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PeerJ 2023The Pollard-Yates transect is a widely used method for sampling butterflies. Data from these traditional transects are analyzed to produce density estimates, which are...
The Pollard-Yates transect is a widely used method for sampling butterflies. Data from these traditional transects are analyzed to produce density estimates, which are then used to make inferences about population status or trends. A key assumption of the Pollard-Yates transect is that detection probability is 1.0, or constant but unknown, out to a fixed distance (generally 2.5 m on either side of a transect line). However, species-specific estimates of detection probability would allow for sampling at farther distances, resulting in more detections of individuals. Our objectives were to (1) evaluate butterfly density estimates derived from Pollard-Yates line transects and distance sampling, (2) estimate how detection probabilities for butterflies vary across sampling distances and butterfly wing lengths, and (3) offer advice on future butterfly sampling techniques to estimate population density. We conducted Pollard-Yates transects and distance-sampling transects in central Iowa in 2014. For comparison to densities derived from Pollard-Yates transects, we used Program DISTANCE to model detection probability (p) and estimate density (D) for eight butterfly species representing a range of morphological characteristics. We found that detection probability among species varied beyond 2.5 m, with variation apparent even within 5 m of the line. Such variation correlated with wing size, where species with larger wing size generally had higher detection probabilities. Distance sampling estimated higher densities at the 5-m truncation for five of the eight species tested. At this truncation, detection probability was <0.8 for all species, and ranged from 0.53 to 0.79. With the exception of the little yellow (), species with median wing length <5.0 mm had the lowest detection probabilities. We recommend that researchers integrate distance sampling into butterfly sampling and monitoring, particularly for studies utilizing survey transects >5 m wide and when smaller species are targeted.
Topics: Animals; Butterflies; Iowa; Population Density; Species Specificity; Surveys and Questionnaires
PubMed: 37842044
DOI: 10.7717/peerj.16165 -
Journal of Mathematical Biology Nov 2023Almost all models used in analysis of infectious disease outbreaks contain some notion of population size, usually taken as the census population size of the community...
Almost all models used in analysis of infectious disease outbreaks contain some notion of population size, usually taken as the census population size of the community in question. In many settings, however, the census population is not equivalent to the population likely to be exposed, for example if there are population structures, outbreak controls or other heterogeneities. Although these factors may be taken into account in the model: adding compartments to a compartmental model, variable mixing rates and so on, this makes fitting more challenging, especially if the population complexities are not fully known. In this work we consider the concept of effective population size in outbreak modelling, which we define as the size of the population involved in an outbreak, as an alternative to use of more complex models. Effective population size is an important quantity in genetics for estimation of genetic diversity loss in populations, but it has not been widely applied in epidemiology. Through simulation studies and application to data from outbreaks of COVID-19 in China, we find that simple SIR models with effective population size can provide a good fit to data which are not themselves simple or SIR.
Topics: Humans; Population Density; Communicable Diseases; Disease Outbreaks; Computer Simulation; COVID-19
PubMed: 37926744
DOI: 10.1007/s00285-023-02016-1 -
BMC Plant Biology Aug 2023Mating system is one of the major determinants of intra- and interspecific genetic structure, but may vary within and between plant populations. Our study model included...
BACKGROUND
Mating system is one of the major determinants of intra- and interspecific genetic structure, but may vary within and between plant populations. Our study model included all known populations of Moehringia tommasinii (Caryophyllaceae), a narrow endemic plant inhabiting rock crevices in the northwestern Adriatic, and some populations of co-occurring and widespread M. muscosa, an ecologically divergent relative with an overlapping flowering period. We performed reciprocal crosses within and between taxa and used molecular markers to assess the extent of gene flow within and between populations and taxa. Using coefficient of inbreeding, population size, seed weight, pollen-to-ovule ratio, and flower display size, we also looked for evidence of a selfing syndrome.
RESULTS
A surprisingly high variation in mating systems was observed among populations of M. tommasinii. These populations exhibited genetic structuring, with their size positively correlated with both seed weight and pollen production. Although a selfing syndrome could not be confirmed as the majority of selfing resulted from allogamous treatments, the occurrence of selfing was notable. In the presence of M. muscosa, at a site where both species coexist closely, a distinct pattern of fruit production was observed in M. tommasinii following various pollination treatments. Molecular and morphometric data provided evidence of hybridization followed by local extinction at this site.
CONCLUSIONS
Population size proved to be the most important factor affecting the mating system in genetically structured populations of M. tommasinii. Lighter seeds and lower pollen production observed in populations with pronounced selfing do not provide enough evidence for the selfing syndrome. Detected gene flow between M. tommasinii and the sympatric M. muscosa suggested weak reproductive barriers between the taxa, which could pose a conservation problems for the former species. Hybridization leading to local extinction may also resulted in floral polymorphism and disruption of mating patterns of M. tommasinii.
Topics: Population Density; Reproduction; Pollination; Inbreeding; Genetics, Population; Flowers
PubMed: 37553615
DOI: 10.1186/s12870-023-04384-8 -
Theory in Biosciences = Theorie in Den... Nov 2023We study the dynamics of a discrete model with two different stages of the population, the pre-adult stage governed by a Beverton-Holt-type map and the adult stage by a...
