小菜蛾颗粒体病毒对小菜蛾防治作用的评价

用以作用因子组配的生命表,种群趋势指数和控制指数评价小菜蛾颗粒体病毒对小菜蛾种群动态的作用。结果表明,施用该病毒对小菜蛾种群动态有明显的控制作用,种群趋势指数为０．９７,干扰作用控制指数为０．１９,即施用病毒后,其种群趋势指数相当于对照的０．１９,施用化学杀虫剂的种群趋势指数为７．２０,干扰作用控制指数为１．４３,即种群趋势指数将增长为对照的１．４３倍。     

Genetic impoverishment of the last black grouse (Tetrao tetrix) population in the Netherlands: detectable only with a reference from the past

We have studied a small isolated population of black grouse (Tetrao tetrix) in the Netherlands to examine the impact of isolation and reduction in numbers on genetic diversity. We compared the genetic diversity in the last extant Dutch population with Dutch museum samples and three other black grouse populations (from England, Austria and Norway, respectively) representing isolated and continuous populations. We found significantly lower allelic richness, observed and expected heterozygosities in the present Dutch population compared to the continuous populations (Austria and Norway) and also to the historical Dutch population. However, using a bottleneck test on each population, signs of heterozygosity excess were only found in the likewise isolated English population despite that strong genetic drift was evident in the present Dutch population in comparison to the reference populations, as assessed both in pairwise F(ST)and STRUCTURE analyses. Simulating the effect of a population reduction on the Dutch population from 1948 onwards, using census data and with the Dutch museum samples as a model for the genetic diversity in the initial population, revealed that the loss in number of alleles and observed heterozygosity was according to genetic drift expectations and within the standard error range of the present Dutch population. Thus, the effect of the strong decline in the number of grouse on genetic diversity was only detectable when using a reference from the past. The lack of evidence for a population reduction in the present Dutch population by using the program bottleneck was attributed to a rapidly found new equilibrium as a consequence of a very small effective population size.     

Regarding the confusion between the population concept and Mayr's "population thinking"

Ernst Mayr said that one of Darwin's greatest contributions was to show scholars the way to population thinking, and to help them discard a mindset of typological thinking. Population thinking rejects a focus on a central representative type, and emphasizes the variation among individuals. However, Mayr's choice of terms has led to confusion, particularly among biologists who study natural populations. Both population thinking and the concept of a biological population were inspired by Darwin, and from Darwin the chain for both concepts runs through Francis Galton who introduced the statistical usage of "population" that appears in Mayr's population thinking. It was Galton's "population" that was modified by geneticists and biometricians in the early 20th century to refer to an interbreeding and evolving community of organisms. Under this meaning, a population is a biological entity and so paradoxically population thinking, which emphasizes variation at the expense of dwelling on entities, is usually not about populations. Mayr did not address the potential for misunderstanding but for him the important part of the population concept was that the organisms within a population were variable, and so he probably thought there should not be confusion between population thinking and the concept of a population.     

Biases in the estimation of the demographic parameters of a snowshoe hare population

1. Survival rates and natalities for a population of snowshoe hares in the Yukon were estimated independently of and simultaneously with estimates of population change during the increase phase of a hare cycle.
2. Simple demographic models are used to show that even though the estimated survival rates and natalities were high relative to previously published estimates, the observed demographic parameters are unable to explain the extent of population increase, and we conclude that some of these parameters must be underestimates.
3. A sensitivity analysis is used to examine the potential influence of changes in these demographic parameters on the population growth rate. During most years of the hare cycle the population growth rate is potentially most sensitive to changes in juvenile postweaning survival. Only during crash years is adult survivorship likely to be a more important determinant of the rate of population change.
4. Examination of previously published data sets on two full population cycles suggests that while survival rates are positively correlated with population growth rates, their incorporation into demographic models results in frequent underestimation of the rate of population increase.     

