共查询到20条相似文献，搜索用时 312 毫秒
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Cannatella DC 《Science (New York, N.Y.)》2008,320(5878):874; author reply 874
Becker et al. (Reports, 14 December 2007, p. 1775) reported that forest amphibians with terrestrial development are less susceptible to the effects of habitat degradation than those with aquatic larvae. However, analysis with more appropriate statistical methods suggests there is no evidence for a difference between aquatic-reproducing and terrestrial-reproducing species. 相似文献
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Cristol DA Brasso RL Condon AM Fovargue RE Friedman SL Hallinger KK Monroe AP White AE 《Science (New York, N.Y.)》2008,320(5874):335
Mercury has contaminated rivers worldwide, with health consequences for aquatic organisms and humans who consume them. Researchers have focused on aquatic birds as sentinels for mercury. However, trophic transfer between adjacent ecosystems could lead to the export of aquatic mercury to terrestrial habitats. Along a mercury-contaminated river in Virginia, United States, terrestrial birds had significantly elevated levels of mercury in their blood, similar to their aquatic-feeding counterparts. Diet analysis revealed that spiders delivered much of the dietary mercury. We conclude that aquatic mercury pollution can move into terrestrial habitats, where it biomagnifies to levels in songbirds that may cause adverse effects. Rivers contaminated with mercury may pose a threat to the many bird species that feed on predatory invertebrates in adjacent riparian habitats. 相似文献
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A synthetic theory of the ecology of amphibian metamorphosis is founded on the observation that the large variation in length of larval period and body size at metamorphosis typical of a particular species of amphibian cannot be directly explained by differences in dates of hatching or egg sizes. It is proposed that as development proceeds, variation in exponential growth coefficients causes a trend from a normal distribution to a skewed distribution of body sizes. The degree of skewing increases and the median of the distribution decreases with increasing initial densities of populations. The relative advantages of the largest members of a cohort may arise from a variety of mechanisms including the production of growth inhibitors, interference competition, and size-selective feeding behavior. These mechanisms result in a nonnormal distribution of competitive ability, a possible source of the density-dependent competition coefficient found in systems with many species (1). In our model the ranges of body sizes and dates of metamorphosis are determined by a minimum body size that must be obtained and a maximum body size that will not be exceeded at metamorphosis. Between these two size thresholds the endocrinological initiation of metamorphosis is expected to be related to the recent growth history of the individual larva. Species that exploit uncertain environments will have a wide range of possible sizes at metamorphosis. Species exploiting relatively certain environments will have a narrower range. The evolution of neoteny and direct development logically follow from