageing can be strongly affected by genetic drift, especially in small populations, and that variation in lifespan and ageing may often be non-adaptive, due to a strong contribution from mutation accumulation to this variation.
Data from: Inbreeding depression and drift load in small populations at demographic disequilibrium
Inbreeding depression is a major driver of mating system evolution and has critical implications for population viability. Theoretical and empirical attention has been paid to predicting how inbreeding depression varies with population size. Lower inbreeding depression is predicted in small populations at equilibrium, primarily due to higher inbreeding rates facilitating purging and/or fixation of deleterious alleles (drift load), but predictions at demographic and genetic disequilibrium are less clear. In this study, we experimentally evaluate how lifetime inbreeding depression and drift load, estimated by heterosis, vary with census (Nc) and effective (estimated as genetic diversity, He) population size across six populations of the biennial Sabatia angularis as well as present novel models of inbreeding depression and heterosis under varying demographic scenarios at disequilibrium (fragmentation, bottlenecks, disturbances). Our experimental study reveals high average inbreeding depression and heterosis across populations. Across our small sample, heterosis declined with He, as predicted, whereas inbreeding depression did not vary with He and actually decreased with Nc. Our theoretical results demonstrate that inbreeding depression and heterosis levels can vary widely across populations at disequilibrium despite similar He and highlight that joint demographic and genetic dynamics are key to predicting patterns of genetic load in nonequilibrium systems.
Data from: Rapid evolution of cheating mitochondrial genomes in small yeast populations
Outcrossed sex exposes genes to competition with their homologues, allowing alleles that transmit more often than their competitors to spread despite organismal fitness costs. Mitochondrial populations in species with biparental inheritance are thought to be especially susceptible to such cheaters because they lack strict transmission rules like meiosis or maternal inheritance. Yet the interaction between mutation and natural selection in the evolution of cheating mitochondrial genomes has not been tested experimentally. Using yeast experimental populations, we show that although cheaters were rare in a large sample of spontaneous respiratory-deficient mitochondrial mutations (petites), cheaters evolve under experimentally enforced outcrossing even when mutation supply and selection are restricted by repeatedly bottlenecking populations.
Data from: An investigation for population maintenance mechanism in a miniature garden: genetic connectivity or independence of small islet populations of the Ryukyu five-lined skink
The Ryukyu five-lined skink (Plestiodon marginatus) is an island lizard that is even found in tiny islets with less than half a hectare of habitat area. We hypothesized that the island populations are maintained under frequent gene flow among the islands or independent of each other. To test our hypotheses, we investigated genetic structure of 21 populations from 11 land-bridge islands that were connected during the latest glacial age, and four isolated islands. Analyses using mitochondrial cytochrome b gene sequence (n = 67) and 10 microsatellite loci (n = 235) revealed moderate to high levels of genetic differentiation, existence of many private alleles/haplotypes in most islands, little contemporary migration, a positive correlation between genetic variability and island area, and a negative correlation between relatedness and island area. These evidences suggest a strong effect of independent genetic drift as opposed to gene flow, favoring the isolation hypothesis even in tiny islet populations. Isolation-by-distance effect was demonstrated and it became more prominent when the four isolated islands were excluded, suggesting that the pattern is a remnant of the land-bridge age. In a few island populations, however, the possibility of occasional overwater dispersals was partially supported and therefore could not be ruled out.
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.