基于GIS和GS的东亚飞蝗卵块空间格局的研究

本文以沿渤海蝗区东亚飞蝗Locusta migratoria manilensis (Meyen) 越冬卵块为研究对象,野外采用450 m和50 m规则栅格取样,包括卵量、植被覆盖度、土壤含水量、含盐量、土壤pH和有机质等,利用地统计学方法,在GIS平台下,分析研究区域内影响蝗虫产卵选择的环境因子、蝗虫卵块的空间异质性及分布格局。结果表明, 植被覆盖度、土壤含盐量和土壤含水量在有卵和无卵的环境中存在极显著的差异,飞蝗产卵时最适宜的植被覆盖度、土壤含水量和盐度范围分别为0～30%、10.1%～20.0%和0.09%～1.99%,且当小环境植被覆盖度>50%、土壤含水量>30%或含盐量>3%时,飞蝗不再选择产卵。蝗虫卵块具有高度空间异质性,其空间自相关范围平均为390 m且呈斑块、聚集分布,蝗虫卵块变异函数曲线为球状模型。利用块段克立格法进行空间局部插值,得到研究区域卵块的空间分布格局图,可较准确地描述飞蝗卵块在研究区域内的空间分布、形状、地理位置及相对位置。研究结果可为地面卵块抽样调查、实时跟踪蝗卵胚胎发育进程、确定蝗灾早期发生点、片防治区域及蝗灾早期遥感预警提供科学依据。     

工业生态学研究足迹迁移——基于Citespace II的分析

由于工业发展与环境关系愈发恶化,可持续发展问题日益突出,有必要通过回顾工业生态学研究来寻找理论指导。利用引文空间分析工具Citespace Ⅱ,通过绘制工业生态学知识图谱,以定量与定性结合方法,系统梳理国内外工业生态学研究成果,挖掘工业生态学的知识基础、发展脉络和研究热点。研究发现:工业生态学是一门交叉性学科,涉及环境科学、生态学、管理学和经济学;生态工业园仍为工业发展重要方向,需要结合生态系统理论与工业流程重构对其加以改善;城市、农业、共生成为当前研究热点;生命周期评估、投入产出分析和工业代谢仍为重要分析工具;我国工业生态问题将成为未来关注重点。     

北方草原牧户心理载畜率与草畜平衡生态管理途径

探讨牧户心理载畜率与草畜平衡生态管理的途径对于草原有效减畜、遏止草原退化、实现可持续发展具有重要意义。从生态学和社会科学相结合的角度,采用问卷调查、情景实验及综合分析等多种方法,探讨了北方草原牧户心理载畜率的存在、计算和影响因素,以及牧户生产决策行为特征和可能的生态管理途径。研究发现,在草甸草原、典型草原和荒漠草原,牧户行为属"有限理性",是有限理性的"生态经济人",风险规避是其基本特征,牧户生产决策表现出禀赋效应、损失厌恶、框架效应等;牧户草场所属草原类型和牲畜存栏数显著影响牧户对草场超载的认知和判断,在不同草原类型区,户主文化水平、性别、民族和是否嘎查干部等亦显著影响牧户对超载的认知和判断;需采取基于进化博弈的分步式、合作式及示范引导式的适应性减畜的生态管理途径,以实现牧户心理载畜率向生态优化载畜率的转移,实现优化牧户生产方式、减少牲畜数量、治理草原退化、北方牧区生态和牧民经济双赢的目标。     

