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Critical Link (critical + link)
Selected AbstractsA metapopulation perspective for salmon and other anadromous fishFISH AND FISHERIES, Issue 4 2007Nicolas Schtickzelle Abstract Salmonids are an important component of biodiversity, culture and economy in several regions, particularly the North Pacific Rim. Given this importance, they have been intensively studied for about a century, and the pioneering scientists recognized the critical link between population structure and conservation. Spatial structure is indeed of prime importance for salmon conservation and management. At first glance, the essence of the metapopulation concept, i.e. a population of populations, widely used on other organisms like butterflies, seems to be particularly relevant to salmon, and more generally to anadromous fish. Nevertheless, the concept is rarely used, and barely tested. Here, we present a metapopulation perspective for anadromous fish, assessing in terms of processes rather than of patterns the set of necessary conditions for metapopulation dynamics to exist. Salmon, and particularly sockeye salmon in Alaska, are used as an illustrative case study. A review of life history traits indicates that the three basic conditions are likely to be fulfilled by anadromous salmon: (i) the spawning habitat is discrete and populations are spatially separated by unsuitable habitat; (ii) some asynchrony is present in the dynamics of more or less distant populations and (iii) dispersal links populations because some salmon stray from their natal population. The implications of some peculiarities of salmon life history traits, unusual in classical metapopulations, are also discussed. Deeper understanding of the population structure of anadromous fish will be advanced by future studies on specific topics: (i) criteria must be defined for the delineation of suitable habitats that are based on features of the biotope and not on the presence of fish; (ii) the collection of long-term data and the development of improved methods to determine age structure are essential for correctly estimating levels of asynchrony between populations and (iii) several key aspects of dispersal are still poorly understood and need to be examined in detail: the spatial and temporal scales of dispersal movements, the origin and destination populations instead of simple straying rates, and the relative reproductive success of immigrants and residents. [source] Arbuscular mycorrhizal propagule densities respond rapidly to ponderosa pine restoration treatmentsJOURNAL OF APPLIED ECOLOGY, Issue 1 2003Julie E. Korb Summary 1Mycorrhizae form a critical link between above-ground plants and the soil system by influencing plant nutrition, nutrient cycling and soil structure. Understanding how mycorrhizae respond to disturbances may lead to important advances in interpreting above-ground plant recovery. 2The inoculum potential for arbuscular mycorrhizae (AM) and ectomycorrhizal (EM) fungi was investigated in thinned-only, thinned and prescribed burned (both restoration treatments) and unthinned and unburned control stands in northern Arizona ponderosa pine forests. The relationships between mycorrhizal fungal propagule densities and plant community and soil properties were quantified. 3The relative amount of infective propagules of AM fungi was significantly higher in samples collected from both restoration treatments than their paired controls (unthinned and unburned stands). In contrast, the same restoration treatments had no significant effect on the relative amount of infective propagules of EM fungi. 4The relative amount of infective propagules of AM fungi was significantly positively correlated with graminoid cover and herbaceous understorey species richness and negatively correlated with overstorey tree canopy cover and litter cover. 5Synthesis and applications. These results indicate that population densities of AM fungi can rapidly increase following restoration treatments in northern Arizona ponderosa pine forests. This has important implications for restoring the herbaceous understorey of these forests because most understorey plants depend on AM associations for normal growth. These results also can be applied to other ecosystems that are in a state of restoration or where the role of fire is just beginning to be understood. [source] Implementing the web of student servicesNEW DIRECTIONS FOR STUDENT SERVICES, Issue 112 2005Janet Ross Kendall Providing high-quality student services to students enrolled in distance education programs is a critical link to the academic success of this growing student population. [source] Intracellular death platform steps-in: Targeting prostate tumors via endoplasmic reticulum (ER) apoptosisTHE PROSTATE, Issue 15 2008Steven R. Schwarze Abstract Molecular targeting of apoptotic signaling pathways has been extensively studied in recent years and directed towards the development of effective therapeutic modalities for treating advanced androgen-independent prostate tumors. The majority of therapeutic agents act through intrinsic or mitochondrial pathways to induce programmed cell death. The induction of apoptosis through endoplasmic reticulum (ER) stress pathways may provide an alternative to treat patients. The functional interaction between the BCL-2 family members and regulation of calcium homeostasis in the ER provides a critical link to the life or death outcome of the cell. Apoptosis induction mediated by ER stress-inducing agents is just beginning to be exploited for therapeutic targeting of prostate tumors. Insightful dissection of recently discovered apoptotic signaling pathways that function through the endoplasmic reticulum may identify novel molecules that could effectively target both androgen-dependent and androgen-independent prostate tumors. In this review, we focus on linking ER stress-induced apoptosis to therapeutic targeting of prostate tumors and dissect its cross-talk with the intrinsic and extrinsic apoptotic pathways. Prostate 68: 1615,1623, 2008. © 2008 Wiley-Liss, Inc. [source] Trapper profiles and strategies: insights into sustainability from hunter behaviourANIMAL CONSERVATION, Issue 6 2009N. F. Kümpel Abstract Hunters are the critical link between demand and supply of bushmeat. An understanding of the incentives that drive hunter behaviour might thus help to predict the impacts of hunting and inform management of bushmeat hunting systems. However, hunter behaviour has been generally under-represented in studies of exploitation, in particular trapper behaviour, despite the fact that trapping is the most common form of hunting in central Africa. We collected data on hunter profiles and measures of catch and effort over 15 months in the Monte Mitra area of continental Equatorial