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Jian Yang Thomas E. Dilts Lea A. Condon P. Lee Turner Peter J. Weisberg 《Landscape Ecology》2011,26(3):381-395
Riparian vegetation is distinct from adjacent upland terrestrial vegetation and its distribution is affected by various environmental
controls operating at the longitudinal scale (along the river) or transverse scale (perpendicular to the river). Although
several studies have shown how the relative importance of transverse or longitudinal influences varies with the scale of observation,
few have examined how the influences of the two scales vary with the level of ecological organization. We modeled vegetation-environment
relationships at three hierarchically nested levels of ecological organization: species, plant community, and vegetation type.
Our hierarchically structured analyses differentiated the spatial extent of riparian zones from adjacent upland vegetation,
the distribution of plant community types within the riparian zone, and the distribution of plant species within community
types. Longitudinal gradients associated with climate and elevation exerted stronger effects at the species level than at
the community level. Transverse gradients related to lateral surface water flux and groundwater availability distinguished
riparian and upland vegetation types, although longitudinal gradients of variation better predicted species composition within
either riparian or upland communities. We concur with other studies of riparian landscape ecology that the relative predictive
power of environmental controls for modeling patterns of biodiversity is confounded with the spatial extent of the study area
and sampling scheme. A hierarchical approach to spatial modeling of vegetation-environment relationships will yield substantial
insights on riparian landscape patterns. 相似文献
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Ovulation rate and pre- and postimplantation survival in mice with a major gene for rapid postweaning gain 总被引:1,自引:0,他引:1
Differences in ovulation rate, embryo survival, litter size, and fertility are presented for four lines of mice that have been selected for growth or are homozygous for a recessive gene (hg) imparting rapid postweaning gain. Two of the lines were hg/hg, one in a growth-neutral and one in a growth-selected background. The remaining two were Hg/Hg (the corresponding normal, dominant allele with no effect on postweaning gain) in the same two backgrounds. Average ovulation rates ranged from 10.9 to 17.1 eggs shed, and litter sizes ranged from 8.6 to 14.0. In the growth-selected background, the hg allele reduced the number of ovulations, implantation, and litter size by nearly three compared with the Hg/Hg controls. The impact of the hg allele in the growth-neutral background was not significant. When males of a different line selected for high litter size were mated to females of the four stocks, more than two additional eggs, implants, and pups were recorded, compared with results of mating to males of the same line as the female. 相似文献
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A mutation in the R body-coding sequence destroys expression of the killer trait in P. tetraurelia 总被引:3,自引:0,他引:3
This report describes a mutant strain of Caedibacter taeniospiralis 169 that does not produce refractile (R) bodies or kill sensitive paramecia, but still renders its host resistant to killing by wild-type strains of Caedibacter taeniospiralis. The mutation is due to insertion of a 7.5-kilobase, transposon-like element into the R body-coding region of the plasmid pKAP169. The results provide strong evidence that R body synthesis is required for expression of the killer trait. 相似文献
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Byer Nathan W. Dilts Thomas E. Larrucea Eveline S. Crowell Miranda M. Shoemaker Kevin T. Weisberg Peter J. Matocq Marjorie D. 《Landscape Ecology》2021,36(12):3575-3590
Landscape Ecology - Environmental changes produce discontinuities in suitable habitat. However, drawing inference into the effects of these changes on contemporary genetic patterns is often... 相似文献
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