共查询到19条相似文献,搜索用时 78 毫秒
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本文报告了沈阳市不同淡水水域枝角类及其分布的调查结果,定性地分析了其分布特征与水质污染状况的关系。 相似文献
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浙江淡水维管束植物的区系特点与地理分布 总被引:16,自引:1,他引:16
根据15年的调查结果,对浙江省水生维管束植物的区系与地理分布特点进行了研究。已知浙江有水生维管束植物150种,隶属于78属,42科。将78属归纳为11个分布区类型,以世界分布类型所占比例最高,热带分布属总数多于温带分布属,泛热带分布和北温带分布比例非常高。将150种植物归纳为13个分布区类型,温带分布远多于热带分布,以东亚分布类型最为突出,体现了中国-日本植物区系的明显特征,探讨了浙江水生植物的水平地带性和垂直地带性分布规律,其分布不仅与气候带有关,更与水生的生境的分布格局有关。最后,报浙江水生植物濒危种的受威胁状况。 相似文献
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面包酵母的投喂密度对3种淡水枝角类种群增长的影响 总被引:2,自引:0,他引:2
面包酵母的投喂密度对3种淡水枝角类种群增长的影响王金秋刘世昌郭东辉(华东师范大学生物系,上海200062)EffectofFeedingDensityofBraker’sYeastonthePopulationGrowthofThreeFr... 相似文献
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海南岛淡水龟类区系特点及保护优先性分析 总被引:11,自引:3,他引:11
海南岛是我国淡水龟类分布较为集中、物种丰富度高、动物区系独特的地区,已知的淡水龟有2科8属11种,占全国淡水龟种数(24种)的46%。海南岛淡水龟物种密度为3.2种/10^4km^2,均为东洋界成分,其中华南区种4种,占36.4%;华中-华南区共有的种7种,占63.6%;海南特有种2种,占岛内淡水龟种数的18.2%。海南岛淡水龟占华南地区淡水龟种数(19种)的57.9%。海南与广东、广西和香港的淡水龟类区系关系也十分密切,与它们的生物相似值分别为0.76、0.64和0.47。目前,中国75%的淡水龟类濒危,海南岛81.8%的淡水龟类濒危。分析表明,海南岛应是我国淡水龟类资源优先保育的地区。 相似文献
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峨眉山槭属植物的地理分布和区系特点 总被引:5,自引:1,他引:5
本文报道了分布于四川峨眉山槭属植物,计26种1变种。讨论了槭属植物在峨眉山的垂直分布与水平分布规律。峨眉山槭属植物的区系组成是亚热带和温带东亚区系成分。 相似文献
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湖北铁线莲属的区系特征及地理分布 总被引:5,自引:0,他引:5
在查阅文献和标本采集鉴定的基础上,确认湖北铁线莲属(Clematis L.)有37种14变种。对湖北铁线莲属的区系地理进行了分析。铁线莲属的分布中心在中国的亚热带地区,在中国范围内云南和四川分布的种类最多(包括变种),然后以此为中心向四周的分布逐渐减少。湖北铁线莲属大部分种类分布在鄂西山区。湖北铁线莲属的地理成分以中国特有分布为主,中国特有成分占湖北种类总数的68.6%。区系的性质是温带性的。根据毛茛科最原始的类群金莲花亚科Subfam.Helleboroideae起源中心的推测和铁线莲属古老类群的分布,推测铁线莲属起源于中国西南地区,并以此解释湖北铁线莲属区系和周围省份铁线莲属区系的关系。 相似文献
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福建大田长兴组的小有孔虫动物群 总被引:1,自引:1,他引:1
首次报道福建省大田崆峒山晚二叠世晚期长兴组中,与Palaeofusulina筵类群共生的小有孔虫动物群,计有22属64种(包含1个新种,2个未定种),称Colaniella-Pachyphloia ovata组合。通过这一动物群的研究,不但为福建地区长兴组补充了新的化石门类,且为该组的时代归属又提供一佐证,对该地区长兴组中的灰岩层古生态特征也作了简要的探讨。 相似文献
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Marco Masseti 《Human Evolution》2006,21(2):85-93
The term “anthropochorous” can be referred to the fauna which has populations or nuclei of individuals brought to and diffused in geographical areas by the direct or indirect action of humans. This definition therefore implicates the role of humans, either conscious or unconscious, in the alteration of the areas of distribution of the fauna. Hence, all the faunal populations that have originated as a consequence of human intervention fully belong to this category. As well as domestic animals in the strict sense, we can also cite several other “wild” species, such as rats and mice, which at present enjoy an artificial diffusion in areas that are completely extraneous to that of their original distribution. 相似文献
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On littoral Cladocera of Iraq 总被引:2,自引:2,他引:0
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Genotypic characteristics of the Cladocera 总被引:1,自引:10,他引:1
Paul D. N. Hebert 《Hydrobiologia》1987,145(1):183-193
Work on the genetics of cladocerans reproducing by cyclic parthenogenesis has indicated that populations usually include a
large number of genotypes, whose frequencies are in close approximation to Hardy-Weinberg equilibrium. Less diverse genotypic
arrays and pronounced instability in genotype frequencies occur only in permanent populations exposed to limited ephippial
recruitment. Genetic diversification among local cladoceran populations is greater than in most other organisms as a consequence
of the inefficiency of passive dispersal. Genotypic characteristics of cladocerans reproducing by obligate parthenogenesis
are markedly different from those of cyclic parthenogens. Local populations include few clones, but genetic distances between
them are often large and accompanied by significant ecological and morphological divergence. When considered over their entire
range, cladoceran taxa reproducing by obligate asexuality are the most genotypically diverse asexual organisms known. This
diversity has originated from the spread of a sex-limited meiosis suppressor through species that originally reproduced by
cyclic parthenogenesis. The confused state of cladoceran taxonomy is partially a consequence of the presence of such obligately
asexual groups, but also results from the occurrence of hybridization and sibling species. The genome size of cladocerans
is exceptionally small and is associated with a large amount of endopolyploidy. Somatic tissues in adult cladocerans show
a range in nuclear DNA content from 2–2048 c. DNA quantification studies have additionally revealed the frequent occurrence
of polyploid clones in obligately asexual taxa. 相似文献