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The taxonomic identity of endangered populations of the Least Tern (Sternula antillarum) has long been debated. Their current conservation status provides even more impetus to examine the taxonomic distinctness of these groups. We used rapidly evolving mitochondrial DNA control-region sequences (840 base pairs; n = 188) and microsatellite DNA data (7 loci; n = 417) to examine genetic structure within and among three subspecies that occur within the United States: California Least Tern (S. a. browni), Interior Least Tern (S. a. athalassos), and Eastern Least Tern (S. a. antillarum). Although significant genetic structure was observed among breeding populations from across the species' range, our data indicated little evidence of genetic structure within traditional subspecific groups. Isolation-by-distance analyses, however, identified subtle patterns that may reflect sex-specific differences in dispersal behavior. Our analyses likewise demonstrated little population subdivision among subspecific groups, which raises questions regarding the taxonomic status of traditionally defined subspecies. Our findings can therefore be used to consider a reevaluation of Least Tern subspecies by the American Ornithologists' Union's Committee on Taxonomy and Nomenclature. We further emphasize the need for studies of range-wide breeding-site fidelity and natal philopatry to better understand interpopulation movements of individuals throughout the annual cycle. Received 9 November 2009, accepted 30 March 2010. Key words: Least Tern, microsatellites, mitochondrial DNA, population structure, Sternula antillarum, subspecies. Por mucho tiempo se ha debatido la identidad taxonomica de las poblaciones en peligro de Sternula antillarum. Su estatus de conservacion actual genera un incentivo aun mayor para examinar la distincion taxonomica de estos grupos. Usamos secuencias de ADN mitocondrial de la region control de rapida evolucion (840 pares de bases; n = 188) y datos de ADN microsatelital (7 loci; n = 417) para examinar la estructura genetica dentro y entre tres subespecies que se encuentran en Estados Unidos: S. a. browni, S. a. athalassos y S. a. antillarum. A pesar de que se observo estructura genetica entre poblaciones reproductivas dentro del area de distribucion de la especie, nuestros datos indicaron poca evidencia de estructura genetica entre grupos subespecificos tradicionales. Los analisis de aislamiento por distancia revelaron patrones que podrian reflejar diferencias sexuales en el comportamiento de dispersion. Nuestros analisis tambien mostraron poca subdivision poblacional entre grupos subespecificos, lo que pone en duda el estatus taxonomico de las subespecies definidas tradicionalmente. Nuestros resultados pueden ser usados para considerar una revaluacion de las subespecies de S. antillarum por el comite de taxonomia y nomenclatura de la American Ornithologists' Union. Ademas, enfatizamos la necesidad de estudios sobre la fidelidad de sitio reproductivo y filopatria natal en toda el area de distribucion de la especie para entender mejor los movimientos de individuos entre poblaciones a lo largo de todo el ciclo anual. DOI: 10.1525/auk.2010.09222

Several disputes between clinical researchers and pharmaceutical manufacturers have highlighted the critical importance of protecting the right of trial subjects to disclosure of risks and the academic freedom of investigators. [...]

Nitrous oxide, or laughing gas, has used since the middle of the 19th century as an anesthetic. Epidemiological studies have revealed that long-term exposure to low levels of nitrous oxide may cause serious health problems such as liver and neurological damage. Exposure to nitrous oxide may also increase the risk of miscarriage and birth defects. A research study found that female dental assistants exposed to high levels of nitrous oxide experienced more difficulty in conceiving a child. Exposure to nitrous oxide may also affect male fertility. The National Institute of Occupational Safety and Health (NIOSH) has recommended a maximal level of exposure to nitrous oxide. Many individuals who work in dental offices may be exposed to levels of nitrous oxide that are higher than those recommended by the NIOSH, despite the use of nitrous oxide scavenging systems. The use of nitrous oxide in dental offices may need to be curtailed, despite its popularity with both clinicians and patients.