Survival rates in a natural population of the damselfly Ceriagrion tenellum: effects of sex and female phenotype

1. Ceriagrion tenellum females show genetic colour polymorphism. Androchrome (erythrogastrum) females are brightly (male‐like) coloured while gynochrome females (typica and melanogastrum) show cryptic colouration. 2. Several hypotheses have been proposed to explain the existence of more than one female morph in damselfly populations. The reproductive isolation and intraspecific mimicry hypotheses predict greater survival of gynochrome females, while the density dependent hypothesis predicts no differential survival between morphs. 3. Mature males had greater recapture probability than females while the survival probability was similar for both sexes. Survival and recapture rates were similar for androchrome and gynochrome females. 4. Gynochrome females showed greater mortality or migration rate than androchrome females during the pre‐reproductive period. This result is not predicted by the above hypotheses or by the null hypothesis that colour polymorphism is only maintained by random factors: founder effects, genetic drift, and migration.     

Optimizing occupancy surveys by maximizing detection probability: application to amphibian monitoring in the Mediterranean region

• Setting up effective conservation strategies requires the precise determination of the targeted species’ distribution area and, if possible, its local abundance. However, detection issues make these objectives complex for most vertebrates. The detection probability is usually <1 and is highly dependent on species phenology and other environmental variables. The aim of this study was to define an optimized survey protocol for the Mediterranean amphibian community, that is, to determine the most favorable periods and the most effective sampling techniques for detecting all species present on a site in a minimum number of field sessions and a minimum amount of prospecting effort. We visited 49 ponds located in the Languedoc region of southern France on four occasions between February and June 2011. Amphibians were detected using three methods: nighttime call count, nighttime visual encounter, and daytime netting. The detection nondetection data obtained was then modeled using site‐occupancy models. The detection probability of amphibians sharply differed between species, the survey method used and the date of the survey. These three covariates also interacted. Thus, a minimum of three visits spread over the breeding season, using a combination of all three survey methods, is needed to reach a 95% detection level for all species in the Mediterranean region. Synthesis and applications: detection nondetection surveys combined to site occupancy modeling approach are powerful methods that can be used to estimate the detection probability and to determine the prospecting effort necessary to assert that a species is absent from a site.

     

Effects of dominance on the probability of fixation of a mutant allele

We consider whether the fixation probability of an allele in a two-allele diploid system is always a monotonic function of the selective advantage of the allele. We show that while this conjecture is correct for intermediate dominance, it is not correct in general for either overdominant or underdominant alleles, and that for some parameter ranges the fixation probability can initially decrease and then increase as a function of the amount of selection. We have partial results that characterize the ranges of parameters for which this happens.      

A stochastic repair—misrepair model for the effects of radiation on cells

The purpose of this paper is to present a stochastic model for effects of radiation on cells. The model includes provisions for lethal effects and for transformation to malignant status. Empirical findings indicate the presence of some repair mechanism in the cells, and a way to incorporate this idea into the model is discussed. Comparisons of the derived survival and transformation probabilities with actual data are favorable. The interpretation of the estimated values leads to questions to be investigated by the experimenters.Supported in part by the Graduate Research Board, University of Maryland     

一种新的放射治疗计划优化方法

在采用多射线束的放射治疗中,治疗计划优化是一个重要的步骤。本文描述了一种新的治疗计划优化方法。它是基于治疗医理由对治疗过程中各因素的综合考虑,弥补了传统方法的不足,具有较高的准确性。     

Estimating the probability of identity among genotypes in natural populations: cautions and guidelines

Individual identification using DNA fingerprinting methods is emerging as a critical tool in conservation genetics and molecular ecology. Statistical methods that estimate the probability of sampling identical genotypes using theoretical equations generally assume random associations between alleles within and among loci. These calculations are probably inaccurate for many animal and plant populations due to population substructure. We evaluated the accuracy of a probability of identity (P(ID)) estimation by comparing the observed and expected P(ID), using large nuclear DNA microsatellite data sets from three endangered species: the grey wolf (Canis lupus), the brown bear (Ursus arctos), and the Australian northern hairy-nosed wombat (Lasiorinyus krefftii). The theoretical estimates of P(ID) were consistently lower than the observed P(ID), and can differ by as much as three orders of magnitude. To help researchers and managers avoid potential problems associated with this bias, we introduce an equation for P(ID) between sibs. This equation provides an estimator that can be used as a conservative upper bound for the probability of observing identical multilocus genotypes between two individuals sampled from a population. We suggest computing the actual observed P(ID) when possible and give general guidelines for the number of codominant and dominant marker loci required to achieve a reasonably low P(ID) (e.g. 0.01-0.0001).     

