JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecological Applications.Abstract. Hawksbill turtles move between nesting colonies and feeding grounds, but in most cases it is not known which reproductive populations occupy a particular feeding habitat. In this study, genetic markers derived from mitochondrial DNA sequences are used to estimate the contribution of Caribbean nesting colonies to a feeding ground at Mona Island, Puerto Rico (n = 41). Maximum likelihood analysis indicates that this feeding population is not composed primarily of turtles from the neighboring nesting colony (also on Mona Island), but is drawn from nesting populations throughout the Caribbean region. A sampled nesting colony in the southern hemisphere (Bahia, Brazil) did not contribute, at detectable levels, to the Mona Island feeding ground. From this evidence, we concluded that hawksbill turtles recruit to feeding grounds over a scale of hundreds of kilometres, but not over the scale of 7000 km that separate Mona Island from Bahia, Brazil. These data indicate that a hawksbill turtle harvest on feeding grounds will reduce nesting populations throughout the Caribbean region.

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We review our studies of the biological impact of magnetic field strengths up to 30 Tesla on transgenic arabidopsis plants engineered with a stress response gene consisting of the alcohol dehydrogenase (Adh) gene promoter driving the β-glucuronidase (GUS) gene reporter. Field strengths in excess of 15 Tesla induce expression of the Adh/GUS transgene in the roots and leaves. Microarray analyses indicate that such field strengths have a far reaching effect on the genome. Wide spread induction of stress-related genes and transcription factors, and a depression of genes associated with cell wall metabolism are prominent examples. MotivationSince earth-based, low-gravity environments are restricted to durations of less than several seconds [1], we have investigated the possibility of using magnetic levitation as a reduced gravity environment appropriate for long-duration (i.e. up to several hours) studies of plant gene expression [2,3]. The possibility of using magnetic levitation to mimic a reduced gravity environment has been explored in a variety of systems [3][4][5][6][7]. During our preliminary studies involving transgenic arabidopsis, we discovered that the plants were stressed by the presence of a strong, static, non-gradient magnetic field [2]. These preliminary, qualitative observations have now been corroborated by a series of systematic, quantitative studies [8].The possibility that strong, static (non-gradient) magnetic fields might have an influence on biological processes has been discussed for many years [9][10][11], including a recent report that implicates high magnetic fields in alterations of the cleavage plane during cell division [12]. Nevertheless, the common viewpoint is that presently achievable static magnetic fields do not have a lasting effect on biological systems [11]. Indeed, magnetic resonance imaging (MRI), utilizing static magnetic fields up to 12 Tesla, is a powerful tool for non-invasive in vivo imaging at the molecular level [13][14][15]. The demands for more precise in vivo imaging have driven the field strengths progressively higher (approaching 20 Tesla) [16], yet information regarding the biological impact of exposing metabolically active cells to fields of this magnitude is limited. We have recently reported about the effect of high magnetic fields on the gene expression profile of the plant Arabidopsis (Arabidopsis thaliana) [8].