Census and effective population sizes of white‐spotted charr (Salvelinus leucomaenis) in a fragmented landscape

Several habitat models have been proposed to predict population size for stream fishes and to guide habitat assessment and monitoring techniques. However, most models do not incorporate the potential advantage of molecular genetic markers. We conducted a field survey and microsatellite DNA analyses to quantify the relationships among genetic diversity, census/effective population size and habitat variables in fragmented populations of white‐spotted charr (Salvelinus leucomaenis). The census population size significantly increased with the stream length, the number of pools and a pool‐riffle sequence index, a proxy for channel‐unit habitat type complexity within reaches. Population density was correlated with the pool‐riffle sequence index only. Genetic diversity and effective population size were not correlated with the habitat variables or census population size. There was a lack of isolation‐by‐distance population structure in the studied populations. Our results suggest that stream length and the number of pools within reaches associated with habitat complexity are the habitat variables that explain the majority of variation in population size of white‐spotted charr. Our findings provide further evidence that census population size per se is a poor indicator of the inclusive genetic diversity within populations in a fragmented landscape.     

奶牛的有机锌应用效果研究进展

就有机锌对奶牛的营养作用效果、影响有机锌作用效果的因素进行综述。认为添加有机锌可提高奶牛的产奶性能、免疫机能、繁殖性能,改善体健康。同时影响有机锌作用效果的因素有:有机锌的产品质量、添加量和添加时期、饲料营养水平、参照物类型和评价指标等。     

接种高效根瘤菌对紫花苜蓿—禾本科混播组合生产性能的影响

利用筛选的高效根瘤菌接种紫花苜蓿,分别与高羊茅、无芒雀麦及1年生黑麦草混播。与对照相比,接种高效根瘤菌后,紫花苜蓿-高羊茅混播组合中苜蓿干草增产17.0%,高羊茅增产15.1%,总计增产16.3%;紫花苜蓿-无芒雀麦混播组合中紫花苜蓿增产14.0%,无芒雀麦增产51%,总生物量增产20.5%;紫花苜蓿-1年生黑麦草混播组合中,紫花苜蓿增产7.6%,1年生黑麦草干草产量比对照增产4.8%,总生物量增产6.8%。从LER(Land equivalent ratio)和CR(Competitive ratio)变化看,接种高效根瘤菌有利于提高LER值和禾本科作物的CR值。     

乌鲁木齐河流域土地灌溉系统的灰色决策模型研究

本文以乌鲁木齐河流域为试验区,介绍了干旱区流域土地灌溉系统的多目标灰色决策模型的构造原理和方法。利用灰色控制系统的理论和方法建立了灰色优势分析模型,并以该模型为基础建造了多目标灰色决策分析模型。对最优局势的效果测度与综合决策矩阵的构成原理进行了深入探讨,并由此构造了地下水位控制模型与土地灌溉系统的灰色决策模型,为流域地下水位的控制提供了一种新的研究方法。     

浅谈农业科研仪器设备的有效利用

科研仪器设备是现代农业科学研究的物质基础和技术手段.指出了农业科研仪器设备在管理和使用中存在的问题,提出了提高农业科研仪器设备有效利用的途径.     

在市场经济条件下建设共同富裕的和谐社会

建设共同富裕的和谐社会，是发展社会主义市场经济的根本目的，也是区别于资本主义市场经济的重要标志；既要运用市场经济建立起增进社会财富、克服平均主义的竞争机制；又要运用市场经济建立起先富带后富，消除两极分化实现社会公平的激励机制和调节机制；也就是要在市场经济条件下建茈起实现共同富裕、促进社会和谐的有效机制。     

Reproductive strategies in small populations: using Atlantic salmon as a case study

Abstract –  Wild salmonid populations with only a few breeding adults may not exhibit a significant reduction in genetic variability compared with larger populations. Such an observation suggests that effective population sizes are larger than population size estimates based on direct adult counts and/or the mating strategy maximises outbreeding, contributing to increased heterozygosity. In the case of wild Atlantic salmon Salmo salar populations, stratification by age classes and sexes on the spawning grounds avoids inbreeding and increases genetic variability. We studied the breeding composition of four Spanish salmon populations. Over a 7-year period we concluded that the probability of within-cohort mating is very low: females generally reproduce after two sea-winters whereas males reproduce mostly as one sea-winter ( grilse ) and/or mature parr. Considering different levels of contribution of mature parr to spawning derived from field surveys, we developed a simple model for estimating effective population sizes and found that they doubled with 65% parr contribution expected for rivers at this latitude (43°N), and ranged from 100–800 individuals. The effect of between-cohort mating was modelled considering different ranges of differences in allele frequencies between cohorts and resulted in 28–50% increases in heterozygosity when considering a 65% parr contribution. The complex mating strategy of Atlantic salmon contributes to explain the high levels of genetic variability found for small populations of this species. This model can probably be extended to other animal species with mating strategies involving different cohorts.     

新时期应用型本科院校师资队伍建设的思考

目前创新创业教育已成为高等院校教育发展的新思路，作为高校中最宝贵资源的师资队伍状况能否适应这一新形式的要求值得探讨。为此，本文从应用型本科院校师资队伍建设的现状着手，分析了适应创新创业教育发展的师资队伍的特点，并总结了适应新形式的应用型本科院校师资队伍培养的有效途径。     

千万不可忽视良种黄牛的保种问题

阐述了良种牛保种的重要意义．基因的随机漂移、选择与杂交、近交是特定基因从群体中消失的主要原因，群体及其有效含量和系统选育的科学组织是保种的重要内容。最后介绍我国良种牛的保种方法及其存在的问题，并提出解决的办法。     

龙薯1号在丘陵山地高产高效栽培技术研究

为探讨龙薯1号在丘陵山地高产高效栽培技术,2005-2006年对龙薯1号进行了栽培试验,试验采用单因子随机区组排列,重复三次进行。产量对比分析结果显示:种植密度应控制在45500~55500株/hm2;施夹心肥的效益比施夹边肥高;每公顷应施纯氮120 kg、五氧化二磷90 kg、氧化钾210 kg、硼砂15 kg;封垄时喷300kg/hm2多效唑溶液1次。