Living with the enemy: parasites and pathogens of the ladybird Harmonia axyridis

Harmonia axyridis is an invasive alien predator in many countries across the world. The rapid establishment and spread of this species is of concern because of the threat it poses to biodiversity as a generalist predator. Understanding the mechanisms that contribute to the success of this species as an invader is not only intriguing but also critical to our understanding of the processes governing such invasions. The enemy release hypothesis (ERH) could explain the rapid population growth of many invasive alien species. However, empirical evidence in support of the ERH is lacking. An alternative hypothesis that could explain rapid population growth is evolution of increased competitive ability (EICA). Here we provide an overview of the parasites and pathogens of coccinellids with a particular focus on H. axyridis as a host. We examine the differential susceptibility of host species and highlight the resilience of H. axyridis in comparison to other coccinellids. We recognise the paucity and limitations of available information and suggest that studies, within a life-table framework, comparing life history traits of H. axyridis in both the native and introduced ranges are necessary. We predict that H. axyridis could benefit from both enemy release and EICA within the introduced range but require further empirical evidence.