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Context Dependent (context + dependent)
Selected AbstractsA comparison of invasive and non-invasive dayflowers (Commelinaceae) across experimental nutrient and water gradientsDIVERSITY AND DISTRIBUTIONS, Issue 5-6 2004Jean H. Burns ABSTRACT Little is known about the traits and mechanisms that determine whether or not a species will be invasive. Invasive species are those that establish and spread after being introduced to a novel habitat. A number of previous studies have attempted to correlate specific plant traits with invasiveness. However, many such studies may be flawed because they fail to account for shared evolutionary history or fail to measure performance directly. It is also clear that performance is context dependent. Thus, an approach that corrects for relatedness and incorporates multiple experimental conditions will provide additional information on performance traits of invasive species. I use this approach with two or three pairs of invasive and closely related non-invasive species of Commelinaceae grown over experimental gradients of nutrient and water availability. Invasive species have been introduced, established, and spread outside their native range; non-invasive species have been introduced, possibly (but not necessarily) established, but are not known to have spread outside their native range. The invasive species had higher relative growth rates (RGR) than non-invasive congeners at high nutrient availabilities, but did not differ from non-invasive species at low nutrient availabilities. This is consistent with a strategy where these particular invasive species are able to rapidly use available resources. Relative growth rates were also higher for two out of three invasive species across a water availability gradient, but RGR did not differ in plasticity between the invasive and non-invasive species. This suggests that nutrient addition, but not changes in water availability, might favour invasion of dayflowers. This approach is novel in comparing multiple pairs of invasive and non-invasive congeners across multiple experimental conditions and allows evaluation of the robustness of performance differences. It also controls for some of the effects of relatedness that might confound multispecies comparisons. [source] Functional benefits of predator species diversity depend on prey identityECOLOGICAL ENTOMOLOGY, Issue 5 2005A. Wilby Abstract., 1.,Determining the functional significance of species diversity in natural enemy assemblages is a key step towards prediction of the likely impact of biodiversity loss on natural pest control processes. While the biological control literature contains examples in which increased natural enemy diversity hinders pest control, other studies have highlighted mechanisms where pest suppression is promoted by increased enemy diversity. 2.,This study aimed to test whether increased predator species diversity results in higher rates of predation on two key, but contrasting, insect pest species commonly found in the rice ecosystems of south-east Asia. 3.,Glasshouse experiments were undertaken in which four life stages of a planthopper (Nilaparvata lugens) and a moth (Marasmia patnalis) were caged with single or three-species combinations of generalist predators. 4.,Generally, predation rates of the three-species assemblages exceeded expectation when attacking M. patnalis, but not when attacking N. lugens. In addition, a positive effect of increased predator species richness on overall predation rate was found with M. patnalis but not with N. lugens. 5.,The results are consistent with theoretical predictions that morphological and behavioural differentiation among prey life stages promotes functional complementarity among predator species. This indicates that emergent species diversity effects in natural enemy assemblages are context dependent; they depend not only on the characteristics of the predators species, but on the identity of the species on which they prey. [source] Context-dependent effects of hippocampal damage on memory in the shock-probe testHIPPOCAMPUS, Issue 1 2005Hugo Lehmann Abstract We assessed the role of the hippocampus in anterograde memory, using the shock-probe test. Rats with sham or neurotoxic lesions of the hippocampus were given a shock-probe acquisition session during which each time they contacted a probe they received a shock; 24 h later, the rats were given a second shock-probe session to test their retention, but in this instance the probe was not electrified. Rats were tested in either the same context as the one used during acquisition or in a different context. The hippocampal lesions impaired avoidance of the probe and burying on the retention test, suggesting that the lesions induced anterograde