Uncovering the tracks of a recent and rapid invasion: the case of the tiger mosquito, Aedes albopictus in Europe.

The dynamic aspects of the invasion process of Aedes albopictus has been inferred using different but complementary molecular markers (ITS2, SSRs and SNPs). The analyses of 79 ITS2 sequences from Asian, American and European populations indicates the absence of great differentiative processes and the presence of high degree of heterogeneity among individuals from these populations. This supports the expansion of this species. Using SSRs to analyze the dispersion of this species, China has been suggested as home range of the species by gene diversity estimates, cluster analyses, Bayesian analyses of ancestry and migration rates. It is clear that Chinese mosquitoes share their genomes both with American and European populations. It is evident that the dispersion pattern from this area was/is not due to natural step-by-step migration but the overall picture seems to be masked by a strong propagule pressure driven by human activities, by continued migration events and commercial traffic. We are also assessing whether this mosquito underwent adaptive processes during its invasion process. Because Ae. albopictus relies on olfactory cues for host-seeking, mating, blood feeding and oviposition, the antennal transcriptomes have been chosen for the identification and characterisation of chemosensory genes. The analysis of these genes in populations throughout the species range will allow us to detect single-nucleotide polymorphisms (SNPs) that may represent markers of adaptation. An outcome of this integrated analysis will be the development of a database of ITS2, SSRs and SNP fingerprints in ancestral and derived invasive populations as a tool for mosquito traceability in order to infer the origins of new outbreaks, and thus to develop risk maps for this mosquito.