Biodiversity of Diptera of veterinary importance in mountain livestock pastures of northeastern Spain

Abstract Background Livestock grazing exposes animals to arthropods of veterinary importance, particularly in the summer. Many species of flies (Diptera) can affect cattle directly (e.g., nuisance swarming and feeding) and indirectly (e.g., transmission of parasites and pathogens), leading to reduced productivity and, in severe cases, mortality. Yet, knowledge of pest species associated with grazing livestock in high-elevation habitats remains limited. Methods We characterized the biodiversity of Diptera associated with cattle in three summer mountain meadows (1100–1200 m.a.s.l.) in northeastern Spain. Suction light traps baited with dry ice were used, complemented by additional sampling methods including netting and larval/pupal dipping. Results A total of 6,372 specimens were collected, representing at least 53 species in eight dipteran families of veterinary importance. Species were identified using classic morphological methods combined with COI DNA barcoding. The specimens included 2,118 Muscidae, including 14 Haematobia irritans ( n = 14), 1,843 Simuliidae of at least 10 species, 1,072 Ceratopogonidae representing 20 species, 708 Culicidae of nine species, 505 Tabanidae of at least seven species, and 105 Psychodidae of two species. In addition, Hippobosca equina (Hippoboscidae) ( n = 6) and Gasterophilus intestinalis (Oestridae) ( n = 1) were recorded. Generalized linear models indicated that total Diptera abundance varied significantly among sampling periods, locations, and target Diptera groups, with most taxa peaking in early or midsummer. Phylogenetic analyses were performed for Muscidae, Simuliidae, and Culicidae to better resolve their taxonomic relationships, resulting in the generation of 55 novel nucleotide sequences corresponding to 16 species. Conclusions This study provides the first comprehensive baseline data on the diversity and seasonal dynamics of Diptera of veterinary importance associated with cattle in mountain meadows of northeastern Spain, supporting future monitoring and management programs for pest and vector flies in European grazing systems.