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141.
Alberto Jiménez-Valverde Silvia Jiménez Mendoza José Martín Cano Miguel L. Munguira 《Biodiversity and Conservation》2006,15(1):177-190
When compiling an inventory of hyperdiverse taxa, it is impossible to record the total number of species during fieldwork.
To ensure the accuracy of species-richness data it is necessary to assess the reliability of inventories. Accumulation curves
are an easy method for doing this and are extensively described in the literature. In this study, we compare the relative
fit of various models of species-accumulation functions for six local butterfly inventories, evaluating them by a consideration
of the values of the fit, coefficient of determination and sum-of-squares, and the residual patterns and Akaike’s Information
Criterion. In general, complex functions, such as the Weibull or Chapman-Richards, performed better than simpler and more
widely used models (e.g., the Clench and negative exponential models). The performance of models varied among sampling plots,
indicating the influence of factors such as land use and community structure. Thus, although the application of more complex
models should replace the use of simple ones, further research into the factors affecting model fit of accumulation functions
is necessary. 相似文献
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144.
Lavoie C Roy L Lanoix J Taheri M Young R Thibault G Farah CA Leclerc N Paiement J 《Progress in histochemistry and cytochemistry》2011,46(1):1-48
The endoplasmic reticulum (ER) is a highly dynamic organelle. It is composed of four subcompartments including nuclear envelope (NE), rough ER (rER), smooth ER (sER) and transitional ER (tER). The subcompartments are interconnected, can fragment and dissociate and are able to reassemble again. They coordinate with cell function by way of protein regulators in the surrounding cytosol. The activity of the many associated molecular machines of the ER as well as the fluid nature of the limiting membrane of the ER contribute extensively to the dynamics of the ER. This review examines the properties of the ER that permit its isolation and purification and the physiological conditions that permit reconstitution both in vitro and in vivo in normal and in disease conditions. 相似文献
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目的:探讨优秀赛艇运动员不同部位肌肉微循环血流灌注量(MB)的变化特点,为无创微循环相关指标更好的应用于运动员机能监控提供参考和借鉴。方法:运用PeriFlux System5000系列激光多普勒血流仪对12名优秀男子赛艇运动员不同部位肌肉微循环血流灌注量进行无创测试,测试环境为室内,温度(25±3)℃,湿度45.O%~65.O%。结果:①基础值:肱二头肌〉肱桡肌〉股四头肌〉腓肠肌,且肱二头肌显著高于肱桡肌(P〈0.05),极显著高于股四头肌和腓肠肌(P〈0.01);②加热后值及加热前后差值:肱桡肌〉肱二头肌〉股四头肌〉腓肠肌,且肱二头肌、肱桡肌显著高于腓肠肌(P〈0.05)。结论:优秀男子赛艇运动员上肢肌肉值MBF值要明显高于下肢肌肉,尤其加热后值上肢肌肉明显高于下肢肌,而上肢肌肉或下肢肌肉之间则不存在明显差异,因此为了使监测结果更具有代表性,赛艇运动员进行微循环血流灌注量及其相关指标监测时应选取上肢相同肌肉上同一空间的解剖位点。 相似文献
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149.
The population density and demography of five species of arctic Collembola were studied in a naturally patchy habitat, consisting
of Carex ursinae tussocks with varying degrees of isolation. Focal predictor variables were those describing the spatial configuration of
tussocks, including tussock size and isolation and the amount of habitat (cover) at a 1-m2 scale surrounding each tussock population. The Collembola populations were heavily influenced by environmental stochasticity
in the form of winter mortality and summer drought, and the influence of patchiness on population characteristics was evaluated
in this context. The five species showed very different responses to the structuring effect of the habitat, depending on life
history characteristics, mobility and habitat requirements. Population density was highly variable in both time and space.
Spring densities indicated larger winter mortality compared to observations from a previous study, and the snow- and ice-free
season from June to August only resulted in population growth for Folsomia sexoculata. In the other species, adult mortality must have been high as there was no net population growth despite observed reproduction.
The exception was Hypogastrura viatica, whose population decline was more likely to have been the result of migration out of the study area. Cover was the most
important variable explaining density. No pure area or isolation effects at the tussock level were detected, even in areas
with very low habitat cover. Drought was probably an important mortality factor, as July was particularly warm and dry. Due
to qualitative differences in the tussocks and the matrix substrate, desiccation risk would be higher during dispersal between
tussocks. We suggest that increased dispersal mortality gave the observed pattern of increased density in relation to cover,
both in general and in F. quadrioculata, an opportunistic species otherwise known for rapid population growth. Onychiurus groenlandicus, which had a similar density response to cover, may also be influenced by a rescue effect sustaining densities in areas with
high cover. The cover effect can be viewed as a large-scale factor which encompasses the general spatial neighbourhood of
each tussock, where inter-population processes are important, as opposed to internal patch dynamics.
Received: 15 March 1999 / Accepted: 22 March 2000 相似文献
150.
A Large-scale Comparative Analysis of Riffle and Pool Fish Communities in an Upland Stream System 总被引:3,自引:0,他引:3
Christopher M. Taylor 《Environmental Biology of Fishes》2000,58(1):89-95
Fishes were sampled in riffle and pool habitats at 74 upland localities in the Little River system, southeastern Oklahoma and southwestern Arkansas, U.S.A. I asked how these two habitat-defined communities differed with regard to species abundance and incidence patterns, and how these differences varied along othree environmental gradients: elevation, stream gradient, and stream size. Riffle and pool communities showed distinct and significant differences when ordinated in multivariate space defined by species abundance patterns. Sites with similar pool communities did not have similar riffle communities, and riffle and pool communities responded to environmental gradients in different ways. Elevation was the best predictor of pool community structure, whereas stream size was the best predictor of riffle communities. Overall, riffle habitats had fewer species than pool habitats and formed significant subsets of pool communities at 12 of 74 sites. I predicted that at small stream localities where riffles were unstable, riffle species would form subsets of the pool species communities, and both community types should show high similarities. The presence of faunal subsets was not associated with stream size, but faunal similarities were significantly higher at small stream localities. At the species level, 14 species were significantly associated with pool habitats, while only two were associated with riffle habitats. Riffle and pool communities, although linked by a continuous habitat gradient at the local scale, responded differently to large-scale environmental gradients. Local differences between these communities were predictable based on stream size. 相似文献