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彭艳  曾燏  张臣  龚建涵  周小云 《水产学报》2018,42(12):1896-1905
为研究蛇(鱼句)耳石的形态特征以及不同环境下的耳石形态差异,以蛇(鱼句)左侧微耳石和星耳石作为研究材料,利用传统形态法测量耳石的14个参数且将其转化为11个形状指标,并利用地标点法在星耳石上选取12个地标点,对2016年6—7月间采自嘉陵江上游、中游、下游的195尾蛇(鱼句)的耳石样本进行形态研究。结果显示,蛇(鱼句)微耳石呈肾形,3个江段微耳石形态无显著差异;蛇(鱼句)星耳石呈圆形、椭圆形,表面粗糙,脊突数少于20,翼叶较基叶发达,中央突不明显,主凹槽轮廓似水滴状。相对扭曲主成分分析将3个江段的蛇(鱼句)星耳石分为两种形态类型:Ⅰ型和Ⅱ型,其中Ⅰ型主要为嘉陵江上游江段蛇(鱼句)的耳石样本,Ⅱ型则包括嘉陵江中游和下游的蛇(鱼句)耳石样本。传统形态法和地标点法的综合结果表明,两种类型耳石形态差异主要表现在整体轮廓、脊突数,以及基叶、主凹槽和背侧距离等特征上,逐步判别分析对Ⅰ型和Ⅱ型星耳石的正判率达95.5%,区分效果较好。研究表明,嘉陵江不同江段蛇(鱼句)星耳石分为两种类型,且存在显著的形态差异;蛇(鱼句)星耳石的形态差异可能是对水温、流速等环境因子主动适应的结果,如在上游生活的蛇(鱼句),其较细长且脊突较多的Ⅰ型星耳石能够较好地适应上游低温、多变的急流环境。  相似文献   
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Environmental variation can shape phenotypic variation in organisms, but most evidence for trait differentiation comes from analyses of dichotomous habitat types that differ in only one or few key environmental factors. In reality, environmental variation is often more subtle, gradual and multifarious. Here, we investigated geographic variation in body shape of two darter species (Etheostoma spectabile and Etheostoma flabellare; Percidae) that occur along river gradients. This study addressed three specific questions: Is there intraspecific geographic variation in the two species across different sites in the Ozark Highlands of Oklahoma (USA)? Is phenotypic variation across sites correlated with abiotic environmental conditions? Do the two species share site‐specific (i.e. convergent) phenotypic variation in areas where they occur together? Our results indicated significant body shape variation in both species. Population differences in body shape were particularly correlated with variation in substrate composition. The combined analysis of both species indicated a small but significant effect of convergence on body shape wherever they are sympatric; shared variation, however, was not related to any environmental variables included in the analysis. While it remains unclear whether phenotypic variation in these species is due to heritable differentiation or environmentally induced plasticity, our results indicate that even subtle and gradual environmental variation can induce substantial variation in phenotypes on a relatively small spatial scale.  相似文献   
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  1. Parasite–host interactions can involve strong reciprocal selection pressure, and may lead to locally adapted specializations. The highly threatened unionoid mussels are temporary parasites on fish, but local adaptation has not yet been investigated for many species.
  2. Patterns of local adaptation of one of Europe's most threatened unionoids, the thick‐shelled river mussel (Unio crassus) were investigated. Eurasian minnows (Phoxinus phoxinus) from two rivers (separate drainage areas) were cross‐infested in the laboratory with sympatric and allopatric mussel larvae, while bullheads (Cottus gobio), inhabiting only one of the rivers, were infested with sympatric or allopatric mussel larvae. Larval encystment, juvenile mussel excystment and survival were measured.
  3. For one river, but not the other, juvenile excystment from P. phoxinus was highest when infested with sympatric mussels. The opposite pattern was found for C. gobio in this river, where juvenile excystment and post‐parasitic juvenile survival from allopatric C. gobio were highest. The results thus cannot confirm local adaptation of U. crassus to P. phoxinus in the study rivers, as excystment was not consistently higher in all sympatric mussel–host combinations, whereas there were potential maladaptive signs of U. crassus in relation to C. gobio. There was no loss of encysted larvae 3 days after infestation until juvenile excystment. Most juveniles were excysted between 17 and 29 days after infestation, and the numbers of excysted juveniles increased with fish size.
  4. The results have implications for parasite–host ecology and conservation management with regard to unionoid propagation and re‐introduction. This includes the need to (1) test suitability and adaptation patterns between U. crassus and multiple host fish species, (2) evaluate the suitability of certain unionoids and host fish strains after more than 3 days, and (3) determine whether large fish produce more juvenile mussels than smaller fish.
