Genomics of invasion of the ladybug Harmonia axyridis – GANDHI_Ukraine

Biological invasions are defined as the successful establishment of species outside their native range. They are a component of global change and induce substantial impact on invaded communities and ecosystems as well as considerable economic loss. While the ecological effects of invasions are well documented, the traits, the evolutionary forces and the genomic responses to selective factors that endow populations with a higher propensity to invade a new environment are largely unknown. The harlequin ladybug Harmonia axyridis, an emblematic insect species to study color polymorphism, has emerged as a model species to study biological invasions. In this proposal, building on our previous work and capitalizing on the genomic resources as well as on the innovative statistical methods that we have recently developed and that we plan to further develop (e.g. ABC Random Forest and BayPass ), we will characterize the molecular footprints of adaptations that promoted the successful worldwide invasion of H. axyridis. Using complementary approaches (cf. genomics, experimental and functional analyses), we will focus on three main objectives. (1) we will consolidate and extend our H. axyridis genomic resources by generating a high-quality annotated genome assembly and a medium-density linkage map; (2) we will explore the genome response of H. axyridis during invasion by refining the routes of invasion and by conducting genome-wide association study to find the genes involved in adaptive processes during invasion; and (3) we will characterize experimentally the genetic architecture of three traits potentially involved in successful invasions by H. axyridis: coloration plasticity and variation of adult elytra, female body mass and age at first reproduction. In a general perspective, understanding the genomic response to novel invaded environments will help us to predict the conditions under which invasiveness can be enhanced or suppressed. Importantly, our methodological approaches can be transposed to any other species characterized by non-equilibrium demographic conditions. Beyond its contributions to fundamental population genomics and evolutionary biology, our project can also support innovating management methods of invasive species, including genetic-based control methods.