Associative learning of odor with food- or blood-meal by Culex quinquefasciatus Say (Diptera: Culicidae)

The ability of many insects to learn has been documented. However, a limited number of studies examining associative learning in medically important arthropods has been published. Investigations into the associative learning capabilities of Culex quinquefasciatus Say were conducted by adapting methods commonly used in experiments involving Hymenoptera. Male and female mosquitoes were able to learn a conditioned stimulus that consisted of an odor not normally encountered in nature (synthetic strawberry or vanilla extracts) in association with an unconditioned stimulus consisting of either a sugar (males and females) or blood (females) meal. Such information could lead to a better understanding of the ability of mosquitoes to locate and select host and food resources in nature.     

Chemical consequences of relocation of the soft coral Lobophytum compactum and its placement in contact with the red alga Plocamium hamatum

Seven colonies of Lobophytum compactum Tixier-Durivault, 1956, which produce isolobophytolide as the major secondary metabolite, were selected from a fringing reef in the Pelorus Channel, Palm Island Group (18°34S; 146°29E), North Queensland, Australia. In September 1991, they were sectioned to afford two portions which were relocated to a grid, and a significant part of the parent colony which was left in place. The aim of the experiment was to determine the effect of relocation and contact with a toxic alga on the secondary metabolite content of a soft coral. A significant increase in the concentration of isolobophytolide was observed for all relocated colonies (n=14, p=0.001) compared to the non-relocated control colonies. This decreased after 2 mo, and was not significantly different from that of the non-relocated control colonies (n=14, p=0.881). After 1 mo, Plocamium hamatum J. Agardh plants were placed in direct contact with 50% of the relocated colonies. All soft-coral colonies in contact with the alga (n=7), showed tissue necrosis on the parts in direct contact with the alga after a further 2 wk. Tissues of the relocated control colonies (n=7), and those portions of treated colonies which were not in direct contact with the alga, were not affected. The parts of the colonies in contact with the alga showed a significant decrease in lipid content over time (n=7, p=0.001) and also a decrease in the concentration of the diterpene isolobophytolide (n=7, p=0.001). The effects of P. hamatum on the soft coral were essentially restricted to contract necrosis; chemical variations in the affected tissue were the outcomes of this necrosis. These results indicate that stress due to relocation is a more important factor in the variation of isolobophytolide levels in the soft coral L. compactum than is contact with the alga P. hamatum.     

Thermal ecology of the neotropical army ant Eciton burchellii.

I explored the thermal ecology of Eciton burchellii, a New World army ant, in primary forest and forest fragments in the Atlantic lowlands of Costa Rica in 2002 and 2003. My primary objective was to determine whether high surface temperatures in pastures surrounding forest fragments posed a thermal barrier to ant colonies within those fragments; secondarily, I assessed whether thermal gradients within continuous moist forest were sufficient to elicit avoidance reactions from foraging colonies. E. burchellii colonies in forest fragments avoided entering open pasture in full sun (51.3 degrees C) on 100% of all edge interactions; however, edges were readily crossed where artificial shaded areas had previously been installed. Ant raids in primary forest avoided artificially established temperatures >43 degrees C but tolerated 45.5 degrees C in the presence of prey baits. Captive ants held at 43 degrees C survived 18.5 min; at temperatures of 51.3 degrees C survival time was only 2.8 min. Ants running on established foraging trails increased running velocity by 18% when substrate temperature was raised from 28.4 degrees to 38.0 degrees C, and they abandoned trails at temperatures >43 degrees C. The standard deviation (s) of temperatures on active raid trails in continuous forest was 2.13 degrees C, while nearby systematic sampling revealed a greater background standard deviation of 4.13 degrees C. E. burchellii colonies in this region appear to be living surprisingly near their upper limits of thermal tolerance. The heat of open pastures alone is sufficient to prevent their exiting forest fragments, or entering similarly hot areas within continuous forest. Shaded vegetative corridors are sufficient to permit mobility between isolated fragments, and their preservation should be encouraged. Despite views that tropical lowland moist forests have an essentially homogenous microclimate, army ants appear to avoid local hot spots on the forest floor, steering daily foraging trails to follow cooler routes than would be expected by chance. As deforestation remakes tropical landscapes worldwide, it is important to consider the thermal consequences of these actions and their effect on keystone organisms such as army ants. Changes in global climate patterns are likely to affect even evergreen tropical systems whose organisms may be sensitive to finer microclimatic variation than previously suspected.     

