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The Journal of Animal Ecology Nov 2022Harvest of wild organisms is an important component of human culture, economy, and recreation, but can also put species at risk of extinction. Decisions that guide...
Harvest of wild organisms is an important component of human culture, economy, and recreation, but can also put species at risk of extinction. Decisions that guide successful management actions therefore rely on the ability of researchers to link changes in demographic processes to the anthropogenic actions or environmental changes that underlie variation in demographic parameters. Ecologists often use population models or maximum sustained yield curves to estimate the impacts of harvest on wildlife and fish populations. Applications of these models usually focus exclusively on the impact of harvest and often fail to consider adequately other potential, often collinear, mechanistic drivers of the observed relationships between harvest and demographic rates. In this study, we used an integrated population model and long-term data (1973-2016) to examine the relationships among hunting and natural mortality, the number of hunters, habitat conditions, and population size of blue-winged teal Spatula discors, an abundant North American dabbling duck with a relatively fast-paced life history strategy. Over the last two and a half decades of the study, teal abundance tripled, hunting mortality probability increased slightly ( ), and natural mortality probability increased substantially ( ) at greater population densities. We demonstrate strong density-dependent effects on natural mortality and fecundity as population density increased, indicative of compensatory harvest mortality and compensatory natality. Critically, an analysis that only assessed the relationship between survival and hunting mortality would spuriously indicate depensatory mortality due to multicollinearity between abundance, natural mortality and hunting mortality. Our findings demonstrate that models that only consider the direct effect of hunting on survival or natural mortality can fail to accurately assess the mechanistic impact of hunting on population dynamics due to multicollinearity among demographic drivers. This multicollinearity limits inference and may have strong impacts on applied management actions globally.
Topics: Animals; Humans; Conservation of Natural Resources; Ducks; Fishes; Population Density; Population Dynamics; Hunting; Animals, Wild
PubMed: 36054772
DOI: 10.1111/1365-2656.13807 -
MBio Jun 2022Quorum sensing (QS) is a mechanism of cell-cell communication that connects gene expression to environmental conditions (e.g., cell density) in many bacterial species,...
Quorum sensing (QS) is a mechanism of cell-cell communication that connects gene expression to environmental conditions (e.g., cell density) in many bacterial species, mediated by diffusible signal molecules. Current functional studies focus on qualitatively distinct QS ON/OFF states. In the context of density sensing, this view led to the adoption of a "quorum" analogy in which populations sense when they are above a sufficient density (i.e., "quorate") to efficiently turn on cooperative behaviors. This framework overlooks the potential for intermediate, graded responses to shifts in the environment. In this study, we tracked QS-regulated protease () expression and showed that Pseudomonas aeruginosa can deliver a graded behavioral response to fine-scale variation in population density, on both the population and single-cell scales. On the population scale, we saw a graded response to variation in population density (controlled by culture carrying capacity). On the single-cell scale, we saw significant bimodality at higher densities, with separate OFF and ON subpopulations that responded differentially to changes in density: a static OFF population of cells and increasing intensity of expression among the ON population of cells. Together, these results indicate that QS can tune gene expression to graded environmental change, with no critical cell mass or "quorum" at which behavioral responses are activated on either the individual-cell or population scale. In an infection context, our results indicate there is not a hard threshold separating a quorate "attack" mode from a subquorate "stealth" mode. Bacteria can be highly social, controlling collective behaviors via cell-cell communication mechanisms known as quorum sensing (QS). QS is now a large research field, yet a basic question remains unanswered: what is the environmental resolution of QS? The notion of a threshold, or "quorum," separating coordinated ON and OFF states is a central dogma in QS, but recent studies have shown heterogeneous responses at a single cell scale. Using Pseudomonas aeruginosa, we showed that populations generate graded responses to environmental variation through shifts in the proportion of cells responding and the intensity of responses. In an infection context, our results indicate that there is not a hard threshold separating a quorate "attack" mode and a subquorate "stealth" mode.
