Meeting Abstract

19.1  Friday, Jan. 4  Testing the melanism-desiccation hypothesis using experimental evolution GIBBS, AG*; RAJPUROHIT, S; PETERSON, LM; ORR, A; Univ. of Nevada; Univ. of Pennsylvania; Univ. of Nevada; Univ. of Nevada allen.gibbs@unlv.edu

Several Sophophora species on the Indian subcontinent show clinal patterns in pigmentation, with darker populations occurring in northern, drier locations. We used experimental evolution to test the ‘melanism-desiccation’ hypothesis, which proposes that dark cuticle in Sophophora is an adaptation for increased desiccation tolerance. We selected for dark and light body pigmentation in replicated populations of S. melanogaster and assayed traits related to water balance. We also scored pigmentation and desiccation tolerance in populations selected for desiccation survival. Populations in both selection regimes showed large differences in the traits directly under selection. However, after over 50 generations of pigmentation selection, dark-selected populations were only slightly more desiccation tolerant than light-selected and control populations. Body pigmentation of desiccation-selected populations did not differ from control populations after over 140 generations of selection. We also found correlated responses in carbohydrate amounts in both selection regimes. Our results do not support an important role for melanization in Sophophora water balance. Supported by NSF award EnGen-0723930.