Tracking invasion events: phylogeography of Hyalomma marginatum in the Mediterranean basin with a focus on Southern France

Hyalomma marginatum is a hard tick vector of various pathogens, including Crimean-Congo Hemorrhagic fever virus, recently detected in French specimens. This species has a wide distribution from North Africa to Eastern Europe and has only recently been considered established in Southern France. These changes in species distribution led us to explore the genetic structure of tick populations in the Mediterranean basin and attempt to infer the origin of French populations. We used two mitochondrial markers (12S rRNA and Cytochrome Oxidase 1) and genotyped ticks from nine Mediterranean countries. We compared genetic indices and haplotypic composition between these countries and the various French geographical populations. Across all countries, we showed significant genetic differentiation, with a certain proximity between neighboring countries. We found very different genetic compositions among the French geographic populations: some exhibited signs of recent expansion, while others suggested the presence of ancient populations. It is possible that small populations of H. marginatum were already present in France and are now more abundant. This recent change in population structure could be due to increased human activity and climate change. These factors, combined with a potentially high level of phenotypic plasticity, could facilitate H. marginatum conquest of more northerly latitudes in France and other European countries.