scholarly journals Estimating individual contributions to population growth: evolutionary fitness in ecological time

2005 ◽  
Vol 273 (1586) ◽  
pp. 547-555 ◽  
Author(s):  
T Coulson ◽  
T.G Benton ◽  
P Lundberg ◽  
S.R.X Dall ◽  
B.E Kendall ◽  
...  
Keyword(s):  
Population Growth ◽  
Quantitative Traits ◽  
Population Level ◽  
Individual Performance ◽  
Evolutionary Change ◽  
Annual Survival ◽  
Soay Sheep ◽  
Individual Contributions ◽  
Novel Method ◽  
Evolutionary Fitness

Ecological and evolutionary change is generated by variation in individual performance. Biologists have consequently long been interested in decomposing change measured at the population level into contributions from individuals, the traits they express and the alleles they carry. We present a novel method of estimating individual contributions to population growth and changes in distributions of quantitative traits and alleles. An individual's contribution to population growth is an individual's realized annual fitness. We demonstrate how the quantities we develop can be used to address a range of empirical questions, and provide an application to a detailed dataset of Soay sheep. The approach provides results that are consistent with those obtained using lifetime estimates of individual performance, yet is substantially more powerful as it allows lifetime performance to be decomposed into annual survival and fecundity contributions.

Assessment of invasive rodent impacts on island avifauna: methods, limitations and the way forward

2015 ◽  
Vol 42 (2) ◽  
pp. 185 ◽  
Author(s):  
Lise Ruffino ◽  
Diane Zarzoso-Lacoste ◽  
Eric Vidal
Keyword(s):  
Population Growth ◽  
Population Level ◽  
Bird Conservation ◽  
Bird Population ◽  
Breeding Parameters ◽  
Population Growth Rates ◽  
Bird Populations ◽  
Field Evidence ◽  
Bird Breeding

Bird conservation is nowadays a strong driving force for prioritising rodent eradications, but robust quantitative estimates of impacts are needed to ensure cost-effectiveness of management operations. Here, we review the published literature to investigate on what methodological basis rodent effects on island bird communities have been evaluated for the past six decades. We then discuss the advantages and limitations of each category of methods for the detection and quantification of impacts, and end with some recommendations on how to strengthen current approaches and extend our knowledge on the mechanisms of impacts. Impact studies (152 studies considered) emphasised seabirds (67%), black rats (63%) and the Pacific Ocean (57%). Among the most commonly used methods to study rodent impacts on birds were the observation of dead eggs or empty nests while monitoring bird breeding success, and the analyses of rodent diets, which can both lead to misleading conclusions if the data are not supported by direct field evidence of rodent predation. Direct observations of rodent–bird interactions (19% of studies) are still poorly considered despite their potential to reveal cryptic behaviours and shed light on the mechanisms of impacts. Rodent effects on birds were most often measured as a change or difference in bird breeding parameters (74% of studies), while estimates of bird population growth rates (4%) are lacking. Based on the outcomes of this literature review, we highlight the need for collecting unbiased population-level estimates of rodent impacts, which are essential prerequisites for predicting bird population growth scenarios and prioritising their conservation needs. This could be achieved by a more systematic integration of long-term monitoring of bird populations into rodent management operations and modelling bird population dynamics. We also strongly recommend including various complementary methods in impact assessment strategies to unravel complex interactions between rodents and birds and avoid faulty evidence. Finally, more research should be devoted to a better understanding of the cases of non-impacts (i.e. long-term coexistence) and those impacts mediated by mechanisms other than predation and ecosystem-level processes.

scholarly journals The shape of density dependence and the relationship between population growth, intraspecific competition and equilibrium population density

2018 ◽  
Author(s):  
Emanuel A. Fronhofer ◽  
Lynn Govaert ◽  
Mary I. O’Connor ◽  
Sebastian J. Schreiber ◽  
Florian Altermatt
Keyword(s):  
Population Growth ◽  
Growth Models ◽  
Population Level ◽  
Logistic Growth ◽  
Population Densities ◽  
Density Regulation ◽  
Logistic Growth Model ◽  
Regulation Functions ◽  
Consumer Resource ◽  
Population Growth Models