中华按蚊CYP6Y亚家族基因的鉴定和生物信息学分析

【目的】鉴定中华按蚊Anopheles sinensis CYP6Y亚家族基因,分析它们的结构和特征,推测其可能的功能。【方法】以冈比亚按蚊An. gambiae CYP6Y1作为询问序列,通过双向Blast方法检索中华按蚊转录组中CYP6Y亚家族基因,并通过生物信息学方法分析基因结构、特征及可能的功能。【结果】从中华按蚊转录组测序数据中鉴定出2条CYP6Y亚家族基因,分别命名为AsCYP6Y1（GenBank登录号：KF709397）和AsCYP6Y2（GenBank登录号：KF709398）。序列分析显示,AsCYP6Y1和AsCYP6Y2全长分别为1 713 bp和1 815 bp,分别编码502和526个氨基酸。基因结构分析显示,该亚家族基因仅含有1个相位1型内含子并与其他P450基因形成保守的共线性分布。蛋白结构分析显示,这2个基因编码的蛋白含P450特有的5个特征序列和6个底物结合位点,且均不存在信号肽,其亚细胞定位为细胞质。3D结构分析显示,AsCYP6Y1有18条α螺旋和13股反向平行的β折叠,AsCYP6Y2有19条α螺旋和11股反向平行的β折叠。通过同样的方法,在达林按蚊An. darlingi中也鉴定出2个CYP6Y亚家族基因。系统进化分析显示,AsCYP6Y1和AsCYP6Y2分别与其他3种按蚊的CYP6Y1和CYP6Y2聚成一支,Bootstrap值均大于90%。替换率分析显示,中华按蚊AsCYP6Y1和AsCYP6Y2与其他3种按蚊同源基因的Ka/Ks均小于1。相对进化速率分析显示,中华按蚊CYP6Y和CYP6M亚家族的相对进化速率均显著快于CYP6P亚家族,而CYP6Y和CYP6M亚家族之间没有显著差异。【结论】在中华按蚊和达林按蚊中存在2个CYP6Y亚家族基因,之前在冈比亚按蚊和不吉按蚊An. funestus中也发现2个CYP6Y亚家族基因,表明CYP6Y亚家族基因可能在按蚊属广泛存在,且可能为按蚊属昆虫所特有。     

视觉信号在中枢的整合：同步振荡产生的机理和功能

神经系统内各信息通道的信号间如何整合？一个可能的途径就是通过同步振荡来协调。本文对同怕研究进展作了回顾,侧重介绍了视皮怪内同步振荡的提出、实验依据、产生的机理和功能意义,并对可能的进展作了展望。     

遥感数据支持下不同地表覆盖的区域蒸散

将地表能量平衡系统(SEBS)扩展成遥感日蒸散估算模型,利用MODIS遥感数据估算了黄淮海地区的区域蒸散,并在地理信息系统的支持下分析了不同地表覆盖下的区域蒸散统计分布特征.在缺乏各地表覆盖类型相应蒸散量实测值进行对比的情况下,以2001年4月17日估算的日蒸散量为例,通过各地表覆盖类型日蒸散量间的相互对比分析表明,SEBS估算的区域日蒸散量具有一定的合理性.分析结果表明：在黄淮海地区,荒地具有最低的蒸散量;森林、灌木、草地等地表覆盖类型具有中等的蒸散量;而水体、湿地以及耕地具有较高的蒸散量.可能由于包含绿地和水面,城镇用地的蒸散量也较高.土壤含水量的空间差异性导致森林、灌木、草地和耕地等地表覆盖类型的蒸散量具有明显的空间差异性.耕地蒸散量的空间差异性可以为制定合理、高效的农田灌溉计划提供指示作用.SEBS遥感日蒸散模型的局限性在于有可能低估水体和湿地等地表覆盖类型的蒸散量.     

Alignments grow, secondary structure prediction improves.

Using information from sequence alignments significantly improves protein secondary structure prediction. Typically, more divergent profiles yield better predictions. Recently, various groups have shown that accuracy can be improved significantly by using PSI-BLAST profiles to develop new prediction methods. Here, we focused on the influences of various alignment strategies on two 8-year-old PHD methods. The following results stood out. (i) PHD using pairwise alignments predicts about 72% of all residues correctly in one of the three states: helix, strand, and other. Using larger databases and PSI-BLAST raised accuracy to 75%. (ii) More than 60% of the improvement originated from the growth of current sequence databases; about 20% resulted from detailed changes in the alignment procedure (substitution matrix, thresholds, and gap penalties). Another 20% of the improvement resulted from carefully using iterated PSI-BLAST searches. (iii) It is of interest that we failed to improve prediction accuracy further when attempting to refine the alignment by dynamic programming (MaxHom and ClustalW). (iv) Improvement through family growth appears to saturate at some point. However, most families have not reached this saturation. Hence, we anticipate that prediction accuracy will continue to rise with database growth.     

