Phylogeography and structure of Hyalomma marginatum populations in the context of Corsica, France

Hyalomma marginatum is a hard tick vector of various pathogens, including Crimean-Congo Haemorrhagic fever. This species has a wide distribution, from North Africa to Eastern Europe. Despite previous regional studies ofHyalomma marginatum, no research has yet focused on its intra-island genetic diversity and population dynamics. This study aims to investigate the introduction zones, genetic variability, and population structure of Hyalomma marginatum in Corsica thereby, enhancing our understanding of how its populations are distributed and maintained across the island. Ticks were collected from cattle and horses across Corsica between 2022 and 2024, and their morphological identification was conducted. DNA was extracted and two mitochondrial genes (12S and COX1) were amplified and sequenced with the Sanger method. Genetic diversity, phylogenetic relationships, and population structure were analyzed. A total of 162Hyalomma marginatum ticks were collected from cattle and horses from 2022 to 2024 and grouped into 133 pools. Genetic analyses focused on the COX1 gene and concatenated COX1 and 12S sequences revealed high haplotype diversity, with 21 COX1 haplotypes and 16 concatenated haplotypes identified, particularly in central and southern Corsica. One dominant COX1 haplotype was widely distributed across the island. AMOVA indicated that most genetic variation occurred within populations (FST = 0.225 for COX1; FST = 0.158 for concatenated sequences; p < 0.01). Corsican haplotypes were closely related to other Eurasian sequences, particularly Croatia, but more divergent from Asian ones like China. This study reveals significant genetic diversity in Hyalomma marginatum across Corsica, with patterns shaped by geography and host movement. The COX1 gene proved to be a considerably more informative genetic marker than 12S, providing higher resolution for haplotype differentiation and phylogenetic analysis. Results suggest a recent population expansion, limited gene flow, and possible roles of livestock in tick dispersal.