American Chemical Journal, February

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Comparison of Two Detailed Models of Aedes aegypti Population Dynamics

The success of control programs for mosquito-­borne diseases can be enhanced by crucial information provided by models of the mosquito populations. Models, however, can differ in their structure, complexity, and biological assumptions, and these differences impact their predictions. Unfortunately, it is typically difficult to determine why two complex models make different predictions because we lack structured side-­by-­side comparisons of models using comparable parameterization. Here, we present a detailed comparison of two complex, spatially explicit, stochastic models of the population dynamics of Aedes aegypti, the main vector of dengue, yellow fever, chikungunya, and Zika viruses. Both models describe the mosquito?s biological and ecological characteristics, but differ in complexity and specific assumptions. We compare the predictions of these models in two selected climatic settings: a tropical and weakly seasonal climate in Iquitos, Peru, and a temperate and strongly seasonal climate in Buenos Aires, Argentina. Both models were calibrated to operate at identical average densities in unperturbedconditions in both settings, by adjusting parameters regulating densities in each model (number of larval development sites and amount of nutritional resources). We show that the models differ in their sensitivityto environmental conditions (temperature and rainfall) and trace differences to specific model assumptions.Temporal dynamics of the Ae. aegypti populations predicted by the two models differ more markedly under strongly seasonal Buenos Aires conditions. We use both models to simulate killing of larvae and/or adults with insecticides in selected areas. We show that predictions of population recovery by the models differ substantially, an effect likely related to model assumptions regarding larval development and (director delayed) density dependence. Our methodical comparison provides important guidance for model improvement by identifying key areas of Ae. aegypti ecology that substantially affect model predictions, and revealing the impact of model assumptions on population dynamics predictions in unperturbed and perturbed conditions.Fil: Legros, Mathieu. University of North Carolina; Estados UnidosFil: Otero, Marcelo Javier. Universidad de Buenos Aires; ArgentinaFil: Romeo Aznar, Victoria Teresa. Universidad de Buenos Aires; ArgentinaFil: Solari, Hernan Gustavo. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Gould, Fred. National Institutes of Health; Estados UnidosFil: Lloyd, Alun L.. National Institutes of Health; Estados Unido

Fur seal microbiota are shaped by the social and physical environment, show mother‐offspring similarities and are associated with host genetic quality

Despite an increasing appreciation of the importance of host‐microbe interactions in ecological and evolutionary processes, the factors shaping microbial communities in wild populations remain poorly understood. We therefore exploited a natural experiment provided by two adjacent Antarctic fur seal (Arctocephalus gazella) colonies of high and low social density and combined 16S rRNA metabarcoding with microsatellite profiling of mother‐offspring pairs to investigate environmental and genetic influences on skin microbial communities. Seal‐associated bacterial communities differed profoundly between the two colonies, despite the host populations themselves being genetically undifferentiated. Consistent with the hypothesis that social stress depresses bacterial diversity, we found that microbial alpha diversity was significantly lower in the high‐density colony. Seals from one of the colonies that contained a stream also carried a subset of freshwater‐associated bacteria, indicative of an influence of the physical environment. Furthermore, mothers and their offspring shared similar microbial communities, in support of the notion that microbes may facilitate mother‐offspring recognition. Finally, a significant negative association was found between bacterial diversity and heterozygosity, a measure of host genetic quality. Our study thus uncovers a complex interplay between environmental and host genetic effects, while also providing empirical support for the leash model of host control, which posits that bacterial communities are driven not only by bottom‐up species interactions, but also by top‐down host regulation. Taken together, our findings have broad implications for understanding host‐microbe interactions as well as prokaryotic diversity in general

Complex population dynamics as a competition between multiple time-scale phenomena

The role of the selection pressure and mutation amplitude on the behavior of a single-species population evolving on a two-dimensional lattice, in a periodically changing environment, is studied both analytically and numerically. The mean-field level of description allows to highlight the delicate interplay between the different time-scale processes in the resulting complex dynamics of the system. We clarify the influence of the amplitude and period of the environmental changes on the critical value of the selection pressure corresponding to a phase-transition "extinct-alive" of the population. However, the intrinsic stochasticity and the dynamically-built in correlations among the individuals, as well as the role of the mutation-induced variety in population's evolution are not appropriately accounted for. A more refined level of description, which is an individual-based one, has to be considered. The inherent fluctuations do not destroy the phase transition "extinct-alive", and the mutation amplitude is strongly influencing the value of the critical selection pressure. The phase diagram in the plane of the population's parameters -- selection and mutation is discussed as a function of the environmental variation characteristics. The differences between a smooth variation of the environment and an abrupt, catastrophic change are also addressesd.Comment: 15 pages, 12 figures. Accepted for publication in Phys. Rev.