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为探索气候变化感知在适应决策过程中的作用机理,本研究以深度访谈数据为基础,基于“感知-适应”分析框架,采用二元Probit模型和泊松回归模型,分析胶州湾地区居民气候变化适应决策和适应选择的影响因素。研究表明,胶州湾地区绝大多数居民已经感知到气候变化,半数以上居民采取了一定的适应措施,大多数居民对适应措施效果的感到满意。居民采取适应措施介于0-4项,平均为1.07项,适应措施的普及率和多样化仍有提升空间。影响胶州湾地区居民气候变化适应决策与适应选择的主要因素存在一定差异性,但“居民对气候变化的感知”不论是对适应决策还是对适应选择的影响都较大,其中又以“对降水变化的感知”和“对气象灾害损失的感知”最为显著。  相似文献   
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【目的】农产品供给与需求的准确分析测定,是农业监测预警能力提升的重要表现。构建产品多品种多环节模型集群理论方法,可高效解决单一环节或单一模型难以解决的分析技术难题。【方法】在农产品供需的重要要素即生产量、消费量、贸易量、价格等分析预测过程中,针对农产品品种间关联性强,自然、社会、经济诸多影响因素纠缠,模型多变量强耦合、非线性、参数时变的特点,提出多品种农产品“因素分类解耦、参数转用适配”方法,以构建多时空维度的监测预警模型集群。【结果】利用“因素分类解耦、参数转用适配”技术方法,研究构建了不同农产品的生产类、消费类、贸易类、价格类的模型集群。这些模型集群可用于对不同时空维度的水稻、玉米、小麦、肉类等主要农产品供需的长中短期的分析预测,支撑形成了农业展望中的主要农产品平衡表,其中主要农产品全国年度生产量6年平均预测精度高于97%。【结论】研究提出的农产品监测预警模型集群构建理论及其方法,有效提升了农产品多品种模型集群的求解效率和准确率,增强了农产品供需分析预测的系统性与智能性,为系统揭示农产品复杂的时空供需变化特征、促进农产品市场调控科学性和可预见性,提供了新技术方法。  相似文献   
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翅多型现象在昆虫中广泛存在,比如蚜虫有有翅蚜和无翅蚜,无翅蚜无翅不能飞行。翅型分化是蚜虫对不良生态环境的适应策略。有翅蚜能飞行,使其逃离不良环境并找到新的栖息地;而无翅蚜繁殖周期短、繁殖量大,有助于维持一定的种群数量。影响蚜虫翅发育的因素有遗传因素和环境因素,由环境因素决定的翅的多型现象被称为翅的非遗传多型性。本文就蚜虫翅型分化的生态学意义、影响因素,以及蚜虫翅型分化的生理和分子机制进行了综述。关于影响蚜虫翅型分化的遗传因素的研究较少,部分研究发现豌豆蚜翅型由X染色体上的一对等位基因所控制。更多的研究表明蚜虫翅型分化受环境因素影响,影响蚜虫翅型分化的环境因素有光周期、温度、种群密度、共生微生物、天敌、杀虫剂及抗生素等,事实上这些环境因素往往不是单方面存在的。保幼激素、蜕皮激素等外源激素会影响包括蚜虫在内昆虫的翅型分化,蚜虫的拥挤效应最终可能也是通过激素调控发挥作用。外源激素可以作用于出生后的低龄若虫也可作用于预产期的成虫,比如给豆蚜中龄若蚜施加保幼激素处理后,会出现超龄若虫,而不是无翅蚜。相反,反-β-法尼烯(EBF)的刺激会诱导有翅蚜后代的产生。另有研究发现,上一代豌豆蚜注射蜕皮激素可以减少有翅后代数量,而通过RNA干扰(RNA interference, RNAi)EcR受体或施加EcR抑制物也会导致后代有翅个体增加。蚜虫翅型分化分子机制的研究起始于对同一基因型蚜虫有翅、无翅成虫个体的差异表达基因或差异表达蛋白。  相似文献   
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Clay is generally considered an important stabiliser that reduces the rate of decomposition of organic matter (OM) in soils. However, several recent studies have shown trends contradicting this widely held view, emphasising our poor understanding of the mechanisms underlying the clay effects on OM decomposition. Here, an incubation experiment was conducted using artificial soils differing in clay content (0, 5, and 50%) at different temperatures (5, 15, and 25 °C) to determine the effects of clay content, temperature and their interaction on fresh OM decomposition. CO2 efflux was measured throughout the experiment. Phospholipid fatty acids (PLFAs), enzyme activities, microbial biomass carbon (MBC), and dissolved organic carbon (DOC) were also measured at the end of the pre-incubation and incubation periods in order to follow changes in microbial community structure, functioning, and substrate availability. The results showed that higher clay contents promoted OM decomposition probably by increasing substrate availability and by sustaining a greater microbial biomass, albeit with a different community structure and with higher activities of most of the extracellular enzymes assayed. Higher clay content induced increases in the PLFA contents of all bacterial functional groups relative to fungal PLFA content. However, clay content did not change the temperature sensitivity (Q10) of OM decomposition. The higher substrate availability in the high clay artificial soils sustained more soil microbial biomass, resulting in a different community structure and different functioning. The higher microbial biomass, as well as the changed community structure and functions, accelerated OM decomposition. From these observations, an alternative pathway to understanding the effects of clay on OM decomposition is proposed, in which clay may not only accelerate the decomposition of organic materials in soils but also facilitate the SOM accumulation as microbial products in the long term. Our results highlight the importance of clay content as a control over OM decomposition and greater attention is required to elucidate the underlying mechanisms.  相似文献   
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