On a property of the exponential distribution

If t is an independent exponentially distributed random variable, the distribution p = [t - x] is a modified geometric distribution, similar to the result of HAWKINS and KOTZ (1976), x is uniform.     

Reconstructing the Pleistocene geography of the Aphelocoma jays (Corvidae)

Understanding historical distributions of species and evolving lineages has been a topic of considerable interest, yet methods used to date have not provided detailed, quantitative distributional hypotheses. Here, we present a technique based on models of species’ ecological niches and Pleistocene climate reconstructions that provides such hypotheses, providing the example of reconstructions for the Aphelocoma jays. We demonstrate in general a greater degree than expected of stability in jay species’ distributional areas back through at least the most recent glaciation event, and that existing patterns of genetic differentiation may date to before the Late Pleistocene glaciations. More generally, the method offers the potential for reconstructing historical distributions of species or lineages, and providing a detailed geographic framework for addressing many biogeographic and systematic questions.     

Modelling potential biotope composition on a regional scale revealed that climate variables are stronger drivers than soil variables

Aim

Environmental conditions define the suitability of an area for biotopes, and any area can be suitable for several biotopes. However, most previous studies modelled the distribution of single biotopes ignoring the potential co-occurrence of biotopes in one area, which limits the usefulness of such models for conservation and restoration planning. In this study, we described the potential biotope composition of an area in response to environmental conditions.

Location

Bavaria, Federal State of Germany.

Methods

Based on the Bavarian biotope mapping data, we modelled the distribution of 29 terrestrial biotopes based on six climate variables and six chemical and four physical soil properties using the species distribution modelling algorithm Maxent.

Results

For most biotopes, we found that climate variables were more important than soil variables for the biotope distribution and that the area of the predicted biotope distribution was larger than the observed distribution. The potential biotope composition illustrated that while 8% of the area in Bavaria was not sufficiently suitable for any analysed biotope, 92% of the modelled area in Bavaria was suitable for at least one biotope, 84% for two and 77% for at least three biotopes. The difference in suitability between the most suitable biotopes in composition was minor. Further, over one-quarter of the modelled area was suitable for 6–8 different biotopes.

Main Conclusions

Our study showed that considering a composition of potentially suitable biotopes in a raster cell, instead of only the most suitable biotope, provides valuable information to identify conservation priorities and restoration opportunities.     

Compound Intervened Poisson Distribution

The nature and characteristics of Intervened Poisson Distribution (IPD) has been well discussed by Shanmugam (1985). In this paper, Compound Intervened Poisson Distribution (CIPD) is introduced and its properties are studied.     

Evaluation of the spatial distribution of Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae) in South Korea combining climate and host plant distribution

Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), a global forest pest, has a potential to damage forests in South Korea, requiring an effective tool for evaluating its potential distribution. This study aimed to evaluate the spatial distribution of A. glabripennis in South Korea by simultaneously considering climate and host plants. Climatic suitability was firstly evaluated using a CLIMEX model; then, it was combined with the areal distribution of host plants using a simple mathematical formulation. We finally projected the spatial distribution of A. glabripennis onto the map of administrative districts to identify hazardous areas to watch. As a result, the developed model predicted that over 40% of areas in South Korea could be exposed to A. glabripennis damage, and most of them were located in mountainous areas with abundant host plants. In addition, climatic suitability was higher in coastal areas, which was different than a previous record of A. glabripennis occurrence, while the prediction by a comprehensive model was consistent with the record. In conclusion, the model including both climate and host plant occurrence was more reliable than the model which only included climate, and could provide useful data for determining areas for monitoring and control.     

On the Discrete POISSON-Inverse GAUSSian Distribution

The discrete POISSON-inverse GAUssian distribution is obtained by compounding the POISSON distribution with the inverse-GAUssian distribution. The maximum likelihood of the parameter is discussed. Comparison with the POISSON, negative binomial, POISSON-LINDLEY and the generalized WARING distribution when fitting a distribution to accident statistics data is given.     

动物种群空间分布Matlab源程序

动物种群空间分布因物种、种群、生境等特点的不同可以分为均匀分布、随机分布、聚集分布（负二项分布、Neyman分布、Poisson-二项分布）等类型,根据上述各分布函数用Matlab语言分别编程,以达到各分布函数理论值计算简化的目的。     

A note on the statistical properties of animal locations

A statistical model of the successive locations of an animal in the plane induces a statistical model of the relative positions of successive locations. A common locational model is that the Cartesian coordinates of successive locations in the plane are independent bivariate normal random variables. This note gives the statistical properties of the direction and length of the vector joining successive locations.     

花曲柳窄吉丁的空间分布

2004年4月~9月,在天津市大港区官港森林公园对花曲柳窄吉丁Agrilus planipennis的空间分布和垂直分布进行了调查研究,应用扩散系数(C)等6种指数法分析测定,确定了该虫在林地中的空间分布呈聚集分布,分布的基本成分是个体群。扩散蔓延规律为聚集型扩散。花曲柳窄吉丁幼虫在树干的垂直分布主要区间在50~150 cm之间。对幼虫垂直分布与树干高度的关系进行分析,其符合立方曲线,曲线方程为:Y=-5.142 9+17.943 7X+21.662 3X2-14.545X3;相关系数R2=0.915,P=0.013。     

Comments on "Improving estimates of the basic reproductive ratio: using both the mean and the dispersal of transition times"

Comments on Heffernan, J. M., Wahl, L. M. (2006). Improving estimates of the basic reproductive ratio: Using both the mean and the dispersal of transition times. Theoretical Population Biology, 70, 135-145.     

科尔沁沙地盐生草甸主要植物群落种群格局的研究

本文采用方差/均值法,Greig-Smith格局分析法及Hill格局分析法,探讨了科尔沁沙地盐生草甸主要植物群落种群格局及其成因。结果表明,羊草群落和野古草群落中的大部分种为聚集分布,羊草与野古草群落交错区中所有种为聚集分布,其最小面积为0.01m~2,最大面积为6.4×6.4m~2。邻接格子最小取样面积应小于0.05×0.05m~2,最适取样面积为40.96m~2,小规模格局是种子扩散和营养繁殖的结果,中规模起因于匍匐和长根茎的扩散,大规模则取决于土壤总盐分及pH值。     

Limits to the estimation of species richness: The use of relative abundance distributions

The present study demonstrates the possibility of estimating species numbers of animal or plant communities from samples using relative abundance distributions. We use log‐abundance–species‐rank order plots and derive two new estimators that are based on log‐series and lognormal distributions. At small to moderate sample sizes these estimators appear to be more precise than previous parametric and nonparametric estimators. We test our estimators using samples from 171 published medium‐sized to large animal and plant communities taken from the literature. By this we show that our new estimators define also limits of precision.