Crossing continents: First record and evidence of establishment of the Australian backyard mosquito Aedes notoscriptus (Diptera: Culicidae) in Europe, Bosnia and Herzegovina

Abstract Background Mosquitoes (Diptera: Culicidae) are important vectors of human and animal pathogens, while globalization, climate change, and human mobility increasingly facilitate the spread of non-native species. Invasive Aedes mosquitoes are particularly successful due to their ecological plasticity, use of artificial containers, and desiccation-resistant eggs, which enable passive long-distance dispersal. Aedes notoscriptus , a medically and veterinary important mosquito native to the Australasian region, has established populations beyond its native range, but until now had not been documented as established in Europe or elsewhere in the Palearctic region. Here, we report the first detection and evidence of establishment of Ae. notoscriptus in Bosnia and Herzegovina, Europe, and the Palearctic, supported by morphological and molecular identification. Methods Mosquito sampling was conducted southern Bosnia and Herzegovina, from September 2024 to June 2026 using CO₂-baited CDC traps and larval collections. After the first confirmation of Ae. notoscriptus in Mostar, targeted study was expanded to surrounding sites to assess its local distribution. Specimens were identified morphologically and confirmed molecularly by sequencing the mitochondrial cytochrome c oxidase subunit I (COI) barcode region. The sequences obtained were compared with GenBank and BOLD reference data, and genetic relationships were assessed using phylogenetic and haplotype analyses. Results Aedes notoscriptus was first sampled in Mostar in September 2024 and was repeatedly recorded at the same site in 2025 and 2026, and additionally surrounding localities in 2026. In total, 86 specimens were collected from eight localities, including larvae found near the initial detection site, providing evidence of local establishment. COI sequencing of nine specimens confirmed their identity as Ae. notoscriptus , with all sequences assigned to BOLD BIN ADM7085. The Bosnia and Herzegovina specimens comprised two closely related haplotypes, also represented among reference sequences from Australia and New Zealand, and phylogenetic analysis placed them within the same major Ae. notoscriptus lineage. Conclusions The detection of Ae. notoscriptus in Bosnia and Herzegovina represents the first documented record of the species in Europe and provides evidence of an established, reproducing population. Its repeated detection, local spread, and ecological adaptability underscore the need for continued surveillance to determine its distribution, potential for further expansion, and medical and veterinary significance.