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211.
James N. Derr Philip W. Hedrick Natalie D. Halbert Louis Plough Lauren K. Dobson Julie King Calvin Duncan David L. Hunter Noah D. Cohen Dennis Hedgecock 《Conservation biology》2012,26(6):1130-1136
Hybridization between endangered species and more common species is a significant problem in conservation biology because it may result in extinction or loss of adaptation. The historical reduction in abundance and geographic distribution of the American plains bison (Bison bison bison) and their recovery over the last 125 years is well documented. However, introgression from domestic cattle (Bos taurus) into the few remaining bison populations that existed in the late 1800s has now been identified in many modern bison herds. We examined the phenotypic effect of this ancestry by comparing weight and height of bison with cattle or bison mitochondrial DNA (mtDNA) from Santa Catalina Island, California (U.S.A.), a nutritionally stressful environment for bison, and of a group of age‐matched feedlot bison males in Montana, a nutritionally rich environment. The environmental and nutritional differences between these 2 bison populations were very different and demonstrated the phenotypic effect of domestic cattle mtDNA in bison over a broad range of conditions. For example, the average weight of feedlot males that were 2 years of age was 2.54 times greater than that of males from Santa Catalina Island. In both environments, bison with cattle mtDNA had lower weight compared with bison with bison mtDNA, and on Santa Catalina Island, the height of bison with cattle mtDNA was lower than the height of bison with bison mtDNA. These data support the hypothesis that body size is smaller and height is lower in bison with domestic cattle mtDNA and that genomic integrity is important for the conservation of the American plains bison. Efectos Fenotípicos del ADN Mitocondrial de Ganado en el Bisonte Americano 相似文献
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214.
Fraser McLeod Gunes Erdogan Tom Cherrett Tolga Bektas Nigel Davies Duncan Shingleton Chris Speed Janet Dickinson Sarah Norgate 《Waste management (New York, N.Y.)》2014,34(2):273-280
Collection costs associated with servicing a major UK charity’s donation banks and collecting unsold goods from their retail shops can account for up to 20% of the overall income gained. Bank and shop collections are commingled and are typically made on fixed days of the week irrespective of the amounts of materials waiting to be collected. Using collection records from a major UK charity, this paper considers what vehicle routing and scheduling benefits could accrue if bank and shop servicing requirements were monitored, the former using remote sensing technology to allow more proactive collection scheduling. A vehicle routing and scheduling algorithm employing tabu search methods was developed, and suggested time and distance savings of up to 30% over the current fixed schedules when a minimum bank and shop fill level of between 50% and 60% was used as a collection trigger. For the case study investigated, this led to a potential revenue gain of 5% for the charity and estimated CO2 savings of around 0.5 tonnes per week across the fleet of six heterogeneous vehicles. 相似文献
215.
A model is created for assessing the redevelopment potential of brownfields. The model is derived from a space and time conceptual framework that identifies and measures the surface and subsurface risk factors present at brownfield sites. The model then combines these factors with a contamination extent multiplier at each site to create an index of redevelopment potential. Results from the application of the model within an urbanized watershed demonstrate clear differences between the redevelopment potential present within five different near-surface geologic units, with those units containing clay being less vulnerable to subsurface contamination. With and without the extent multiplier, the total risk present at the brownfield sites within all the geologic units is also strongly correlated to the actual costs of remediation. Thus, computing the total surface and subsurface risk within a watershed can help guide the remediation efforts at broad geographic scales, and prioritize the locations for redevelopment. 相似文献
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The Sonoran night-blooming cereus ( Peniocereus striatus ) is a rare cactus found in the Sonoran Desert. Its survival is dependent on maintenance of its habitat and its ability to recruit. This study evaluates the role of nurse plants in P. striatus survival and the floral and pollination ecology controlling recruitment. A strong association was detected between P. striatus and its nurse plants, which include Olneya tesota and Larrea tridentata . Because of the harvesting of Olneya tesota and Prosopis velutina for charcoal over a 20,000 square km area of its range, this night-blooming cereus is vulnerable to rapid habitat degradation in both Sonora (Mexico) and adjacent Arizona (U.S.A.). The temporal and local scarcity of sphingid moths available for pollination caused by pesticides and small flower numbers, appear to produce low recruitment rates. These two important threats to the biotic associates of this cactus have increased its natural rarity. This can only be alleviated through international cooperation. 相似文献
219.
Madeleine Beekman Amy L. Gilchrist Michael Duncan David J. T. Sumpter 《Behavioral ecology and sociobiology》2007,61(7):985-995
A honeybee colony needs to divide its workforce so that each of the many tasks it performs has an appropriate number of workers
assigned to it. This task allocation system needs to be flexible enough to allow the colony to quickly adapt to an ever-changing
environment. In this study, we examined possible mechanisms by which a honeybee colony regulates the division of labor between
scouts (foragers that search for new food sources without having been guided to them) and recruits (foragers that were guided
via recruitment dances toward food sources). Specifically, we examined the roles that the availability of recruitment dances
and worker genotype has in the colony-level regulation of the number of workers engaged in scouting. Our approach was threefold.
We first developed a mathematical model to demonstrate that the decision to become a scout or a recruit could be regulated
by whether a potential forager can find a recruitment dance within a certain time period. We then tested this model by investigating
the effect of dance availability on the regulation of scouts in the field. Lastly, we investigated if the probability of being
a scout has a genetic basis. Our field data supported the hypothesis that scouts are those foragers that have failed to locate
a recruitment dance as predicted by our model, but we found no effect of genotype on the propensity of foragers to become
scouts. 相似文献
220.
G.T. Cook M.S. Baxter H.J. Duncan R. Malcolmson 《Journal of environmental radioactivity》1984,1(2):119-131
Geochemical associations of plutonium and artificial γ-emitting radionuclides have been investigated in soils and marine particulate material from the immediate vicinity of the Dounreay Nuclear Power Development Establishment (DNPDE) Caithness. The artificial radionuclides present in these materials arise from a variety of sources: world-wide nuclear weapons test fallout, direct deposition from atmospheric discharges at DNPD, and the return to land of activity previously discharged to sea (containing contributions from Dounreay and Sellafield). The levels, although sufficient to permit satisfactorily low counting errors, are of negligible radiological significance, the plutonium being more than 1000 times less than the NRPB Generalised Derived Limit (GDL) for well-mixed soil. Sequential leaching using selective extractants was performed to quantify the percentages of each nuclide in the following notional fractions: (a) readily available, (b) exchangeable and bound at specific adsorption sites, (c) chelated as insoluble organic complexes, (d) associated with sesquioxides, and (e) residual. Plutonium was found to be associated mainly with phases (c) and (d), while the γ-emitters present in the marine particulate material showed quite varied distributions. The degree of chemical fixation in the particulates follows the sequence 40K137Cs106Ru125Sb239,240Pu144Ce60Co154,155Eu. 相似文献