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11.
KIRK E. LAGORY LEROY J. WALSTON CELINE GOULET ROBERT A. VAN LONKHUYZEN STEPHEN NAJJAR CHRISTIAN ANDREWS 《The Journal of wildlife management》2009,73(8):1387-1393
ABSTRACT The decline of many snake populations is attributable to habitat loss, and knowledge of habitat use is critical to their conservation. Resource characteristics (e.g., relative availability of different habitat types, soils, and slopes) within a landscape are scale-dependent and may not be equal across multiple spatial scales. Thus, it is important to identify the relevant spatial scales at which resource selection occurs. We conducted a radiotelemetry study of eastern hognose snake (Heterodon platirhinos) home range size and resource use at different hierarchical spatial scales. We present the results for 8 snakes radiotracked during a 2-year study at New Boston Air Force Station (NBAFS) in southern New Hampshire, USA, where the species is listed by the state as endangered. Mean home range size (minimum convex polygon) at NBAFS (51.7 ± 14.7 ha) was similar to that reported in other parts of the species’ range. Radiotracked snakes exhibited different patterns of resource use at different spatial scales. At the landscape scale (selection of locations within the landscape), snakes overutilized old-field and forest edge habitats and underutilized forested habitats and wetlands relative to availability. At this scale, snakes also overutilized areas containing sandy loam soils and areas with lower slope (mean slope = 5.2% at snake locations vs. 6.7% at random locations). We failed to detect some of these patterns of resource use at the home range scale (i.e., within the home range). Our ability to detect resource selection by the snakes only at the landscape scale is likely the result of greater heterogeneity in macrohabitat features at the broader landscape scale. From a management perspective, future studies of habitat selection for rare species should include measurement of available habitat at spatial scales larger than the home range. We suggest that the maintenance of open early successional habitats as a component of forested landscapes will be critical for the persistence of eastern hognose snake populations in the northeastern United States. 相似文献
12.
TERESA SCHWARZKOPF SUSAN J. RIHA TIMOTHY J. FAHEY STEPHEN DEGLORIA 《Austral ecology》2011,36(3):280-289
Cloud forest vegetation structure and composition were studied in the Venezuelan Andes at three sites in Mérida State. Although the sites are within 10 to 30 km of each other, climatic, geologic and topographic differences are remarkable. The main purpose of the study was to determine the relationship of specific environmental variables to forest vegetation characteristics, including basal area, tree height, density and diversity, and leaf area index (LAI). At 51 plots, all trees' diameter at breast height >10 cm were recorded and identified. Although the environment at the three sites is distinctive, the tree species composition of the most abundant species was very similar. None of the measured environment variables were significantly correlated with the measured vegetation structure variables, except LAI, which was correlated with slope orientation; LAI showed higher values at south‐facing plots. Tree height was relatively uniform, while basal area was highly variable and reached very high values. Stem densities were in the range reported elsewhere in cloud forests. Multivariate analysis using structure or composition data shows segregation of the plots by site. Principal component analyses by site indicate a minor impact of environmental factors on forest variables. At each site, a particular group of species are correlated with the ordination axes. We conclude that species pools and forest dynamics add to the complexity of the structure of the studied cloud forests. 相似文献
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STEPHEN HUNTER 《Ibis》1991,133(4):343-350
While ashore King Penguins Aptenodytes patagonicus are fed upon by a guild of five predator-scavenger seabirds. During the winter (April-October) male Southern Giant Petrels Macronectes giganteus killed an estimated 6430 (11.2%) of Marion Island's King Penguin chicks, although most birds only scavenged in the colonies. The rate of predation varied, with peaks in April-May and in September. The proportion of successful attacks was 22.7%. There was a strong correlation between colony size and the rate of accumulation of chick corpses. Kelp Gulls Larus dominicanus and Lesser Sheathbills Chionis minor also scavenged penguin corpses but Northern Giant Petrels M. halli and female Southern Giant Petrels rarely entered the colonies. During the summer predation was mainly by Sub-Antarctic Skuas Catharacta lonnbergi which took eggs and small chicks. 相似文献
15.
KNEE MICHAEL; HATFIELD STEPHEN G. S.; BRAMLAGE WILLIAM J. 《Journal of experimental botany》1987,38(6):972-979
Knee, M., Hatfield, S. G. S. and Bramlage, W. B. 1987. Responseof developing fruits to ethylene treatment.J. exp. Bot.38: 972979. Fruits of apple (Malus domestica Borkh. cv. Cox's Orange Pippin)were treated with various concentrations of ethylene usuallyfor 48 h to determine their response in relation to stage ofdevelopment. The main response recorded was the reduction byethylene of the delay in onset of rapid ethylene production(DEP) in individual fruits. Early in development low concentrationsof ethylene had little effect but DEP was progressively reducedby concentrations up to 107 mm3 m3. As the fruit approachedthe natural onset of rapid ethylene synthesis concentrationsof 102 and 103 mm3 m3 became increasingly effective.Increasing the duration of treatments with a fixed concentrationreduced DEP proportionately. Delay after harvest in applyinga 48 h treatment had little effect on the relation between DEPand concentration of ethylene applied. Although resistance todiffusion of gas in fruits increased during fruit developmentthis resistance was never large enough to affect the relationof concentration and response. Key words: ethylene, fruit ripening, Malus domestica 相似文献
16.
