Abstract
IntroductionOrganisms use environmental cues to match their phenotype with the future availability of resources and environmental conditions. Changes in the magnitude and frequency of environmental cues such as photoperiod and temperature along latitudes can be used by organisms to predict seasonal changes. While the role of temperature variation on the induction of plastic and seasonal responses is well established, the importance of photoperiod for predicting seasonal changes is less explored.Materials and methodsHere we studied changes in life‐history and thermal stress resistance traits in Drosophila subobscura in response to variation in photoperiod (6:18, 12:12 and 18:6 light:dark cycles) mimicking seasonal variations in day length. The populations of D. subobscura were collected from five locations along a latitudinal gradient (from North Africa and Europe). These populations were exposed to different photoperiods for two generations, whereafter egg‐to‐adult viability, productivity, dry body weight, thermal tolerance, and starvation resistance were assessed.ResultsWe found strong effects of photoperiod, origin of populations, and their interactions on life‐history and stress resistance traits. Thermal resistance varied between the populations and the effect of photoperiod depended on the trait and the method applied for the assessment of thermal resistance.PerspectivesOur results show a strong effect of the origin of population and photoperiod on a range of fitness‐related traits and provide evidence for local adaptation to environmental cues (photoperiod by population interaction). The findings emphasize an important and often neglected role of photoperiod in studies on thermal resistance and suggest that cues induced by photoperiod may provide some buffer enabling populations to cope with a more variable and unpredictable future climate.
Highlights
Organisms use environmental cues to match their phenotype with the future availability of resources and environmental conditions
Variation in environmental conditions in nature can be dramatic, and it is predicted that the magnitude and frequency of extreme local weather events will increase in the coming decades due to global climate changes (IPCC, 2013)
The evolutionary importance of physiological processes as a consequence of variation in ambient temperature is strongly supported by data from clinical studies, where latitudinal gradients in thermal conditions have resulted in intraspecific clinal variation in stress resistance (Castaneda, Rezende, & Santos, 2015; Hoffmann, Anderson, & Hallas, 2002; Kingsolver & Buckley, 2017; Pratt & Mooney, 2013; Yampolsky, Schaer, & Ebert, 2014)
Summary
Ectotherms must cope with daily and seasonal changes in environmental conditions (Bahrndorff, Loeschcke, Pertoldi, Beier, & Holmstrup, 2009; Cossins & Bowler, 1987; Dahlhoff & Rank, 2007), among which temperature extremes and lack of adequate nutrition can affect population viability and individual fitness (Andersen, Kristensen, Loeschcke, Toft, & Mayntz, 2010; Braby & Jones, 1995; Dahlhoff & Rank, 2007; Fischer & Fiedler, 2001). The importance of photoperiod and stress resistance has been investigated in a lowland population of Drosophila buzzatii, in which different light regimes changed the heat knock‐down resistance so that flies increased resistance during the hours of the day with light where they were most active and thermal conditions were most favorable (Sørensen & Loeschcke, 2002). The pitcher‐plant mosquito Wyeomyia smithii has over a period of 24 years (from 1972 to 1996) shifted toward shorter photoperiods to initiate the larval dormancy (Bradshaw & Holzapfel, 2001) These results show the adaptive potential of photoperiodism and the importance of photoperiod in relation to coping with climate change through evolutionary responses. We further hypothesize that photoperiod‐dependent responses are more pronounced for high‐latitude populations evolved to cope with highly variable and unpredictable thermal environments (Bahrndorff et al, 2009; Sniegula, Nilsson‐ Örtman, & Johansson, 2012)
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