海南山蛭种群数量动态与气象因素关系研究

在海南岛橡胶林内,每月观测海南山蛭Ｈａｅｍａｄｉｐｓａ ｈａｉｎａｎａ种群数量Ｂａ,用逐步回归分析方法研究了１０个气象因子对海南山６种数量的影响,结果表明,１）每年海南山蛭种群数量不同,６ａ间影响海南山蛭种群数量的主要气候因素是Ｘ１（月雨量）、Ｘ３（月雨日）和Ｘ５（月有露日数）;２）海南岛５～１０月份为雨季,海南山蛭这种群数量明显增大,影响山蛭种群数量的主要气候因素是Ｘ５和Ｘ１６（月最大风速和）和     

Estimating the area under the ROC curve when transporting a prediction model to a target population

We propose methods for estimating the area under the receiver operating characteristic (ROC) curve (AUC) of a prediction model in a target population that differs from the source population that provided the data used for original model development. If covariates that are associated with model performance, as measured by the AUC, have a different distribution in the source and target populations, then AUC estimators that only use data from the source population will not reflect model performance in the target population. Here, we provide identification results for the AUC in the target population when outcome and covariate data are available from the sample of the source population, but only covariate data are available from the sample of the target population. In this setting, we propose three estimators for the AUC in the target population and show that they are consistent and asymptotically normal. We evaluate the finite-sample performance of the estimators using simulations and use them to estimate the AUC in a nationally representative target population from the National Health and Nutrition Examination Survey for a lung cancer risk prediction model developed using source population data from the National Lung Screening Trial.     

Population Genetic Consequences of the Allee Effect and the Role of Offspring-Number Variation

A strong demographic Allee effect in which the expected population growth rate is negative below a certain critical population size can cause high extinction probabilities in small introduced populations. But many species are repeatedly introduced to the same location and eventually one population may overcome the Allee effect by chance. With the help of stochastic models, we investigate how much genetic diversity such successful populations harbor on average and how this depends on offspring-number variation, an important source of stochastic variability in population size. We find that with increasing variability, the Allee effect increasingly promotes genetic diversity in successful populations. Successful Allee-effect populations with highly variable population dynamics escape rapidly from the region of small population sizes and do not linger around the critical population size. Therefore, they are exposed to relatively little genetic drift. It is also conceivable, however, that an Allee effect itself leads to an increase in offspring-number variation. In this case, successful populations with an Allee effect can exhibit less genetic diversity despite growing faster at small population sizes. Unlike in many classical population genetics models, the role of offspring-number variation for the population genetic consequences of the Allee effect cannot be accounted for by an effective-population-size correction. Thus, our results highlight the importance of detailed biological knowledge, in this case on the probability distribution of family sizes, when predicting the evolutionary potential of newly founded populations or when using genetic data to reconstruct their demographic history.     

Surviving north of the natural range: the importance of density independence in determining population size

The relative importance of density-dependent and -independent processes in determining population density has been predicted to vary according to whether the population concerned is located near the centre or the periphery of the species' range. Thus, density-independent processes should be more pronounced near the periphery. The long-tailed wood mouse Apodemus sylvaticus in Iceland is at the northern and western edge of its geographical range. We estimated the autumn population density in an open habitat in south-western Iceland in 9 years out of 10 during 1996–2005 in order to monitor the annual maximum population size. Furthermore, we estimated population density and survival at c . 5-week intervals from September 2001 to October 2003 and from September 2004 to November 2005 in order to reveal the causes of variation in maximum population size. The estimated autumn population density was low, ranging from 2.7 to 8.9 mice ha⁻¹ while spring densities ranged from 0.4 to 0.8 mice ha⁻¹. Apparent monthly survival probabilities ranged from 0.4 to 0.7 per month in autumn and 0.7 to 0.9 in winter. Our results suggest that low temperature in early winter (October–December) is the major determinant of population density in the following autumn, explaining 74% of the variation in autumn population density. No significant correlation was found between either the NAO index or the NAO winter index and variation in wood mouse population density in autumn. Differential mortality in early winter results in variation in spring population size. This study shows clear evidence of density-independent control of a mammal population at the edge of its geographical range as opposed to the mostly density-dependent control previously recorded near its centre of distribution.     

