Characterisation of the South African Culicoides imicola (Kieffer, 1913) species complex, and its phylogenetic status in Europe
C. imicola has been described as a species complex in South Africa on the basis of taxonomy, with at least seven species world-wide. Phylogenetic validity of five taxa within the Imicola group, namely C. imicola s.s., C. loxodontis, C. bolitinos and two currently unconfirmed species - Culicoides Sp. 30 (tuttifruitti) and Culicoides Sp. 107 (kwagga), were established using mtDNA COI sequence data, which confirmed their identity, not only as separate genetic entities, but also in exact correlation with the sibling species based on morphological and ecological parameters. In addition, the separate species status was reinforced for C. kwagga and C. tuttifrutti, which showed BCL of 100 with respect to C. imicola, using sequence data from the ITS-2 nuclear rRNA gene spacer region, and the mtDMA 16S gene respectively. Phylogeographical studies were undertaken using all three genomic regions, and revealed that C. imicola is present in Europe as C. imicola in sensu stricto, which acts as the vector for AHSV and BTV in this region. Intra-specific variation was highest in the COI amplicon, and extremely low in both ITS-2 and 16S regions. Phylogenetic resolution of internal clades was poorly supported for each gene region, and haplotype sharing suggests that the C. imicola populations across this wide geographical range are highly heterogeneous, with a high degree of haplotype mixing. Ecological field studies were carried out in farmyards in Spain and Portugal. When population composition of C. imicola was determined alongside host preference, it was found that although C. imicola are present in farms around cows, domestic fowl and pigs, they are present in higher numbers, comprise a higher total % of Culicoides caught and are present in a more stable population around horses. These results have serious implications for the spread of AHSV in these regions of Iberia where equestrian stud farms, producing quality polo and racing horses, play a significant part in the economy of the area.