Population Cycles Research Articles

Biology of Diapausing Population of Pink Bollworm <i>Pectinophora gossypiella</i> (Saunders)

This study on the comparative biology Pectinophora gossypiella (Saunders) was carried out at the University of Agricultural Sciences, Raichur, Karnataka, in insect rearing growth chamber (25 ± 1°C, 65 ± 5% RH and photoperiod of 14:10 hr, L: D) during 2018-19. The results revealed that the incubation period was 3.5 ± 0.82 and 3.05 ± 0.55 days in non-diapausing and diapausing populations, respectively; a total larval period of 18.60 ± 2.28 and 19.65 ± 1.53 days, respectively was observed without any significant difference; and adult longevity of male and female was 9.05 ± 0.55 and 9.55 ± 0.83 days, respectively in non-diapausing population, while in diapausimg population it was 9.75 ± 0.26 and 10.25 ± 0.43 days. Total life cycle of non-diapausing population was significantly shorter (42.85 ± 4.99 days) as compared to diapausing one (134.3 ± 12.91 days) with fecundity of 112.34 ± 10.31 and 104.54 ± 9.96 eggs, respectively. The longer lifecycle of diapausing population was due to long resting diapausing period ranging from 72 to 108 days.

P16INK4A-dependent senescence in the bone marrow niche drives age-related metabolic changes of hematopoietic progenitors

AbstractRapid and effective leukocyte response to infection is a fundamental function of the bone marrow (BM). However, with increasing age, this response becomes impaired, resulting in an increased burden of infectious diseases. Here, we investigate how aging changes the metabolism and function of hematopoietic progenitor cells (HPCs) and the impact of the BM niche on this phenotype. We found that, in response to lipopolysaccharide-induced stress, HPC mitochondrial function is impaired, and there is a failure to upregulate the TCA cycle in progenitor populations in aged animals compared with young animals. Furthermore, aged mesenchymal stromal cells (MSCs) of the BM niche, but not HPCs, exhibit a senescent phenotype, and selective depletion of senescent cells from the BM niche, as well as treatment with the senolytic drug ABT-263, improves mitochondrial function of HPCs when stressed with lipopolysaccharide. In summary, age-related HPC metabolic dysfunction occurs indirectly as a “bystander phenomenon” in the aging BM niche and can be restored by targeting senescent MSCs.

How does genetic architecture affect eco-evolutionary dynamics? A theoretical perspective.

Recent studies have revealed the importance of feedbacks between contemporary rapid evolution (i.e. evolution that occurs through changes in allele frequencies) and ecological dynamics. Despite its inherent interdisciplinary nature, however, studies on eco-evolutionary feedbacks have been mostly ecological and tended to focus on adaptation at the phenotypic level without considering the genetic architecture of evolutionary processes. In empirical studies, researchers have often compared ecological dynamics when the focal species under selection has a single genotype with dynamics when it has multiple genotypes. In theoretical studies, common approaches are models of quantitative traits where mean trait values change adaptively along the fitness gradient and Mendelian traits with two alleles at a single locus. On the other hand, it is well known that genetic architecture can affect short-term evolutionary dynamics in population genetics. Indeed, recent theoretical studies have demonstrated that genetic architecture (e.g. the number of loci, linkage disequilibrium and ploidy) matters in eco-evolutionary dynamics (e.g. evolutionary rescue where rapid evolution prevents extinction and population cycles driven by (co)evolution). I propose that theoretical approaches will promote the synthesis of functional genomics and eco-evolutionary dynamics through models that combine population genetics and ecology as well as nonlinear time-series analyses using emerging big data.This article is part of the theme issue ‘Genetic basis of adaptation and speciation: from loci to causative mutations’.