Topics: Bacteria; Gene Expression Regulation, Bacterial; Population Density; Pseudomonas aeruginosa; Quorum Sensing
PubMed: 35583321
DOI: 10.1128/mbio.00745-22 -
Proceedings of the National Academy of... Mar 2023The concept of fitness is central to evolution, but it quantifies only the expected number of offspring an individual will produce. The actual number of offspring is...
The concept of fitness is central to evolution, but it quantifies only the expected number of offspring an individual will produce. The actual number of offspring is also subject to demographic stochasticity-that is, randomness associated with birth and death processes. In nature, individuals who are more fecund tend to have greater variance in their offspring number. Here, we develop a model for the evolution of two types competing in a population of nonconstant size. The fitness of each type is determined by pairwise interactions in a prisoner's dilemma game, and the variance in offspring number depends upon its mean. Although defectors are preferred by natural selection in classical population models, since they always have greater fitness than cooperators, we show that sufficiently large offspring variance can reverse the direction of evolution and favor cooperation. Large offspring variance produces qualitatively new dynamics for other types of social interactions, as well, which cannot arise in populations with a fixed size or with a Poisson offspring distribution.
Topics: Humans; Cooperative Behavior; Game Theory; Population Dynamics; Population Density; Selection, Genetic
PubMed: 36927152
DOI: 10.1073/pnas.2216218120 -
Ciencia & Saude Coletiva Nov 2022This paper describes the structure and results of Primary Health Care (PHC) in Brazil between 2008 and 2019. The medians of the following variables were calculated: PHC...
This paper describes the structure and results of Primary Health Care (PHC) in Brazil between 2008 and 2019. The medians of the following variables were calculated: PHC spending per inhabitant covered, PHC coverage, and rates of mortality and hospitalizations due to primary care sensitive conditions (PCSC), in 5,565 Brazilian municipalities stratified according to population size and quintile of the Brazilian Deprivation Index (IBP), and the median trend in the period was analyzed. There was a 12% increase in median PHC spending. PHC coverage expanded, with 3,168 municipalities presenting 100% coverage in 2019, compared to 2,632 in 2008. The median rates of PCSC mortality and hospitalizations increased 0.2% and decreased 44.9%, respectively. PHC spending was lower in municipalities with greater socioeconomic deprivation. The bigger the population and the better the socioeconomic conditions were in the municipalities, the lower the PHC coverage. The greater the socioeconomic deprivation was in the municipalities, the higher the median PCSC mortality rates. This study showed that the evolution of PHC was heterogeneous and is associated both with the population size and with the socioeconomic conditions of the municipalities.
Topics: Humans; Brazil; Primary Health Care; Hospitalization; Cities; Population Density; Socioeconomic Factors
PubMed: 36259849
DOI: 10.1590/1413-812320222711.02272022 -
Current Biology : CB Jul 2020Population density can modulate the developmental trajectory of Caenorhabditis elegans larvae by promoting entry into dauer diapause, which is characterized by metabolic...
Population density can modulate the developmental trajectory of Caenorhabditis elegans larvae by promoting entry into dauer diapause, which is characterized by metabolic and anatomical remodeling and stress resistance [1, 2]. Genetic analysis of dauer formation has identified the involvement of evolutionarily conserved endocrine signaling pathways, including the DAF-2/insulin-like receptor signaling pathway [3-7]. Chemical and metabolomic analysis of dauer-inducing pheromone has identified a family of small molecules, ascarosides, which act potently to communicate increased population density and promote dauer formation [1, 8-10]. Here, we show that adult animals respond to ascarosides produced under conditions of increased population density by increasing the duration of reproduction. We observe that the ascarosides that promote dauer entry of larvae also act on adult animals to attenuate expression of the insulin peptide INS-6 from the ASI chemosensory neurons, resulting in diminished neuroendocrine insulin signaling that extends the duration of reproduction. Genetic analysis of ins-6 and corresponding insulin-signaling pathway mutants showed that the effect of increased population density on reproductive span was mimicked by ins-6 loss of function that exerted effects on duration of reproduction through the canonical DAF-2-DAF-16 pathway. We further observed that the effect of population density on reproductive span acted through DAF-16-dependent and DAF-16-independent pathways upstream of DAF-12, paralleling in adults what has been observed for the dauer developmental decision of larvae. Our data suggest that, under conditions of increased population density, C. elegans animals prolong the duration of reproductive egg laying, which may enable the subsequent development of progeny under more favorable conditions.