AbstractThe logistic growth model is one of the most frequently used formalizations of density dependence affecting population growth, persistence and evolution. Ecological and evolutionary theory and applications to understand population change over time often include this model. However, the assumptions and limitations of this popular model are often not well appreciated.Here, we briefly review past use of the logistic growth model and highlight limitations by deriving population growth models from underlying consumer-resource dynamics. We show that the logistic equation likely is not applicable to many biological systems. Rather, density-regulation functions are usually non-linear and may exhibit convex or both concave and convex curvatures depending on the biology of resources and consumers. In simple cases, the dynamics can be fully described by the continuous-time Beverton-Holt model. More complex consumer dynamics show similarities to a Maynard Smith-Slatkin model.Importantly, we show how population-level parameters, such as intrinsic rates of increase and equilibrium population densities are not independent, as often assumed. Rather, they are functions of the same underlying parameters. The commonly assumed positive relationship between equilibrium population density and competitive ability is typically invalid. As a solution, we propose simple and general relationships between intrinsic rates of increase and equilibrium population densities that capture the essence of different consumer-resource systems.Relating population level models to underlying mechanisms allows us to discuss applications to evolutionary outcomes and how these models depend on environmental conditions, like temperature via metabolic scaling. Finally, we use time-series from microbial food chains to fit population growth models and validate theoretical predictions.Our results show that density-regulation functions need to be chosen carefully as their shapes will depend on the study system’s biology. Importantly, we provide a mechanistic understanding of relationships between model parameters, which has implications for theory and for formulating biologically sound and empirically testable predictions.

scholarly journals Self-Directedness and Cooperativeness, Psychosocial Dysfunction and Suffering in ESSENCE

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Danilo Garcia ◽  
Henrik Anckarsäter ◽  
Sebastian Lundström
Keyword(s):  
Developmental Coordination Disorder ◽  
Population Level ◽  
Autism Spectrum ◽  
Severe Form ◽  
Therapeutic Interventions ◽  
Psychosocial Dysfunction ◽  
Hyperactivity Disorder ◽  
Character Inventory ◽  
Novel Method ◽  
The Impact

Background. The acronym ESSENCE (Early Symptomatic Syndromes Eliciting Neurodevelopmental Clinical Examinations) highlights that children seeking clinical treatment are often multiply impaired, thus requiring treatment from several specialties. The aim was to map and relate, on a population level, ESSENCE to two salient predictors of health and adaptation to adversities, namely, Self-Directedness and Cooperativeness and also to dysfunction and suffering.Methods. Participants were twins(N=1892)aged 9 or 12 whose parents were interviewed with the Autism-Tics, ADHD and other Comorbidities inventory (A-TAC), and the Junior Temperament and Character Inventory (J-TCI). The A-TAC was first used to discern four ESSENCE-related screening diagnoses: autism spectrum disorders, attention deficit hyperactivity disorder, learning disabilities, and developmental coordination disorder; second, to quantify dysfunction and suffering in important social areas.Results. ESSENCE symptoms were continuously and categorically associated with deficiency in Self-Directedness and Cooperativeness and higher ratings of dysfunction and suffering. The impact of ESSENCE symptoms on these measures of mental health was found in a milder form in about 16% of all children and in a severe form in about 2%.Conclusion. Therapeutic interventions focusing on Self-Directedness and Cooperativeness might provide a novel method for child psychiatry in its approach to ESSENCE.

scholarly journals Bayesian inference reveals positive but subtle effects of experimental fishery closures on marine predator demographics