Comparison of sexual compatibility in crosses between the southern and northern populations of the cabbage beetle Colaphellus bowringi

It is widely accepted that the genetic divergence and reproductive incompat- ibility between closely related species and/or populations is often viewed as an important step toward speciation. In this study, sexual compatibility in crosses between the southern XS population and the northern TA population of the polyandrous cabbage beetle Co- laphellus bowringi was investigated by testing their mating preferences, mating latency, copulation duration, and reproductive performances of post-mating. In choice mating ex- periments, the percentages ofmatings were significantly higher in intra-population crosses than in inter-population crosses. Both isolation index （/） and index of pair sexual isolation （/PSi） indicated partial mating incompatibility or assortative mating in crosses between the two different geographical populations. In single pair mating experiments, XS females in inter-population crosses mated significantly later and copulated significantly shorter than those in intra-population crosses. However, TA females in inter-population crosses mated significantly earlier and copulated longer than those in intra-population crosses, suggesting that larger XS males may enhance heterotypic mating. The lifetime fecundity was highest in XS homotypic matings, lowest in TA homotypic matings, and intermedi- ate in heterotypic rnatings between their parents. The inter-population crosses resulted in significantly lower egg hatching rate and shorter female longevity than intra-population crosses. These results demonstrated that there exist some incompatibilities in premating, postmating-prezygotic, and postzygotic stages between the southern XS population and northern TA population of the cabbage beetle Colaphellus bowringi.     

The impact of disease on the survival and population growth rate of the Tasmanian devil

1. We investigated the impact of a recently emerged disease, Devil Facial Tumour Disease (DFTD), on the survival and population growth rate of a population of Tasmanian devils, Sarcophilus harrisii, on the Freycinet Peninsula in eastern Tasmania. 2. Cormack-Jolly-Seber and multistate mark-recapture models were employed to investigate the impact of DFTD on age- and sex-specific apparent survival and transition rates. Disease impact on population growth rate was investigated using reverse-time mark-recapture models. 3. The arrival of DFTD triggered an immediate and steady decline in apparent survival rates of adults and subadults, the rate of which was predicted well by the increase in disease prevalence in the population over time. 4. Transitions from healthy to diseased state increased with disease prevalence suggesting that the force of infection in the population is increasing and that the epidemic is not subsiding. 5. The arrival of DFTD coincided with a marked, ongoing decline in the population growth rate of the previously stable population, which to date has not been offset by population compensatory responses.     

On the number of New World founders: a population genetic portrait of the peopling of the Americas

The founding of New World populations by Asian peoples is the focus of considerable archaeological and genetic research, and there persist important questions on when and how these events occurred. Genetic data offer great potential for the study of human population history, but there are significant challenges in discerning distinct demographic processes. A new method for the study of diverging populations was applied to questions on the founding and history of Amerind-speaking Native American populations. The model permits estimation of founding population sizes, changes in population size, time of population formation, and gene flow. Analyses of data from nine loci are consistent with the general portrait that has emerged from archaeological and other kinds of evidence. The estimated effective size of the founding population for the New World is fewer than 80 individuals, approximately 1% of the effective size of the estimated ancestral Asian population. By adding a splitting parameter to population divergence models it becomes possible to develop detailed portraits of human demographic history. Analyses of Asian and New World data support a model of a recent founding of the New World by a population of quite small effective size.     

Modelling the population consequences of age- and sex-related differences in winter mortality in the oystercatcher, Haematopus ostralegus

A modelling approach is used to explore the effect of age and sex differences in oystercatcher ( Haematopus ostralegus ) winter mortality on population size, population structure and the population response to habitat loss or change. Increasing the mortality of first and second year birds reduced population size, but had very little effect on the proportion of the population that were adults. Increasing female mortality reduced population size and resulted in a male-biased population. A sex bias amongst birds of breeding age meant that there were fewer potential breeding pairs for a given population size, reducing the size of the breeding population and the breeding output. Increasing the mortality of one sex relative to the other reduced population size, even when mean adult mortality rates remained unchanged. Increasing the strength of density-dependent mortality in young birds caused a greater reduction in population size as habitat was lost. Increasing the strength of female density-dependent mortality had the same effect, even though male density-dependent mortality had been correspondingly reduced. Increasing density-independent or density-dependent winter mortality in one sex relative to another also exaggerated the disproportional effect of winter habitat loss on separate breeding subpopulations using the same overwintering area. These results suggest that any study of population dynamics should be aware of both age and sex differences in mortality. Conservationists should be particularly aware of any age or sex differences in diet or habitat use that may result in a differential response to environmental change.     

