Empirically simulated study to compare and validate sampling methods used in aerial surveys of wildlife populations

This paper compares the distribution, sampling and estimation of abundance for two animal species in an African ecosystem by means of an intensive simulation of the sampling process under a geographical information system (GIS) environment. It focuses on systematic and random sampling designs, commonly used in wildlife surveys, comparing their performance to an adaptive design at three increasing sampling intensities, using the root mean square errors (RMSE). It further assesses the impact of sampling designs and intensities on estimates of population parameters. The simulation is based on data collected during a prior survey, in which geographical locations of all observed animals were recorded. This provides more detailed data than that usually available from transect surveys. The results show precision of estimates to increase with increasing sampling intensity, while no significant differences are observed between estimates obtained under random and systematic designs. An increase in precision is observed for the adaptive design, thereby validating the use of this design for sampling clustered populations. The study illustrates the benefits of combining statistical methods with GIS techniques to increase insight into wildlife population dynamics.     

An under-appreciated difficulty: sampling of plant populations for analysis using molecular markers

Results of studies using molecular markers for determining demographic and genetical population parameters especially in plants or sessile animals under field conditions are strongly dependent on the sampling strategy adopted. There are two critical decisions to make when determining this strategy: (i) what is the unit to be sampled?, (ii) how should units to be sampled in the field be selected? For the first decision, there are two conceptually different approaches: sampling ramets of clonal plants as units (to get information about within-genet parameters, such as genet sizes or numbers) and sampling genets of clonal or non-clonal plants as units (to get information of the genetic structure of the population). For the second decision, it is critically important to make the goal of the study explicit. We argue that in this case fully random sampling is needed only when an estimate of the true value of the population parameter is needed; if a comparison between populations is the goal, however, other sampling schemes may be adopted. The efficiency of different types of sampling strategies to recover relative values in a spatially extended population is studied by means of a spatially explicit simulation model. The results show that a regular pattern of sampling is best for obtaining information on genet sizes or inbreeding coefficients; in contrast, random or hierarchical sampling strategies are better for obtaining information on parameters that are based on comparison of pairs of individuals, such as distribution of genet sizes or autocorrelation in genetic structure. A set of recommendations is provided for designing a good sampling strategy.     

北京地区红脂大小蠹空间分布型与抽样技术研究

对北京地区红脂大小蠹Dendroctonus valens LeConte空间分布型进行了研究。结果表明红脂大小蠹成聚集分布,其聚集原因是由红脂大小蠹本身的聚集行为或聚集行为与环境的异质性共同作用引起。同时,应用Iwao统计方法,提出了最适理论抽样数和最佳序贯抽样模型。     

The genetic consequences of selection in natural populations

The selection coefficient, s, quantifies the strength of selection acting on a genetic variant. Despite this parameter's central importance to population genetic models, until recently we have known relatively little about the value of s in natural populations. With the development of molecular genetic techniques in the late 20th century and the sequencing technologies that followed, biologists are now able to identify genetic variants and directly relate them to organismal fitness. We reviewed the literature for published estimates of natural selection acting at the genetic level and found over 3000 estimates of selection coefficients from 79 studies. Selection coefficients were roughly exponentially distributed, suggesting that the impact of selection at the genetic level is generally weak but can occasionally be quite strong. We used both nonparametric statistics and formal random‐effects meta‐analysis to determine how selection varies across biological and methodological categories. Selection was stronger when measured over shorter timescales, with the mean magnitude of s greatest for studies that measured selection within a single generation. Our analyses found conflicting trends when considering how selection varies with the genetic scale (e.g., SNPs or haplotypes) at which it is measured, suggesting a need for further research. Besides these quantitative conclusions, we highlight key issues in the calculation, interpretation, and reporting of selection coefficients and provide recommendations for future research.     

拉缘蝽空间格局及抽样技术的研究

拉缘蝽空间格局测定结果表明,拉缘蝽的1—3龄若虫、4—5龄若虫和成虫等各虫态的空间格局均属于聚集分布,拉缘蝽1—3龄若虫聚集度最高,4—5龄若虫聚集度下降,成虫聚集度更低。在拉缘蝽空间格局的基础上,确定了Kuno风险决策序贯抽样表和1wao—Kuno（1968）理论抽样数。     

The conflict between natural and artificial selection in finite populations

Summary A single locus model of the interaction between natural selection and artificial selection for a quantitative character in a finite population, assuming heterozygote superiority in natural fitness but additive action on the character, has been studied using transition probability matrices.If natural selection is strong enough to create a selection plateau in which genetic variance declines relatively slowly, then the total response to artificial selection prior to the plateau will be much less than that expected in the absence of natural selection, and the half-life of response will be shorter. Such a plateau is likely to have a large proportion, if not all, of the original genetic variance still present. In selection programmes using laboratory animals, it seems likely that the homozygote favoured by artificial selection must be very unfit before such a plateau will occur. A significant decrease in population fitness as a result of artificial selection does not necessarily imply that the metric character is an important adaptive character.These implications of this model of natural selection are very similar to those derived by James (1962) for the optimum model of natural selection. In fact, there seems to be no aspect of the observable response to artificial selection that would enable anyone to distinguish between these two models of natural selection.     