the application of these ideas to the ecological context of the evolution of amphibian life histories. Species that live in constant aquatic habitats surrounded by hostile environments (desert ponds, caves, high-altitude lakes) may evolve permanent larvae genetically incapable of metamorphosis. Other populations may evolve a facultative metamorphosis such that populations are a mixture of neotenes and terrestrial adults. Direct development results from selection to escape the competition, predation, and environmental uncertainty characteristic of some aquatic habitats and is usually accompanied by parental care. The relation between our ecological model and the physiological mechanisms that initiate metamorphosis can only be suggested and it remains an open problem for developmental biologists. 相似文献
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为探讨安徽通江湖泊4种典型生境浮游植物群落结构及其影响因子，于2018年4月、7月、10月和2019年1月，对4种典型生境中24个采样点的浮游植物群落进行了调查分析。4种典型生境分别为自然湖泊生境（H1）、沉水植被生境（H2）、挺水植被生境（H3）和人工养鱼塘生境（H4）。在4种典型生境中共鉴定出浮游植物235种，隶属8门94属。物种数最多的生境为H1（196种），物种数量最少的生境为H4（89种）。4种生境中H1优势种以硅藻门为主，其中颗粒直链藻（Melosira granulata）优势度最高，为1.384；H2优势种主要分布在绿藻门；在H3中尖针杆藻（Synedra acus）优势度最高，为1.153；H4中蓝藻门的固氮鱼腥藻（Anabaena azotica）占优势明显。4种典型生境中浮游植物生物量H4 > H3 > H1 > H2，细胞密度H4 > H2 > H3 > H1。H1浮游植物Shannon-Wiener多样性指数最大、Pielou均匀度指数和Margalef丰富度指数的最大值均出现在H2。4种典型生境的环境条件具有空间异质性，总氮、总磷和透明度等在统计上存在显著差异，Pearson相关性分析与RDA分析结果表明，影响浮游植物群落结构的主要因子有水生植被盖度、营养盐和透明度等。 相似文献
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Holm-Hansen O 《Science (New York, N.Y.)》1963,139(3559):1059-1060
Algae from terrestrial and fresh-water habitats in Antarctica were examined for ability to fix atmospheric nitrogen. Nostoc commune was the only species capable of growing in nitrogen-free medium; nitrogen fixation by this species was verified by assimilation of N(15). The importance of nitrogen-fixing algae to terrestrial life in the Antarctic is discussed. 相似文献
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Schell DM 《Science (New York, N.Y.)》1983,219(4588):1068-1071
Inputs of terrestrial peat carbon to the nearshore Alaskan Beaufort Sea from erosion and fluvial transport are of the same magnitude as in situ primary production within 10 kilometers of shore. Nevertheless, carbon-13/carbon-12 ratios and carbon-14 abundances in marine organisms show that only small amounts of the terrestrial carbon are transferred beyond the microbial level. Freshwater organisms, however, are heavily dependent on peat, as shown by pronounced seasonal radiocarbon depressions in resident fish and ducks. Tundra ponds and lakes are areas where accumulated terrestrial peat carbon is apparently transferred to aquatic insect larvae and passed on to higher organisms. The lack of functionally analogous abundant marine prey organisms may explain why peat carbon is not efficiently transferred to apical food web species in the marine environment. 相似文献
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为了解食蚊鱼Gambusia affinis对华南地区水生昆虫多样性的影响,在实验室条件下,以食蚊鱼栖境中有代表性的3种水生昆虫为猎物,研究食蚊鱼的捕食选择性.结果表明,在单捕食者-多种猎物作用系统中,当猎物密度较低时,食蚊鱼对不同猎物的捕食选择性差异不显著.但随猎物密度的增加,食蚊鱼对白纹伊蚊Aedes albopictus幼虫和蛹的捕食量明显增加,对摇蚊Chironomus kiiensis幼虫和蜉蝣Cloeon bengalense稚虫的捕食量下降.在单捕食者-2种猎物的作用系统中,在猎物比例相同的情况下,食蚊鱼更喜欢捕食白纹伊蚊幼虫;但是在猎物总数不变的情况下,改变猎物比例,对食蚊鱼总的捕食量影响不大.说明食蚊鱼喜欢捕食漂浮于水面上、会动的活体猎物,对死的或不动的猎物不敏感,且对蚊子幼虫具有明显的嗜好性. 相似文献
