Ladybird community change induced by the harlequin ladybird Harmonia axyridis: evidence from a long-term field study in the UK

Abstract: This study examines changes in ladybird (Coleoptera: Coccinellidae) communities at four sites (two lime tree sites, one pine tree site and one nettle site) in East Anglia, UK, over an 11-year period (2006-2016) following invasion by the non-native ladybird species Harmonia axyridis (Pallas). Overall, H. axyridis represented 41.5% of all ladybirds sampled and was over three times more abundant than the second commonest species, Coccinella septempunctata L. There was a significant negative relationship between H. axyridis and Adalia bipunctata (L.) adults at the lime tree sites, but not between H. axyridis and adults of any of the other main ladybird species sampled. Adalia bipunctata adults and Adalia spp. larvae were the only native ladybirds that significantly declined. Our study shows a clear change in the ladybird community on lime trees over an 11-year period. Intraguild predation is hypothesised to be an important driver of the changes observed.