Meeting Abstract

P2.55  Thursday, Jan. 5  Trophic and metamorphic discrimination of hydrogen isotopes in cabbages (Brassica oleracea) and cabbage loopers (Trichoplusia ni): Implications for stable isotope ecology PETERS, JP*; WOLF, N; STRICKER, CA; COLLIER, TR; MARTINEZ DEL RIO, C; Univ. of Wyoming; Univ. of Wyoming; U. S. Geological Survey, Fort Collins Science Center, Denver Federal Center; Univ. of Wyoming; Univ. of Wyoming jpeter50@uwyo.edu

The use of stable isotopes in ecological studies requires that we know the magnitude of discrimination factors between consumer and element sources. The causes of variation in discrimination factors for carbon and nitrogen have been relatively well studied. In contrast, we know very little about the incorporation of hydrogen isotopes. Understanding these processes in hydrogen isotopes is essential to the study of animal migrations with stable isotope analysis. We reared cabbage looper moths (Trichoplusia ni) on cabbage (Brassica oleracea) plants irrigated with four treatments of deuterium-enriched water. δD values of plants, caterpillars, and moths were linearly correlated with the isotopic composition of irrigation water. However, the δD values of plants did not show a 1 to 1 relationship to irrigation water, suggesting that ambient water vapor (which did not vary in δD across treatments), contributes a large fraction of the hydrogen incorporated into leaves (c. 40%). We also documented a substantial trophic enrichment of deuterium between plants and caterpillars (c. 32‰) and metamorphic depletion of deuterium between moths and caterpillars (c. 14‰). We believe that accounting for the effects of exchange of hydrogen between plants and ambient hydrogen sources, trophic enrichment and metamorphic depletion on hydrogen signatures will greatly improve the use of hydrogen isotopes in the study of migratory movements.