We study the dynamics of a discrete model with two different stages of the population, the pre-adult stage governed by a Beverton-Holt-type map and the adult stage by a [Formula: see text]-Ricker map. The composition of both maps gives the dynamics. The existence of the Allee effect is easily observed. We check that the model can evolve from a sure extinction to complicated dynamics. The presence of an almost sure extinction is proved to exist when the dynamical complexity is the highest possible.
Topics: Population Dynamics; Models, Biological; Population Density
PubMed: 37783964
DOI: 10.1007/s12064-023-00407-y -
The Journal of Experimental Biology Mar 2024From bacteria to metazoans, higher density populations have lower per capita metabolic rates than lower density populations. The negative covariance between population...
From bacteria to metazoans, higher density populations have lower per capita metabolic rates than lower density populations. The negative covariance between population density and metabolic rate is thought to represent a form of adaptive metabolic plasticity. A relationship between density and metabolism was actually first noted 100 years ago, and was focused on spermatozoa; even then, it was postulated that adaptive plasticity drove this pattern. Since then, contemporary studies of sperm metabolism specifically assume that sperm concentration has no effect on metabolism and that sperm metabolic rates show no adaptive plasticity. We did a systematic review to estimate the relationship between sperm aerobic metabolism and sperm concentration, for 198 estimates spanning 49 species, from protostomes to humans from 88 studies. We found strong evidence that per capita metabolic rates are concentration dependent: both within and among species, sperm have lower metabolisms in dense ejaculates, but increase their metabolism when diluted. On average, a 10-fold decrease in sperm concentration increased per capita metabolic rate by 35%. Metabolic plasticity in sperm appears to be an adaptive response, whereby sperm maximize their chances of encountering eggs.
Topics: Humans; Male; Semen; Sperm Motility; Spermatozoa; Energy Metabolism
PubMed: 38380562
DOI: 10.1242/jeb.246674 -
Emerging Infectious Diseases Sep 2023The SARS-CoV-2 Delta variant, first identified in October 2020, quickly became the dominant variant worldwide. We used publicly available data to explore the...
The SARS-CoV-2 Delta variant, first identified in October 2020, quickly became the dominant variant worldwide. We used publicly available data to explore the relationship between illness and death (peak case rates, death rates, case-fatality rates) and selected predictors (percentage vaccinated, percentage of the population >65 years, population density, testing volume, index of mitigation policies) in 45 high-income countries during the Delta wave using rank-order correlation and ordinal regression. During the Delta-dominant period, most countries reported higher peak case rates (57%) and lower peak case-fatality rates (98%). Higher vaccination coverage was protective against peak case rates (odds ratio 0.95, 95% CI 0.91-0.99) and against peak death rates (odds ratio 0.96, 95% CI 0.91-0.99). Vaccination coverage was vital to preventing infection and death from COVID-19 during the Delta wave. As new variants emerge, public health authorities should encourage the uptake of COVID-19 vaccination and boosters.
Topics: Humans; COVID-19; SARS-CoV-2; COVID-19 Vaccines; Developed Countries
PubMed: 37494699
DOI: 10.3201/eid2909.230142 -
BioRxiv : the Preprint Server For... Mar 2024Decisions made over long time scales, such as life cycle decisions, require coordinated interplay between sensory perception and sustained gene expression. The dauer...
Decisions made over long time scales, such as life cycle decisions, require coordinated interplay between sensory perception and sustained gene expression. The dauer (or diapause) exit developmental decision requires sensory integration of population density and food availability to induce an all-or-nothing organismal-wide response, but the mechanism by which this occurs remains unknown. Here, we demonstrate how the ASJ chemosensory neurons, known to be critical for dauer exit, perform sensory integration at both the levels of gene expression and calcium activity. In response to favorable conditions, dauers rapidly produce and secrete the dauer exit-promoting insulin-like peptide INS-6. Expression of in the ASJ neurons integrate population density and food level and can reflect decision commitment since dauers committed to exiting have higher expression levels than those of non-committed dauers. Calcium imaging in dauers reveals that the ASJ neurons are activated by food, and this activity is suppressed by pheromone, indicating that sensory integration also occurs at the level of calcium transients. We find that expression in the ASJ neurons depends on neuronal activity in the ASJs, cGMP signaling, a CaM-kinase pathway, and the pheromone components ascr#8 and ascr#2. We propose a model in which decision commitment to exit the dauer state involves an autoregulatory feedback loop in the ASJ neurons that promotes high INS-6 production and secretion. These results collectively demonstrate how insulin-like peptide signaling helps animals compute long-term decisions by bridging sensory perception to decision execution.
PubMed: 38586049
DOI: 10.1101/2024.03.20.586022 -
Pest Management Science Oct 2023Spodoptera frugiperda is an invasive, widespread agricultural pest in China. However, there have been no reports assessing feeding damage on wheat caused by S....