Variability in Arrival Time of White Storks (Ciconia ciconia L.): Impact of Age, Interindividual Variation, and Global Change

Global changes are inducing migratory birds to advance their annual cycle. However, changes in the time of arrival at their breeding grounds have significant fitness implications. This study aims to identify factors affecting the variability in arrival time of migratory white storks (Ciconia ciconia L.) and to determine if their arrival at North African breeding grounds is occurring earlier. We monitored the arrival of ringed white storks at a breeding colony in Algeria between 2017 and 2021. The birds arrived at this breeding colony over an extended period spanning mid-December to mid-June each year. We found that stork arrival was negatively correlated with age and year of arrival, with older birds arriving first and stragglers consisting of first- and second-year birds arriving later. Notably, arrivals have been shifting toward earlier dates at this breeding ground. Furthermore, cluster analysis of arrival dates for each age-class revealed two distinct groups comprising early and late arrivals. Advancement of the annual cycle of the North African white stork population is consistent with phenological shifts induced by global changes and that have been recorded globally in a wide range of living organisms.

Boom and bust cycles of black-tailed prairie dog populations in the Thunder Basin grassland ecosystem

AbstractBlack-tailed prairie dogs (Cynomys ludovicianus) exhibit boom and bust cycles in landscapes where they are affected by outbreaks of plague caused by the introduced bacterium Yersinia pestis. We examined spatiotemporal dynamics of black-tailed prairie dog colonies in the Thunder Basin National Grassland, Wyoming over a period of 21 years. The colony complex experienced three plague epizootics during that time, and consequently three boom and bust cycles. The entire prairie dog colony complex collapsed over a 1-year period during the first and third epizootics, and over a 3-year period during the second epizootic. The boom and bust cycles were characterized by relatively rapid contractions in total area occupied by prairie dogs during a plague outbreak (e.g., >99% decline from 10,604 ha to 47 ha over 1 year [2017–2018]) followed by much slower recovery times (e.g., an increase from 410 ha to 10,604 ha over 11 years [2006–2017]). Prairie dogs occupied a total of 10,604 ha during at least one survey within the study period, but much of the area was not continuously occupied over time. We found that each of the three plague outbreaks occurred in years with highly connected prairie dog colonies and slightly above-average temperatures and summer precipitation, which were preceded by a dry year. Although plague outbreaks were associated with climatic conditions, we were unable to detect a role of climate in driving colony expansion. Our results illustrate the cyclic and extreme nature of fluctuations in black-tailed prairie dog colony size and distribution in a landscape where plague occurs and illuminate some of the drivers of these cycles. Further, our work shows how introduced diseases can dramatically influence populations of a keystone species, with important consequences for the broader ecological system.

Distribution Characteristics of Soil Viruses Under Different Precipitation Gradients on the Qinghai-Tibet Plateau.

Viruses are extremely abundant in the soil environment and have potential roles in impacting on microbial population, evolution, and nutrient biogeochemical cycles. However, how environment and climate changes affect soil viruses is still poorly understood. Here, a metagenomic approach was used to investigate the distribution, diversity, and potential biogeochemical impacts of DNA viruses in 12 grassland soils under three precipitation gradients on the Qinghai-Tibet Plateau, which is one of the most sensitive areas to climate change. A total of 557 viral operational taxonomic units were obtained, spanning 152 viral families from the 30 metagenomes. Both virus-like particles (VLPs) and microbial abundance increased with average annual precipitation. A significant positive correlation of VLP counts was observed with soil water content, total carbon, total nitrogen, soil organic matter, and total phosphorus. Among these biological and abiotic factors, SWC mainly contributed to the variability in VLP abundance. The order Caudovirales (70.1% of the identified viral order) was the predominant viral type in soils from the Qinghai-Tibet Plateau, with the Siphoviridae family being the most abundant. Remarkably, abundant auxiliary carbohydrate-active enzyme (CAZyme) genes represented by glycoside hydrolases were identified, indicating that soil viruses may play a potential role in the carbon cycle on the Qinghai-Tibet Plateau. There were more diverse hosts and abundant CAZyme genes in soil with moderate precipitation. Our study provides a strong evidence that changes in precipitation impact not only viral abundance and virus–host interactions in soil but also the viral functional potential, especially carbon cycling.

