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691.
We analyzed tandem-running pairs of the termites Reticulitermes flavipes and Reticulitermes virginicus utilizing 13 and 12 microsatellite loci, respectively. Newly formed pairs in both species were significantly related to one
another, but this average relatedness was considerably higher in R. flavipes (0.130 vs 0.060). These average relatedness levels resulted from some tandem pairs forming between nestmate termites: more
than one quarter of all R. flavipes pairs (26.1%) met this criterion, while this was the case for only about one of every 20 R. virginicus pairs (5.1%). The likelihood that termites paired with siblings was inversely related to the inferred dispersal ability of
the two species. F
ST, measured over identical spatial scales, was significantly higher in R. flavipes (0.034) than in R. virginicus (0.008). A comparison in R. flavipes of the observed proportion of nestmate pairs observed during tandem running vs the proportion found in established colonies
revealed a significant excess of close relatives when pairs were first formed. There are two possible causes of this discrepancy:
inbreeding depression (ID) may eliminate inbred colonies early in development, or related pairs may part late in the tandem-running
phase or after it is completed. The latter explanation of inbreeding avoidance implies either historical or contemporary ID,
and these results therefore suggest that, either directly or indirectly, ID could be a more potent force in the evolution
of termite mating systems than is generally appreciated.
This work was funded by grants from the United States Department of Agriculture National Research Initiative Competitive Grants
Program (nos. 00-35302-9377 and 2002-35302-12490). 相似文献
692.
Aluminum is a ubiquitous substance with over 4,000 uses. Aluminum, as aluminum sulfate, is commonly used in the United States as a coagulant in the treatment of drinking water. For many years aluminum was not considered to be toxic to humans. However, reports associating aluminum with several skeletal and neurological disorders in humans suggest that exposure to aluminum may pose a health hazard. In 1983 the US Environmental Protection Agency (EPA) announced plans to regulate a number of substances, including aluminum, in drinking water. Aluminum was considered because of its occurrence and apparent toxicity. Upon further evaluation of the health effects data the EPA proposed not to regulate aluminum as a result of the uncertainty of the toxicity of ingested aluminum. Putative causal associations between aluminum exposure and neurological disorders such as Alzheimer's disease have yet to be substantiated. Although several issues regarding the toxicity of ingested aluminum are unresolved, aluminum has been specified in the 1986 Amendments to the Safe Drinking Water Act, as one of 83 substances in drinking water to be regulated by 1989. Additional data are needed before the potential risk of aluminum can be assessed; therefore the EPA has deferred possible regulation until 1991. 相似文献
693.
694.
Edward E. Lawler 《组织行为杂志》1994,15(1):3-15
The efficacy of designing organizations around job structures is challenged. Although this approach has dominated the fields of organizational behavior and human resource management for decades, a number of forces have converged to suggest that a competency-based approach often is more appropriate. In the global competitive environment which large, complex organizations face, the competency-based approach and the capabilities that individuals need to acquire and develop should be the major focus. Reward systems, career tracks, selection systems, and the structure of organizations need to change to focus on competencies. The challenges and opportunities for research, theory, and practice development that a change to a competency-based approach raises are many and diverse. For example, new pay systems are needed, new selection systems are needed, indeed whole new concepts about what constitutes selection validity and career development are needed. 相似文献
695.
Agis D. Veroutis Andrew L. Ullman James A. Fava Daniel C. Steinmetz Edward J. Kerfoot 《环境质量管理》1996,6(2):67-72
Companies have achieved competitive advantage by expanding the boundaries of their concern beyond the product life-cycle stage that they directly control. By using product stewardship and life-cycle information, coupled with business analysis, companies can successfully outperform their competitors by improving their product or product system by reducing costs, increasing revenue, reducing liabilities, and enhancing their image. Life-cycle information and its use within a product stewardship management framework goes beyond traditional life-cycle applications. Used wisely, it can help companies establish a sustainable framework for long-term success. 相似文献
696.
Edward E. DeMartini Todd W. Anderson Alan M. Friedlander James P. Beets 《Marine Biology》2011,158(11):2437-2447
Group incidence and size are described for recruit parrotfishes, wrasses, and damselfishes on Hawaiian reefs over 3 years
(2006–2008) at sites spanning the archipelago (20–28°N, 155–177°W). Coral-poor and coral-rich areas were surveyed at sites
with both low (Hawaii Island) and high (Midway Atoll) predator densities, facilitating examination of relations among predator
and recruit densities, habitat, and group metrics. Predator and recruit densities varied spatially and temporally, with a
sixfold range in total recruit densities among years. Group (≥2 recruits) metrics varied with time and tracked predator and
recruit densities and the proportion of schooling species. Groups often included heterospecifics whose proportion increased
with group size. A non-saturating relationship between group size and recruit density suggests that the anti-predator benefits
of aggregation exceeded competitive costs. Grouping behavior may have overarching importance for recruit survival–even at
high recruit densities–and merits further study on Hawaiian reefs and elsewhere. 相似文献
697.
698.
Chiou-Shuang Yan An-Min Chung Edward C Koziara Andrew G Verzilli 《Journal of Environmental Economics and Management》1975,2(1):60-68
The purpose of this study was to ascertain, through the use of an input-output model, the impact of air pollution control costs on income groups in the Philadelphia Region. The range of increases in consumption expenditure was found to be fairly narrow, with the middle-income group bearing the largest increase (2.9%) and the highest and lowest groups slightly lower increases (about 2%). This finding lends support to the proposition that all income groups would probably share the costs of control equally, which leads to a slightly regressive effect on income distribution. The sharing of the region's air quality costs by other areas was also analyzed. 相似文献
699.