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1.
Summary The sequential steps in the behavioral process of a California stock of the entomophagous parasite,Venturia canescens (Grav.), parasitizingAnagasta kühniella (Zeller) was studied. In host-habitat finding, food media infested with hosts were very attractive to the parasites. Host finding was not covered in detail in this paper as it is presented in subsequent papers. Briefly, in all experiments host density was the most influential factor affecting the efficiency of the parasite. When three age stages of the host were exposed to a parasite, all tests showed that the large, last instar larvae was the preferred age stage but it was not the most suitable (when parasitized) for successful parasite development. Small larvae were less preferred but more suitable for parasite development when accepted. These studies were conducted as a partial fulfillment in the Ph. D. program of one of us (B. M. Matsumoto) and form a part of a broad investigation into the processes operating in the dynamics of arthropod populations under grants toC. B. Huffaker from the U. S. Public Health Service, National Institutes of Health and the U. S. Department of Agriculture.  相似文献   
2.
ABSTRACT Emerging methods in habitat and wildlife population modeling promise new horizons in conservation but only if these methods provide robust population-habitat linkages. We used Breeding Bird Survey (BBS) data to verify and validate newly developed habitat suitability index (HSI) models for 40 priority landbird species in the Central Hardwoods and West Gulf Coastal Plain/Ouachitas Bird Conservation Regions. We considered a species’ HSI model verified if there was a significant rank correlation between mean predicted HSI score and mean observed BBS abundance across the 88 ecological subsections within these Bird Conservation Regions. When we included all subsections, correlations verified 37 models. Models for 3 species were unverified. Rank correlations for an additional 5 species were not significant when analyses included only subsections with BBS abundance >0. To validate models, we developed generalized linear models with mean observed BBS abundance as the response variable and mean HSI score and Bird Conservation Region as predictor variables. We considered verified models validated if the overall model was an improvement over an intercept-only null model and the coefficient on the HSI variable in the model was >0. Validation provided a more rigorous assessment of model performance than verification, and models for 12 species that we verified failed validation. Species whose models failed validation were either poorly sampled by BBS protocols or associated with woodland and shrubland habitats embedded within predominantly open landscapes. We validated models for 25 species. Habitat specialists and species reaching their highest densities in predominantly forested landscapes were more likely to have validated models. In their current form, validated models are useful for conservation planning of priority landbirds and offer both insight into limiting factors at ecoregional scales and a framework for monitoring priority landbird populations from readily available national data sets.  相似文献   
3.
Busseola fusca (Fuller) is one of the most important pest of cereals in sub-Saharan Africa. Cotesia sesamiae (Cameron) is the predominant parasitoid attacking B. fusca larvae in many parts of Africa. An exotic parasitoid, Cotesia flavipes Cameron, was introduced into Kenya in 1993 for the control of Chilo partellus (Swinhoe). Laboratory studies indicated that although C. flavipes would search for, and attack B. fusca , it was not able to complete its development in this host. The aim of the present study was to investigate the outcome of multiple parasitism of B. fusca by the two Cotesia species. The study showed that when both parasitoid species stung a B. fusca larva at the same time, both parasitoids emerged from more than half of the host larvae, C. flavipes alone emerged from 17%, and C. sesamiae alone emerged from 9%. When the larvae were parasitized by C. sesamiae first, and then 2 h later by C. flavipes , and vice versa, most of the progeny were C. flavipes . However, when B. fusca larvae were stung by C. sesamiae three days before oviposition by C. flavipes , significantly more C. sesamiae emerged from the larvae. When C. flavipes oviposited first, no larvae produced C. flavipes only. The interaction of parasitoids and the host immune system, and the implications of these results for the biological control of stem borers in East Africa are discussed.  相似文献   
4.
An attempt is made to consolidate and extend some of our current thoughts on insect epidemiology using graphical reproduction models. Starting with a simple model with a single equilibrium point, the elementary hypothesis is proposed that epidemics erupt when this equilibrium point increases substantially through improvement of the insect's habitat. The extension of this model to more than one coincident equilibria, some of which may be locally stable, is discussed and generalized using the theory of habitat suitability. Use of equilibrium manifolds is suggested to permit greater dimensionality. Lastly, an explanation of insect epidemics, based on the effects of time delays in the response of density-dependent processes, is elaborated and generalized. The influence of spatial dimensions and insect dispersal on the theory is discussed.  相似文献   
5.
针对物种分布格局与其环境变量关系的研究,对于生态廊道规划与环境恢复研究具有重要意义。本文以白头叶猴(Trachypithecus leucocephalus)为研究对象,针对广西崇左白头叶猴国家级自然保护区51个白头叶猴分布点和11个环境变量数据,利用MaxEnt模型(maximum entropy modeling)对栖息地适宜性进行综合评价,通过模型生成栖息地适宜度指数(habitat suitability index,HSI)阈值,划定研究区域为低适生区、适生区和高适生区3种类型,其中低适生区面积为5 061.43 km2,适生区和高适生区面积分别为42.80 km2和20.63 km2。主要环境变量分析表明:年均降水量、土地利用分类、坡度和年平均气温的综合贡献值分别为54.6%、17.4%、11.8%和9.5%,4项环境变量累积贡献值达到93.3%,是影响白头叶猴分布的主要环境因素。为更有效保护白头叶猴及其栖息地,建议在保护区规划生态廊道,扩大恢复区内白头叶猴适宜栖息地面积,以促进白头叶猴种群间基因交流。  相似文献   
6.
