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Correlated responses to selection for increased resistance against a fungal competitor in Drosophila melanogaster
Monika Trienens, Susanne Wölfle, Marko Rohlfs
Zoologisches Institut, Tierökologie,
Christian-Albrechts-Universität zu Kiel
Natural antagonists pose a continuous challenge to an organism’s evolutionary fitness. Consequently, diverse and sophisticated morphological, physiological and behavioural mechanisms that avoidor mitigate the opponent’s impact are an outstanding hallmark of biological systems. Defence orresistance strategies may offer flexibility to organisms in terms of responsiveness to the negativeinfluence of antagonists, but are accompanied by disadvantages because using defences is likely tohave impact on an organism’s energy and resource budget. Additionally, given that there is geneticvariation in the ability to withstand the impact of antagonists, organisms suffer costs not only of usingbut also of possessing effective defences. We recently selected for resistance against a competingfilamentous fungus in saprophagous Drosophila melanogaster. Interestingly, we found no indication of impaired survival or reproduction in resistant populations under mould-free conditions. However,by looking at resistance to various abiotic and biotic stresses, increased fungus resistance negatively correlates with survival when flies were confronted with low humidity and temperature extremes, and with the ability to fend off endogenous macroparasites. Our results suggest that evolution of resistance against microbial competitors may be constrained by ecological stresses rather than by decrements in fitness related to life-history traits.