Gametogenic cycle of the marine gastropod Trophon geversianus in a harsh Patagonian intertidal environment

ABSTRACT The edible marine gastropod Trophon geversianus shows a large geographic distribution along the southern tip of South America, inhabiting both rocky intertidal and shallow subtidal zones, with distinct behavioural responses to environmental stressful conditions (desiccation, temperature amplitude and high irradiation). Nevertheless, its reproductive biology has been poorly reported to date. We studied the gametogenic cycle of an intertidal rocky shore population from northern Patagonia (Argentina), in order to investigate the relation between gonadal changes and seasonal environmental variables. Mature individuals were taken monthly during an annual reproductive season and processed by standard histology procedures (haematoxylin and eosin). Adults of T. geversianus registered different gonadal maturation stages along the year, showing a marked seasonal variation without a resting period. The highest gamete evacuation season in both sexes was registered when the environmental stress was minimum (winter), while a greater number of individuals with gonads in proliferation and growth were predominant during maximum environmental stress (summer). The reproduction pattern presented an extended period of evacuation and a short phase of non-evacuation, associated to drastic seasonal environmental changes in the intertidal zone of Atlantic Patagonia. This information is useful to protect the resource and assure the sustainability of intertidal populations.

Host in reserve: The role of common shrews (Sorex araneus) as a supplementary source of tick hosts in small mammal communities influenced by rodent population cycles.

Rodents often act as important hosts for ticks and as pathogen reservoirs. At northern latitudes, rodents often undergo multi‐annual population cycles, and the periodic absence of certain hosts may inhibit the survival and recruitment of ticks. We investigated the potential role of common shrews (Sorex araneus) to serve as a supplementary host source to immature life stages (larvae and nymphs) of a generalist tick Ixodes ricinus and a small mammal specialist tick I. trianguliceps, during decreasing abundances of bank voles (Myodes glareolus). We used generalized mixed models to test whether ticks would have a propensity to parasitize a certain host species dependent on host population size and host population composition across two high‐latitude gradients in southern Norway, by comparing tick burdens on trapped animals. Host population size was defined as the total number of captured animals and host population composition as the proportion of voles to shrews. We found that a larger proportion of voles in the host population favored the parasitism of voles by I. ricinus larvae (estimate = −1.923, p = .039) but not by nymphs (estimate = −0.307, p = .772). I. trianguliceps larvae did not show a lower propensity to parasitize voles, regardless of host population composition (estimate = 0.875, p = .180), while nymphs parasitized shrews significantly more as vole abundance increased (estimate = 2.106, p = .002). These results indicate that common shrews may have the potential to act as a replacement host during periods of low rodent availability, but long‐term observations encompassing complete rodent cycles may determine whether shrews are able to maintain tick range expansion despite low rodent availability.

Isotopic niche partitioning and individual specialization in an Arctic raptor guild

Intra- and inter-specific resource partitioning within predator communities is a fundamental component of trophic ecology, and one proposed mechanism for how populations partition resources is through individual niche variation. The Niche Variation Hypothesis (NVH) predicts that inter-individual trait variation leads to functional trade-offs in foraging efficiency, resulting in populations composed of individual dietary specialists. The degree to which niche specialization persists within a population is plastic and responsive to fluctuating resource availability. We quantified niche overlap and tested the NVH within an Arctic raptor guild, focusing on three species that employ different foraging strategies: golden eagles (generalists); gyrfalcons (facultative specialists); and rough-legged hawks (specialists). Tundra ecosystems exhibit cyclic populations of arvicoline rodents (lemmings and voles), providing a unique system in which to examine predator diet in response to interannual fluctuations in resource availability. Using blood δ13C and δ15N values from 189 raptor nestlings on Alaska's Seward Peninsula (2014-2019), we calculated isotopic niche width and used Bayesian stable isotope mixing models (BSIMMs) to characterize individual specialization and test the NVH. Nest-level specialization estimated from stable isotopes was strongly correlated with indices of specialization based on camera trap data. We observed a high degree of isotopic niche overlap between the three species and gyrfalcons displayed a positive relationship between individual specialization and population niche width on an interannual basis consistent with the NVH. Our findings suggest plasticity in niche specialization may reduce intra- and inter-specific resource competition under dynamic ecological conditions.

Inter-annual fluctuations of sociability in the common shrew (Sorex araneus L.) as determined by a preference test: A case of balancing selection?

