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TODD C. ATWOOD ERIC M. GESE KYRAN E. KUNKEL 《The Journal of wildlife management》2007,71(4):1098-1106
Abstract: Numerous studies have documented how prey may use antipredator strategies to reduce the risk of predation from a single predator. However, when a recolonizing predator enters an already complex predator—prey system, specific antipredator behaviors may conflict and avoidance of one predator may enhance vulnerability to another. We studied the patterns of prey selection by recolonizing wolves (Canis lupus) and cougars (Puma concolor) in response to prey resource selection in the northern Madison Range, Montana, USA. Elk (Cervus elaphus) were the primary prey for wolves, and mule deer (Odocoileus hemionus) were the primary prey for cougars, but elk made up an increasingly greater proportion of cougar kills annually. Although both predators preyed disproportionately on male elk, wolves were most likely to prey on males in poor physical condition. Although we found that the predators partitioned hunting habitats, structural complexity at wolf kill sites increased over time, whereas complexity of cougar kill sites decreased. We concluded that shifts by prey to structurally complex refugia were attempts by formerly naïve prey to lessen predation risk from wolves; nevertheless, shifting to more structurally complex refugia might have made prey more vulnerable to cougars. After a change in predator exposure, use of refugia may represent a compromise to minimize overall risk. As agencies formulate management strategies relative to wolf recolonization, the potential for interactive predation effects (i.e., facilitation or antagonism) should be considered. 相似文献
104.
Seasonal Water Acquisition and Redistribution in the Australian Woody Phreatophyte, Banksia prionotes 总被引:6,自引:0,他引:6
BURGESS STEPHEN S. O.; PATE JOHN S.; ADAMS MARK A.; DAWSON TODD E. 《Annals of botany》2000,85(2):215-224
Sap flows in the xylem of plant roots in response to gradientsin water potential, either between soil and atmosphere (transpiration)or soil layers of different moisture content (termed hydraulicredistribution). The latter has the potential to influence waterbudgets and species interactions, but we lack information forall but a few plant communities. We combined heat pulse measurementsof sap flow with dye and isotope tracing techniques to gaugethe movement of xylem sap within, and exudation from, rootsof Banksia prionotes (Lindley). We demonstrated hydrauliclift during the dry season and provide some evidencethat extremely dry soils limit hydraulic lift. In addition wereport difficulties posed by spiralled xylem tissue in rootsfor the application of heat pulse techniques. Copyright 2000Annals of Botany Company Banksia prionotes, sap flow, hydraulic lift, heat ratio method, deuterium, stable isotopes, root architecture. 相似文献
105.
JAMIE A. RUDNICK TODD E. KATZNER EVGENY A. BRAGIN J. ANDREW DeWOODY 《Molecular ecology resources》2007,7(5):757-762
Genetic analysis of noninvasively collected bird feathers is of growing importance to avian ecology; however, most genetic studies that utilize feathers make no mention of the need to verify their species of origin. While plumage patterns and collection location often are indicative of species identity, broad‐scale feather collections may require definitive species identification prior to analysis. Genetic species identification has been applied to noninvasively collected samples from a wide range of taxa but, to date, these techniques have not been widely used on bird feathers. Here, we develop and test a polymerase chain reaction (PCR)‐based technique for identifying eastern imperial eagle (Aquila heliaca) samples among a vast number of noninvasively collected feathers. Species identification is accomplished by amplifying a fragment of the mitochondrial cytochrome c oxidase I gene, then digesting that fragment with a restriction enzyme. The resulting species‐specific restriction fragment length polymorphisms (RFLPs) are easily visualized by gel electrophoresis. We tested this PCR‐RFLP assay on over 300 individuals that had been genetically identified from noninvasively collected feathers and demonstrated that the assay is both reliable and robust for DNA of low quality and quantity. The genetic methods of species identification used to develop this assay can readily be applied to other bird assemblages, making them particularly relevant to a broad range of future avian research. 相似文献
106.
Pea Root Regeneration After Tip Excisions at Different Levels: Polarity of New Growth 总被引:1,自引:0,他引:1
The roots of light-grown pea seedlings (Pisum sativum L. cv.Alaska) were excised at 250, 500 or 1500 µm from the body/capjuncture. Tips were sampled for 7 d after excision to monitorthe polarity and structure of the regeneration response. Inroots excised at 250 µm a new single apex regeneratedwithout swelling or any sign of repair. The new root cap appearedidentical to the control. After the 500 µm excision tworesponses occurred. In 45% of the roots examined, a single newapex regenerated, in 55% two or three new apices regeneratedto form a dichotomized or trichotomized root in the same longitudinalaxis as the primary root. In roots excised at 1500 µm,one, two or three lateral roots formed adjacent to the xylemat right angles to the primary root axis. In most instancesthe new roots developed triarch xylem. The discussion concentrateson the relationship of the differentiation state of the vascularcylinder and the pericycle, at the excision site, to the regenerationresponse. Root regeneration, Pisum sativum, Pericycle, Root apex 相似文献
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This paper examines the hypothesis that the primary physiologicalroles of the different structures of fern gametophytes haveacted as significant evolutionary constraints on the growthforms of these structures. Geometric models of absorptive andphotoreceptive structures were constructed to describe the spherical,tip-growing, and planar growth forms, which are actually orcould hypothetically be adopted by each gametophytic structure.The surface-to-volume ratios calculated for the different absorptivestructures suggest that the tip-growing form of the fern rhizoidprovides the most favorable geometric circumstance for waterand nutrient absorption; thus, the selection pressure to optimizeabsorptive processes has apparently influenced the growth formof the absorptive structure. In contrast, similar calculationsfor photoreceptive structures demonstrate that these forms havealmost identical surface-to-volume relationships; thus, thepresumptive need to increase photoreceptive efficiency has notacted as a selection pressure for a specific photoreceptiveform. This result is interpreted in terms of how different growthforms may offer specific advantages for accomplishing otheraspects of the photosynthetic process, e.g. phototropic growthand assimilate transport, which are unrelated to photoreceptionper se. Fern gametophyte, photoreception, absorption, optimal shape, spore, protonema, prothallus 相似文献
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A resistance-capacitance model of oscillatory transpirationin a cotton plant under constant environmental conditions isdiscussed. Experimental results showed that a cotton plant exposedto a sudden and large evaporative demand went through a periodof self-adjustment indicating the presence of negative feedbackmechanisms. Phase relationships between flow in stem, leaf waterpotential, water uptake by roots, and leaf turgor were characterizedthrough the day. The water-based oscillatory processes are explainedthrough a proposed model based upon a hysteresis-controlledfunction and delayed coupling in the leaf component. The periodof oscillation was found to be about 30 min. Results also indicatedthat the lag between the transpiration and water uptake ratesduring oscillations was strongly influenced by the capacitanceof the leaf and that stem capacitance was negligible. 相似文献