amnesia. However, the impairment was context dependent. The hippocampal lesions impaired avoidance only when the rats were tested in the context in which they received the conditioning. The results of the shock-probe test suggest that the anterograde amnesia following hippocampal lesions is due mainly to an inability to associate the context with the shock more than to an inability to associate the probe with shock. © 2004 Wiley-Liss, Inc. [source] Avian distribution in treefall gaps and understorey of terra firme forest in the lowland AmazonIBIS, Issue 1 2005JOSEPH M. WUNDERLE JR We compared the bird distributions in the understorey of treefall gaps and sites with intact canopy in Amazonian terra firme forest in Brazil. We compiled 2216 mist-net captures (116 species) in 32 gap and 32 forest sites over 22.3 months. Gap habitats differed from forest habitats in having higher capture rates, total captures, species richness and diversity. Seventeen species showed a significantly different distribution of captures between the two habitats (13 higher in gap and four higher in forest). Gap habitats had higher capture rates for nectarivores, frugivores and insectivores. Among insectivores, capture rates for solitary insectivores and army ant followers did not differ between the two habitats. In contrast, capture rates were higher in gaps for members of mixed-species insectivore flocks and mixed-species insectivore,frugivore flocks. Insectivores, especially members of mixed-species flocks, were the predominant species in gap habitats, where frugivores and nectarivores were relatively uncommon. Although few canopy species were captured in gap or forest habitats, visitors from forest mid-storey constituted 42% of the gap specialist species (0% forest) and 46% of rare gap species (38% forest). Insectivore, and total, captures increased over time, but did so more rapidly in gap than in forest habitats, possibly as a response to gap succession. However, an influx of birds displaced by nearby timber harvest also may have caused these increases. Avian gap-use in Amazonian terra firme forests differs from gap-use elsewhere, partly because of differences in forest characteristics such as stature and soil fertility, indicating that the avian response to gaps is context dependent. [source] Mechanisms of regulatory T-cell suppression , a diverse arsenal for a moving targetIMMUNOLOGY, Issue 1 2008Dorothy K. Sojka Summary Naturally-occurring regulatory T cells (Tregs) are emerging as key regulators of immune responses to self-tissues and infectious agents. Insight has been gained into the cell types and the cellular events that are regulated by Tregs. Indeed, Tregs have been implicated in the control of initial activation events, proliferation, differentiation and effector function. However, the mechanisms by which Tregs disable their cellular targets are not well understood. Here we review recent advances in the identification of distinct mechanisms of Treg action and of signals that enable cellular targets to escape regulation. Roles for inhibitory cytokines, cytotoxic molecules, modulators of cAMP and cytokine competition have all been demonstrated. The growing number of inhibitory mechanisms ascribed to Tregs suggests that Tregs take a multi-pronged approach to immune regulation. It is likely that the relative importance of each inhibitory mechanism is context dependent and modulated by the inflammatory milieu and the magnitude of the immune response. In addition, the target cell may be differentially susceptible or resistant to distinct Treg mechanisms depending on their activation or functional status at the time of the Treg encounter. Understanding when and where each suppressive tool is most effective will help to fine tune therapeutic strategies to promote or constrain specific arms of Treg suppression. [source] Ecosystem properties determined by plant functional group identityJOURNAL OF ECOLOGY, Issue 2 2010Jennie R. McLaren Summary 1.,Ecosystem properties may be determined by the number of different species or groups of species in a community, the identity of those groups, and their relative abundance. The mass ratio theory predicts that the effect of species or groups of species on ecosystem properties will be dependent on their proportional abundance in a community. 2.,Single plant functional groups (graminoids, legumes, non-leguminous forbs) were removed from a natural grassland in northern Canada to examine the role of group identity in determining both ecosystem properties and biomass compensation by remaining species. Removals were conducted across two different environmental treatments (fertilization and fungicide) to examine the context dependency of functional group identity effects. 