BACKGROUND
Spodoptera frugiperda is an invasive, widespread agricultural pest in China. However, there have been no reports assessing feeding damage on wheat caused by S. frugiperda. To clarify the fitness and potential damage of S. frugiperda to wheat, this study analyzed the population parameters of S. frugiperda fed on wheat in a laboratory and simulated the potential damage in field conditions.
RESULTS
The population parameters of S. frugiperda were compared using life tables on wheat at the seedling and adult plant stages. The adult female longevity of S. frugiperda varied from 12.29 days on seedling plants to 16.60 days on adult plants. Egg production was significantly higher when fed on wheat at the seedling stage (646.34 eggs) than when fed on adult plants (495.86 eggs). On wheat at the seedling and adult plant stages, the mean generation times were 35.42 and 38.34 days, respectively, and the intrinsic rates of increase were 0.15 and 0.14, respectively. Spodoptera frugiperda completed development and increased its population in wheat at both plant growth stages. In the field, the effect of different larval densities on the 1000-kernel weight of wheat was significantly different. An action threshold of 40 larvae per m was estimated, and the higher population densities caused a yield loss of 17.7%.
CONCLUSION
Spodoptera frugiperda can complete its life cycle on wheat at different stages. Wheat can serve as an alternative host for S. frugiperda. If S. frugiperda reaches 320 larvae per m density during wheat growth, it will cause yield loss exceeding 17%. © 2023 Society of Chemical Industry.
Topics: Animals; Larva; Spodoptera; Population Density; Triticum; Life Tables; Zea mays
PubMed: 37291074
DOI: 10.1002/ps.7602 -
Nutrients Dec 2023Santiago, Chile is a very segregated city, with higher childhood obesity rates observed in vulnerable areas. We compared the counts and proximity of unhealthy food...
Santiago, Chile is a very segregated city, with higher childhood obesity rates observed in vulnerable areas. We compared the counts and proximity of unhealthy food outlets (UFOs) around a 400 m buffer of 443 public schools (municipal and subsidized) located in socioeconomically diverse neighborhoods in 14 municipalities of Santiago. This was a cross-sectional study in which the socioeconomic status (SES) of the population living inside the buffer was classified as middle-high, middle, and low. We used the Kruskal-Wallis test for comparisons of density and proximity between type of school, SES, and population density. We used a negative binomial model (unadjusted and adjusted by population density) to determine the expected change in counts of UFOs by SES, which was compared to the reference (middle-high). Low SES neighborhoods had significantly more counts of UFOs, and these were located much closer to schools. Low and middle SES neighborhoods had an 88% and 48% higher relative risk of having UFOs compared to middle-high SES areas; (IRR = 1.88; 95% CI 1.59-2.23) and (IRR = 1.48; 95% CI 1.20-1.82), respectively. A socio-spatial segregation of UFOs associated with childhood obesity across public schools was observed in Santiago.
Topics: Child; Humans; Chile; Cross-Sectional Studies; Pediatric Obesity; Food; Schools
PubMed: 38201938
DOI: 10.3390/nu16010108 -
Ecological Applications : a Publication... Sep 2023Metapopulations are often managed as a single contiguous population despite the spatial structure underlying their local and regional dynamics. Disturbances from human...
Metapopulations are often managed as a single contiguous population despite the spatial structure underlying their local and regional dynamics. Disturbances from human activities can also be spatially structured with mortality impacts concentrated to just a few local populations among the aggregate. Scale transitions between local and regional processes can generate emergent properties whereby the whole system can fail to recover as quickly as expected for an equivalent single population. Here, we draw on theory and empirical case studies to ask: what is the consequence of spatially structured ecological and disturbance processes on metapopulation recoveries? We suggest that exploring this question could help address knowledge gaps for managing metapopulations including: Why do some metapopulations recover quickly while others remain collapsed? And, what risks are unaccounted for when metapopulations are managed at aggregate scales? First, we used model simulations to examine how scale transitions among ecological and disturbance conditions interact to generate emergent metapopulation recovery outcomes. In general, we found that the spatial structure of disturbance was a strong determinant of recovery outcomes. Specifically, disturbances that unevenly impacted local populations consistently generated the slowest recoveries and highest conservation risks. Ecological conditions that dampened metapopulation recoveries included low dispersal, variable local demography, sparsely connected habitat networks, and spatially and temporally correlated stochastic processes. Second, we illustrate the unexpected challenges of managing metapopulations by examining the recoveries of three USA federally listed endangered species: Florida Everglade snail kites, California and Alaska sea otters, and Snake River Chinook salmon. Overall, our results show the pivotal role of spatial structure in metapopulation recoveries whereby the interplay between local and regional processes shapes the resilience of the whole system. With this understanding, we provide guidelines for resource managers tasked with conserving and managing metapopulations and identify opportunities for research to support the application of metapopulation theory to real-world challenges.
Topics: Humans; Animals; Population Dynamics; Ecosystem; Salmon; Population Density; Endangered Species; Models, Biological
PubMed: 37303288
DOI: 10.1002/eap.2898