2018 ◽  
Vol 285 (1871) ◽  
pp. 20172443 ◽  
Author(s):  
Richard B. Sherley ◽  
Barbara J. Barham ◽  
Peter J. Barham ◽  
Kate J. Campbell ◽  
Robert J. M. Crawford ◽  
...  
Keyword(s):  
South Africa ◽  
Bayesian Inference ◽  
Population Growth ◽  
Prey Availability ◽  
Population Level ◽  
Marine Ecosystems ◽  
Forage Fish ◽  
Chick Survival ◽  
Marine Predator ◽  
Management Interventions

Global forage-fish landings are increasing, with potentially grave consequences for marine ecosystems. Predators of forage fish may be influenced by this harvest, but the nature of these effects is contentious. Experimental fishery manipulations offer the best solution to quantify population-level impacts, but are rare. We used Bayesian inference to examine changes in chick survival, body condition and population growth rate of endangered African penguins Spheniscus demersus in response to 8 years of alternating time–area closures around two pairs of colonies. Our results demonstrate that fishing closures improved chick survival and condition, after controlling for changing prey availability. However, this effect was inconsistent across sites and years, highlighting the difficultly of assessing management interventions in marine ecosystems. Nevertheless, modelled increases in population growth rates exceeded 1% at one colony; i.e. the threshold considered biologically meaningful by fisheries management in South Africa. Fishing closures evidently can improve the population trend of a forage-fish-dependent predator—we therefore recommend they continue in South Africa and support their application elsewhere. However, detecting demographic gains for mobile marine predators from small no-take zones requires experimental time frames and scales that will often exceed those desired by decision makers.

scholarly journals Noise-driven growth rate gain in clonal cellular populations

2016 ◽  
Vol 113 (12) ◽  
pp. 3251-3256 ◽  
Author(s):  
Mikihiro Hashimoto ◽  
Takashi Nozoe ◽  
Hidenori Nakaoka ◽  
Reiko Okura ◽  
Sayo Akiyoshi ◽  
...  
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Single Cell ◽  
Single Cells ◽  
Population Level ◽  
Growth Conditions ◽  
Cell Dynamics ◽  
Generation Times ◽  
Complex Population ◽  
The Mean

Cellular populations in both nature and the laboratory are composed of phenotypically heterogeneous individuals that compete with each other resulting in complex population dynamics. Predicting population growth characteristics based on knowledge of heterogeneous single-cell dynamics remains challenging. By observing groups of cells for hundreds of generations at single-cell resolution, we reveal that growth noise causes clonal populations of Escherichia coli to double faster than the mean doubling time of their constituent single cells across a broad set of balanced-growth conditions. We show that the population-level growth rate gain as well as age structures of populations and of cell lineages in competition are predictable. Furthermore, we theoretically reveal that the growth rate gain can be linked with the relative entropy of lineage generation time distributions. Unexpectedly, we find an empirical linear relation between the means and the variances of generation times across conditions, which provides a general constraint on maximal growth rates. Together, these results demonstrate a fundamental benefit of noise for population growth, and identify a growth law that sets a “speed limit” for proliferation.

scholarly journals Fertility control to mitigate human–wildlife conflicts: a review

2014 ◽  
Vol 41 (1) ◽  
pp. 1 ◽  
Author(s):  
Giovanna Massei ◽  
Dave Cowan
Keyword(s):  
Population Growth ◽  
Wildlife Management ◽  
Population Level ◽  
Fertility Control ◽  
Public Consultation ◽  
Human Populations ◽  
Wildlife Diseases ◽  
Isolated Populations ◽  
Wild Mammals ◽  
Practical Applications