Prospects for Gene lntrogression from Hordeum bulbosum L. into Barley (H. vulgare L.).

Hybridizations between Hordeum vulgare L. (cultivated barley) and H. bulbosum L. have been performed over many years with two aims. First, the production of doubled haploid barley cultivars (Kasha and Kao 1970); second, the transfer of desirable traits such as resistance to fungal and viral pathogens from the wild species into barley. Apart from the report of an occasional recombinant (Xu and Kasha 1992; Pickering et al 1994), successful gene introgression has been hampered by several barriers. In this report we will describe recent progress in overcoming these barriers

China\u27s hegemonic intentions and trajectory: Will it opt for benevolent, coercive, or Dutch‐style hegemony?

China\u27s unprecedented economic growth led some scholars to conclude that it will replace the United States as the future global hegemon. However, China\u27s intentions in exercising future global leadership are yet unknown and difficult to extrapolate from its often contradictory behaviour. A preliminary overview of China\u27s island building in the South China Sea reveals its potentially coercive intentions. This inference is consistent with the analysis of those who prognosticate China\u27s violent rise. Conversely and simultaneously, China\u27s participation in peacekeeping operations and its global investments evince its benevolent hegemonic intentions, which are congruent with the argument of those who predict China\u27s peaceful hegemonic ascent. Confronted with these divergent tendencies in China\u27s recent international relations, and assuming its continued rise, it is, thus, essential to examine China\u27s strategic intentions and how these may ultimately project its violent or peaceful hegemonic rise. This article argues that the “Third Way” or “Dutch‐style” hegemony is highly instructive in this context and, thus, should be examined and added to the existing debate on China\u27s rise as either a benevolent or coercive hegemon. We argue that Dutch‐style hegemony may be the most viable way for China to proceed in its global hegemonic ascendancy

Mating patterns influence vulnerability to the extinction vortex

Earth's biodiversity is undergoing mass extinction due to anthropogenic compounding of environmental, demographic and genetic stresses. These different stresses can trap populations within a reinforcing feedback loop known as the extinction vortex, in which synergistic pressures build upon one another through time, driving down population viability. Sexual selection, the widespread evolutionary force arising from competition, choice and reproductive variance within animal mating patterns could have vital consequences for population viability and the extinction vortex: (a) if sexual selection reinforces natural selection to fix ‘good genes’ and purge ‘bad genes’, then mating patterns encouraging competition and choice may help protect populations from extinction; (b) by contrast, if mating patterns create load through evolutionary or ecological conflict, then population viability could be further reduced by sexual selection. We test between these opposing theories using replicate populations of the model insect Tribolium castaneum exposed to over 10 years of experimental evolution under monogamous versus polyandrous mating patterns. After a 95‐generation history of divergence in sexual selection, we compared fitness and extinction of monogamous versus polyandrous populations through an experimental extinction vortex comprising 15 generations of cycling environmental and genetic stresses. Results showed that lineages from monogamous evolutionary backgrounds, with limited opportunities for sexual selection, showed rapid declines in fitness and complete extinction through the vortex. By contrast, fitness of populations from the history of polyandry, with stronger opportunities for sexual selection, declined slowly, with 60% of populations surviving by the study end. The three vortex stresses of (a) nutritional deprivation, (b) thermal stress and (c) genetic bottlenecking had similar impacts on fitness declines and extinction risk, with an overall sigmoid decline in survival through time. We therefore reveal sexual selection as an important force behind lineages facing extinction threats, identifying the relevance of natural mating patterns for conservation management

Punctuated equilibria and 1/f noise in a biological coevolution model with individual-based dynamics

