Chemical Usurpation of a Nest by Paper Wasp Parasites

The paper wasp Polistes atrimandibularis is an obligatory social parasite of another Polistes species, P. biglumis bimaculatus. To control the host nest, the parasite sequentially changes the composition of its chemical signature, the cuticular hydrocarbons, during the colonial cycle. Gas chromatography-mass spectrometry of the cuticular hydrocarbons at every stage of the cycle showed that the parasite can switch on and off an entire chemical family, namely, the unsaturated hydrocarbons. In this way the parasite can match the host signature at a critical moment of the colonial cycle.     

Photoemission studies of high-tc superconductors: the superconducting gap

Over the last several years there have been great improvements in the energy resolution and detection efficiency of angle-resolved photoemission spectroscopy. These improvements have made it possible to discover a number of fascinating features in the electronic structure of the high transition temperature (T(c)) superconductors: apparently bandlike Fermi surfaces, flat-band saddle points, and nested Fermi surface sections. Recent work suggests that these features, previously thought explainable only by one-electron band theory, may be better understood with a many-body approach. Furthermore, other properties of the high-T(c) superconductors, which are difficult to understand with band theory, are well described using a many-body picture. Angle-resolved photoemission spectroscopy has also been used to investigate the nature of the superconducting pairing state, revealing an anisotropic gap consistent with a d-wave order parameter and fueling the current debate over s-wave versus d-wave superconductivity.     

Footwall refrigeration along a detachment fault: implications for the thermal evolution of core complexes

Oxygen isotope compositions of epidote and quartz from chloritic breccias that underlie the detachment fault in the metamorphic core complex of the Whipple Mountains yielded quartz-epidote fractionations that range from 4.1 to 6.4 per mil and increase systematically toward the fault. These fractionations give mean temperatures that decrease from approximately 432 degrees C at 50 meters below the fault to approximately 350 degrees C at 12 meters below the fault. This extreme thermal gradient of 82 degrees C over 38 meters (2160 degrees C per kilometer) is best explained by advective heat extraction by means of circulating surface-derived fluids. Models of lithospheric extension consider only conductive cooling resulting from tectonic denudation and thus require revision to include fluid-induced fault-zone refrigeration.     

Trade and <Emphasis Type="Italic">Totomoxtle</Emphasis>: Livelihood strategies in the Totonacan region of Veracruz,Mexico

Following the implementation of the North American Free Trade Agreement (NAFTA), Mexican farmers altered their livelihood strategies to respond to changing market incentives. While many commercial farmers responded to falling maize prices brought on by NAFTA by shifting into the production of vegetables for export, the coping strategies of low-income farmers have been varied, from diversifying income sources through off-farm employment, to migration, to searching for niche markets for new or added-value products. In the Totonocan region of the state of Veracruz, Mexico, many farmers who can no longer earn sufficient income from the sale of maize grain are turning to a byproduct of maize to generate income. The commercialization of totomoxtle, or maize husks, for domestic and international markets has not only enabled farmers to continue to profit from maize production, but it has also encouraged farmers to utilize and conserve criollo maize varieties that serve as important reservoirs of genetic diversity. Moreover, the growing importance of totomoxtle in livelihood strategies has caused some farmers to alter their maize management, selecting for better quality husks rather than for grain production. The purpose of this paper is to understand both the broad impact of NAFTA on the local agricultural economy and its more specific effects on the management of maize in the Zona Totonaca. Participation in international trade can lead to unexpected outcomes, in some cases creating new values for goods with a long history of local consumption. Commercialization of maize husks is likely to be only a temporary solution for the relief of rural poverty. Given the volatility of international markets, the long-term welfare of farmers may depend on the development of more diversified production strategies. Amanda King Amanda King holds an MSc from the University of California-Berkeley in Environmental Science, Policy, and Management. She was a Mickey Leland International Hunger Fellow based at the International Center for Maize and Wheat Improvement (CIMMYT) in El Batán, Mexico in 2003 and at the International Food Policy Research Institute (IFPRI) in Washington DC in 2004. She is currently conducting research in East Kalimantan, Indonesia on oil palm plantations and changes in local livelihoods.     

Impact of West Nile virus and other mortality factors on American white pelicans at breeding colonies in the northern plains of North America

American white pelicans (Pelecanus erythrorhynchos) are colonial-nesting birds and their breeding sites are concentrated in a few small areas, making this species especially vulnerable to factors that can influence productivity, such as disease, disturbance, predation, weather events and loss of nesting habitat. Nearly half of the American white pelican population breeds at four colonies in the northern plains: Chase Lake National Wildlife Refuge (NWR) in North Dakota, Bitter Lake (Waubay NWR) in South Dakota, Medicine Lake NWR in Montana, and Marsh Lake in Minnesota. Thus, sustained productivity at these colonies is crucial to the health of the entire species. During the latter half of the 2002 and 2003 breeding seasons, unusually high mortality of pelican chicks was observed at these colonies. West Nile virus (WNv) was identified as one source of these losses. In 2004–2007 we monitored three major colonies in the northern plains to assess mortality of chicks during the late breeding season. We documented severe weather events, disturbance, and WNv as factors contributing to chick mortality. Before WNv arrived in the region in 2002, chick mortality after mid-July was 4%, and then jumped to as high as 44% in the years since WNv arrived. WNv kills older chicks that are no longer vulnerable to other common mortality factors (e.g., severe weather, gull predation) and typically would have survived to fledge; thus WNv appears to be an additive mortality factor. Persistence of lower productivity at American white pelican colonies in the northern plains might reduce the adult breeding population of this species in the region.