As human populations grow, conflicts with wildlife increase. Concurrently, concerns about the welfare, safety and environmental impacts of conventional lethal methods of wildlife management restrict the options available for conflict mitigation. In parallel, there is increasing interest in using fertility control to manage wildlife. The present review aimed at analysing trends in research on fertility control for wildlife, illustrating developments in fertility-control technologies and delivery methods of fertility-control agents, summarising the conclusions of empirical and theoretical studies of fertility control applied at the population level and offering criteria to guide decisions regarding the suitability of fertility control to mitigate human–wildlife conflicts. The review highlighted a growing interest in fertility control for wildlife, underpinned by increasing numbers of scientific studies. Most current practical applications of fertility control for wild mammals use injectable single-dose immunocontraceptive vaccines mainly aimed at sterilising females, although many of these vaccines are not yet commercially available. One oral avian contraceptive, nicarbazin, is commercially available in some countries. Potential new methods of remote contraceptive delivery include bacterial ghosts, virus-like particles and genetically modified transmissible and non-transmissible organisms, although none of these have yet progressed to field testing. In parallel, new species-specific delivery systems have been developed. The results of population-level studies of fertility control indicated that this approach may increase survival and affect social and spatial behaviour of treated animals, although the effects are species- and context-specific. The present studies suggested that a substantial initial effort is generally required to reduce population growth if fertility control is the sole wildlife management method. However, several empirical and field studies have demonstrated that fertility control, particularly of isolated populations, can be successfully used to limit population growth and reduce human–wildlife conflicts. In parallel, there is growing recognition of the possible synergy between fertility control and disease vaccination to optimise the maintenance of herd immunity in the management of wildlife diseases. The review provides a decision tree that can be used to determine whether fertility control should be employed to resolve specific human–wildlife conflicts. These criteria encompass public consultation, considerations about animal welfare and feasibility, evaluation of population responses, costs and sustainability.

scholarly journals Aridity weakens population-level effects of multiple species interactions on Hibiscus meyeri

2017 ◽  
Vol 115 (3) ◽  
pp. 543-548 ◽  
Author(s):  
Allison M. Louthan ◽  
Robert M. Pringle ◽  
Jacob R. Goheen ◽  
Todd M. Palmer ◽  
William F. Morris ◽  
...  
Keyword(s):  
Population Growth ◽  
Species Interactions ◽  
Abiotic Factors ◽  
Population Level ◽  
Distinct Species ◽  
High Elevation ◽  
Relative Strength ◽  
Herbaceous Plant ◽  
Species Abundances ◽  
Multiple Species

Predicting how species’ abundances and ranges will shift in response to climate change requires a mechanistic understanding of how multiple factors interact to limit population growth. Both abiotic stress and species interactions can limit populations and potentially set range boundaries, but we have a poor understanding of when and where each is most critical. A commonly cited hypothesis, first proposed by Darwin, posits that abiotic factors (e.g., temperature, precipitation) are stronger determinants of range boundaries in apparently abiotically stressful areas (“stress” indicates abiotic factors that reduce population growth), including desert, polar, or high-elevation environments, whereas species interactions (e.g., herbivory, competition) play a stronger role in apparently less stressful environments. We tested a core tenet of this hypothesis—that population growth rate is more strongly affected by species interactions in less stressful areas—using experimental manipulations of species interactions affecting a common herbaceous plant, Hibiscus meyeri (Malvaceae), across an aridity gradient in a semiarid African savanna. Population growth was more strongly affected by four distinct species interactions (competition with herbaceous and shrubby neighbors, herbivory, and pollination) in less stressful mesic areas than in more stressful arid sites. However, contrary to common assumptions, this effect did not arise because of greater density or diversity of interacting species in less stressful areas, but rather because aridity reduced sensitivity of population growth to these interactions. Our work supports classic predictions about the relative strength of factors regulating population growth across stress gradients, but suggests that this pattern results from a previously unappreciated mechanism that may apply to many species worldwide.

scholarly journals Genetic architecture and lifetime dynamics of inbreeding depression in a wild mammal

2020 ◽  
Author(s):  
M.A. Stoffel ◽  
S.E. Johnston ◽  
J.G. Pilkington ◽  
J.M Pemberton
Keyword(s):  
Life History ◽  
Inbreeding Depression ◽  
Genetic Architecture ◽  
Rate Variation ◽  
Wild Mammal ◽  
Annual Survival ◽  
Soay Sheep ◽  
Genome Wide ◽  
A Genome ◽  
Recombination Rate Variation

