农作物保护产品安全与有效使用的管理

通过研究与开发,农作物保护工业开发了当在一体化农作物管理(ICM)框架内使用时会对可持续农业目标作出很大贡献的技术和方法.各成员公司采取措施,以确保开发与生产方法符合最高环境标准,并遵守所有层次的法规.农作物保护工业的管理项目力求确保农作物保护产品安全而有效地流通和使用,从而有利于农业生产,并对发达和发展中世界的环境保护作出贡献.     

Genetic structure of fissiparous populations of Holothuria (Halodeima) atra on the Great Barrier Reef

Allozyme variation at five polymorphic loci was surveyed in a total of 311 individuals of the sea cucumber Holothuria (Halodeima) atra (Jäger, 1833) collected from two nearshore and two midshelf populations in the Great Barrier Reef in November 1996. Strong deviations in genotype frequencies from those expected under Hardy–Weinberg equilibrium, particularly a large number of heterozygote excesses, confirmed the occurrence of asexual reproduction. Females and males differed significantly in genotype frequencies as a result of differences in either the amount of fission in each sex or in the mortality of asexually produced recruits. The estimated maximum sexual input (number of sexually produced individuals: sample size = N*:N_i) to the two nearshore reefs (38 to 67%) was low relative to that to the two midshelf reefs (74 to 87%). The three ratios and G _o :G _e , N _go :N _i , N*:N _i , (where G _o = observed genotypic diversity, G _e = expected genotypic diversity, N _go = number of genotypes) considered to be indicators of the extent of asexual reproduction, showed a consistent trend in the degree of asexual reproduction similar to that derived from the number of regenerating individuals observed in the populations for which data were available. F-statistic analyses of clonal gene frequencies demonstrated that all populations received sexual recruits from the same gene pool. There was evidence of restricted sexual recruitment to the Fantome population, suggesting that asexual reproduction was dominant only in areas where sexual recruitment was limited by other factors.     

Testes mass in megachiropteran bats varies in accordance with sperm competition theory

Sperm competition is a widespread phenomenon influencing a range of characters, including investment in gonadal tissue. Conspecific proximity is one factor which can influence the risk of sperm competition and hence testicular investment, and decreased confidence of paternity may be one cost of group living. Aspects of female biology may also influence spermatogenic investment and sperm morphology. This study examines the associations between relative testes mass and roost-group size across 17 species of Megachiroptera. Associations between breeding season duration and investment in spermatogenesis are also examined, as are associations between female reproductive tract dimensions and testes mass and dimensions of spermatozoa across all bats. Relative testes mass was significantly positively associated with roost-group size at a species level and after appropriate phylogenetic control (pairwise comparisons and comparison of independent contrasts). There were no significant relationships between breeding season duration and relative testes mass. Across all bats, neither testes mass nor sperm length were significantly related to dimensions of the female tract. The results are discussed in the context of sperm competition. Received: 7 January 1998 / Accepted after revision: 8 August 1998