Levels of asymmetry in Formica pratensis Retz. (Hymenoptera, insecta) from a chronic metal‐contaminated site

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Abstract
Asymmetries of bilaterally symmetrical morphological traits in workers of the ant Formica pratensis Retzius were compared at sites with different levels of metal contamination and between mature and pre‐mature colonies. Statistical analyses of the right‐minus‐left differences revealed that their distributions fit assumptions of fluctuating asymmetry (FA). No direct asymmetry or antisymmetry were present. Mean measurement error accounts for a third of the variation, but the maximum measurement error was 65%. Although significant differences of FA in ants were observed, the inconsistent results render uncovering a clear pattern difficult. Lead, cadmium, and zinc concentrations in the ants decreased with the distance from the contamination source, but no relation was found between FA and the heavy metal levels. Ants from the premature colonies were more asymmetrical than those from mature colonies but accumulated less metals. The use of asymmetry measures in ecotoxicology and biomonitoring is criticized, but should remain widely applicable if statistical assumptions are complemented by genetic and historical data.