AbstractInbreeding depression is a phenomenon of long-standing importance, but we know surprisingly little about its genetic architecture, precise effects and life-history dynamics in wild populations. Here, we combined 417K imputed SNP genotypes for 5952 wild Soay sheep with detailed long-term life-history data to explore inbreeding depression on a key fitness component, annual survival. Inbreeding manifests in long runs of homozygosity (ROH) and these are abundant in Soay sheep, covering on average 24% of the autosomal genome and up to 50% in the most inbred individuals. The ROH landscape is shaped by recombination rate variation and differs widely across the genome, including islands where up to 87% of the population have an ROH and deserts where the ROH prevalence is as low as 4%. We next quantified individual inbreeding as the proportion of the autosomal genome in ROH (FROH) and estimated its effect on annual survival. The consequences of inbreeding are severe; a 10% increase in FROH was associated with a 68% [95% CI 55-78%] decrease in the odds of survival. However, the strength of inbreeding depression is dynamic across the lifespan. We estimate depression to peak in young adults, to decrease into older ages and to be weaker in lambs, where inbreeding effects are possibly buffered by maternal care. Finally, using a genome-wide association scan on ROH, we show that inbreeding causes depression predominantly through many loci with small effects, but we also find three regions in the genome with putatively strongly deleterious mutations. Our study reveals population and genome-wide patterns of homozygosity caused by inbreeding and sheds light on the strength, dynamics and genetic architecture of inbreeding depression in a wild mammal population.

scholarly journals Using image-based haplotype alignments to map global adaptation of SARS-CoV-2

2021 ◽  
Author(s):  
Tom W. Ouellette ◽  
Jim Shaw ◽  
Philip Awadalla
Keyword(s):  
Deep Learning ◽  
Positive Selection ◽  
Population Genetic ◽  
Fold Increase ◽  
Evolutionary Change ◽  
Learning Methods ◽  
Viral Genomes ◽  
Evolutionary Inference ◽  
The Uk ◽  
Evolutionary Fitness

AbstractQuantifying evolutionary change among viral genomes is an important clinical device to track critical adaptations geographically and temporally. We built image-based haplotype-guided evolutionary inference (ImHapE) to quantify adaptations in expanding populations of non-recombining SARS-CoV-2 genomes. By combining classic population genetic summaries with image-based deep learning methods, we show that different rates of positive selection are driving evolutionary fitness and dispersal of SARS-CoV-2 globally. A 1.35-fold increase in evolutionary fitness is observed within the UK, associated with expansion of both the B.1.177 and B.1.1.7 SARS-CoV-2 lineages.

scholarly journals How Much Group is Necessary? Group-To-Individual Transfer in Estimation Tasks

2017 ◽  
Vol 3 (1) ◽  
Author(s):  
Alexander Stern ◽  
Thomas Schultze ◽  
Stefan Schulz-Hardt
Keyword(s):  
Quantitative Estimation ◽  
Group Interaction ◽  
Individual Performance ◽  
Differential Weighting ◽  
Nominal Groups ◽  
Population Bias ◽  
Individual Contributions ◽  
Group Members ◽  
Research Gap ◽  
Initial Interaction

G-I transfer denotes an increase in individual performance due to group interaction, for example, because of acquiring certain skills or knowledge from the other group members. Whereas such G-I transfer has been successfully shown for problem-solving tasks, evidence for G-I transfer on quantitative estimation tasks is scarce. We address this research gap with a focus on how often a group has to interact in order to fully exploit the benefit of this learning effect. Results from two experiments support the idea that a single group interaction is sufficient to induce a stable G-I transfer, which reduces group members’ metric error. Smaller metric errors indicate that people improved their representation of the correct upper and lower boundaries, or what range of values is plausible. In contrast to nominal groups, both members of continuously interacting groups and members of groups with only one initial interaction exhibited stable G-I transfer, and the size of this transfer did not significantly differ between the latter two conditions. Furthermore, we found evidence for differential weighting of group members’ individual contributions that goes beyond sheer individual capability gains under certain circumstances, namely in tasks with a population bias.

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