Possible impacts of changes in UV-B radiation on North American trees and forests

Approximately 35 species representing 14 tree genera have been evaluated for responses to UV-B radiation in North America. The best representation has been in the conifers where some 20 species representing three genera have been studied. Overall, about 1/3 of these have demonstrated some deleterious response to UV-B. However, most negative impacts have been observed under controlled environment conditions where sensitivity may be enhanced. Therefore, it seems unlikely that expected levels of ozone depletion will result in direct losses in productivity. However, the role that ambient or enhanced levels of UV-B may play in forest ecosystem processes is more difficult to access. One possible indirect response of forests to changes in UV-B radiation levels could be via alterations in plant secondary metabolites. Increases in phenolics and flavonoids that enhance epidermal UV-screening effectiveness may also influence leaf development, water relations or ecosystem processes such as plant-herbivore interactions or decomposition.     

Enforcement and price controls in emissions trading

This paper examines how enforcement affects the structure and performance of emissions trading programs with price controls under uncertainty about firms' abatement costs. The analysis highlights how an enforcement strategy can cause abatement-cost risk to be transmitted to enforcement costs via the price of permits. When this occurs, accommodating the effect of abatement-cost risk with an optimal policy results in higher expected emissions and lower expected permit price than their second-best optimal values. However, it is possible to design an enforcement strategy that shields enforcement costs from abatement-cost risk by tying sanctions directly to permit prices. This enforcement strategy stabilizes enforcement effort, the optimal permit supply and price controls are independent of enforcement costs, and the policy produces the second-best optimal outcome.     

Remediating TCE‐contaminated groundwater in low‐permeability media using hydraulic fracturing to emplace zero‐valent iron/organic carbon amendment

A field pilot test in which hydraulic fracturing was used to emplace granular remediation amendment (a mixture of zero‐valent iron [ZVI] and organic carbon) into fine‐grained sandstone to remediate dissolved trichloroethene (TCE)‐contaminated groundwater was performed at a former intercontinental ballistic missile site in Colorado. Hydraulic fracturing was used to enhance the permeability of the aquifer with concurrent emplacement of amendment that facilitates TCE degradation. Geophysical monitoring and inverse modeling show that the network of amendment‐filled fractures extends throughout the aquifer volume targeted in the pilot test zone. Two years of subsequent groundwater monitoring demonstrate that amendment addition resulted in development of geochemical conditions favorable to both abiotic and biological TCE degradation, that TCE concentrations were substantially reduced (i.e., greater than 90 percent reduction in TCE mass), and that the primary degradation processes are likely abiotic. The pilot‐test data aided in re‐evaluating the conceptual site model and in designing the full‐scale remedy to address a larger portion of the TCE‐contaminated groundwater plume. © 2012 Wiley Periodicals, Inc.     

Effects of flow regimes altered by dams on survival, population declines, and range-wide losses of California river-breeding frogs