The specific aim of our study was to test individual common shrews from a population monitored long-term. In a preference test, we revealed sex-related differences in behavioral traits of young common shrews and consistent individual differences in sociability, boldness and in an exploration pattern that have not been reported previously. More active animals were bolder and more superficial in the exploration of non-social objects as compared to shier shrews. Significant inter-annual differences in sociability, boldness and exploratory activity were observed. When we assessed correlations of sociability with population density, non-residents’ abundance, activity shared in space, survivorship and home range size, we found a positive association with shared spatial activity and home range size. Contrary to expectation, sociability did not correlate with the density of residents and survivorship. A significant negative association of sociability with non-residents’ abundance was documented. Survivorship was associated only with an exploration pattern. The thoroughness of exploration positively correlated with non-residents’ abundance. We regard the inter-annual changes in sociability that we observed in the test as a by-product of survival of shrews with various exploration patterns that are associated with dispersal. We can hypothesize that the personality differences registered in this study are maintained by balancing frequency-dependent selection of animals that is associated with differences in habitat quality throughout the population cycle.

The regulating effect of growth plasticity on the dynamics of structured populations

Plasticity is the extent to which life history processes such as growth and reproduction depend on the environment. Plasticity in individual growth varies widely between taxa. Nonetheless, little is known about the effect of plasticity in individual growth on the ecological dynamics of populations. In this article, we analyse a physiologically structured population model of a consumer population in which the individual growth rate can be varied between entirely plastic to entirely non-plastic. We derive this population level model from a dynamic energy budget model to ensure an accurate energetic coupling between ingestion, somatic maintenance, growth and reproduction within an individual. We show that the consumer population is either limited by adult fecundity or juvenile survival up to maturation, depending on the level of growth plasticity and the non-plastic individual growth rate. Under these two regimes, we also find two different types of population cycles which again arise due to fluctuation in, respectively, juvenile growth rate or adult fecundity. In the end, our model not only provides insight into the effects of growth plasticity on population dynamics, but also provides a link between the dynamics found in age- and size-structured models.

ACCESS TO HEALTHCARE SERVICES AMONG SYRIAN REFUGEES IN TURKEY

The Syrian population influx has dislocated a significant number of people (6.7 million of people outside the Syrian borders, 6.5 million of people among the different provinces of Syria). The biggest group among this moving population between borders has integrated into the Turkish society, and economy. From the macro and micro perspectives, the health system integration is significantly graded by the Syrian population. We will focus on the early age group, among the refugees, as their health vulnerabilities, and health improvements will create much larger effects throughout their lifetime. What we aim in this paper is to bring forward an objective micro-level outcome that will allow us to measure two things that was crucial in the life cycle of the refugee population: the war effect which will create a push factor for them to start moving, and an integration effect which will measure the time-continuous, and time-discrete increase in their health outcomes, as a result of relatively cost-free integration into a more developed health system. The Demographic Health Survey (DHS) 2018 data that we utilize gives us an empirical advantage for identification for two reasons; it differentiates the health outcome of children, in multi-child families depending on where they were born, which we will call an intra-Syrian effect, and it allows us to compare the situation of the Syrian children vis-a-vis the average child health outcomes in the society they are integrating into (what we call the inter-Syrian effect). The results suggest that Syrians remain underneath the Turkish average, for many early child development, and vital health access, however, after integration significant positive developments occur, in terms of compensating for the negative war effect, and in terms of the second effect (integration/adaptation effect) that they have started to converge to the Turkish average, as they have spent more years in Turkey.

What is the optimum number of follicular flushes in mono-follicular in-vitro fertilization cycles in a poor responder population?