OLGA V. TSYUSKO TRACEY D. TUBERVILLE MAUREEN B. PETERS NICHOLAS CRAWFORD CRIS HAGEN STEPHEN G. WELLER ANN K. SAKAI TRAVIS C. GLENN 《Molecular ecology resources》2007,7(6):1284-1286
Twelve polymorphic microsatellite loci were isolated from polyploid alpine wood‐sorrel, Oxalis alpina (Oxalidaceae), and optimized for future studies of its breeding system. The loci were screened for variability among 72 individuals from Pinos Altos, New Mexico. The primers amplified loci with allele number ranging from two to 17 per locus and with estimates of Nei's genetic diversity varying from 0.10 to 0.99. These primers provide an opportunity to use polymorphic DNA markers to study the causes of breeding system variability in this species. 相似文献
17.
MURALITHARAN MORLEY S.; CHANDLER STEPHEN F.; VAN STEVENINCK REINHARD F. M. 《Annals of botany》1992,69(5):459-465
Non-selected and Na2SO-, K2SO4- or KCl-selected callus culturesof Vaccinium corymbosum L. cv. Blue Crop were grown on mediasupplemented with 0, 25 and 50 mM Na2SO4 (non-selected and Na2SO(-selectedonly), 0, 25 and 50mMK2SO4 (non-selected and K2SO4-selectedonly) or 0, 50 and 100 mM KCl (non-selected and KCl-selectedonly). On all media, growth of selected callus (on a fresh-weightor dry-weight basis) was greater than that of non-selected callus,and selected callus grew optimally on the level and type ofsalt on which it was selected. Selected callus was friable andmaintained a higher f. wt:d. wt ratio. Tissue water potentialin selected callus was more negative than in non-selected callus. Flame photometry and chloridometry showed Na+, K+ and Claccumulated in callus to concentrations equal to or greaterthan the initial concentration in the medium. Turbidometry showedthat tissue SO42- concentration was lower than the concentrationin the medium. In most cases selected callus accumulated moreNa+, Ksup, SO42 or Cl than non-selected callus.Vacuolar ion concentration was measured by electronprobe X-raymicroanalysis, and on most media selected callus had highervacuolar ion concentrations than non-selected callus. SO42and Cl were accumulated in the vacuoles at concentrationshigher than the external medium, but vacuolar Na+ concentrationdid not reach external concentration on Na2SO4 and on potassiumsalts was maintained between 12 and 17 mM. Vacuolar K+ concentration(approx. 142191 mM on no salt) decreased on Na2SO4 andincreased on K2SO4 and KCl. There was no precise correlation between total or specific ionaccumulation (Na+, K+, SO42 and Cl and fresh-weightyield. Results suggest that selection results in adaptationin response to decreased water potential of the medium. Vaccinium corymbosum, blueberry, electronprobe X-ray microanalysis, callus, in vitro selection, salt tolerance, KCl, K2SO4, Na2SO4 相似文献
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Peptidyl transferase, the ribosomal enzyme which synthesizes peptide bonds, can catalyse the formation of ester linkages between α-hydroxyacyl-tRNA and aminoacyl-tRNA when ribosomes carry out a specific translation of phage R17 RNA in vitro. 相似文献
20.
MATTHEW J. BUTLER WARREN B. BALLARD MARK C. WALLACE STEPHEN J. DEMASO BRADY K. MCGEE 《The Journal of wildlife management》2007,71(5):1639-1645
Abstract: Aerial surveys have been used to estimate abundance of several wild bird species including wild turkeys (Meleagris gallopavo). We used inflatable turkey decoys at 3 study sites in the Texas Rolling Plains to simulate Rio Grande wild turkey (M. g. intermedia) flocks. We evaluated detectability of flocks and errors in counting flock size during fixed-wing (Cessna 172) aerial surveys using logistic and linear regression models. Flock detectability was primarily influenced by flock size and vegetative cover, and errors in counting flock size were primarily influenced by size of flocks. We conducted computer simulations to evaluate the accuracy and precision of fixed-wing aerial surveys and examined power to detect trends in population change. Our simulations suggested abundance estimates from fixed-wing aerial surveys may be underestimated by 10-15% (2.0-4.8% CV). Power analyses suggested that fixed-wing aerial surveys can provide sufficient power (>0.80) to detect a population change of 10-25% over a 4-5-year period. We concluded fixed-wing aerial surveys are feasible on ecoregion scales. 相似文献