Two models for the evolution of polygyny

Summary Two models of conditions for the evolution of polygyny are treated axiomatically. Both models assume a social system based on female mate choice in situations in which a female is better off if she mates polygynously with an already mated male on a superior territory than if she selects a bachelor on an inferior territory. One model, the competitive female choice model, assumes that the females of a harem compete for the limited resources of the harem and thus that their fitness decreases as co-wives are added. The cooperative female choice model assumes that, within limits, a female's fitness is improved by the addition of co-wives to her mate's harem, as a result of cooperative interactions within the group. For each model, a sufficient set of independent assumptions is provided. Implications of the models are indicated and methods for testing them are discussed.     

Levels and composition of volatile organic compounds on commuting routes in Detroit, Michigan

Vehicle emissions can constitute a major share of ambient concentrations of many volatile organic compounds (VOCs) and other air pollutants in urban areas. Especially high concentrations may occur at curbsides, vehicle cabins, and other microenvironments. Such levels are not reflected by monitoring at fixed sites. This study reports on measurements of VOCs made from buses and cars in Detroit, MI. A total of 74 adsorbent tube samples were collected on 40 trips and analyzed by GC-MS for 77 target compounds. Three bus routes, selected to include residential, commercial and heavily industrialized areas, were sampled simultaneously on four sequential weeks during morning and afternoon rush hour periods. Nineteen compounds were regularly detected and quantified, the most prevalent of which included hexane/2-methyl pentane (15.6±5.8 μg m⁻³), toluene (10.2±7.9 μg m⁻³), m,p-xylene (6.8±4.7 μg m⁻³), benzene (4.5±3.0 μg m⁻³), 1,2,4-trimethylbenzene (4.0±2.6 μg m⁻³), o-xylene (2.2±1.6 μg m⁻³), and ethylbenzene (2.1±1.5 μg m⁻³). VOC levels in bus interiors and outdoor levels along the roadway were similar. Despite the presence of large industrial sources, route-to-route variation was small, but temporal variation was large and statistically significant. VOC compositions and trends indicate the dominance of vehicle sources over the many industrial sources in Detroit with the possible exceptions of styrene and several chlorinated VOCs. In-bus levels exceeded concentrations at fixed site monitors by a factor of 2–4. VOC concentrations in Detroit traffic are generally comparable to levels measured elsewhere in the US and Canada, but considerably lower than measured in Asia and Europe.     

The normal fetus of an acardiac twin pregnancy: Perinatal management based on echocardiographic and sonographic evaluation

Experience with three prenatally diagnosed pregnancies complicated by an acardiac twin reveals that ultrasonography and echocardiography are helpful in detecting early signs of in-utero congestive heart failure in the normal twin. The use of Doppler blood flow analysis to determine direction of blood flow, post-mortem placental and fetal angiography, and umbilical cord blood gas determination provided proof that retrograde arterial perfusion occurs in the acardiac fetus. In a fourth pregnancy, an experimental approach to occlude the acardiac twin's umbilical cord was attempted, but was unsuccessful.     

Bringing feedback and resilience of high-latitude ecosystems into the corporate boardroom

This paper discusses the role of companies in high-latitude regions, which are conceptualized as socially and economically mediated ecosystems, and identifies a number of important social actors within the business environment. We present three examples of corporate activity at high latitudes and discuss a variety of common threads. Notably, we argue that business theory and practice needs to move beyond a narrow social or economic concept of organizational resilience and embrace the ecological resilience of high-latitude regions as a business management goal. We also suggest that regional ecosystem resilience needs to become a meaningful measure of sustainable corporate governance, one that corporate boards of directors can review and commit to. The paper concludes with a call for a detailed research agenda on the role of transnational and national companies within high-latitude regions.     