The red imported fire ant Solenopsis invicta Buren (RIFA), an invasive pest that has diverse detrimental impacts on the communities it invades, was recently discovered in China and has the potential to colonize numerous other regions. Using the model of Korzukhin et al. as modified by Morrison et al. and the biological and ecological characteristics of RIFA, we show that Jiangsu Province is a potentially suitable establishment area of RIFA. An isotherm map made by ArcMap, a Geographic Information System, indicated that several regions of Jiangsu Province (Changzhou, Liyang, Wuxian Dongshan, Nanjing and Lvsi) are at higher risk of S. invicta infestation, especially from late July and early August. Quarantine officials should be vigilant for any accidental introductions of this pest in the susceptible regions and time.  相似文献   
7.
Tetrastichus giffardii Silvestri is a gregarious eulophid endoparasitoid of several tephritid fruit fly species. Host stage suitability was studied using nine age groups of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), namely, eggs less than 24 h and between 24 and 48 h old, and 1- to 7-day-old larvae. Life table studies for T. giffardii using C. capitata as host were done at 26 ± 5 °C and 55–60% RH. Egg load in relation to age of the female parasitoid was also assessed as was the effect of host deprivation on adult longevity. Host acceptance and suitability were examined with respect to eight species of tephritids. Potential hosts so tested were five Ceratitis species, the Medfly, C. capitata, the mango fruit fly, Ceratitis cosyra (Walker), the Natal fruit fly, Ceratitis rosa Karsch, Ceratitis fasciventris (Bezzi), and Ceratitis anonae Graham; two Bactrocera species, the melon fruit fly, Bactrocera cucurbitae (Coquillett) and the newly invasive Bactrocera invadens Drew, Tsuruta, and White; and one Dacus species, the lesser pumpkin fly, Dacus ciliatus Loew. No parasitoids were obtained from eggs while all larval stages were suitable though at varying degrees. Parasitism and number of progeny was related to host age in a curvilinear manner with maxima at 4- to 5-day-old larvae. By contrast, development time decreased with age of host larvae while sex ratio was not affected. The intrinsic rate of increase was 0.17 ± 0.01; gross and net reproductive rates were 64.9 ± 4.3 and 44.9 ± 3.8, respectively. Non-ovipositing females lived significantly longer than ovipositing ones. The females accepted all host species tested, but only C. capitata, D. ciliatus and, to a much lesser extent, C. cosyra were suitable. In the remaining host species, most eggs were encapsulated. In C. capitata and D. ciliatus, percent parasitism was similar, but number of progeny was lower and the sex ratio, as the proportion of females, was higher when the parasitoid was reared on D. ciliatus. Progeny per puparium were also similar for the two hosts. In the light of these results it can be concluded that T. giffardii has a narrow host range, but it attacks and successfully develops in larvae representing a wide range of ages.  相似文献   
8.
Conservation breeding management aims to reduce inbreeding and maximize the retention of genetic diversity in endangered populations. However, breeding management of wild populations is still rare, and there is a need for approaches that provide data-driven evidence of the likelihood of success of alternative in situ strategies. Here, we provide an analytical framework that uses in silico simulations to evaluate, for real wild populations, (i) the degree of population-level inbreeding avoidance, (ii) the genetic quality of mating pairs, and (iii) the potential genetic benefits of implementing two breeding management strategies. The proposed strategies aim to improve the genetic quality of breeding pairs by splitting detrimental pairs and allowing the members to re-pair in different ways. We apply the framework to the wild population of the Critically Endangered helmeted honeyeater by combining genomic data and field observations to estimate the inbreeding (i.e., pair-kinship) and genetic quality (i.e., Mate Suitability Index) of all mating pairs for seven consecutive breeding seasons. We found no evidence of population-level inbreeding avoidance and that ~91.6% of breeding pairs were detrimental to the genetic health of the population. Furthermore, the framework revealed that neither proposed management strategy would significantly improve the genetic quality or reduce inbreeding of the mating pairs in this population. Our results demonstrate the usefulness of our analytical framework for testing the efficacy of different in situ breeding management strategies and for making evidence-based management decisions.  相似文献   
9.
基于最大信息熵模型的能源物种麻疯树潜在适宜区   总被引:1,自引:0,他引:1       下载免费PDF全文
麻疯树(Jatropha curcas L.)为传统能源植物,是作为生物柴油最具希望的植物资源之一。本研究通过收集麻疯树分布点的经纬度数据,基于气候、土壤和地形等37个相关生态因子,采用最大信息熵模型,预测麻疯树的潜在适宜区域,分析影响其生长的主要生态因子特征。结果显示,麻疯树生长最适宜区域主要分布在我国华南地区的广东、海南、香港、台湾和西南地区的广西、云南、四川;对麻疯树分布贡献率较大的主要生态因子为:最暖季度降水量(53.5%)、温度季节性变化标准差(15.8%)、降水量变异系数(9.3%)、年均温变化范围(5.8%)、最湿季度降水量(3.6%)、最干月降水量(3.2%);Maxent模型预测的AUC值大于0.9,表明对麻疯树潜在分布的预测结果较准确。本文对麻疯树潜在分布区域以及影响其分布的主要生态条件的研究结果,可为麻疯树的种植栽培提供科学依据。  相似文献   
10.
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