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.     

医科与农科大学生SCL——90测查比较研究

用心理卫生自评量表(SCL———90)调查了内蒙古蒙医学院和哲里木畜牧学院两高校大学生的心理健康和差异,结果表明,两高校学生男女总体心理健康水平无明显差异,存在的心理问题各具特点,而医科学生心理问题较多,强度较大。     

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     

南京市自主创新能力的现状分析

运用企业自主创新能力的评价指标体系,对南京市自主创新能力水平进行纵向和横向比较,可以比较好地把握其自主创新能力的现状。通过对南京市近四年自主创新能力指标的纵向比较,不难发现除了自主创新环境之外,南京市的自主创新资源、自主创新活动以及自主创新产出能力均有较大幅度的增长;通过将南京市与三大科技竞争力较强的城市自主创新能力指标进行横向比较,指出了南京市在自主创新能力上存在的突出问题。一是工业增加值率过低,二是研发经费过低。并在此基础上提出一系列对策和建议。对于提高南京自主创新能力水平,无疑具有重大的理论意义和现实意义。     

SCP视角的资源产业组织及其优化的理论分析

SCP理论是现代西方产业组织(IO)理论中占主导地位的理论。文章试图将该理论运用于自然资源产业问题研究中,也就是运用SCP理论的分析框架来研究资源产业组织问题即自然资源产业内部的资源生产经营企业之间的相互关系,这种理论分析旨在促进资源产业组织不断地趋于合理化和优化。     

福柯和自由主义:理性,革命和反抗

在1978-1979年法兰西学院的演讲中,福柯引入了"管治能力"的概念.这个概念来自于基督教的牧师形象.由此出发,与马克思主义的政治经济学批判不同,福柯对自由主义持一定的赞赏态度.福柯和马克思都参与了宏大叙事的一般构架的建立,但他们的政治和哲学前提是不同的.马克思根植于自然法的传统走向革命,福柯则继承了英国激进主义传统走向反抗.这两种传统是可以进行深入对话的.