3.,The degree of biomass compensation in the first 4 years after removal was influenced by the identity of the functional group removed and also of those remaining. When graminoids were removed, none of the remaining functional groups compensated for the loss of biomass. Graminoids partially compensated for the removal of forbs or legumes, with the degree of compensation depending on environmental treatments. 4.,Light interception, soil moisture and soil nutrients were all influenced by functional group identity, with graminoids having a greater impact than expected based on their biomass contribution to the community. Legumes, in contrast, had very little effect on any of the ecosystem properties measured. 5.,For most ecosystem properties measured, the role of plant functional groups was not context dependent; functional groups had the same effect on ecosystem properties regardless of fertilization or fungicide treatments. 6.,Synthesis. We have shown that the effects of losing a functional group do not solely depend on the group's dominance. In this northern grassland, there are greater effects of losing graminoids than one would predict based on their biomass contributions to the community, and functional group identity plays a critical role in determining the effects of diversity loss. [source] Names That Show Time: Turkish Jews as "Strangers" and the Semiotics of ReclassificationAMERICAN ANTHROPOLOGIST, Issue 3 2010Marcy Brink-Danan ABSTRACT, In this article, I discuss the anthropological value of focusing on ontological processes in which seemingly local, native, or indigenous people are reclassified as foreigners. Building on theories of language and time, I show, through the ethnographic example of Jewish naming in Istanbul, how names come to signify foreignness. I also explore naming as a process through which the subjects of reclassification themselves understand present-day ontologies as historically informed and context dependent. By studying moments of categorical reassignment, I detail the social semiotic processes that drive the classification of signs as indices of belonging or exclusion. Anthropologists increasingly study military, juridical, and economic ontologies that reorder, relocate, and restrict human (and nonhuman) groups. I illuminate a quieter space, that of naming, through which classifications are made and undone. ÖZET, Bu makalede, yerel, yöreye ait ve do,ma büyüme yerli ki,ilerin yabanc, olarak yeniden s,n,fland,r,lmas,n,n görüldü,ü varl,ksal (ontolojik) süreçlere odaklanman,n antropolojik de,erini tart,,aca,,m. Çal,,may, dil ve zaman kuramlar,üzerine kurarak, ,stanbul Musevilerinin adland,r,lmas,n, konu alan etnografik bir örnekleme arac,l,,, ile, isimlerin nas,l bir yabanc,l,k anlam, yüklendi,ini göstermeyi umuyorum. Ayn, zamanda, yeniden s,n,fland,rmaya mazur kalanlar,n kendilerinin güncel ontolojileri tarihsel olarak belirlenmi, ve ba,lama dayal, olarak kavrayageldikleri süreçleri de ara,t,r,yorum. Kategorilerin yeniden tayin edildi,i belirli anlar, irdeleyerek, göstergelerin s,n,fland,r,lmas,n, aidiyet ve d,,lama endeksine dönü,türen toplumsal göstergebilimsel süreçleri ayr,nt,land,r,yorum. Antropologlar gün geçtikçe insan (ve insan olmayan) gruplar, tekrar düzene sokan, yerinden eden ya da k,s,tlayan askeri, hukuksal ve ekonomik ontolojilerin üzerine e,iliyorlar. Bense daha sessiz sedas,z bir mekana e,ilerek, s,n,fland,rmalar,n in,a edilip tekrar bozuldu,u isimlendirme alan,na ,,,k tutmaya çal,,,yorum. RÉSUMÉ, Cet article interroge, d'un point de vue anthropologique, le bien-fondé des processus ontologiques par lesquels des populations dites locales, natives ou autochtones sont (re-)catégorisées comme étrangčres. A travers l'exemple ethnographique des noms juifs ŕ Istanbul, et en m'appuyant sur les théories du langage et du temps, je montre comment les noms en viennent ŕ signifier "étranger." J'explore également la nomination en tant que processus ŕ travers lequel les sujets de cette reclassification eux-męmes perçoivent ces schémas de catégorisation comme déterminés par une histoire et dépendants d'un contexte. En étudiant certains moments de réassignation fondamentaux, je précise les processus sémiotiques sociaux qui conduisent ŕ la classification de signes comme indices d'appartenance ou d'exclusion. Les anthropologues étudient de plus en plus les ontologies militaires, juridiques et économiques qui réordonnent, resituent et restreignent des groupes humains (et nonhumains). Mon étude met en lumičre les mécanismes d'un espace plus discret, celui de la nomination, ŕ travers lequel des classifications sont faites et défaites. [source] Female saints and the practice of Islam in Sylhet, BangladeshAMERICAN ETHNOLOGIST, Issue 3 2008ALYSON CALLAN ABSTRACT Unlike the saintly power of her male counterpart, which is conceived as an attribute of the individual, the