We present a study by linear stability analysis and large-scale Monte Carlo simulations of a simple model of biological coevolution. Selection is provided through a reproduction probability that contains quenched, random interspecies interactions, while genetic variation is provided through a low mutation rate. Both selection and mutation act on individual organisms. Consistent with some current theories of macroevolutionary dynamics, the model displays intermittent, statistically self-similar behavior with punctuated equilibria. The probability density for the lifetimes of ecological communities is well approximated by a power law with exponent near -2, and the corresponding power spectral densities show 1/f noise (flicker noise) over several decades. The long-lived communities (quasi-steady states) consist of a relatively small number of mutualistically interacting species, and they are surrounded by a ``protection zone'' of closely related genotypes that have a very low probability of invading the resident community. The extent of the protection zone affects the stability of the community in a way analogous to the height of the free-energy barrier surrounding a metastable state in a physical system. Measures of biological diversity are on average stationary with no discernible trends, even over our very long simulation runs of approximately 3.4x10^7 generations.Comment: 20 pages RevTex. Minor revisions consistent with published versio

Assessing the impact of university students’ involvement in the first year of Nurture-U: a national student wellbeing research project

This is the final version. Available on open access from BMC via the DOI in this recordAvailability of data and materials: Anonymised data is available from the corresponding author on reasonable request.Background Students experience lower levels of wellbeing than the general, age-matched population. A whole-university approach to mental health is encouraged, which must work for individuals from all backgrounds and experiences. Student input is vital in researching and designing these solutions. Nurture-U is a national, large-scale research project exploring better ways to support student wellbeing, with a Student Advisory Group (SAG) that feeds into project decision making. With the first year of the project now completed, we now critically review the processes and effectiveness of the SAG and how well the project is engaging and working with students. Methods Assessment of the SAG’s impact on the project, the student advisors, and the researchers was undertaken through a content analysis of team meetings and collection of advisor and researcher feedback using the Patient Engagement Quality Guidance Tool. Results 142 students worked on different tasks in the first year of the Nurture-U project. The SAG was involved in the project branding and marketing, and in the development and co-design of interventions and tools. They reported a positive experience, with involvement boosting confidence. They felt valued but reported not always knowing whether their input was implemented in final decisions. They also recommended different methods of providing feedback. Researchers found student input beneficial to communicate the viewpoint of a different generation and increase the relevance of the study, but also suggested improvements for communication between the research team and the student group. Conclusions This critical reflection of the SAG’s public advisor role in this large-scale research project was important in highlighting what worked well and areas to improve. As the project unfolds, we aim to adapt our methods of student input, increase the transparency of decision-making processes, and in turn increase student-led decision making within the project.Medical Research Council (MRC

Development and Initial Validation of a Self-Scored COPD Population Screener Questionnaire (COPD-PS)

COPD has a profound impact on daily life, yet remains underdiagnosed and undertreated. We set out to develop a brief, reliable, self-scored questionnaire to identify individuals likely to have COPD. COPD-PS™ development began with a list of concepts identified for inclusion using expert opinion from a clinician working group comprised of pulmonologists (n = 5) and primary care clinicians (n = 5). A national survey of 697 patients was conducted at 12 practitioner sites. Logistic regression identified items discriminating between patients with and without fixed airflow obstruction (AO, postbronchodilator FEV1/FVC < 70%). ROC analyses evaluated screening accuracy, compared scoring options, and assessed concurrent validity. Convergent and discriminant validity were assessed via COPD-PS and SF-12v2 score correlations. For known-groups validation, COPD-PS differences between clinical groups were tested. Test-retest reliability was evaluated in a 20% sample. Of 697 patients surveyed, 295 patients met expert review criteria for spirometry performance; 38% of these (n = 113) had results indicating AO. Five items positively predicted AO (p < 0.0001): breathlessness, productive cough, activity limitation, smoking history, and age. COPD-PS scores accurately classified AO status (area under ROC curve = 0.81) and reliable (r = 0.91). Patients with spirometry indicative of AO scored significantly higher (6.8, SD = 1.9; p < 0.0001) than patients without AO (4.0, SD = 2.3). Higher scores were associated with more severe AO, bronchodilator use, and overnight hospitalization for breathing problems. With the prevalence of COPD in the studied cohort, a score on the COPD-PS of greater than five was associated with a positive predictive value of 56.8% and negative predictive value of 86.4%. The COPD-PS accurately classified physician-reported COPD (AUC = 0.89). The COPD-PS is a brief, accurate questionnaire that can identify individuals likely to have COPD