Effects of sterile insect releases on a population under predation or parasitism

Summary A continuous-time differential equation model was constructed which describes the population dynamics of a predator prey system in which sterile prey are released in a program designed to eradicate or reduce the prey population. It was found that the dynamics of the system behave quite differently when predators are present. Two conditions were found which have differing implications for the control program. If the predators still exist when the wild prey population declines to extinction, then the SIRM is assisted by the predators, sometimes to a considereble extent. If the predators decline to extinction before the wild prey population goes extinct, then the predators may or may not assist the SIRM depending on the parameters of the system. If the predators do assist the SIRM, then a potentially dangerous situation exists in which an explosion of the prey population could occur after the predators go extinct. Predator polyphagy would probably minimize this danger of an explosion since it would stabilize the predator population.     

Seasonal forcing on the dynamics ofClethrionomys rufocanus: Modeling geographic gradients in population dynamics

We interpret gradients in population dynamics of the gray-sided vole from the southwestern part of the island of Hokkaido to its northeastern part within the framework of a phenomenological model involving the relative length of summer and winter. In Hokkaido, as in other northern regions, both spring and fall is considered as short transition periods between the two main seasons — summer (the primary breeding season) and winter (the non-reproductive or secondary breeding season). We show that the geographic transition in dynamics may be understood as the combined consequence of different patterns of density-dependence during summer and winter, and geographically varying season lengths. Differences are shown to exist between summer and winter with respect to strength of density-dependence. Direct density-dependence, in particular, is stronger during winter than during summer. A model is presented to show how relative lengths of seasons can induce both stable and periodically fluctuating population dynamics. The results are compared and contrasted with what is otherwise known about the gradient in rodent dynamics in Fennoscandia.     

Hybridization and speciation in the carabid beetles of the subgenusOhomopterus (Coleoptera, Carabidae, genusCarabus)

Natural hybridization among wingless carabid beetles of the subgenusOhomopterus (Carabidae, genusCarabus) is reviewed, and its significance in the evolution of this subgenus discussed. Natural hybridization occurs between parapatric species of similar size. Two case studies of natural hybridization suggest that natural hybridization could have affected the evolution of this subgenus in different ways. When there is a large difference in genital morphology between hybridizing species, interspecific copulation often results in genital injuries that causes mortality of copulating individuals, and hence reduces the fitness of hybridizing individuals greatly. In such a case, hybridization may be effective in maintaining the parapatric distribution of the two species, and in the long term, may promote reinforcement selection for traits which are effective in prezygotic reproductive isolation. When the morphological difference in genitalia is not so large as to cause genital injury, a hybrid population may be established at the intermediate zone between two parental species, provided that the immigration rates of the two species into the intermediate zone are small. Thus, natural hybridization may have contributed to both divergence and reticulate evolution in this subgenus.     

Preference in flower visits and partitioning in pollen diets of stingless bees in an Asian tropical rain forest

Floral resource partitioning among stingless bees (Trigona, Meliponini, Apidae) in a lowland rain forest in Sarawak, Malaysia, was investigated using tree towers and walkways in a 4-year study that included a general flowering period. We obtained 100 collections of insect visitors to flowers of varying floral location and shape representing 81 plant species. The tendency of 11 species of stingless bees to visit specific flowers with a particular floral location and shape was analyzed by logistic regression analysis. This analysis showed that the proportion of flower visitor collections containing Trigona fuscobalteata and T. melanocephala differed according to floral location. The former was frequently collected at canopy and gap flowers, whereas the latter was most often collected at understory flowers. The analysis also suggested that T. erythrogastra was more rarely collected at shallow flowers than at deep flowers. Analysis of the pollen diets of T. collina, T. fuscobalteata, T. melanocephala, and T. melina revealed that similarity of pollen sources differed among the six permutated pairs of the four species. The lowest mean rank of similarity found was between T. fuscobalteata and T. melanocephala. This result supports the hypothesis that preference in visiting flowers in different locations leads to pollen resource partitioning. Received: May 14, 1997 / Accepted: April 23, 1999     

21世纪广西与东盟贸易发展趋势分析

21世纪以来,我国对东盟的贸易有了长足的进展,但广西对东盟贸易的发展与我国与东盟贸易的发展有所不同,我国对东盟贸易以入超为主,而广西与东盟贸易则以出超为主,近年来发展进出口额之间的差距在缩小。广西与东盟贸易尽管比过去已有较大发展,但在我国与东盟贸易中的比重还不大,发展速度也还有限,广西与东盟的人均贸易额还远远低于全国水平,但广西对东盟贸易的增长速度呈现出较强的后劲,广西与全国对东盟贸易的差距将不断的缩小。     

绿色数字普惠金融服务创新模式分析

文章在分析我国环保中小企业融资困境的基础上,基于对江苏宜兴环科园的实地调研,分析宜兴环科园绿色数字普惠金融服务创新模式,进一步探究其运行机理。分析发现,借助大数据、区块链等现代信息技术,数字供应链融资模式和人民普惠金融平台能够有效降低环保中小企业的融资成本,提高融资效率,控制融资风险。在此基础上,文章提出了相应的政策建议,以期为我国环保产业发展提供经验,推进我国经济的绿色发展。     

论计划生育村民自治

建立健全“依法管理、村(居)民自治、优质服务、政策推动、综合治理”的长效工作机制,是《中共中央国务院关于全面加强人口和计划生育工作统筹解决人口问题的决定》(2006)对我国未来计划生育管理提出的基本要求,也是全国部分地区在人口和计划生育综合改革实践中探索出的一条基本经验。然而,对长效工作机制中的“村民自治”,人们在认识上还存在一些误区,从而导致了工作实践中的一些偏差。本文拟就计划生育村民自治中的几个基本问题谈点意见。1计划生育村民自治的概念村民自治是我国广大人民群众直接行使民主权利的一项基本社会政治制度。“计…     

家庭托育点管理实践及启示：政策工具的视角

家庭托育点的规范化对婴幼儿健康成长至关重要。通过文献收集和访谈获得既往管理举措和当前试点政策,运用政策工具进行分析和总结,探究管理家庭托育点的背景、对象和措施。结果表明：家庭托育点因经济优势而被纳入管理,现有征求意见稿管理对象偏向小规模邻托,但试点和市场偏向较大收托规模;消防审查依托既有消防验收,师资准入要求偏低,质量监管依靠政府。管理建议：应根据收托规模区分小型和大型家庭托育点开展试点;完善三方协同的管理架构,设定专门空间环境要求,提高师资准入要求,建立综合质量监管。