Does fluctuating asymmetry of wing traits capture relative environmental stress in a lepidopteran?

Fluctuating asymmetry (FA) may 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.

In the present study, a laboratory experiment subjected immature butterflies (Vanessa cardui) to a range of diet and temperature conditions of varying stress levels. Variation in dietary macronutrient ratio (protein: carbohydrate) and rearing temperature (optimal: 25°C; elevated: 32°C) were introduced as stressors.

Individuals subjected to stressful conditions were predicted to show elevated FA of three wing size traits.

While FA of all three traits proved measurable, it did not vary across diet and temperature treatments. Instead, treatment levels impacted viability: the combined incidence of death prior to eclosion and expression of significant wing malformations increased in treatment levels predicted to increase FA. V...