Origin, divergence and migration routes of psyllids of the Cacopsylla pruni complex (Hemiptera: Psylloidea) inferred by Approximate Bayesian Computation methods

Population genetics is essential to decipher the evolutionary history of pests and insect vectors from both a theoretical point of view and to predict and mitigate the future of epidemics. We attempt to shed light on the evolutionary history and phylogeography of two cryptic psyllid species (namely A and B) of the Cacopsylla pruni complex, vectors of Candidatus phytoplasma prunorum. It is known to cause the European stone fruit yellows (ESFY), a disease affecting Prunus trees and causing significant crop losses each year. Analyses were conducted to decipher the origin, order and time of divergence, as well as the migration routes of the species complex in the Western Palearctic. We used mitochondrial and nuclear gene data to infer the population genetic diversity and structure of the complex, and to reconstruct a dated phylogenetic tree of the Psyllinae family in order to subsequently perform Approximate Bayesian Computation analyses. Both species have diverged in what is now France from a common ancestor, around 20.19 Mya, before expanding into Spain around 6.61 Mya for species A and Eastern Europe around 6.36 Mya for species B. Then species B seem to have passed into Corsica during the Messinian salinity crisis (5.96-5.33 Mya) from French or Italian B populations. No apparent admixture was found between both species after their divergence, which would indicate an absence of gene flow between them at the point when they recolonised common ecological niches. This strong genetic differentiation confirms previous work on reproductive barriers between the two species.