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采用样线法,结合使用归纳法和访问法,于2011年3～7月对已获国家批准进行水电规划的四川省雷波县豆沙溪流域内的两栖爬行动物作了专项调查.结果表明,该流域两栖爬行动物共有3目11科23种,其中两栖动物有2目7科12种,爬行动物1目4科11种;该流域内两栖爬行动物均为东洋界种类,无古北界种类,分布类型以喜马拉雅—横断山区型为主.根据流域两栖类栖息的生态特点,其生态环境划分为流水、静水、陆地(含陆地—流水、陆地—静水),分布的种类较为均衡;爬行类栖息的生态环境划分为林地、灌草丛、田地,其中灌草丛生态类型是该流域爬行类主要的分布区域.预测分析了该流域水电规划对两栖爬行动物的影响,并提出了相应的环保对策. 相似文献
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把鹤类及其生境作为整体研究对象,利用Vanderploeg选择系数评估鹤对生境的选择性,利用Neu方法通过可获得性系数与可利用性系数比较评估鹤对生境类型的偏好,研究了2001—2006年黄河三角洲鹤类与生境的对应关系。结果表明:芦苇沼泽是鹤类偏好性选择的生境,为白头鹤、白枕鹤、灰鹤优先选择的生境。潮间带是鹤类回避性选择生境,为白鹤和丹顶鹤优先选择的生境。河道、养殖池、农田和草地4类生境受人为活动的影响较重,鹤类利用较低,年度间利用情况变化大。当生境类型发生改变时,鹤类会自主选择更为适宜的生境并导致对其它生境的选择性改变。 相似文献
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神农架自然保护区川金丝猴退化生境特征及恢复技术 总被引：1，自引：0，他引：1
对神农架川金丝猴分布区218个样地进行调查,比较川金丝猴未退化生境与退化生境群落特征的差异,并依据未退化生境群落分类构建生境恢复模式群落。结果表明:神农架保护区川金丝猴的针阔混交林和针叶林生境退化较为严重,落叶阔叶林生境退化较轻;退化生境与未退化生境群落的乔木物种组成大致相同,但灌木种数和食源灌木种数均少于未退化生境;森林砍伐、病虫害危害、生境过度利用是导致生境退化的主要原因;生境群落的郁闭度和乔木平均高随退化程度加重而降低;轻度和中度退化生境的灌木盖度和食源灌木盖度也低于未退化生境;重度退化生境具有最高的灌木盖度、食源灌木盖度和灌木高度。根据未退化生境群落分类总结出神农架川金丝猴生境恢复的8个模式群落,提出了轻度、中度和重度退化生境的恢复模式和技术。 相似文献
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针对栖息地受损,河流生态完整性受到严重威胁的现状,以MesoHABSIM模型为基础,选取易采集、分布广且能较好反映栖息地条件的大型底栖动物为目标水生生物,对其栖息地适宜度进行了探索。针对缺乏反映河道底部特征的水文形态参数和大型底栖动物群落结构功能分析两方面的不足,为实现定量化表征大型底栖动物栖息地适宜度的目标,改进了水文形态模型和生物模型,建立了改进的大型底栖动物中尺度栖息地适宜度模型。水文形态模型中增加了反映河道底部条件的底部剪切力参数;生物模型中,除单一目标物种外,增加功能摄食类群分析,研究偏好不同流速、基质条件的底栖动物,主要包含撕食者、牧食收集者、滤食收集者、刮食者、捕食者等。 相似文献
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基于MaxEnt模型的紫椿适生区预测 总被引：4，自引：4，他引：0
气候变化通过改变物种的生境进而影响生物多样性。紫椿是一种具有高生态、经济、药用价值的用材树种,在我国与其他香椿属物种一起被称为“中国桃花心木”。了解该物种对生境要求、评价其生境质量、预测其适生区分布有助于紫椿的保护、引种及其人工林的发展。MaxEnt模型的优点在于能利用现存不完整、小样本、离散型分布数据构建物种适生区预测模型,且用受试者工作曲线下面积(AUC)检验预测模型的精度,面积越大精度越高。研究应用紫椿在云南分布数据及MaxEnt软件构建其适生区分布模型,结果表明:适生区分布模型平均训练AUC和平均测试AUC分别为0.959和0.818,说明对紫椿适生区的预测是可靠的;温度季节性变化的标准差、最冷月最低温(℃)、最干季度平均温度(℃)、最冷季度降水量(mm)、年均温变化范围是决定紫椿适生区分布的重要因素。对当代和未来(21世纪50年代,21世纪70年代)气候变暖条件下(RCP2.6情景)的紫椿在云南省和全国适生区面积进行了计算,结果直观、定量反映了气候变化下紫椿适生区的变迁,预测云南省及全国的紫椿适生区随全球变暖而萎缩。 相似文献
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Geographic variation in the number of coexisting plant and animal species (species density) often follows repeated patterns; best known is the general increase in species richness from temperate to tropical latitudes. Here we undertake a quantitative analysis of geographic trends in species density for the terrestrial vertebrate faunas of the United States and Australia. Trends in numbers of species of amphibians, reptiles, birds, and mammals are described and are correlated with geographic variation in abiotic environmental measures. Intercontinental comparisons reveal general patterns as well as intriguing and profound differences in vertebrate distributions. 相似文献
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【目的】调查分析柳州市不同生境冬季鸟类群落的多样性,探究影响鸟类多样性的生境因素,为城市生态建设提供参考。【方法】采用样线法进行调查,计算鸟类群落的多样性指数（H）、均匀度指数（J）和相似性指数（S）,并分析鸟类群落的基本结构和多样性特征。【结果】共记录到鸟类13目42科118种,以雀形目占绝对优势,有26科85种。留鸟是柳州市冬季鸟类的主要组成部分,共记录鸟种79种,而冬候鸟共记录34种,旅鸟5种。从鸟类区系来看,东洋种67种,古北种31种,广布种20种。各生境鸟类群落多样性顺序为：城市园林〉农田居民区〉石山灌丛〉湖泊洼地〉商品林区。农田居民区与湖泊洼地鸟类群落的相似性最高。【结论】空间异质性和食物资源是影响柳州市冬季鸟类群落多样性的重要因素,可通过优化树种结构、改善生境、加强保护宣传等方式,提高城市冬季鸟类多样性。 相似文献