Rapoport's rule claims that latitudinal ranges of plant and animal species are generally smaller at low than at high latitudes.
However, doubts as to the generality of the rule have been expressed, because studies providing evidence against the rule
are more numerous than those in support of it. In groups for which support has been provided, the trend of increasing latitudinal
ranges with latitude is restricted to or at least most distinct at high latitudes, suggesting that the effect may be a local
phenomenon, for example the result of glaciations. Here we test the rule using two models, a simple one-dimensional one with
a fixed number of animals expanding in a northern or southerly direction only, and the evolutionary/ecological Chowdhury model
using birth, ageing, death, mutation, speciation, prey-predator relations and food levels. Simulations with both models gave
results contradicting Rapoport's rule. In the first, latitudinal ranges were roughly independent of latitude, in the second,
latitudinal ranges were greatest at low latitudes, as also shown empirically for some well-studied groups of animals. 相似文献
Carduus acanthoides and Carduus nutans (plumeless and musk thistles) are among the most noxious weeds in the United States of America, presenting a serious challenge
in cropping and pasture systems. Unfortunately, a lack of detailed spatial distribution information hampers both our ability
to understand the factors affecting their invasive success, and the effectiveness of monitoring and management efforts. To
examine patterns of distribution and co-occurrence at a local level, we sampled a 5000 km2 area of central Pennsylvania that cut a transect across known areas of C. acanthoides and C. nutans infestation. A number of potential environmental explanatory variables were recorded and analyzed to examine whether they
correlated with observed species distribution patterns. Patterns of forest density and spatial aggregation of the thistles
were the primary covariates that significantly impacted both species’ distributions. The survey established that the frequency
of sightings for each species diminished as the ranges converged, with only brief overlap: the two species are strongly negatively
correlated in space. Understanding environmental correlates of infestation and the pattern of spatial dissociation of these
two invasive species is an important step towards an improved understanding of the mechanisms underlying their invasive potential,
and hence towards effective weed control. 相似文献
Restoration models and practise to date have been applied mainly to ecosystems. More recently, there has been a focus on the “landscape perspective” of ecosystem restoration in order to improve nature conservation and management effectiveness.
Here, we clarify some of the differences between ecosystem- and landscape-oriented restoration, and propose four components that should be considered in planning and conceptualising: (a) landscape composition and configuration; (b) traditional land management techniques; (c) linear and point features; and (d) other heritage features. We further discuss the concept of reference landscapes, and the contrasts between restoration and rehabilitation. Spatial approaches to restoration are explored, comparing small areas with complete restoration (“museum landscapes”) from large areas with rehabilitation of landscape physiognomy or point and linear features. The linkages with nature conservation and the sustainable use and management of natural resources are examined in the context of a rapidly changing world. 相似文献
Development data of eggs and pupae ofXyleborusfornicatus Eichh. (Coleoptera: Scolytidae), the shot-hole borer of tea in Sri Lanka, at constant temperatures were used to evaluate a linear and seven nonlinear models for insect development. Model evaluation was based on fit to data (residual sum of squares and coefficient of determination or coefficient of nonlinear regression), number of measurable parameters, the biological value of the fitted coefficients and accuracy in the estimation of thresholds. Of the nonlinear models, the Lactin model fitted experimental data well and along with the linear model, can be used to describe the temperature-dependent development of this species. 相似文献
Based on the traditional polygene inheritance model of quantitative traits,the author suggests the major gene and polygene mixed inheritance model.The model was considered as a general one,while the pure major gene and pure polygene inheritance model was a specific case of the general model.Based on the proposed theory,the author established the segregation analysis procedure to study the genetic system of quantitative traits of plants.At present,this procedure can be used to evaluate the genetic effect of individual major genes (up to two to three major genes),the collective genetic effect of polygene,and their heritability value.This paper introduces how to establish the procedure,its main achievements,and its applications.An example is given to illustrate the steps,methods,and effectiveness of the procedure. 相似文献
Climate change will alter the abundance and distribution of species. Predicting these shifts is a challenge for ecologists and essential information for the formation of public policy. Here, I use a mechanistic mathematical model of the interaction between grass growth physiology and aphid population dynamics, coupled with the climate change projections from the UK's Hadley Centre HadCM3 global circulation model (GCM) and Canada's Center for Climate Modeling and Analysis CGCM2 GCM to predict the changes in the abundance and distribution of summer cereal aphid populations in wheat-growing regions of Canada. When used with the HadCM3 projections, the model predicts a latitudinal shift northward in abundances but there is longitudinal variation as well. However, when used with the CGCM2 projections the model predicts that continental regions will see a decline while coastal regions will see an increase in summer cereal aphid populations. These effects are stronger under the higher emissions scenarios. 相似文献