Morphological and genetic variation in the Ornithomya avicularia (Diptera: Hippoboscidae) populations across...

Generalist parasites provide valuable systems for examining how broad ecological niches influence patterns of evolutionary diversification. The louse fly Ornithomya avicularia (Diptera: Hippoboscidae) is a widespread avian ectoparasite parasitizing a broad range of bird hosts across Eurasia, Australia and Africa. However, the extent to which geographic structure contributes to morphological and genetic differentiation within this species remains poorly resolved. Morphological and molecular variation in Ornithomya avicularia was investigated using specimens from seven populations spanning Europe, West Siberia, and the Russian Far East. Morphological variation was largely continuous across most of the studied range, although populations from Siberia and the Russian Far East exhibited consistent differences in wing microtrichial patterns and wing vein ratios. Genetic analyses identified three major haplotype groups, including a widespread European-West Siberian cluster and two deeply divergent lineages restricted to the Russian Far East. One Far Eastern lineage showed genetic distances approaching interspecific levels and was strongly separated in multivariate morphospace, consistent with its recognition as a distinct species described elsewhere. Isolation-by-distance analyses revealed a significant association between geographic distance and morphological differentiation, whereas genetic differentiation showed weaker geographic structuring.