Widespread alteration of natural hydrologic patterns by large dams combined with peak demands for power and water delivery during summer months have resulted in frequent aseasonal flow pulses in rivers of western North America. Native species in these ecosystems have evolved with predictable annual flood-drought cycles; thus, their likelihood of persistence may decrease in response to disruption of the seasonal synchrony between stable low-flow conditions and reproduction. We evaluated whether altered flow regimes affected 2 native frogs in California and Oregon (U.S.A.) at 4 spatial and temporal extents. We examined changes in species distribution over approximately 50 years, current population density in 11 regulated and 16 unregulated rivers, temporal trends in abundance among populations occupying rivers with different hydrologic histories, and within-year patterns of survival relative to seasonal hydrology. The foothill yellow-legged frog (Rana boylii), which breeds only in flowing water, is more likely to be absent downstream of large dams than in free-flowing rivers, and breeding populations are on average 5 times smaller in regulated rivers than in unregulated rivers. Time series data (range = 8 - 19 years) from 5 populations of yellow-legged frogs and 2 populations of California red-legged frogs (R. draytonii) across a gradient of natural to highly artificial timing and magnitude of flooding indicate that variability of flows in spring and summer is strongly correlated with high mortality of early life stages and subsequent decreases in densities of adult females. Flow management that better mimics natural flow timing is likely to promote persistence of these species and others with similar phenology.     

Role of winter temperature and climate change on the survival and future range expansion of the hemlock woolly adelgid (Adelges tsugae) in eastern North America

Global climate change has already affected the abundances, range limits, and interactions of many species. The hemlock woolly adelgid (Adelges tsugae), an invasive insect introduced to eastern North America from Japan, has decimated stands of eastern hemlock (Tsuga canadensis) and Carolina hemlock (T. caroliniana) from Georgia to Connecticut. However, its spread across central and northern New England has been slowed substantially by its inability to tolerate cold winter temperatures. Using data from previous lab and field studies collected over the past 17 years, including adelgid spread and overwintering mortality, we first characterize the temperature conditions that may limit adelgid spread. We then show how, in the future, rising winter temperatures due to climate change are likely to remove the conditions currently limiting adelgid spread, and facilitate the northward expansion as more suitable habitat becomes available.     

X-ray microspectroscopy and chemical reactions in soil microsites

Soils provide long-term storage of environmental contaminants, which helps to protect water and air quality and diminishes negative impacts of contaminants on human and ecosystem health. Characterizing solid-phase chemical species in highly complex matrices is essential for developing principles that can be broadly applied to the wide range of notoriously heterogeneous soils occurring at the earth's surface. In the context of historical developments in soil analytical techniques, we describe applications of bulk-sample and spatially resolved synchrotron X-ray absorption spectroscopy (XAS) for characterizing chemical species of contaminants in soils, and for determining the uniqueness of trace-element reactivity in different soil microsites. Spatially resolved X-ray techniques provide opportunities for following chemical changes within soil microsites that serve as highly localized chemical micro- (or nano-)reactors of unique composition. An example of this microreactor concept is shown for micro-X-ray absorption near edge structure analysis of metal sulfide oxidation in a contaminated soil. One research challenge is to use information and principles developed from microscale soil chemistry for predicting macroscale and field-scale behavior of soil contaminants.     

Mangrove vulnerability modelling in parts of Western Niger Delta, Nigeria using satellite images, GIS techniques and Spatial Multi-Criteria Analysis (SMCA)

Mangroves are known for their global environmental and socioeconomic value. Despite their importance, mangrove like other ecosystems is now being threatened by natural and human-induced processes that damage them at alarming rates, thereby diminishing the limited number of existing mangrove vegetation. The development of a spatial vulnerability assessment model that takes into consideration environmental and socioeconomic criteria, in spatial and non-spatial formats has been attempted in this study. According to the model, 11 different input parameters are required in modelling mangrove vulnerability. These parameters and their effects on mangrove vulnerability were selected and weighted by experts in the related fields. Criteria identification and selection were mainly based on effects of environmental and socioeconomic changes associated with mangrove survival. The results obtained revealed the dominance of socioeconomic criteria such as population pressure and deforestation, with high vulnerability index of 0.75. The environmental criteria was broadly dispersed in the study area and represents vulnerability indices ranging from 0.00?C0.75. This category reflects the greater influence of pollutant input from oil wells and pipelines and minimal contribution from climatic factors. This project has integrated spatial management framework for mangrove vulnerability assessment that utilises information technology in conjunction with expert knowledge and multi-criteria analysis to aid planners and policy/ decision makers in the protection of this very fragile ecosystem.