QUANTITATIVE GENETIC VARIANCE MAINTAINED BY FLUCTUATING SELECTION WITH OVERLAPPING GENERATIONS: VARIANCE COMPONENTS AND COVARIANCES

The quantitative genetic variance-covariance that can be maintained in a random environment is studied, assuming overlapping generations and Gaussian stabilizing selection with a fluctuating optimum. The phenotype of an individual is assumed to be determined by additive contributions from each locus on paternal and maternal gametes (i.e., no epistasis and no dominance). Recurrent mutation is ignored, but linkage between loci is arbitrary. The genotype distribution in the evolutionarily stable population is generically discrete: only a finite number of polymorphic alleles with distinctly different effects are maintained, even though we allow a continuum of alleles with arbitrary phenotypic contributions to invade. Fluctuating selection maintains nonzero genetic variance in the evolutionarily stable population if the environmental heterogeneity is larger than a certain threshold. Explicit asymptotic expressions for the standing variance-covariance components are derived for the population near the threshold, or for large generational overlap, as a function of environmental variability and genetic parameters (i.e., number of loci, recombination rate, etc.), using the fact that the genotype distribution is discrete. Above the threshold, the population maintains considerable genetic variance in the form of positive linkage disequilibrium and positive gamete covariance (Hardy-Weinberg disequilibrium) as well as allelic variance. The relative proportion of these disequilibrium variances in the total genetic variance increases with the environmental variability.     

Male sterility at extreme temperatures: a significant but neglected phenomenon for understanding Drosophila climatic adaptations

The thermal range for viability is quite variable among Drosophila species and it has long been known that these variations are correlated with geographic distribution: temperate species are on average more cold tolerant but more heat sensitive than tropical species. At both ends of their viability range, sterile males have been observed in all species investigated so far. This symmetrical phenomenon restricts the temperature limits within which permanent cultures can be kept in the laboratory. Thermal heat sterility thresholds are very variable across species from 23 degrees C in heat sensitive species up to 31 degrees C in heat tolerant species. In Drosophila melanogaster, genetic variations are observed among geographic populations. Tropical populations are more tolerant to heat induced sterility and recover more rapidly than temperate ones. A genetic analysis revealed that about 50% of the difference observed between natural populations was due to the Y chromosome. Natural populations have not reached a selection limit, however: thermal tolerance was still increased by keeping strains at a high temperature, close to the sterility threshold. On the low temperature side, a symmetrical reverse phenomenon seems to exist: temperate populations are more tolerant to cold than tropical ones. Compared to Mammals, drosophilids exhibit two major differences: first, male sterility occurs not only at high temperature, but also at a low temperature; second, sterility thresholds are not evolutionarily constrained, but highly variable. Altogether, significant and sometimes major genetic variations have been observed between species, between geographic races of the same species, and even between strains kept in the laboratory under different thermal regimes. In each case, it is easily argued that the observed variations correspond to adaptations to climatic conditions, and that male sterility is a significant component of fitness and a target of natural selection.     

使用估计的反应自由能预测组成性和可变剪接位点

基因结构预测中的一个重要步骤是精确地识别剪接位点。基于剪接反应的基本物理原则,最大信息原理被应用到剪接反应的理论分析中,进而导出了反应自由能估计表达式。作为一个简化模型,这个表达式能被用来估计一个5′剪接区或者3′剪接区所参与的剪接反应中的自由能变化。它不但较全面地概括了各个碱基之间的关联,而且还考虑了基因组背景概率的影响。这个反应自由能表达式被用来预测了人类基因中的组成性和可变剪接位点,预测结果是令人满意的,其预测能力比得上当前的一些流行方法。这说明最大信息原理可以作为研究某些核酸-蛋白质相互作用系统（如剪接反应）的理论出发点,导出的反应自由能表达式较好地符合了剪接反应过程。