The regulation of the dynamics of human populations

The important aspects of population dynamics are shown in a model along with the changes of population structure, the reasons for these changes and the conditions under which such changes take place. Subsequently, the reasons for these population dynamic processes which can be arranged in a three step scale are shown. Here, it must be differentiated between endogenous processes, due to factors inherent in the population, and exogenous ones caused by external forces effecting structural changes. The population political trends has to be incorporated as a part of the exogenous factors. The questions of regularities in the population dynamics are shown in the examples of important population theories in history. At the same time the theoretically possible borders are described, within which, due to purely physiological reasons, a population dynamic process has to occur. However, these borders will never be reached. Examination of the inertia of the population dynamic processes suggests an examination of the questions about the probability of the self-destructive processes in population dynamics. Considering the strong self-regulatory processes within a population the hypothesis of a population extinction is refuted.     

Relation of population changes to the distribution of genetic factors

Abstract

During the 1800's, the population of Ireland underwent a rapid increase and subsequent decrease in population size. The effects of this change upon population structure were assessed using a simulation of the isolation by distance model and comparing the results to those obtained assuming constant population size. These results indicate that changes in within‐group genetic similarity (kinship) brought about by a rapid increase in population size are cancelled by the effects of a rapid decrease in population size. Parameters of the isolation by distance model are hardly affected by population size changes. These results suggest that violation of the assumption of constant population size for population structure models may not be that serious when population size changes rapidly and in both directions.     

Comparative study of the variability of morpho-physiological traits and polymorphic genetic markers in migrant and local Russian population of the Western region of the Baikal-Amur railway

Morpho-physiological traits and variation of gene markers of 119 complete families from Russian migrant population inhabiting the Western area of Baikal-Amur Railway and 92 such families from Russian native population from the same area were compared. In migrant women body length was 2 cm higher and age of menarche was 8 months earlier than in native population. Average values of 5 anthropometric measurements of newborns in migrant population were higher than in native population. No significant differences in gene frequencies of 9 blood groups and proteins between these groups were found. Marked deficiency of observed heterozygosity (11%) was found in native population as consequence of the genetical drift.     

Resolving the tragedy of the commons: the feedback between intraspecific conflict and population density

Competition and conflict among individuals can favour exploitative strategies that undermine the common good. Theory suggests that this can lead to a tragedy of the commons and ultimately population extinction, a phenomenon known as evolutionary suicide. Here, I present a model of the evolutionary tragedy of the commons that explicitly considers the population dynamics where individuals invest in individually costly competitive traits. In the simplest form, this supports the notion that selection for high levels of conflict can cause evolutionary suicide. However, as competition comes with survival and fecundity costs, a feedback between the investment in competition and population density can act to reduce the level of conflict and prevent the population from going extinct. This suggests that the interaction between population ecology and the evolution of competition and conflict among individuals may be an important mechanism in resolving the level of competition and conflict among individuals.     

Estimation of the number of individuals founding colonized populations

A method for estimating the number of founding chromosomes in an isolated population is introduced. The method assumes that n/2 diploid individuals are sampled from a population and that alleles are identified at L unlinked loci. The population is assumed to have been founded T generations in the past by individuals carrying c chromosomes drawn randomly from a known source population, which has also been sampled. If c is small and the population grew rapidly after it was founded, accurate estimates of c can be obtained and those estimates are not sensitive to details of the history of population sizes. If c is larger or the population remained small after it was founded, then estimates of c depend on the history of population sizes. We test the performance of our method on simulated data and demonstrate its use on data from a rainbow trout (Oncorhynchus mykiss) population.     

