Wing shape-mediated carry-over effects of a heat wave during the larval stage on post-metamorphic locomotor ability
Two key insights to better assess the ecological impact of global warming have been poorly investigated to date: global warming effects on the integrated life cycle and effects of heat waves. We tested the effect of a simulated mild (25 °C) and severe (30 °C) heat wave experienced during the larval stage on the flight ability of the damselfly Ischnura elegans. To get a mechanistic understanding of how heat stress may translate into reduced post-metamorphic flight ability, we evaluated the hypothesized mediatory role of adult size-related traits, and also tested alternative pathways operating through changes in wing shape and two flight-related traits (both relative fat and flight muscle contents). Exposure to a heat wave, and particularly the severe one, shortened the larval stage, reduced adult size-related traits and modified the wing shape but did not significantly affect emergence success, relative fat content and relative flight muscle mass. Notably, the heat wave negatively affected all components of flight ability. Unexpectedly, the heat wave did not reduce flight ability through reducing size. Instead, we identified a novel size-independent mechanism bridging metamorphosis to link larval environment and adult flight ability in males: through affecting wing shape. The present study advances mechanistic insights in the still poorly understood coupling of life stages across metamorphosis. Additionally, our results underscore the need for integrative studies across life stages to understand the impact of global warming.
KeywordsCarry-over effects Heat stress Geometric morphometrics Temperature-size rule Wing shape
We thank an anonymous reviewer and the associate editor for constructive feedback that improved our manuscript. HA was supported by the French Ministry of Ecology, Sustainable Development and Energy and by the French National Research Institute of Science and Technology for Environment and Agriculture. ISV was supported by a FPI grant of the Spanish Ministry (BES-2012-052005). Financial support for this research came from grants of FWO, Belspo project Speedy and the KU Leuven Centre of Excellence program PF/2010/07 to RS.
Author contribution statement
HA, ISV and RS conceived and designed the experiments. HA and ISV performed the experiments. HA analyzed the data. HA, ISV and RS wrote the manuscript.
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