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991.
992.
Peter Eckersley 《环境政策》2017,26(6):1160-1162
993.
The aim of this study was to investigate reproductive strategies and their consequences in gray mouse lemurs (Microcebus murinus), small solitary nocturnal primates endemic to Madagascar. Previous reports of sexual dimorphism in favor of males and females,
respectively, a high potential for sperm competition and pheromonal suppression of mating activity among captive males, led
us to investigate mechanisms of intrasexual competition in a wild population. Based on 3 years of mark-recapture data, we
demonstrate that sexual dimorphism in this species fluctuated annually as a result of independent changes in male and female
body mass. Male body mass increased significantly prior to the short annual mating season. Because their testes increased
by 100% in the same period and because their canines are not larger than those of females, we suggest that large male size
may be advantageous in searching for estrous females and in enabling them to sustain periods of short-term torpor. In contrast
to reports from captive colonies, we found no evidence for two morphologically distinct classes of males. Finally, we also
show that most adult males are active throughout the cool dry season that precedes the mating season, whereas most adult females
hibernate for several months. This is in contrast to other solitary hibernating mammals, where males typically emerge 1–2
weeks before females. Thus, this first extended field study of M.␣murinus clarified previous conflicting reports on sexual dimorphism and male reproductive strategies in this primitive primate by
showing that their apparent deviation from predictions of sexual selection theory is brought about by specific environmental
conditions which result in sex-specific life history tactics not previously described for mammals. A general conclusion is
that sexual selection can operate more strongly on males without resulting in sexual dimorphism because of independent selection
on the same traits in females.
Received: 6 July 1997 / Accepted after revision: 28 March 1998 相似文献
994.
995.
To assist transport modeling in assessments of the radiological impact of a geological repository for radioactive wastes, the mobility of various elements was studied in arable and wetland soils in the Forsmark region, Sweden. Pore water and total element contents were determined for five types of unconsolidated deposits (regolith), spanning a wide range of soil properties with respect to pH and organic matter content. Two soil depths were sampled to capture element mobility in regolith layers affected and unaffected by soil-forming processes. The solid/liquid partition coefficients (K d values) for most elements varied significantly among regolith types. For most elements, the observed variations in K d values could be explained by variations in soil properties. For many elements, mobility increased with decreasing soil pH. The results provide a significant addition of data on radionuclide retention in soils, taking account of soil properties and processes. 相似文献
996.
There have been great transitions in the science of air pollution and science publishing since the journal began as the International Journal of Air Pollution in 1958. Atmospheric Environment witnessed the increased understanding of smog photochemistry in the late 1950s and the emerging fears of ozone depletion in the 1970s. The journal has grown, but not without the need to change and occasionally fragment only to reintegrate at a later date. At 9000 pages a year it represents an enormous editorial task that has had to be undertaken by more professional offices. This transition has been helped through the development of electronic tools, but the editorial offices strive to retain their personal relationship with authors and reviewers. An enhanced international perspective recognises the widening contributions made by scientists beyond Europe and North America. 相似文献
997.
Kristen M. Waring Danielle M. Reboletti Lauren A. Mork Ching-Hsun Huang Richard W. Hofstetter Amanda M. Garcia Peter Z. Fulé T. Seth Davis 《Environmental management》2009,44(4):824-835
Predicted climate warming is expected to have profound effects on bark beetle population dynamics in the southwestern United
States. Temperature-mediated effects may include increases in developmental rates, generations per year, and changes in habitat
suitability. As a result, the impacts of Dendroctonus frontalis and Dendroctonus mexicanus on forest resources are likely subject to amplification. To assess the implications of such change, we evaluated the generations
per year of these species under three climate scenarios using a degree-day development model. We also assessed economic impacts
of increased beetle outbreaks in terms of the costs of application of preventative silvicultural treatments and potential
economic revenues forgone. Across the southwestern USA, the potential number of beetle generations per year ranged from 1–3+ under
historical climate, an increase of 2–4+ under the minimal warming scenario and 3–5+ under the greatest warming scenario. Economic
benefits of applying basal area reduction treatments to reduce forest susceptibility to beetle outbreaks ranged from 7.75/ha (NM) to7.75/ha
(NM) to 95.69/ha (AZ) under historical conditions, and 47.96/ha (NM) to47.96/ha (NM) to 174.58/ha (AZ) under simulated severe drought conditions.
Basal area reduction treatments that reduce forest susceptibility to beetle outbreak result in higher net present values than
no action scenarios. Coupled with other deleterious consequences associated with beetle outbreaks, such as increased wildfires,
the results suggest that forest thinning treatments play a useful role in a period of climate warming. 相似文献
998.
999.
Multivariate abundance data are commonly collected in ecology, and used to explore questions of “community composition”—how
relative abundance of different taxa changes with environmental conditions. In this paper, we propose a log-linear marginal
modeling approach for analyzing such compositional count data, via generalized estimating equations. This method exploits
the multiplicative nature of log-linear models for counts, by reparameterizing models that describe marginal effects on mean
abundance. This allows partitioning into “main effects” and compositional effects, which is appealing for interpretation.
We apply the proposed approach to reanalyze compositional counts of benthic invertebrates from Delaware Bay, and data of invertebrate
communities inhabiting Acacia plants in eastern Australia. In both cases we resort to a resampling approach to make inferences about regression parameters,
because the number of clusters was not large compared to cluster size. 相似文献
1000.