桃潜叶蛾在桃园的空间分布型和取样技术研究

应用聚集度指标法、Iwao回归分析和频次比较法．研究了桃树重要害虫桃潜叶蛾成虫的空间分布型。结果表明桃潜叶蛾成虫在桃园呈负二项分布,分析提出了该害虫适宜的调查抽样方法。     

Dynamics of age- and size-structured populations in fluctuating environments: Applications of stochastic matrix models to natural populations

Recent developments of the theory of stochastic matrix modeling have made it possible to estimate general properties of age- and size-structured populations in fluctuating environments. However, applications of the theory to natural populations are still few. The empirical studies which have used stochastic matrix models are reviewed here to examine whether predictions made by the theory can be generally found in wild populations. The organisms studied include terrestrial grasses and herbs, a seaweed, a fish, a reptile, a deer and some marine invertebrates. In all the studies, the stochastic population growth rate (ln λ _s ) was no greater than the deterministic population growth rate determined using average vital rates, suggesting that the model based only on average vital rates may overestimate growth rates of populations in fluctuating environments. Factors affecting ln λ _s include the magnitude of variation in vital rates, probability distribution of random environments, fluctuation in different types of vital rates, covariances between vital rates, and autocorrelation between successive environments. However, comprehensive rules were hardly found through the comparisons of the empirical studies. Based on shortcomings of previous studies, I address some important subjects which should be examined in future studies.     

三叶斑潜蝇幼虫种群空间格局及抽样技术研究

三叶斑潜蝇Liriomyza trifolii是我国重要的园艺及蔬菜害虫,研究三叶斑潜蝇种群的空间格局和抽样技术,可为该虫的危害调查与防治提供理论依据。应用Iwao m*-m回归分析法、Taylor的幂法则及6个聚集指标,对三叶斑潜蝇幼虫在番茄和豇豆上的空间分布型和抽样技术进行了研究,并做了影响因素分析。结果表明:三叶斑潜蝇幼虫在番茄和豇豆上均呈聚集分布,分布的基本成分是以个体群形式存在,通过分布型参数,采用Kc法、Iwao法及Taylor幂法计算出了在不同精度下三叶斑潜蝇田间的理论抽样数。     

玉米田斜纹夜蛾空间分布型及抽样技术

对秋甜玉米田的斜纹夜蛾不同发生密度田块调查 ,取得了 7组样本资料 ,运用聚集度指标法、Iwao法和Taylor法等对其空间分布型进行测定检验 ,结果表明斜纹夜蛾幼虫呈聚集分布 ,其聚集原因经Blackith种群聚集均数测定 ,当m <3 .2 60 4时 ,其聚集是由于某些环境如气侯、土壤湿度、植株生长状况等所致 ;当m >3 .2 60 4时 ,其聚集是由于害虫本身的群集行为与环境条件综合影响所致。在此基础上 ,通过几种抽样方式比较以五点式为最佳 ,并提出了最佳理论抽样数和最佳序贯抽样模型 :N =1 D2 (3 .8981 m +0 .75 0 3 ) ,To(n) =0 .5n± 2 .865n。     

Worldwide distribution of transposable element copy number in natural populations of Drosophila simulans

Abstract.— Transposable elements (TEs), which promote various kinds of mutations, constitute a large fraction of the genome. How they invade natural populations and species is therefore of fundamental importance for understanding the dynamics of genetic diversity and genome composition. On the basis of 85 samples of natural populations of Drosophila simulans , we report the distributions of the genome insertion site numbers of nine TEs that were chosen because they have a low average number of sites. Most populations were found to have 0–3 insertion sites, but some of them had a significantly higher number of sites for a given TE. The populations located in regions outside Africa had the highest number of sites for all elements except HMS Beagle and Coral , suggesting a recent increase in the activity of some TEs associated with the colonization patterns of Drosophila simulans . The element Tirant had a very distinctive pattern of distribution: it was identified mainly in populations from East Africa and some islands in the Indian Ocean, and its insertion site number was low in all these populations. The data suggest that the genome of the entire species of Drosophila simulans may be being invaded by TEs from populations in which they are present in high copy number.     

