Phenotypic coupling of sleep and starvation resistance evolves in D. melanogaster
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RESEARCH ARTICLE
Open Access
Phenotypic coupling of sleep and starvation resistance evolves in D. melanogaster Didem P. Sarikaya1,2* , Julie Cridland1, Adam Tarakji1, Hayley Sheehy1, Sophia Davis1, Ashley Kochummen1, Ryan Hatmaker1, Nossin Khan1, Joanna Chiu3 and David J. Begun1
Abstract Background: One hypothesis for the function of sleep is that it serves as a mechanism to conserve energy. Recent studies have suggested that increased sleep can be an adaptive mechanism to improve survival under food deprivation in Drosophila melanogaster. To test the generality of this hypothesis, we compared sleep and its plastic response to starvation in a temperate and tropical population of Drosophila melanogaster. Results: We found that flies from the temperate population were more starvation resistant, and hypothesized that they would engage in behaviors that are considered to conserve energy, including increased sleep and reduced movement. Surprisingly, temperate flies slept less and moved more when they were awake compared to tropical flies, both under fed and starved conditions, therefore sleep did not correlate with population-level differences in starvation resistance. In contrast, total sleep and percent change in sleep when starved were strongly positively correlated with starvation resistance within the tropical population, but not within the temperate population. Thus, we observe unexpectedly complex relationships between starvation and sleep that vary both within and across populations. These observations falsify the simple hypothesis of a straightforward relationship between sleep and energy conservation. We also tested the hypothesis that starvation is correlated with metabolic phenotypes by investigating stored lipid and carbohydrate levels, and found that stored metabolites partially contributed towards variation starvation resistance. Conclusions: Our findings demonstrate that the function of sleep under starvation can rapidly evolve on short timescales and raise new questions about the physiological correlates of sleep and the extent to which variation in sleep is shaped by natural selection. Keywords: Local adaptation, Sleep, Starvation resistance, Behavior, Trade-off, Plasticity
Background Sleep is an ancestral animal behavior [1–3]. The ancient nature of the trait demonstrates its biological importance, yet the functions of sleep remain contentious. It is connected to memory consolidation [4, 5], energy conservation [6, 7], * Correspondence: [email protected] 1 Department of Evolution and Ecology, University of California Davis, Davis, California, USA 2 Department of Molecular and Cellular Biology, University of California Davis, Davis, California, USA Full list of author information is available at the end of the article
and reducing exposure to hazards during periods where foraging is not advantageous [8]. While sleep itself is ancient, it nevertheless evolves. For example, duration of sleep is highly variable across different species, and may evolve in response to foraging demands [9], predation ri
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