Control of Tamarix in the Western United States: Implications for Water Salvage, Wildlife Use, and Riparian Restoration

Non-native shrub species in the genus Tamarix (saltcedar, tamarisk) have colonized hundreds of thousands of hectares of floodplains, reservoir margins, and other wetlands in western North America. Many resource managers seek to reduce saltcedar abundance and control its spread to increase the flow of water in streams that might otherwise be lost to evapotranspiration, to restore native riparian (streamside) vegetation, and to improve wildlife habitat. However, increased water yield might not always occur and has been substantially lower than expected in water salvage experiments, the potential for successful revegetation is variable, and not all wildlife taxa clearly prefer native plant habitats over saltcedar. As a result, there is considerable debate surrounding saltcedar control efforts. We review the literature on saltcedar control, water use, wildlife use, and riparian restoration to provide resource managers, researchers, and policy-makers with a balanced summary of the state of the science. To best ensure that the desired outcomes of removal programs are met, scientists and resource managers should use existing information and methodologies to carefully select and prioritize sites for removal, apply the most appropriate and cost-effective control methods, and then rigorously monitor control efficacy, revegetation success, water yield changes, and wildlife use.     

ACIDIFICATION AND FISH OCCURRENCE IN THE UPPER CHEAT RWER DRAINAGE,WEST VIRGINIA1

ABSTRACT: The decline of many fish populations within the mid-Appalachian region has been attributed to stream acidification as a result of acid precipitation. Many previous attempts to examine relationships between fish occurrence and acidification have been hindered by a lack of data on water quality and fish distributions. To assess relationships between water quality and bedrock type in the upper Cheat River drainage, we used EPA STORET water quality data (1969–1993) and calculated mean pH and mean alkalinity of streams associated with four bedrock types (Hampshire, Chemung, Mauch Chunk, and Pottsville). We examined the relationship between fish occurrence and bedrock type for 53 headwater streams. We found that acidity in headwater streams associated with Pottsville and Mauch Chunk groups often exceeded biological thresholds for acid-sensitive fish species (pH < 5.5). Streams associated with the Pottsville group typically had fewer cyprinid species and fewer total species than those associated with Mauch Chunk, Chemung, and Hampshire bedrock types. The congruent occurrence of streams with low buffering capacity, streams with pH > 5.5, and streams with low fish species richness indicate that acidification has influenced fish distributions in the upper Cheat River drainage.     

Remotely Sensed Data for Ecosystem Analyses: Combining Hierarchy Theory and Scene Models

Remotely sensed data have been used extensively for environmental monitoring and modeling at a number of spatial scales; however, a limited range of satellite imaging systems often constrained the scales of these analyses. A wider variety of data sets is now available, allowing image data to be selected to match the scale of environmental structure(s) or process(es) being examined. A framework is presented for use by environmental scientists and managers, enabling their spatial data collection needs to be linked to a suitable form of remotely sensed data. A six-step approach is used, combining image spatial analysis and scaling tools, within the context of hierarchy theory. The main steps involved are: (1) identification of information requirements for the monitoring or management problem; (2) development of ideal image dimensions (scene model), (3) exploratory analysis of existing remotely sensed data using scaling techniques, (4) selection and evaluation of suitable remotely sensed data based on the scene model, (5) selection of suitable spatial analytic techniques to meet information requirements, and (6) cost–benefit analysis. Results from a case study show that the framework provided an objective mechanism to identify relevant aspects of the monitoring problem and environmental characteristics for selecting remotely sensed data and analysis techniques.     

全球变化和北方森林:阈值,移动态或逐渐变化?

21世纪所表现出来的北方气候变化的巨大性忌是引起植被的变化,其变化之大足以引起重要的社会影响.但植被变化的速度和格局却难以预测.我们评述了一些能够表明在北方森林限界上或那些种子散播限制了物种分布的地区,植被是逐渐变化的证据.但是,在一个物种分布区的中心,森林组成对气候变化是相当有弹性的,除非超过了某些阈值.在阈值点上,变化是迅速且预想不到的,常常转换至截然不同的生态系统类型.很多这类变化的诱因易受管理的影响,这说明我们在今后几十年的政策抉择将对目前气候变化的生态社会后果产生重大影响.