Cardinium symbiosis as a potential confounder of mtDNA based phylogeographic inference in Culicoides imicola (Diptera: Ceratopogonidae), a vector of veterinary viruses

Abstract

Culicoides imicola (Diptera: Ceratopogonidae) is an important Afrotropical and Palearctic vector of disease, transmitting viruses of animal health and economic significance. The apparent incursions of C. imicola into mainland Europe via wind-movement events has made it important to trace this species to better predict new areas of arbovirus outbreaks. A widely used method for tracking dispersal patterns of C. imicola employs a phylogeographic approach anchored on the mtDNA marker COI (cytochrome c oxidase subunit I). However, a problem with this approach is that maternally-inherited symbiotic bacteria can alter the frequency of COI mitochondrial haplotypes (mitotypes), masking the true patterns of movement and gene flow. In this study, we investigate possible associations of the symbiont Cardinium with C. imicola mitotype distribution. Haplotype network analysis indicates the concordance of specific mitotypes with Cardinium infection status in C. imicola populations from the Mediterranean basin and South Africa. This observation urges caution on the single usage of the COI marker to determine population structure and movement in C. imicola, and instead suggests the complementary utilisation of additional molecular markers (e.g. microsatellites and nuclear markers).