Transgenerational effects of pest management strategy on fluctuating asymmetry in the European earwig Forficula auricularia: Being the progeny of a mother who lived in conventional orchards makes you more asymmetric than having a mother who lived in insecticide free orchards

Fluctuating asymmetry (FA), defined as the random non-directional deviation from perfect bilateral symmetry, is considered to reflect developmental instability in bilaterally symmetrical organisms. It has been commonly used as a reliable biomarker of environmental stresses in natural populations. In agroecosystems, FA may arise through transgenerational influence of insecticides. We measured fluctuating asymmetry on unexposed progeny of Forficula auricularia mothers sampled in orchards that used no to frequent insecticides’ applications. Seven morphometric traits were measured on both right and left side and fluctuating asymmetry was calculated. Among these seven traits, four were more asymmetric when the progeny was born from a mother who lived in conventional orchards that used insecticides frequently compared to a mother who lived in insecticide free orchards. Males were more asymmetric than females for all traits but pest management strategy influenced FA in a similar way for both sexes. Measuring FA on unexposed daughters and sons of individuals originating from natural ecosystems may thus be a reliable easy-to-use tool to monitor mid-term effects of insecticides in the environment.