Objective:Assessment of the optimal number of follicular flushes on retrieval rate and quality of oocytes in mono-follicular in-vitro fertilization (IVF) cycles.Material and Methods:A retrospective analysis of 246 oocyte pick-up procedures in mono-follicular IVF cycles of 226 poor responder women was performed. The primary endpoint was oocyte retrieval rate in the initial aspirate versus subsequent flushing episodes. The secondary endpoints were oocyte maturity, fertilization rates and embryo cleavage.Results:The procedure was successful in 187 cycles (76%), of which 160 metaphase-II oocytes were retrieved. Retrieval rates were similar for natural and modified natural cycles (p=0.595). The initial aspirate provided 54% of the total yield and the rest was obtained from up to four episodes of flushing. Follicular flushing increased oocyte recovery rate from 41.1% to 76%. None of the oocytes retrieved after three flushes fertilized. Oocyte maturity, fertilization and embryo cleavage rates were comparable for oocytes from the initial aspirate and one or two episodes of flushing. Oocytes obtained after the third flushing episode developed into poor quality embryos.Conclusion:Flushing confers a benefit for oocyte recover rates in mono-follicular IVF cycles in poor responder women. However, more than three attempts at flushing were not associated with good outcome.

Host phenology regulates parasite-host demographic cycles and eco-evolutionary feedbacks.

Parasite–host interactions can drive periodic population dynamics when parasites overexploit host populations. The timing of host seasonal activity, or host phenology, determines the frequency and demographic impact of parasite–host interactions, which may govern whether parasites sufficiently overexploit hosts to drive population cycles. We describe a mathematical model of a monocyclic, obligate‐killer parasite system with seasonal host activity to investigate the consequences of host phenology on host–parasite dynamics. The results suggest that parasites can reach the densities necessary to destabilize host dynamics and drive cycling as they adapt, but only in some phenological scenarios such as environments with short seasons and synchronous host emergence. Furthermore, only parasite lineages that are sufficiently adapted to phenological scenarios with short seasons and synchronous host emergence can achieve the densities necessary to overexploit hosts and produce population cycles. Host‐parasite cycles also generate an eco‐evolutionary feedback that slows parasite adaptation to the phenological environment as rare advantageous phenotypes can be driven extinct due to a population bottleneck depending on when they are introduced in the cycle. The results demonstrate that seasonal environments can drive population cycling in a restricted set of phenological patterns and provide further evidence that the rate of adaptive evolution depends on underlying ecological dynamics.

Temporal and spatial topography of cell proliferation in cancer.

Proliferation is a fundamental trait of cancer cells but its properties and spatial organization in tumors are poorly characterized. Here we use highly multiplexed tissue imaging to perform single-cell quantification of cell cycle regulators and then develop robust, multivariate, proliferation metrics. Across diverse cancers, proliferative architecture is organized at two spatial scales: large domains, and smaller niches enriched for specific immune lineages. Some tumor cells express cell cycle regulators in the (canonical) patterns expected of freely growing cells, a phenomenon we refer to as “cell cycle coherence”. By contrast, the cell cycles of other tumor cell populations are skewed toward specific phases or exhibit non-canonical (incoherent) marker combinations. Coherence varies across space, with changes in oncogene activity and therapeutic intervention, and is associated with aggressive tumor behavior. Thus, multivariate measures from high-plex tissue images capture clinically significant features of cancer proliferation, a fundamental step in enabling more precise use of anti-cancer therapies.

A vicious cycle of health (in)equity: Migrant inclusion in light of COVID-19

ObjectivesWhilst mass vaccination is suggested as an important means to contain COVID-19 pandemic, vaccination policies across many countries have systematically excluded some groups of population, especially migrants. This study aims to document the impact of diversified vaccination strategies as a preventative and control measure for the health and safety of the wider population within a country. MethodsWe selected five countries that have experienced the changes in migrant inflows to the most extreme among OECD countries in 2020: The United States, Australia, Canada, Japan, and South Korea. We conducted an extensive qualitative documentary analysis focused on policies and interventions implemented in these countries since January 2020 till the end of September 2021. We also analyzed publicly available epidemiological data (released by the governments and other international organizations). ResultsWe find that achieving migrants’ health and vaccination equity is not without challenges, and a failure to address those multiplicity of concerns may result in a vicious cycle for the vulnerable population at the fringes of our economy. Migrants continue to face extenuating circumstances with higher risks to their health and safety, when they are excluded or disadvantaged in vaccination policies. The more inclusive and proactive the governments are in consideration of diversity of migrant populations, the better they can manage the pandemic, which leads to overall societal benefit of ensuring public health. ConclusionsEquity-based policies can mitigate disparities in access to vaccination and healthcare, thereby reducing the spread of COVID-19 in the community.

