scholarly journals Models of poisoning effects on vulture populations show that small but frequent episodes have a larger effect than large but rare ones

Web Ecology ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 79-93
Author(s):  
Rigas Tsiakiris ◽  
John M. Halley ◽  
Kalliopi Stara ◽  
Nikos Monokrousos ◽  
Chryso Karyou ◽  
...  
Keyword(s):  
Minimum Size ◽  
Management Tool ◽  
Initial Population ◽  
Gyps Fulvus ◽  
Large Numbers ◽  
Poison Baiting ◽  
Successful Establishment ◽  
Initial Population Size ◽  
Population Reinforcement ◽  
Future Population

Abstract. Vultures are among the most threatened avian taxa in the world. When vultures aggregate in large numbers to feed, poisoned carcasses can extirpate entire populations at once. In the light of shrinking numbers worldwide, restocking and reintroduction projects, where wild or captive-bred vultures are released back into nature, constitute a crucial management tool, successfully implemented in many countries. However, reestablishment of sustainable vulture populations to their historical ranges remains a serious challenge, especially if the threat of poisoning persists, which is usually the case. In this study, we model the outcome of a restocking project where an initial colony is subject to repeated poisoning events. We use as an example the isolated population of the griffon vulture (Gyps fulvus) in Cyprus. Mathematical considerations and model simulations show that the probability of colony persistence depends on the initial population size and the intensity and frequency of the poisoning incidents. This type of scenario creates an Allee effect that requires a colony to exceed a minimum size in order to survive. Also in this scenario, a sequence of small but frequent poisoning episodes is worse on average than a few large and rare ones of the same cumulative mortality. Future population reinforcement efforts for vultures should focus on the release of adult birds in adequate numbers for the successful establishment of sustainable colonies and should involve a reduction in small but persistent sources of mortality such as the poison baiting of small canids that until now has been neglected by conservation scientists.

scholarly journals Population viability analysis and conservation of Chinese Grouse Bonasa sewerzowi in Lianhuashan Nature Reserve, north-west China

2010 ◽  
Vol 21 (1) ◽  
pp. 49-58 ◽  
Author(s):  
NAN LU ◽  
YUE-HUA SUN
Keyword(s):  
Population Size ◽  
Human Activity ◽  
Western China ◽  
Management Tool ◽  
Initial Population ◽  
Current Population ◽  
Initial Population Size ◽  
Bonasa Sewerzowi ◽  
Nest Loss ◽  
Chinese Grouse

SummaryChinese Grouse Bonasa sewerzowi is threatened by human activity, especially during the breeding season, in the Lianhuashan Mountains, Gansu Province, north-western China. We conducted a series of simulations on the viability of this population using the computer program VORTEX. The simulations suggested that the population had an extinction probability of 17% in 100 years using data gathered from current field work. Sensitivity analysis revealed that the predicted population trend was most sensitive to chick mortality, offspring per female per year, and adult male mortality. The first two parameters are correlated with human activity such as nest loss due to egg collecting by local people. When we set initial population size to the same size as carrying capacity, 2,500 individuals would constitute a minimum viable population (MVP). This would require a forest area of about 3,780 ha, which is smaller than the size of the Lianhuashan reserve, but the current population does not constitute an MVP due to the small initial population size. Furthermore, we found that if chick mortality declined by 5% or the number of offspring produced per female increased by 5% (i.e. reducing nest loss) under the current situation, local reserve size and current population would constitute an MVP. Therefore, the most practical and simple conservation management tool would be to increase the breeding success of Chinese Grouse, especially by limiting human activity during the incubation period.

scholarly journals Comparative Analysis of SNP Discovery and Genotyping in Fagus sylvatica L. and Quercus robur L. Using RADseq, GBS, and ddRAD Methods

Forests ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 222
Author(s):  
Bartosz Ulaszewski ◽  
Joanna Meger ◽  
Jaroslaw Burczyk
Keyword(s):  
Population Genomics ◽  
De Novo ◽  
Genetic Studies ◽  
Genomic Libraries ◽  
Reduced Representation ◽  
Large Numbers ◽  
Broadleaved Tree Species ◽  
Fagus Sylvatica L ◽  
Reference Genomes ◽  
Future Population

Next-generation sequencing of reduced representation genomic libraries (RRL) is capable of providing large numbers of genetic markers for population genetic studies at relatively low costs. However, one major concern of these types of markers is the precision of genotyping, which is related to the common problem of missing data, which appears to be particularly important in association and genomic selection studies. We evaluated three RRL approaches (GBS, RADseq, ddRAD) and different SNP identification methods (de novo or based on a reference genome) to find the best solutions for future population genomics studies in two economically and ecologically important broadleaved tree species, namely F. sylvatica and Q. robur. We found that the use of ddRAD method coupled with SNP calling based on reference genomes provided the largest numbers of markers (28 k and 36 k for beech and oak, respectively), given standard filtering criteria. Using technical replicates of samples, we demonstrated that more than 80% of SNP loci should be considered as reliable markers in GBS and ddRAD, but not in RADseq data. According to the reference genomes’ annotations, more than 30% of the identified ddRAD loci appeared to be related to genes. Our findings provide a solid support for using ddRAD-based SNPs for future population genomics studies in beech and oak.

