Abstract
Fluctuating asymmetry (FA) is hypothesized to be a useful predictor of population canalization, especially for organisms at risk from environmental change.Identification of traits that meet statistical criteria as FA measures remains a challenge.Here, a laboratory experiment subjected immature butterflies (Vanessa cardui) to diet and temperature conditions of varying stress levels. Variation in dietary macronutrient ratio (protein: carbohydrate) and rearing temperature (optimal: 25°C; elevated: 32°C) was introduced as stressors. Temperature and nutrition are key variables influencing ectotherm growth and fitness and so are likely to be important stressors that influence FA.Individuals subjected to stressful conditions were predicted to show elevated FA of three wing size traits, as well as increased mortality and decreased adult body size.Trait FA did not vary across treatments. Instead, treatment levels impacted viability: The combined incidence of pupal death and expression of significant wing malformations increased in treatment levels designated as stressful. Variation in adult dry mass also reflected predicted stress levels. Results suggest that individuals predicted to display increased FA either died or displayed gross developmental aberrations.This experiment illustrates important constraints on the investigation of FA, including selection of appropriate traits and identification of appropriate levels of stressors to avoid elevated mortality. The latter concern brings into question the utility of FA as an indicator of stress in vulnerable, natural populations, where stress levels cannot be controlled, and mortality and fitness effects are often not quantifiable.
Highlights
The clade that includes about 99% of all extant metazoan species (Freeman et al, 2014), fluctuating asymmetry (FA) of a trait is defined as deviation from perfect symmetry that is random in its direction and normally distributed around a mean of zero (Palmer & Strobeck, 2003)
Homeostatic mechanisms operating during development buffer effects of perturbations, a phenomenon often termed “developmental stability” (Gibbs & Breuker, 2006; Habel et al, 2012; Ludoski et al, 2014; Takahashi, 2018); effective buffering mechanisms result in low FA (Graham et al, 1998; Møller, 2006; Van Valen, 1962)
The primary objective of this experiment was to determine whether temperature and diet stressors imposed during butterfly development would influence FA of adult wing traits
Summary
The clade that includes about 99% of all extant metazoan species (Freeman et al, 2014), fluctuating asymmetry (FA) of a trait is defined as deviation from perfect symmetry that is random in its direction (left- or right-side biased) and normally distributed around a mean of zero (Palmer & Strobeck, 2003). Prediction set A is that individuals raised under temperature and diet conditions mirroring those typically experienced by lab-adapted stock will display the least FA as adults They will display the largest body size and lower mortality than individuals reared on chemically defined diets (diets with known macronutrient constituents and no unknown additives). Prediction set D is that individuals reared on (chemically defined) diets other than the commercial painted lady diet will have greater FA and/or mortality and/or lower dry mass than those reared on the commercial diet This prediction is based on the assumption that the commercial diet was developed over time to improve butterfly performance and knowledge that the captive stock had had multiple generations to adapt to the diet.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
