Inhibition of alcohol dehydrogenase after 2–propanol exposure in different geographic races of Drosophila mojavensis: Lack of evidence for selection at the Adh2 Locus

Authors

  • Edward Pfeiler,

    Corresponding author
    1. Centro de Investigación en Alimentación y Desarrollo, A.C., Unidad Guaymas, Apartado Postal 284, Guaymas, Sonora 85480, Mexico
    2. School of Life Sciences, Arizona State University, Tempe, Arizona 85287–4501
    • CIAD, A.C., Unidad Guaymas, Apartado Postal 284, Guaymas, Sonora, Mexico C.P. 85480
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  • Laura K. Reed,

    1. Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, 85721
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  • Therese A. Markow

    1. Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, 85721
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Abstract

High frequencies of the fast allele of alcohol dehydrogenase–2 (Adh2F) are found in populations of Drosophila mojavensis that inhabit the Baja California peninsula (race BII) whereas the slow allele (Adh2S) predominates at most other localities within the species' geographic range. Race BII flies utilize necrotic tissue of pitaya agria cactus (Stenocereus gummosus) which contains high levels of 2–propanol, whereas flies from most other localities utilize different cactus hosts in which 2–propanol levels are low. To test if 2–propanol acts as a selective force on Adh2 genotype, or whether some other yet undetermined genetic factor is responsible, mature males of D. mojavensis lines derived from the Grand Canyon (race A) and Santa Catalina Island (race C), each with individuals homozygous for Adh2F and Adh2S, were exposed to 2–propanol for 24 h and ADH–2 specific activity was then determined on each genotype. Flies from five other localities homozygous for either the fast or slow allele also were examined. Results for all reported races of D. mojavensis were obtained. 2–propanol exposure inhibited ADH–2 specific activity in both genotypes from all localities, but inhibition was significantly less in two populations of race BII flies homozygous for Adh2F. When F/F and S/S genotypes in flies from the same locality were compared, both genotypes showed high 2–propanol inhibition that was not statistically different, indicating that the F/F genotype alone does not provide a benefit against the inhibitory effects of 2–propanol. ADH–1 activity in female ovaries was inhibited less by 2–propanol than ADH–2. These results do not support the hypothesis that 2–propanol acts as a selective factor favoring the Adh2F allele. J. Exp. Zool. (Mol. Dev. Evol.) 304B:159–168, 2005. © 2005 Wiley-Liss, Inc.

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