Guinea, through interviews, hunter follows and an offtake survey. Younger trappers, and those not born in the village, were found to expend the greatest trapping effort. Trappers operated under three distinct strategies, reflecting different levels of effort and impact: low-impact village trappers, medium-impact forest trappers and high-impact forest trappers. Among different measures of effort, time expended and distance travelled were found to be less important in predicting trapping success than the number of effective traps, a measure that incorporates trap age. Regular checking of traps was found to be important in reducing wastage and therefore increases trapping success. Trapping is currently the main hunting method in Monte Mitra, due to lower barriers to entry and higher profits compared with gun hunting, but increasing affordability and availability of guns and cartridges warns of a possible future switch to gun hunting in the area, which is likely to have adverse impacts on vulnerable species, particularly arboreal primates. An understanding of the influence of a hunter's profile on hunting effort and success enables a prediction of the impacts of socioeconomic changes on wildlife populations and management actions to improve hunting sustainability. [source] Use of Premontane Moist Forest and Shade Coffee Agroecosystems by Army Ants in Western PanamaCONSERVATION BIOLOGY, Issue 1 2000Dina L. Roberts Behavioral and distributional studies of these two species have been confined largely to humid lowland forest. We conducted intensive systematic area searches at elevations between 1200 and 1800 m in western Panama to assess the distribution of both species in intact premontane moist forest, shade coffee plantations, and sun coffee plantations. Both species were repeatedly observed in forest, shade coffee plantations close to forest, and shade coffee plantations distant from forest. Neither species was observed in sun coffee plantations. We believe that retention of certain forest-like characteristics in the traditional shade coffee farm contributes to the persistence of these forest organisms in modified landscapes. Large canopy trees not only provide shade that buffers temperature extremes but also supply the ground layer with regular inputs of leaf litter and coarse woody debris from fallen trunks. Both E. burchelli and L. praedator hunt in leaf litter, and E. burchelli uses coarse woody debris as nesting sites ( bivouacs). There were significantly fewer potential bivouacs available in sun coffee plantations than in forest and shade coffee habitats. Also, litter depth was less in sun coffee than in forest and shade coffee. Our results provide the first evidence that shade coffee plantations can provide additional habitat for E. burchelli and L. praedator, top predators of the leaf litter arthropod community. E. burchelli and L. praedator act as critical links between swarm-attendant bird species and leaf-litter arthropods, providing an easily exploited food resource that would otherwise be unavailable for many birds. Continued conversion of shade coffee plantations to sun coffee plantations could have negative effects on army ants and associated biodiversity. Resumen: Las hormigas arrierras Neotropicales, Eciton burchelli y Labidus praedator ( Hymenoptera: Formicidae: Ecitoninae) son especies que requieren de extensas áreas de hábitat para cazar. Los estudios conductuales y de la distribución de estas especies se han realizado principalmente en bosques húmedos en tierras bajas. Desarrollamos búsquedas sistemáticas intensivas en elevaciones entre 1200 y 1800 msnm en Panama occidental para determinar la distribución de ambas especies en bosque húmedo premontano intacto, en plantaciones de café con y sin sombra. Las dos especies fueron observadas recurrentemente en bosque y en plantaciones de café de sombra cercanos y lejanos al bosque. Consideramos que la retención de ciertas características del bosque en las plantaciones de café de sombra contribuye a la persistencia de estos organismos de bosque en ambientes modificados. Los árboles no solo proporcionan sombra que amortigua la temperatura, sino que proporcionan hojarasca y restos leñosos de troncos caídos. Tanto E. burchelli como L. praedator cazan en la hojarasca, E. burchelli utiliza restos leñosos para anidar (vivaques). Encontramos significativamente menos vivaques en plantaciones de café sin sombra al compararlos con bosque y plantaciones de café con sombra. Asimismo, la profundidad de la capa de hojarasca fue menor en plantaciones de café sin sombra en comparación con bosque y plantaciones de café con sombra. Nuestros resultados proporcionan la primera evidencia de que las plantaciones con sombra proporcionan hábitat adicional para E. burchelli y L. praedator, depredadores de la comunidad de artrópodos en la hojarasca. E. burchelli y L. praedator actúan como eslabones críticos entre especies de aves que se alimentan de hormigas y los artrópodos de la hojarasca, proporcionando un recurso alimenticio fácilmente explotado que de otra manera no estaría disponible para muchas aves. La continua transformación de plantaciones de café con sombra a plantaciones sin sombra pudiera tener efectos negativos sobre las hormigas arrieras y la biodiversidad asociada. [source] Great Expectations?: The Dubious Financial Legacy of Quality AuditsBRITISH JOURNAL OF MANAGEMENT, Issue 1 2000Tracey A. Swift In recent years there appears to have been a veritable boom in the provision of ,quality audits', that is, audits of organizations' production processes and management systems. Despite the rising significance of this international audit movement affecting hundreds of thousands of organizations world-wide, there has been limited interest in, or critique of, the practice of quality audit by academic auditing researchers. This paper traces the history of quality assurance standards and auditing and finds that quality auditing is not simply an outgrowth of an engineering inspection function. Rather, for several decades, quality auditors have consciously modelled their practice on that of the statutory financial audit, which in turn, exposes them to similar issues with regard to the long standing ,expectations gap' debate. Yet, despite what the authors argue are critical links with the financial audit, there has not been any notable involvement on the part of the accounting profession with quality auditing. The growing demand for ,added-value' audits poses considerable questions for the future development and organizational significance of quality auditing. Current developments in both quality and financial audit services suggest that these two influential audit movements are now competing against each other to promote business excellence and contribute to business strategy. [source] | ||||||||||