Resources and predation: drivers of sociality in a cyclic mesopredator

In socially flexible species, the tendency to live in groups is expected to vary through a trade-off between costs and benefits, determined by ecological conditions. The Resource Dispersion Hypothesis predicts that group size changes in response to patterns in resource availability. An additional dimension is described in Hersteinsson’s model positing that sociality is further affected by a cost–benefit trade-off related to predation pressure. In the arctic fox (Vulpes lagopus), group-living follows a regional trade-off in resources’ availability and intra-guild predation pressure. However, the effect of local fluctuations is poorly known, but offers an unusual opportunity to test predictions that differ between the two hypotheses in systems where prey availability is linked to intra-guild predation. Based on 17-year monitoring of arctic fox and cyclic rodent prey populations, we addressed the Resource Dispersion Hypothesis and discuss the results in relation to the impact of predation in Hersteinsson’s model. Group-living increased with prey density, from 7.7% (low density) to 28% (high density). However, it remained high (44%) despite a rodent crash and this could be explained by increased benefits from cooperative defence against prey switching by top predators. We conclude that both resource abundance and predation pressure are factors underpinning the formation of social groups in fluctuating ecosystems.

Ecological potential of pasture ecosystems of desolate steppes in the conservation of the saiga population of the NorthWestern Caspian Sea

The destruction of natural ecosystem resulting in reduction or even destruction of saiga habitat is the consequence of anthropogenic impact. The degradation of pasture ecosystem in Kalmykia reached a crucial level and the republic was announced as the disaster zone in 1988. The year 1998 witnessed the reduction of saiga population size from 220 thousand to 55 thousand animals. Registration works in 2014 showed further reduction of saiga to 12 thousand- 12.8 thousand animals. In general, the population of saiga in the North-Western Caspian region continues to be in depression despite low losses of new born saiga (6.2%). The degradation of pastures led to the next stage of population cycle characterized by lower reproduction ability of animals and high level of mortality. This process deteriorates due to worse living conditions during some seasons as well as by decreasing the ability of pastures to give feed.

The ecology of infectious diseases: an homage to multi-factor perspectives

Decades ago, a multi-factor perspective offered valuable insights into the causes of population cycles in arvicoline (= microtine) rodents. Multi-factor perspectives are also critical for understanding the ecology of infectious diseases. Here, we provide examples of how these perspectives inform our ability to predict variation in disease risk through space and time. We focus in particular on the evidence that many emerging zoonotic pathogens of humans have multiple hosts rather than just one, that most host species harbor more than one pathogen and that these pathogens interact, and that understanding variation in the abundance of species that transmit pathogens often requires deep exploration of the ecological community in which those hosts are embedded.

Simple deterministic modeling can guide the design of breeding pipelines for self‐pollinated crops

AbstractGenetic gains delivered by plant breeding programs in the developing world must increase to deliver adaptation to a changing climate. Programs should be planned and optimized, with respect to gains per year and per dollar invested, as cyclic population improvement pipelines whose selection response is described by the breeder's equation (BE). We present a spreadsheet‐implemented model for the BE that includes operating costs. The model can be easily used to compare predicted selection response per cycle for different pipeline designs and resource allocation scenarios for self‐pollinated crops or hybrid crops that use inbred lines as parents. We modeled breeding programs that generate and select among F2– to F6–derived or doubled‐haploid (DH) lines, advance populations from one to three generations annually, and conduct agronomic testing in one to three stages during the main cropping season. Reducing cycle time is the most efficient method of increasing genetic gain under most circumstances. Although gains increase with increased population size and selection intensity, clear optima exist, in terms of the cost of a unit of gain, at relatively small population sizes and moderate selection intensities. Investments in reducing cycle length to three or even two years generate large increases in genetic gain and are more cost‐effective than increasing population size and standardized selection differential. High rates of genetic gain can be delivered by small breeding programs that complete cycles quickly.