柑橘全爪螨空间格局与抽样技术的研究

本应用空间分布型统计参数IwaoM-X模型中α,β及6个聚集指标分析了柑橘全爪螨的空间格局,并对抽样技术进行了探讨。结果表明,柑橘全爪螨的空间格局为聚集型;田间的抽样部位是上、中、下三部的叶片。提出了估算柑橘全爪螨在不同虫口密度下的理论抽样数。     

中国陆域地表人类活动与自然环境的空间关系研究

在人类活动主导人地矛盾的当代背景下,从空间关联角度测度人类活动与自然环境相互作用是推动区域可持续发展的基本前提。以2015年数据为基础,通过选取特征变量构建综合测度指标体系,利用小波多尺度分析、双变量局域空间自相关、人地系统耦合协调度模型等方法多层次刻画中国陆域地表人类活动与自然环境的空间相关关系、空间匹配关系、空间耦合关系。研究结果表明:①人类活动与自然地理基础的空间相关关系随着地域尺度增大而趋于增强,说明自然环境条件对人类活动格局的基础性作用;②人类活动与自然资源支撑的空间匹配关系呈现非均衡性特征,华北地区人类活动规模与自然资源支撑空间错位显著、区域可持续发展面临严峻挑战;③人类活动与自然环境承载的空间耦合协调度从东南向西北递减,调整人类活动的结构与方式是化解区域人地矛盾的理性选择。     

杨扇舟蛾卵和幼虫的空间分布型及抽样技术

研究了杨扇舟蛾Clostera anachoreta(Fabricius)卵和幼虫的空间分布型及抽样技术,结果表明杨扇舟蛾卵和幼虫在杨树林的分布型均为聚集型中的负二项分布。几种抽样方法中,卵以棋盘式最好,幼虫以平行线法最好。同时建立了杨扇舟蛾卵的下层抽样模型为y=2.4481x 0.4243;幼虫的中、下层抽样模型为y=2.4605x 3.9126。     

甘薯象空间格局及抽样技术研究

通过空间分布型指数分析,甘薯象对薯块、著株危害空间分布型为随机分布或均匀分布;同时确定了理论抽样数     

Genetic variation in natural and laboratory populations of the marsupial Sminthopsis crassicaudata

Gel electrophoresis of blood proteins has detected allelic variation at five loci (TRF, PGD, SOD, ADA, GPI) in a laboratory colony of the dasyurid marsupial Sminthopsis crassicaudata. Family data show no significant departures from Mendelian expectations. Analysis of blood from wild-caught progenitors of the colony revealed significant differences in gene frequency between groups of animals captured from different parts of southern and central Australia and showed that there are two major population clusters. These interpopulation differences are particularly marked at the TRF locus and indicate that the river Murray is a barrier for this species.This project was supported by a grant from the Australian Research Grants Scheme.     

黑角直缘跳甲幼虫空间分布型及抽样技术的研究

通过运用二种回归方法和六种聚集度指标对黑角直缘跳甲幼虫的空间格局和抽样技术进行了研究。所有的指标表明黑角直缘跳甲幼虫在林间呈聚集分布,分布的基本成分是个体群,且个体间相互吸引。在空间分布型研究的基础上提出了理论抽样数和序贯抽样方案。通过不同抽样方式的精确度比较,表明对角线抽样方式最佳。     

Genetic diversity in a seed production population vs. natural populations of Sitka Spruce

Isozyme analysis was applied to estimate the level of variation and the genetic structure of a seed-production population (i.e., seed orchard) and 10 range-wide natural populations of Sitka spruce (Picea sitchensis (Bong.) Carr.). Gene diversity and heterozygosity estimates were comparatively high in both the seed orchard and the natural populations studied. The seed orchard population showed a significantly higher number of alleles per locus and percentage of polymorphic loci. Though not significant, mean heterozygosity of the seed orchard was higher than that observed for all natural populations. Genetic distance analysis indicated that the seed-orchard population was genetically similar to three natural populations from which the parent trees were selected. Parent trees sampling breadth has been identified as the major cause for the observed increased level. The impact of recurrent selection and seed orchard biology and management on maintaining the genetic diversity is discussed.     

Evaluation ofChaoborus predation on natural populations of herbivorous zooplankton in a eutrophic lake

Hydrobiologia - The effect ofChaoborus predation on natural zooplankton communities was tested in enclosure experiments during June, July and August in the eutrophic Frederiksborg Slotssø,...