scholarly journals Agglomeration economies, congestion diseconomies, and fertility dynamics in a two-region economy

2021 ◽  
Author(s):  
Madoka Muroishi ◽  
Akira Yakita
Keyword(s):  
Population Size ◽  
Stability Condition ◽  
Fertility Rate ◽  
Model Parameters ◽  
Initial Population ◽  
Interregional Migration ◽  
Stable Path ◽  
Regional Population ◽  
Initial Population Size

AbstractUsing a small, open, two-region economy model populated by two-period-lived overlapping generations, we analyze long-term agglomeration economy and congestion diseconomy effects of young worker concentration on migration and the overall fertility rate. When the migration-stability condition is satisfied, the distribution of young workers between regions is obtainable in each period for a predetermined population size. Results show that migration stability does not guarantee dynamic stability of the economy. The stationary population size stability depends on the model parameters and the initial population size. On a stable trajectory converging to the stationary equilibrium, the overall fertility rate might change non-monotonically with the population size of the economy because of interregional migration. In each period, interregional migration mitigates regional population changes caused by fertility differences on the stable path. Results show that the inter-regional migration-stability condition does not guarantee stability of the population dynamics of the economy.

The Nuts and Bolts of Implementing Large-Scale Longitudinal Studies

1992 ◽  
Vol 7 (1) ◽  
pp. 63-78 ◽  
Author(s):  
Magda Stouthamer-Loeber ◽  
Welmoet van Kammen ◽  
Rolf Loeber
Keyword(s):  
Staff Training ◽  
Large Scale ◽  
Longitudinal Research ◽  
Data Entry ◽  
Management Tool ◽  
Academic Training ◽  
Scientific Journals ◽  
Training And Supervision ◽  
Large Numbers ◽  
Set Up

Studies that assess large numbers of subjects for longitudinal research, for epidemiological purposes, or for the evaluation of prevention and intervention efforts, are very costly and should be undertaken with the greatest care to ensure their success. The success of a study, apart from its scientific merit, depends largely on the ability of the researcher to plan and set up a smoothly running operation. However, the skills required for such a task are often not acquired in academic training, nor do scientific journals abound with information on the practical aspects of running a large study. This paper summarizes the experience gained in executing a longitudinal study and covers aspects of planning, hiring of staff, training and supervision of interviewers, data collection and data entry and management. The importance of the use of the computer as a management tool is stressed.

Estimation of the parameters of a branching process from migrating binomial observations

1998 ◽  
Vol 30 (4) ◽  
pp. 948-967 ◽  
Author(s):  
C. Jacob ◽  
J. Peccoud
Keyword(s):  
Confidence Interval ◽  
Asymptotic Behaviour ◽  
Population Size ◽  
Branching Process ◽  
Total Population ◽  
Initial Population ◽  
Asymptotic Confidence Interval ◽  
Total Population Size ◽  
Initial Population Size ◽  
Watson Process

This paper considers a branching process generated by an offspring distribution F with mean m < ∞ and variance σ2 < ∞ and such that, at each generation n, there is an observed δ-migration, according to a binomial law Bpvn*Nnbef which depends on the total population size Nnbef. The δ-migration is defined as an emigration, an immigration or a null migration, depending on the value of δ, which is assumed constant throughout the different generations. The process with δ-migration is a generation-dependent Galton-Watson process, whereas the observed process is not in general a martingale. Under the assumption that the process with δ-migration is supercritical, we generalize for the observed migrating process the results relative to the Galton-Watson supercritical case that concern the asymptotic behaviour of the process and the estimation of m and σ2, as n → ∞. Moreover, an asymptotic confidence interval of the initial population size is given.

scholarly journals Experimental demonstration of a two-phase population extinction hazard

2011 ◽  
Vol 8 (63) ◽  
pp. 1472-1479 ◽  
Author(s):  
John M. Drake ◽  
Jeff Shapiro ◽  
Blaine D. Griffen
Keyword(s):  
Population Size ◽  
Time Distribution ◽  
Proportional Hazards ◽  
Initial Population ◽  
Extinction Time ◽  
Habitat Size ◽  
Two Phase ◽  
Population Extinction ◽  
Initial Population Size ◽  
Phase Population

