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61.
62.
Jonathan B. Losos 《Oecologia》1986,68(3):338-343
Summary Step-wise multiple regression was employed to probe the determinants of species diversity of day geckos (Phelsuma) in the Indian Ocean. Independent variables were area, elevation, and two measures of isolation. Distance from Madagascar and island height (an indicator of habitat diversity) were the two most important predictors of species richness. Similar studies on other taxa rarely find isolation to be a major factor. The relatively poor dispersal abilities of reptiles may explain why isolation, rather than attributes of the islands, are more important in this case. The regressions also indicate that habitat diversity (assumed to correlate with maximum island elevation) is more important than area per se in determining species diversity. These results agree with predictions of the equilibrium theory of island biogeography, but historical processes have also greatly influenced species richness. 相似文献
63.
Summary Settlement rates of the high intertidal barnacle, Balanus glandula, were monitored at three sites in the rocky intertidal zone in Central California simultaneously with measurements of larval concentrations in the adjacent water column. In both 1983 and 1984, settlement rates onto vacant substrate differed among the sites by nearly two orders of magnitude. For all sampling dates, this spatial variation in settlement mirrored the spatial distribution of Balanus glandula cyprid concentration in the water column. A perfect rank correlation was found between cyprid concentrations near a site and subsequent settlement. A noteworthy observation was that the sites switched rank in their settlement rates from 1983 to 1984. This change in settlement rankings matched a switch in rankings for cyprid concentrations.Settlement itself appears to be an important cause of the spatial pattern of cyprid concentrations. Comparing the rates of settlement to estimates of the number of cyprids available at a site suggests that settlement causes a large drain on the cyprid population as a water mass passes over successive sites. No consistent spatial patterns were found in the distribution of other major plankton groups (calanoid copepods) that are similar in size to Balanus cyprids but do not settle.The large differences in settlement rates among these sites were previously shown to be a leading cause of large differences in the structure of benthic barnacle populations. The close correspondence shown here between these large differences in settlement and differences in larval concentrations suggests that nearshore oceanic processes affecting larval arrival contribute to the control of benthic community structure. 相似文献
64.
Summary The use of low-pressure steam autohydrolysis in the pretreatment of corn stover and hybrid poplar has been assessed. In terms of yield of prehydrolyzed solids, minimal by-product formation and extent of subsequent enzymatic saccharification, the results of low-pressure steam pretreatment were found to be as good as or better than those reported for more severe pretreatment processes. Almost complete saccharification of the cellulose in the prehydrolyzed biomass solids was obtained within 24h with a commercial cellulase preparation — Celluclast. The presence of grinding elements (glass beads) during the enzymatic hydrolysis was found to increase the extent of saccharification by 40% to 50% over controls without any grinding elements. 相似文献
65.
Carbon content of the neritic scyphomedusa Chrysaora fuscescens 总被引:1,自引:0,他引:1
An analysis of the role of scyphomedusae in a planktonic ecosystemrequires that biomass or numerical abundance estimates be convertibleinto standard units for comparison with other components ofthe planktonic community. One species under investigation isthe brown sea nettle, Chrysaora fuscescens, which is very abundantin coastal waters of the west coast of North America (Shenker,1984). For this species, the carbon content of whole immatureanimals and the body components of sexually mature medusae weredetermined. Immature medusae contained a mean carbon content0.202% of the wet weight. The bell, oral arms and gonadal tissueof mature medusae had mean carbon levels 0.156, 0.554 and 0.576%of the wet weight, respectively. When the relative proportionsof these body tissues were calculated, the mean carbon contentof whole mature medusae was determined to be 0.280% of the wetweight. 相似文献
66.
Distorted segregation and linkage of alcohol dehydrogenase genes in Camellia japonica L. (Theacease)
Alcohol dehydrogenase isozymes in Camellia japonica are encoded by two genes, Adh-1 and Adh-2. Both loci are expressed in seeds, and their products randomly associate into intragenic and intergenic dimers. Electrophoresis of leaf extracts reveals only the products of Adh-2. Formal genetic analysis indicated that the two Adh loci are tightly linked (combined estimate of r=0.004). Most segregations fit expected Mendelian ratios, but in some families distorted segregation was observed at Adh-1, Adh-2, or both loci. The deficient progeny class varied across families, and in two apparent backcrosses three rather than two phenotypic classes were recovered. The mechanism underlying these distortions is not known, but evidence is presented that suggests that the phenomenon is genic or segmental in nature. Plausible hypotheses include linkage of the Adh structural genes with a gametophytic self-incompatibility locus, translocation heterozygosity involving the segment bearing Adh-1 and Adh-2, or a combination of these two mechanisms. 相似文献
67.
Meria E. Penttilä K. M. Helena Nevalainen Alain Raynal Jonathan K. C. Knowles 《Molecular & general genetics : MGG》1984,194(3):494-499
Summary The possibility of cloning filamentous fungal genes by expression in the yeast Saccharomyces cerevisiae has been studied. A genome bank of Aspergillus niger was made in E. coli using a yeast cosmid shuttle vector and over 10,000 different cosmid clones were individually isolated. Yeast transformants carrying Aspergillus DNA were screened for the expression of the genes for fungal secreted glycoproteins, -galactosidase, -glucosidase, and amyloglucosidase, and for the expression of fungal genes complementing yeast ura3 and leu2 mutations.Of the five Aspergillus genes studied, only one, -glucosidase, was found to be expressed in yeast, and this at a low level. This suggests that there are essential differences between the genes of yeast and filamentous fungi. 相似文献
68.
69.
Efficient preparation of spheroplasts fromCandida utilis, Saccharomyces cerevisiae, andSchizosaccharomyces pombe, using a purified mixture of enzymes fromTrichoderma harzianum, is described. Limitations of other methods, and differences between yeasts are demonstrated. 相似文献
70.
Gordon S. A. B. Stewart Sharon Lubinsky-Mink Clive G. Jackson Aliza Cassel Jonathan Kuhn 《Plasmid》1986,15(3):172-181
During the construction of the Messing pUC plasmid series, the rop(rom) gene of pBR322 which mediates the activity of RNAI was deleted. This has resulted in an elevated copy number for the pUC plasmids which makes the expression of beta-galactosidase activity constitutive in a host containing the Iqtss lac repressor. We describe the construction of a new series of vectors which retain the pUC multiple cloning site (MCS) but in which copy number control has been recovered. In addition, the lac alpha/lac promoter expression region has been inserted into a HpaI cassette. This facilitates the movement of recombinant DNA clones within the MCS. It also increases the complementation activity of the lac alpha peptide by an order of magnitude, allowing selection of recombinants by their Lac- phenotype on MacConkey agar. 相似文献