个体运动的病毒传播行为模拟

提出了一个基于二维规则网格的SIS(Susceptible-Infected-Susceptible)动态疾病传播模型,并用元胞自动机方法进行计算机模拟,考查该模型中感染概率、治愈概率、人群密度及人群的流动对疾病传播的影响,结果表明,系统的稳态感染比例随感染概率和人群密度的增加而增大,随治愈概率的增加而减小,同等条件下流动人群比静止人群更容易传播疾病,根据这些研究结论最后给出了对应的疾病预防和控制措施。     

Site occupancy models with heterogeneous detection probabilities

Models for estimating the probability of occurrence of a species in the presence of imperfect detection are important in many ecological disciplines. In these "site occupancy" models, the possibility of heterogeneity in detection probabilities among sites must be considered because variation in abundance (and other factors) among sampled sites induces variation in detection probability (p). In this article, I develop occurrence probability models that allow for heterogeneous detection probabilities by considering several common classes of mixture distributions for p. For any mixing distribution, the likelihood has the general form of a zero-inflated binomial mixture for which inference based upon integrated likelihood is straightforward. A recent paper by Link demonstrates that in closed population models used for estimating population size, different classes of mixture distributions are indistinguishable from data, yet can produce very different inferences about population size. I demonstrate that this problem can also arise in models for estimating site occupancy in the presence of heterogeneous detection probabilities. The implications of this are discussed in the context of an application to avian survey data and the development of animal monitoring programs.     

On the Analysis and Synthesis of a Four-Field-Table

The real four-field-table measure k is calculable as follows: K₁ for V(a, b, c, d) with k₁ = (arc K₁)/100, K₁₁ for V(a, b, 0, 0) with k₁₁ = (arc K₁₁)/100, K₁₂ for V(c, d, 0, 0) with k₁₂ = (arc K₁₂)/100 and K₁₂₁ for V(0, 0, c, d) with k₁₂₁ = – k₁₂. The equation k₁ = k₁₁ – k₁₂ holds good. It is possible to calculate the probability of error of a four-field-table with small frequencies, indirectly from component values. Two examples are given.     

Assessing probability of paternity and the product rule in DNA systems

The genetic resolution of paternity disputes begins with an intricate detection of inherited traits and finishes with a statistical inference (the probability of paternity,W). Notwithstanding some initial fanfare, statistical inference is a necessary component of DNA-based paternity tests because band patterns may be rare but not yet unique, and even rare events in a vacuum are meaningless. The genetic match must be combined with other evidence for relevancy, thus a Bayesian approach is preferred when computingW. This paper reviews the standard model used to computeW and discusses the model's various properties and assumptions. The standard model is extended to include DNA systems in which alleles are operationally continuous due to measurement error. This extension avoids problems associated with matched/non-matched binned decisions. After outlining the model assumptions for a single DNA system, particular attention is given to the product rule-the procedure of multiplying intermediate probabilities across genetic loci to form a combinedW. An empirical alternative to the product rule is also assessed and correlated with standard procedures.Editor's commentsThe authors present a carefully reasoned account of Bayesian inference in the paternity context. Their presentation of an alternative to the product rule for Paternity Index values offers a means of avoiding objections to the rule.     

On estimating the polyclonal fraction in lineage-marker studies of tumor origin

Insight into the biology of tumor formation is provided by studies which demonstrate through the use of cell-lineage markers that some tumors have a polyclonal origin. Novelli et al. (1996) proposed to use the proportion of heterotypic tumors among the tumors that are either heterotypic or pure and of the minority marker type as a lower bound on the marginal fraction of polyclonal tumors. Generally, Novelli's ratio does not provide a valid lower bound for the marginal polyclonal fraction, as we demonstrate by analyzing relevant conditional probabilities. Estimation of the polyclonal fraction requires modeling assumptions on the distribution of the number of involved clones. Using three elementary models, we develop maximum likelihood estimation of the polyclonal fraction. We establish robustness of our estimates to misspecification of the clone-marking process, though the estimates are sensitive to assumptions about polyclonal mechanisms. On data from several published studies, our estimates of the polyclonal fraction are substantially smaller than Novelli's ratio.     

Lower Confidence Limits for the Positive Linear Combination of two Variances

An alternative method for determining the approximate lower confidence limits for the positive linear combination of two variances based on an approach similar to BULMER (1957) has been proposed. The probability coverage of the proposed alternative limits has been compared with the other existing methods.     

