Symbiont-mediated invasive success of the ladybird Harmonia axyridis

Andreas Vilcinskas, andreas.vilcinskasagrar.uni-giessen.de, Institute for Phytopathology and Applied Zoology, University of Gießen

An increasing number of invasive species characterized by rapid growth and spread of populations after their establishment in new habitats impact negatively both biodiversity and economy. Their invasive success is promoted by several factors among which a strong immune system has been predicted because invasive species have to cope with pathogens which they face in their new environments. To test this hypothesis, we analysed the immune system of the ladybird Harmonia axyridis because after being introduced in many countries as a biological control agent, it has become an invasive species threatening biodiversity of native ladybirds. Our study elucidates that H. axyridis exhibits a strong constitutive antimicrobial activity in the hemolymph which is mediated by a microbial symbiont. Because the latter probably originates from a parasite, we postulate that host-parasite-coevolution can result in a invasive holobiont species.