spiritual power of the female saint in Sylhet, Bangladesh, is attributed to a supernatural entity that is temporarily affiliated with her. This difference cannot simply be regarded as an example of gendered domains of religious practice, in which men study the Qu'ran and women traffic with spirits, as in Sylhet, male healers practice with the aid of spirits. I describe how one woman's saintly status allowed her to resist the virilocal rule of residence, a patriarchal structure that is said to underpin women's subordinate position in Bangladesh. Her story demonstrates that Islam cannot be conflated with patriarchy and that it may support women's emancipation from structures of male authority. The meaning of Islam is context dependent and revised through practice. [Islam, gender, agency, sainthood, Bangladesh, spirit possession, healing] [source] Toward Quantifying the Relative Importance of Invertebrate Consumption and Bioturbation in Puerto Rican StreamsBIOTROPICA, Issue 4 2008Wyatt. ABSTRACT Although many tropical stream consumers have large effects on resource quantity and quality, little is known about the relative importance of consumption versus bioturbation. We quantified egestion rates of freshwater shrimps (Atya spp. and Xiphocaris elongata) and mayflies (Leptophlebiidae) in two forest streams within the Luquillo Experimental Forest, Puerto Rico. Consumer body size was a strong predictor of egestion rates, with mass-specific egestion rates declining with body size and per-individual egestion rates increasing with body size. We used these egestion rates, together with published rates of epilithon removal by consumers and epilithon accrual by particle deposition and periphytic growth (i.e., with and without consumer access), to estimate the importance of consumption and bioturbation after storm events and during base-flow conditions. Our estimates suggest that direct consumption of epilithon can only account for a minor proportion (< 5%) of material removed following storm events, with most removal likely resulting from bioturbation. During base-flow conditions, we found that consumers (largely shrimps) may be capable of consuming a significant proportion of the material that would otherwise accrue on benthic substrata, but this result was limited to one high-elevation site. Our study suggests that bioturbation is the dominant process that redistributes and entrains fine particles after storm events, and that a variable fraction of deposited and accrued benthic material may be consumed during base-flow conditions. Our results underscore the importance of tropical stream animals in altering the benthic environment through both consumption and bioturbation, and suggest that consumer-mediated material cycling is likely to be context dependent. RESUMEN A pesar de que muchos de los consumidores en ríos tropicales tienen grandes efectos en la cantidad y calidad de los recursos, se sabe poco sobre la importancia relativa del consumo y los biodisturbios. Por ello, cuantificamos las tasas de egestión de los camarones (Atya spp. y Xiphocaris elongata) y los efemerópteros (Leptophlebiidae) en dos quebradas dentro del Bosque Experimental de Luquillo, Puerto Rico. El tamańo corporal de los consumidores fue un buen indicador de las tasas de egestión, y las tasas de egestión por masa disminuyeron con el tamańo corporal y las por individuo aumentaron con el tamańo corporal. Usamos estas tasas de egestión, junto con tasa publicadas de remoción de perifiton por los consumidores y acumulación de epiliton por la deposición y el crecimiento de perifiton (ej. con y sin consumidores), para estimar la importancia del consumo y los biodisturbios luego de tormentas y durante condiciones de flujo basal. Nuestros resultados sugieren que el consumo directo de epiliton representa una proporción menor (< 5%) del material removido luego de las tormentas, la mayor parte de la remoción es probablemente el resultado de los biodisturbios. Durante condiciones de flujo basal, encontramos que los consumidores (mayormente camarones) pueden ser capaces de consumir una proporción importante del material que de otra forma se acumularía sobre el substrato béntico, pero este resultado se limita a uno solo de los sitios. Nuestro estudio sugiere que los biodisturbios son el proceso que predomina en la redistribución y mueve partículas luego de las tormentas, y que una fracción variable del material béntico depositado y acumulado puede ser consumida durante condiciones de flujo basal. Nuestros resultados enfatizan la importancia de los animales en alterar el ambiente béntico de los ríos tropicales a través del consumo y los biodisturbios, y sugiere que el reciclaje de los materiales por los consumidores es un proceso que probablemente depende del contexto. [source] | |||||||||||||