Analysis of the relationship between allozyme heterozygosity and fitness in the rare Gentiana pneumonanthe L.

Especially for rare species occurring in small populations, which are prone to loss of genetic variation and inbreeding, detailed knowledge of the relationship between heterozygosity and fitness is generally lacking. After reporting on allozyme variation and fitness in relation to population size in the rare plant Gentiana pneumonanthe, we present a more detailed analysis of the association between heterozygosity and individual fitness. The aim of this study was to test whether increased fitness of more heterozygous individuals is explained best by the ‘inbreeding’ hypothesis or by the ‘overdominance’ hypothesis. Individual fitness was measured during 8 months of growth in the greenhouse as the performance for six life-history parameters. PCA reduced these parameters to four main Fitness Components. Individual heterozygosity was scored for seven polymorphic allozyme loci. For some of these loci (e.g. Aat3, Pgm1 and 6Pgdh2) heterozygotes showed a significantly higher relative fitness than homozygotes. To test the inbreeding model, regression analyses were performed between each Fitness Component and the number of heterozygous loci per individual. Multiple regressions with the adaptive distance of five loci as independent variables were used to test the overdominance model. Only the inbreeding model was a statistically significant explanation for the relationship between heterozygosity and fitness in G. pneumonanthe. The number of heterozygous loci was significantly negatively correlated with the coefficients of variation of three of the six initially measured fitness parameters. This suggests a lower developmental stability among more homozygous plants and may explain the higher phenotypic variation in small populations of the species observed earlier. The importance of the results for conservation biology is discussed.     

半自然农田边界与相邻农田步甲和蜘蛛的时空分布

分别于小麦、玉米收获前后,采用陷阱法调查了华北地区典型农业景观中具有不同植被结构的农田边界及其相邻农田中两类重要天敌类群步甲和蜘蛛的多样性.通过比较农田生境及相邻农田边界间两类天敌群落的时空分布格局及其与相邻半自然生境植被群落的相关关系,探讨半自然农田边界对两类天敌类群的保护作用.结果表明: 整个取样季节农田边界处蜘蛛的多度显著高于农田内部;而步甲多样性在农田与边界间无显著性差异,仅呈现不同的群落结构;作物收获后蜘蛛分科数在边界处的增加以及在农田的减少,显示了蜘蛛在农田和边界之间的迁移活动.边界植被结构对蜘蛛和步甲多样性有不同影响:边界较高的草本层盖度和较低的乔木层盖度有利于增加农田中某些步甲优势种的多样性;而较高的草本层盖度有利于增加皿蛛科蜘蛛的多样性.因此,半自然生境的存在可以通过天敌在农田和边界之间的迁移运动促进农田天敌多样性的维持;但不同类型半自然生境植被群落结构可能影响其对不同天敌群落多样性的维持和保护作用.为促进农业景观对天敌的保护作用,提高其害虫控制功能,需要深入了解不同天敌的生境需求及食物需求,精心设计有利于天敌多样性维持的半自然生境.     

中国海绵天然产物的研究

据统计,从海洋生物的天然产物中获得药物或药物先导化合物的几率要比陆源生物高,海绵是海洋中除珊瑚以外的第二大生物资源。在海绵体内已发现许多高活性的化合物。中国海绵的研究主要集中在南海。南海海绵种类多、数量大,样品采集比较容易。本文统计调查了国内外海绵研究的现状,重点综述中国已研究的海绵种类、所获得的天然化合物以及相关产物的药理研究结果,对上述研究的特点与存在的不足进行了分析、讨论。     

复杂天然产物合成人工生物系统的设计与构建

天然产物是人类疾病预防和治疗药物的最重要来源。合成生物学技术的蓬勃发展为天然产物的开发注入了全新的活力。文中重点介绍了如何利用合成生物技术进行复杂天然产物合成人工生物系统的设计与构建,包括与此相关的生物元件理性设计、生物元件挖掘、途径装配与集成,模块的组装与系统的适配等内容。     

广东省主要水系罗非鱼的建群状况

【背景】罗非鱼是华南地区自然水域的常见种,是我国主要的外来鱼类之一,但对其在自然水域的分布和数量缺乏详细的描述。【方法】对广东省的主要河流珠江(西江、北江、东江)、韩江、鉴江和潭江等的多个样点进行了调查,主要对各样点渔获物中罗非鱼的比例进行了统计,并对各种群的年龄结构、性比、性腺发育和食性等进行了研究。【结果】广东省各主要水系均有罗非鱼野生个体的存在,其中,鉴江袂花江段数量最多,约占渔获物总质量的60%,西江、北江数量相对较少,不到渔获物总质量的1%;在各种群中均发现了2龄以上个体和性成熟个体,并在调查中采集到大量仔、幼鱼。【结论与意义】以上结果表明罗非鱼在广东各主要河流已能完成越冬和繁殖,并建立自然种群。     

Resource Abundance and Invasiveness: A Simple Model

The 'invasiveness' of an alien species depends partly on its ability to become abundant and widespread in its new environment. While competitiveness may be an important component of this ability, so too is the abundance of resource or habitat. First, the local carrying capacity will depend on the local favourability of the habitat, hence the global density will depend on how widespread the habitat is. Second, and more subtly, the local density will also be affected by the global extent of favourable habitat, because of losses occasioned by dispersal when the population redistributes; these losses should be fewer the greater the contiguous area of favourable habitat or the more patches of such habitat across the landscape. Here we describe a model which demonstrates how habitat availability affects an invading speciesèquilibrium abundance, hence its invasiveness. The model shows that local density is likely to be an increasing function of global habitat abundance, and global density to be a non-linear, concave-up function of global habitat abundance. Examples are given to support the model's predictions, taken largely from alien species in New Zealand.     

基因组学技术解码天然产物合成

天然产物一直以来都是新药发现的重要来源。自20世纪末以来,随着组学技术的不断发展,许多生物的基因组被破译并解析,发现基因组中潜藏着众多未知的天然产物生物合成基因簇,而这些基因簇在实验室生长条件下无法表达或低表达。因此,需要综合运用多种学科深入挖掘生物中潜藏的具有新型结构和生物活性的天然产物,使其广泛应用于人类的生产生活。文中将从天然产物合成基因簇的挖掘、“沉默”天然产物合成途径的激活和生物底盘构建3个方面简述基因组学技术在天然产物挖掘中的研究进展。     

Genetic Structure of Blastocerus dichotomus Populations in the Paraná River Basin (Brazil) Based on Protein Variability

The population structure of 147 marsh deer (Blastocerus dichotomus) from three areas in the Paraná River basin, Brazil, was studied by observing protein polymorphism at 17 loci. Six loci were polymorphic and 11 monomorphic. The proportion of polymorphic loci (P) was 35.29% and the average heterozygosity (H) was 6.31%. Wright's F_ST indicated that only 4.9% of the total variation in allelic frequencies was due to genetic differences between the three groups. The high value of F_IS (0.246) indicated inbreeding in the marsh deer. Genetic distance values (D = 0.014–0.051) showed little divergence between the three areas. We suggest that probable mechanisms accounting for the genetic structure are female phylopatry and polygyny and also that inbreeding has resulted from decreasing areas of wetland leading to isolation, overhunting, and diseases transmitted by cattle.