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71.
EDWARD C. RHODES JONATHAN D. BATES ROBERT N. SHARP KIRK W. DAVIES 《The Journal of wildlife management》2010,74(4):755-764
Abstract: We evaluated 6 years of vegetation response following prescribed fire in Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis) steppe on vegetation cover, productivity, and nutritional quality of forbs preferred by greater sage-grouse (Centrocercus urophasianus), and abundance of common arthropod orders. Habitat cover (shrubs and tall herbaceous cover [>18 cm ht]) was about 50% lower after burning compared to unburned controls because of the loss of sagebrush. Perennial grasses and an invasive annual forb, pale alyssum (Alyssum alyssoides), increased in cover or yield after fire. There were no increases in yield or nutritional quality of forb species important in diets of sage-grouse. Abundance of ants (Hymenoptera), a significant component in the diet of young sage-grouse, decreased after fire. These results suggest that prescribed fire will not improve habitat characteristics for sage-grouse in Wyoming big sagebrush steppe where the community consists of shrubs, native grasses, and native forbs. 相似文献
72.
A. J. RIBBINK A. C. MARSH B. A. MARSH B. J. SHARP 《Zoological Journal of the Linnean Society》1983,79(3):223-243
Two species of Labeotropheus are currently recognized, but an earlier study of aquarium specimens caused doubt to be cast upon their specific distinctness. This doubt was removed by a field and laboratory study which showed that L. fuelleborni differed from L. trewavasae morphologically, in coloration, in geographic distribution, preferred habitat and ability to penetrate depth. The two species practise assortative mating.
Labeotropheus fuelleborni feeds predominantly from upper surfaces of rocks while L. trewavasae favours under surfaces. Although both species are specialized to crop epilithic algae they also feed secondarily on other food resources (e.g. plankton, insects) when these are available.
Gene flow between many populations of rock-frequenting cichlids is restricted by their sedentary nature and apparent inability to cross open water between rocky areas. Consequently, numerous geographic races, incipient species and species are found in the lake. This suggests that intralacustrine allopatric speciation may account for much of the species diversity of cichlids of rocky zones.
It is recommended that biologists working on cichlids from Lake Malawi should ascertain the precise location at which their specimens were caught and avoid using aquarium reared fish. 相似文献
Labeotropheus fuelleborni feeds predominantly from upper surfaces of rocks while L. trewavasae favours under surfaces. Although both species are specialized to crop epilithic algae they also feed secondarily on other food resources (e.g. plankton, insects) when these are available.
Gene flow between many populations of rock-frequenting cichlids is restricted by their sedentary nature and apparent inability to cross open water between rocky areas. Consequently, numerous geographic races, incipient species and species are found in the lake. This suggests that intralacustrine allopatric speciation may account for much of the species diversity of cichlids of rocky zones.
It is recommended that biologists working on cichlids from Lake Malawi should ascertain the precise location at which their specimens were caught and avoid using aquarium reared fish. 相似文献
73.
74.
Floyd Matthew Mizuyama Masaru Obuchi Masami Sommer Brigitte Miller Mark GR Kawamura Iori Kise Hiroki Reimer James D. Beger Maria 《Coral reefs (Online)》2020,39(5):1361-1376
Coral Reefs - Global warming is leading to range shifts of marine species, threatening the structure and functioning of ecological communities and human populations that rely on them. The largest... 相似文献
75.
GR Hunt 《New Zealand journal of zoology.》2013,40(1):68-76
Woodpeckers and certain passerine species secure encased food in the environment in various ways to facilitate the extraction of the contents with their bills. They do this by securing the food items in locations such as crevices and holes, newly defined in this paper as ‘vice-anvils’. Here I report that free-living New Caledonian crows (Corvus moneduloides) and rooks (Corvus frugilegus, in New Zealand) also use vice-anvils to process candlenuts and walnuts, respectively. New Caledonian crows placed candlenut sections in vice-anvils to aid kernel extraction, after the candlenuts had been dropped onto an anvil to break them open. In contrast, rooks used vice-anvils to secure walnuts while they broke the shell with their bills. Long-term use by rooks of a vice-anvil in a tree had produced a ‘purpose-made’ nut-cracking site. My findings extend the persistent use of specific vice-anvils to Corvus species and further demonstrate their innovative and flexible foraging behaviour. 相似文献
76.