Population extinction is a fundamental biological process with applications to ecology, epidemiology, immunology, conservation biology and genetics. Although a monotonic relationship between initial population size and mean extinction time is predicted by virtually all theoretical models, attempts at empirical demonstration have been equivocal. We suggest that this anomaly is best explained with reference to the transient properties of ensembles of populations. Specifically, we submit that under experimental conditions, many populations escape their initially vulnerable state to reach quasi-stationarity, where effects of initial conditions are erased. Thus, extinction of populations initialized far from quasi-stationarity may be exposed to a two-phase extinction hazard. An empirical prediction of this theory is that the fit Cox proportional hazards regression model for the observed survival time distribution of a group of populations will be shown to violate the proportional hazards assumption early in the experiment, but not at later times. We report results of two experiments with the cladoceran zooplankton Daphnia magna designed to exhibit this phenomenon. In one experiment, habitat size was also varied. Statistical analysis showed that in one of these experiments a transformation occurred so that very early in the experiment there existed a transient phase during which the extinction hazard was primarily owing to the initial population size, and that this was gradually replaced by a more stable quasi-stationary phase. In the second experiment, only habitat size unambiguously displayed an effect. Analysis of data pooled from both experiments suggests that the overall extinction time distribution in this system results from the mixture of extinctions during the initial rapid phase, during which the effects of initial population size can be considerable, and a longer quasi-stationary phase, during which only habitat size has an effect. These are the first results, to our knowledge, of a two-phase population extinction process.

scholarly journals Mutualistic cross-feeding in microbial systems generates bistability via an Allee effect

2019 ◽  
Author(s):  
Stefan Vet ◽  
Lendert Gelens ◽  
Didier Gonze
Keyword(s):  
Allee Effect ◽  
Positive Influence ◽  
Initial Population ◽  
Explicit Model ◽  
Experimental Parameters ◽  
Initial Population Size ◽  
Strong Allee Effect ◽  
Relationship Of ◽  
Microbial Systems ◽  
Explicit Relation

ABSTRACTMutualistic interactions are characterized by the positive influence that two species exert on each other. Such mutualism can lead to bistability. Depending on the initial population size species will either survive or go extinct. Various phenomenological models have been suggested to describe bistability in mutualistic systems. However, these models do not account for interaction mediators such as nutrients. In contrast, nutrient-explicit models do not provide an intuitive understanding of what causes bistability. Here, we reduce a theoretical nutrient-explicit model of two mutualistic cross-feeders in a chemostat, uncovering an explicit relation to a growth model with an Allee effect. We show that the dilution rate in the chemostat leads to bistability by turning a weak Allee effect into a strong Allee effect. This happens as long as there is more production than consumption of cross-fed nutrients. Thanks to the explicit relationship of the reduced model with the underlying experimental parameters, these results allow to predict the biological conditions that sustain or prevent the survival of mutualistic species.

scholarly journals Simulation of Ecological and Evolutionary Interactions of Darwin's Finches—A Multimedia Learning Tool

HortScience ◽  
1997 ◽  
Vol 32 (6) ◽  
pp. 983b-983
Author(s):  
R.D. Quinn
Keyword(s):  
Population Size ◽  
Pilot Project ◽  
Early Summer ◽  
Initial Population ◽  
Introductory Biology ◽  
Web Based ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
Large Numbers ◽  
Bill Morphology

Dr. Quinn is one of a team of six biology professors from six different CSU campuses collaborating on this pilot project. EvolvelT is a web-based method for students to learn the fundamentals of natural selection and speciation by simulating natural processes. The simulation will be modeled on the evolution of Darwin's Finches in the Galapagos Islands. Learners will manipulate variables such as initial population size, variability and heritability of bill morphology, and quantity and quality of seeds, and then observe changes with time in population size and bill morphology. The interactive model will allow variables to be changed and simulations to be repeated, producing results that can be graphed and statistically analyzed. The Integrated Technology Strategy (ITS) of the California State University System (CSU) is using the Internet to create new and more flexible learning opportunities. Recently the ITS brought together biologists from several CSU campuses to explore ways to use technology to improve learning in introductory biology laboratories for non-science students. These laboratories were chosen because they affect large numbers of students at all campuses. Development criteria include applicability across the CSU, improvement in learning quality, accessibility to large numbers of students, and measurable success. We selected evolution as a topic for web-based learning because it is a central concept of biology, and it is relatively difficult to teach in conventional introductory biology laboratories. Our development team will work with multimedia design specialists to insure that the web presentation promotes scientifically sound and efficient learning. We are collaborating via e-mail and occasional video conferences and face-to-face meetings. We will work on the actual teaching materials via a web page. The initial prototype will be ready by early summer 1997 and will be tested, modified, and released for beta testing by summer's end.

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