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Subtree analysis and three area satements (TASS) procedure are used to deal with the area relationship in historical biogeography. On the basis of the taxon cladogram, the procedure could identify and eliminate the paralogy node and determine the informative subtree. The area relationships are generally illustrated in several subtrees and the consensus tree. The distribution pattern of the genus Caragana comprising about 72 species and occurring in 13 areas, was analyzed by using subtree method and TASS procedure in this study. The results showed seven subtrees representing the area relationships of section and series of the genus, and the consensus tree provided the 13 area relationships. These results are congruent with our former result using component analysis for Caragana. 相似文献
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NELSON R. COOLEY JAMES M. KELTNER JERROLD FORESTER 《The Journal of eukaryotic microbiology》1973,20(3):443-445
SYNOPSIS. Effects of 2 polychlorinated biphenyls, Aroclor 1248 and 1260, on axenic Tetrahymena pyriformis strain W were investigated and compared with published data on Aroclor 1254. Aroclors 1248 and 1260 at 1 mg/liter in the presence of 0.1% (v/v) polyethylene glycol 200 reduced significantly (P < 0.005) growth rates and 96-hr populations of T. pyriformis grown at 26 C. Both toxicants were ~ 0.001 as toxic as Aroclor 1254. Ciliates were exposed for 7 days to concentrated Aroclors 1248 40X, 1254 60X, and 1260 79X over initial concentrations in the media. Accumulation of Aroclors increased with increased chlorination. It is suggested that if levels in the environment reached those used in these studies, the chief ecologic effect of Aroclor 1254 would be reduction of availability of the ciliates as food and as nutrient regenerators, but with Aroclors 1248 and 1260, this effect would be secondary to accumulation of the toxicants by the ciliates. Accumulation of polychlorinated biphenyls by ciliates would permit the toxicants to enter aquatic food chains. Thus the compounds could exert toxic effects at higher trophic levels. 相似文献
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WE have demonstrated quantitative transformation of cells from primary or secondary Syrian hamster cultures derived from whole embryos by treatment with carcinogens1 and the development of lines that produce tumours in hamsters2. We now report some of the factors which affect the type and number of cells transformed. 相似文献