Rates of decay for the survival probability of a mutant gene

If qk is the extinction probability of a slightly supercritical branching process with offspring distribution P _kr : r = 0, 1, 2,..., then it is shown that if sup _r r ³ p _kr , < , inf ² _k > 0, and m _k 1, then 1 – q _k 2(m _k –1) _k ^–2, where m _k = _r rp _kr , ² _k = ^k _r r ² p _kr – m _k ². This provides a simple set of sufficient conditions for the validity of a conjecture of Ewens (1969) for the survival probability of a slightly advantageous mutant gene.Research supported in part by NSF grants DMS-8803639 and DMS-9007182     

Towards the automated detection and occupancy estimation of primates using passive acoustic monitoring

Recent advancements in technology have made possible the use of novel, cost-efficient biomonitoring techniques which facilitate monitoring animal populations at larger spatial and temporal scales. Here, we investigated using passive acoustic monitoring (PAM) for wild primate populations living in the forest of Taï National Park, Côte d’Ivoire. We assessed the potential of using a customized algorithm for the automated detection of multiple primate species to obtain reliable estimates of species occurrence from acoustic data. First, we applied the algorithm on continuous rainforest recordings collected using autonomous recording units (ARUs) to detect and classify three sound signals: chimpanzee buttress drumming, and the loud calls of the diana and king colobus monkey. Using an occupancy modelling approach we then investigated to what extent the automated, probabilistic output needs to be listened to, and thus manually cleaned, by a human expert, to approach occupancy probabilities derived from ARU data fully verified by a human. To do this we explored the robustness of occupancy probability estimates by simulating ARU datasets with various degrees of cleaning for false positives and false negative detections. We further validated the approach by comparing it to data collected by human observers on point transects located within the same study area. Our study demonstrates that occurrence estimates from ARU data, combined with automated processing methods such as our algorithm, can provide results comparable to data collected by humans and require less effort. We show that occupancy probabilities are quite robust to cleaning effort, particularly when occurrence is high, and suggest that for some species even naïve occupancy, as derived from ARU data without any cleaning, could provide a quick and reliable indicator to guide monitoring efforts. We found detection probabilities to be most influenced by time of day for chimpanzee drums while temperature and, likely, poaching pressure, affected detection of diana monkey loud calls. None of the covariates investigated appeared to have strongly affected king colobus loud call detection. Finally, we conclude that the semi-automated approach presented here could be used as an early-warning system for poaching activity and suggest additional techniques for improving its performance.     

Logical Probability and Risk Assessment

A risk assessment is intended to provide a statement of current knowledge which is intended to inform a decision-maker of the current state of knowledge in response to a particular concern. Because answering the concerns of decision-makers often requires inferences to be drawn, doubt often arises over how the inference is to be drawn. In quantitative risk assessment, where a mathematical equation or model is used to draw the inference, this uncertainty is referred to as model uncertainty. A two-step process, which is referred to as logical probability, is proposed as a technique for representing model uncertainty in a risk assessment. The first step involves assigning model weights in which the degree of evidential support for each of the alternative models is considered. The second step involves assigning a unique interval in the range of 0 to 1 for each model which reflects the models' weight, to form a probability distribution. While the second step is straightforward, the first step is not. Assigning model weights requires consideration of any line of evidence that may reasonably impact the validity of the assertion of a model. While the development of a procedure for doing so may be expected to be a process which reflects the subjective preferences of whomever is involved in creating it, there are some historical precedents on which to build. Foremost among these are (1) the use of a correlation coefficient or other goodness-of-fit criteria to measure the degree of correspondence between a given model and a set of observations which are used as evidence to support it, and (2) preference given to models which are simpler, which may be ascertained as the number of adjustable parameters the model contains. Additional principles, which have little or no tradition to stand on, must be used to reflect the impact of other empirically supported beliefs on model preference. The procedure proposed is comparable to the procedure known as decision analysis, in which probabilities are assigned to alternative models based on expert or subjective input. The principal difference in the present case is that it is suggested that principles which transcend the decision at hand should be sought and articulated in order to generate a consistent measure of uncertainty arising from interpretation.     

Geneva量表在肺栓塞诊断中的意义

随着认识水平的提高,已发现肺栓塞是临床很常见的疾病。对于如何更好地进行肺栓塞危险性的评估和组织相对复杂的检查,Geneva量表将是临床非常实用的工具。Geneva量表更精确和稳定,较少受临床经验的影响。对于合并慢性阻塞性肺病的患者诊断也有意义。同时,对于预测肺栓塞后3月内不良事件也有价值,临床试验证实对CT检查阴性患者Geneva量表评分为低中度危险不进行抗凝治疗也是安全的。本文将对目前国际上对Geneva量表的应用进展做一综述。