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RADIOCARBON DATES AND VEGETATIONAL HISTORY OF THE BRITISH ISLES   总被引:2,自引:10,他引:2  
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AN ECOLOGICAL ACCOUNT OF ATLANTIC BRYOPHYTES IN THE BRITISH ISLES   总被引:6,自引:5,他引:1  
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D. W. Snow 《Ibis》1953,95(2):242-270
This paper aims to bring together the chief observations that have been recorded so far on visible migration in the British Isles.
The autumn movements that have been seen on the various coasts, and inland, are briefly described, and the few spring observations are summarized.
Maps show the directions which migrating Corvidae, Starlings, Chaffinches and Skylarks have been seen to take in autumn, and there is some discussion of the autumn movements of these four species. The observed movements of some of the other chief passerines, and of the Wood-pigeon, Stock-dove and Lapwing, are more briefly mentioned.
Some of the differences in the migratory behaviour of different species are mentioned, and some of the most obvious gaps in knowledge of visible migration in the British Isles are pointed out.  相似文献   

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原羚属分类地位研究兼论中国羚羊的分类   总被引:5,自引:0,他引:5  
中国羚羊类动物在世界羚羊类动物中有着特殊的地位,其中普氏原羚、藏原羚和藏羚是中国特有的珍稀物种,普氏原羚是极度濒危动物.开展中国羚羊类动物的分类和进化研究是当务之急.本研究利用形态特征、头骨测量及线粒体DNA的12S rRNA(440 bp)和16S rRNA(590 bp)对原羚属的分类地位及中国其他几种羚羊分类地位进行了探讨,发现对质量性状和数量性状数据的聚类分析的结果差异大,而且质量性状的聚类结果比较符合传统的分类系统.分子分类也得到相似结果,但在属下的分析存在较大差异.7种牛科动物的12S rRNA和16S rRNA序列差异分别为0.2%~7.1%和0.3%~8.4%.系统进化分析表明原羚属3种羚羊形成单系群,且蒙古瞪羚与普氏原羚的关系较藏原羚与普氏原羚的关系近.赛加羚应归宿于羚羊亚科,而不是与羊亚科的藏羚形成独立的赛加羚亚科.原羚属的进化可能与青藏高原的隆起有关.  相似文献   

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《Ibis》1948,90(1):112-115
The diagnostic criteria, ranges, hybrid zones, and migrations of the three indigenous British races of Turdus ericetorum are defined. The migratory dispersal of T. e. catherinœ is traced, and its identity as the innominate "small, dark migrant Song-thrush" of workers is established. An explanation of the distributions of T. ericetorum races in the British Isles is advanced. T. e. ericetorum and T. e. hebridensis are ascertained to be moderately migratory, T. e. catherinœ strongly so. The findings on early records of T. e. hebridensis on passage evidence confusion between that form and T. e. catherinœ. Irish, Stornoway (Lewis, Outer Hebrides), and Orkney and Shetland breeding populations require further racial study.  相似文献   

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The very common green seaweeds Enteromorpha intestinalis (L.) Nees and E. compressa (L.) Nees are important fouling organisms and have commonly been used as indicators of eutrophication, but their taxonomic status is problematic. The genus presents extreme difficulties because there is wide intraspecific variation in morphology, but morphological differences between species are small and difficult to detect. In this study, molecular data were used in parallel with morphological characters to resolve the taxonomic problems. Phylogenetic analysis of sequences of the internal transcribed spacers ITS1 and ITS2 and the 5.8S gene distinguished two groups of samples, which were identified by morphological characters as E. compressa (branched) and E. intestinalis (normally unbranched). There was a low level of sequence divergence within each group of samples, but divergence between groups was as great as that between either of the two species and the outgroup E. prolifera. Clades representing E. compressa and E. intestinalis were also found in analyses of an independent molecular data set, chloroplast DNA restriction fragment length polymorphisms (RFLPs). Enteromorpha intestinalis and E. compressa represent two distinct, genetically divergent species. Reinterpretation of published studies shows that these species are reproductively isolated. However, E. compressa and E. intestinalis are sometimes very difficult to distinguish from each other and could be regarded as cryptic species. The presence or absence of branching was the most useful character distinguishing these two species, but there was an element of ambiguity because low salinity or salinity shock can induce branching in E. intestinalis. If environmental factors such as salinity are taken into account, branching can be used to identify the great majority of thalli correctly. This study therefore provides a basis for identifying the two most important marine fouling macroalgae and for their use in environmental monitoring and experimentation. Typification of these two Linnaean species showed that current usage of the names accords with the lectotype and protologue of both species. Samples that resembled E. usneoides did not form a clade in any of the trees, and constraining the data to support the monophyly of this group incurred a penalty. Enteromorpha usneoides appears to be an ecotype of E. compressa.  相似文献   

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