Prevention of aluminium toxicity with supplemental boron. I. Maintenance of root elongation and cellular structure 总被引:1,自引:1,他引:0
M. E. LENOBLE D. G. BLEVINS R. E. SHARP B. G. CUMBIE 《Plant, cell & environment》1996,19(10):1132-1142
Aluminium toxicity is an important factor limiting plant growth mi acid soils. Symptoms of B deficiency and Al toxicity are very similar and generally associated with impaired membrane Function and root growth. Thus the objective of this study was to determine whether supplemental B prevents Al inhibition of root growth and development. Squash (Cucurbita pepo L. cv. Sunbar) was grown in hydroponic nutrient media with 44 mmol m?3 free Al and B concentrations extending from 5 to 100 mmol m?3. Our results establish that B protects against Al inhibition of root growth. Protection was apparent at all levels of organization examined: primary root and lateral root lengths; primary root cell elongation, cell production rate, tissue organization and cell structure; primary root morphology and maturation. Protection against Al inhibition was also apparent for shoot growth. These studies were undertaken in solution culture to limit the variables examined; however, the underlying motivation for this study is the problem of worldwide Al toxicity in soils. Therefore, the effect of adding additional B to a high-Al soil was also investigated and is the subject of the companion paper (Le Noble. Blevins & Miles 1996, Plant, Cell and Environment 19, 1143–1148). 相似文献
77.
Phylogenetic relationships among prokaryotic and eukaryotic catalases 总被引:13,自引:1,他引:12
Seventy-four catalase protein sequences, including 29 bacterial, 8 fungal,
7 animal, and 30 plant sequences, were compiled, and 70 were used for
phylogenetic reconstruction. The core of the resulting tree revealed
unique, separate groups of plant and animal catalases, two groups of fungal
catalases, and three groups of bacterial catalases. The only overlap of
kingdoms occurred within one branch and involved fungal and bacterial
large-subunit enzymes. The other fungal branch was closely linked to the
group of animal enzymes. Group I bacterial catalases were more closely
related to the plant enzymes and contained such diverse taxa as the
Gram-positive Listeria seeligeri, Deinocococcus radiodurans, and
gamma-proteobacteria. Group III bacterial sequences were more closely
related to fungal and animal sequences and included enzymes from a broad
range of bacteria including high- and low-GC Gram positives,
proteobacteria, and a bacteroides species. Group II was composed of
large-subunit catalases from diverse sources including Gram positives
(low-GC Bacilli and high-GC Mycobacteria), proteobacteria, and species of
the filamentous fungus Aspergillus. These data can be interpreted in terms
of two gene duplication events that produced a minimum of three catalase
gene family members that subsequently evolved in response to environmental
demands. Horizontal gene transfer may have been responsible for the group
II mixture of bacterial and fungal large-subunit catalases.
相似文献
78.
79.
Abstract. Seasonal variations in mosquito larval head capsule width and adult female wing length were investigated in a field population of Anopheles merus Donitz at Nceswana Lake, Ophansi, within the endemic malaria area of Natal, South Africa. An inverse relationship was detected between each of these morphological characters and seasonal fluctuations in air/water temperatures. Mean head capsule width in all larval instars decreased by 4.8-7.9% in summer, while mean wing length decreased by 19.6%. These changes are discussed in relation to the annual range in mean air temperature in southern Africa and the distribution of An. merus. Implications for the use of such morphological characteristics in existing taxonomic keys are discussed. 相似文献
80.
Mice of the TO Swiss strain received diets containing different amounts of saturated or unsaturated fat throughout life. These diets produced characteristic changes in cardiac phospholipid fatty acid composition, but produced no significant differences in fatty acid composition of phospholipids from a crude membrane fraction of brain. When littermates of these animals were exposed to ethanol vapour in an inhalation chamber it was observed that mice which had received a diet high in saturated fat lost the righting reflex at an estimated concentration of ethanol in blood higher than that required for mice receiving a control diet, or a diet rich in polyunsaturated fat. Analysis of the brain membrane fraction from those animals which had received ethanol revealed that mice receiving the highly saturated fat diet now had a significantly greater proportion of saturated fatty acids in brain membrane phospholipids. These results are discussed in relation to the hypothesis that brain membrane lipid composition may influence the behavioural response to ethanol. 相似文献