Topics: Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Insulin; Population Density; Reproduction; Sex Attractants; Signal Transduction
PubMed: 32442457
DOI: 10.1016/j.cub.2020.04.056 -
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 -
Nature Communications Feb 2022The spread of dengue and other arboviruses constitutes an expanding global health threat. The extensive heterogeneity in population distribution and potential complexity...
The spread of dengue and other arboviruses constitutes an expanding global health threat. The extensive heterogeneity in population distribution and potential complexity of movement in megacities of low and middle-income countries challenges predictive modeling, even as its importance to disease spread is clearer than ever. Using surveillance data at fine resolution from Rio de Janeiro, we document a scale-invariant pattern in the size of successive epidemics following DENV4 emergence. Using surveillance data at fine resolution following the emergence of the DENV4 dengue serotype in Rio de Janeiro, we document a pattern in the size of successive epidemics that is invariant to the scale of spatial aggregation. This pattern emerges from the combined effect of herd immunity and seasonal transmission, and is strongly driven by variation in population density at sub-kilometer scales. It is apparent only when the landscape is stratified by population density and not by spatial proximity as has been common practice. Models that exploit this emergent simplicity should afford improved predictions of the local size of successive epidemic waves.
Topics: Brazil; Dengue; Epidemics; Humans; Population Density; Serogroup
PubMed: 35194017
DOI: 10.1038/s41467-022-28231-w -
Philosophical Transactions of the Royal... Mar 2023Distributed adaptations are cases in which adaptation is dependent on the population as a whole: the adaptation is conferred by a structural or compositional aspect of...
Distributed adaptations are cases in which adaptation is dependent on the population as a whole: the adaptation is conferred by a structural or compositional aspect of the population; the adaptively relevant information cannot be reduced to information possessed by a single individual. Possible examples of human-distributed adaptations are song lines, traditions, trail systems, game drive lanes and systems of water collection and irrigation. Here we discuss the possible role of distributed adaptations in human cultural macro-evolution. Several kinds of human-distributed adaptations are presented, and their evolutionary implications are highlighted. In particular, we discuss the implications of population size, density and bottlenecks on the distributed adaptations that a population may possess and how they in turn would affect the population's resilience to ecological change. We discuss the implications that distributed adaptations may have for human collective action and the possibility that they played a role in colonization of new areas and niches, in seasonal migration, and in setting constraints for minimal inter-population connectivity. This article is part of the theme issue 'Human socio-cultural evolution in light of evolutionary transitions'.
Topics: Humans; Adaptation, Physiological; Biological Evolution; Acclimatization; Population Density; Cultural Evolution
PubMed: 36688390
DOI: 10.1098/rstb.2021.0401 -
Proceedings. Biological Sciences Jan 2023For decades, biogeographers have sought a better understanding of how organisms are distributed among islands. However, the island biogeography of humans remains largely...
For decades, biogeographers have sought a better understanding of how organisms are distributed among islands. However, the island biogeography of humans remains largely unknown. Here, we investigate how human population size varies among 486 islands at two spatial scales. At a global scale, we tested whether population size increases with island area and declines with island elevation and nearest mainland, as is common in non-human species, or whether humans escape such biogeographic constraints. At a regional scale, we tested whether population sizes vary among islands within archipelagos according to the positioning of different cultural source pools. Results illustrate that on a global scale, human populations increased in size with island area, similar to non-human species, yet they did not decline in size with elevation and distance to nearest mainland. At a regional scale, human population size often varied among islands within archipelagos relative to the location of different cultural source pools. Despite broad-scale similarities in the geographical distribution of human and non-human species among islands, results from this study indicate that the island biogeography of humans may also be influenced by archipelago-specific social, political and historical circumstances.
Topics: Humans; Islands; Biodiversity; Population Density
PubMed: 36651052
DOI: 10.1098/rspb.2022.2084