梨小食心虫自然种群与室内继代饲养种群生物学特性比较

【目的】为明确梨小食心虫Grapholita molesta自然种群与室内继代饲养种群生物学特性的差异, 以期为梨小食心虫的人工饲养以及测报与防治提供理论依据。【方法】本研究对室内继代饲养的和从田间采集的梨小食心虫, 在室内同等条件下饲养, 较系统地观察两者的生物学特性并对其主要生命表参数进行了比较。【结果】在本试验条件下, 梨小食心虫室内继代饲养种群的蛹期极显著长于自然种群（t=-10.78, df=4, P=0.0004）; 卵期、 幼虫期以及预蛹期均稍长于自然种群, 但无显著差异。室内继代饲养种群的幼虫存活率、 化蛹率、 羽化率极显著高于自然种群（存活率： t=-7.61, df=4, P=0.0016; 化蛹率： t=-24.32, df=4, P=0.0017; 羽化率： t=-6.96, df=4, P=0.0022）; 两个种群的卵孵化率、 蛹重、 成虫寿命、 产卵前期、 产卵期及单雌产卵量均无显著差异。自然种群蛀果率高于室内继代饲养种群, 但差异不显著。生命表分析表明, 梨小食心虫室内继代饲养种群的种群趋势指数I、 净增殖率R₀、 内禀增长率r_m、 平均世代周期T、 周限增长率λ均极显著高于自然种群（I： t=-12.20, df=4, P=0.0003; R₀： t=-11.72, df=4, P=0.0003; r_m： t=-9.77, df=4, P=0.0006; T： t=-12.05, df=4, P=0.0003; λ： t=-9.79, df=4, P=0.0006）, 种群加倍时间Dt极显著低于自然种群（t=7.17, df=4, P=0.0020）。【结论】室内继代饲养种群在室内连续饲养50多代后, 与自然种群比较, 不仅各生命表参数和钻蛀危害果实的能力没有下降, 反而在与自然种群同等的室内饲养条件下, 表现了更好的适应性, 在本供试条件下, 后代具有更大的种群增长潜力。所以, 利用室内继代饲养种群进行的相关试验研究结果可以作为梨小食心虫预测预报与防治实践的依据。     

基于Vortex模型分析金沙江水电开发对圆口铜鱼种群生存力的影响

圆口铜鱼(Coreius guichenoti)是长江上游特有鱼类,研究金沙江梯级水电开发背景下圆口铜鱼种群生存力变化对该物种的保护具有重要意义。Vortex模型在传统种群评估方法的基础上,引入种群年龄结构、繁殖体制、性比等因素,并考虑了环境、灾害、遗传等随机性对种群的影响,可模拟种群数量和生存力变化特征,是一种应用广泛的种群生存力分析模型。基于1981-2021年金沙江圆口铜鱼资源调查数据,采用Vortex模型构建了金沙江中下游干流大规模水电开发前、后两个时期圆口铜鱼种群生存力分析模型,考虑了水电开发下,水温、流速等环境变化对圆口铜鱼种群的影响,对比了两个时期圆口铜鱼种群数量、结构及生存力等。结果表明:水电开发前,严重过度捕捞对圆口铜鱼种群产生了显著威胁,10年内种群数量下降了12.5%,百年内种群内禀增长率为0.085,种群的生存和繁殖能力较稳定,灭绝概率为1%;水电开发后,10年内种群数量下降了42%,百年内种群内禀增长率降至-0.087,灭绝概率增大至36.1%,种群平均灭绝时间为83.7年,圆口铜鱼抵抗环境干扰的种群恢复能力降低,种群生存力受到影响。     

兔肠道厌氧菌的分离培养条件研究

兔肠道厌氧菌的分离培养条件研究牛钟相朱瑞良张绍学常维山唐珂心徐海花柴家前（山东农业大学动物科学院,泰安２７１０１８）ＳｔｕｄｉｅｓｏｆｔｈｅＣｏｎｄｉｔｉｏｎｓａｂｏｕｔＳｅｐｅｒａｔｉｎｇａｎｄＣｕｌｔｕｒｉｎｇｏｆｔｈｅＡｎａｅｒｏｂｉｏｎｉｎＲ...