DNA Barcoding Reveals an Increased Diversity Within the Genus Culex (Diptera: Culicidae) in Ireland

Global arthropod populations are changing due to the combined impacts of climate change, land-use transformation, globalisation and trade. These changes can potentially result in the decline and extinction of some native and/or endemic arthropod species, while other species that potentially pose threats to human and animal populations may increase. Such dynamics lead to weakened ecosystem resilience, which can facilitate the establishment and spread of species with vector capacities, such as mosquitoes. While many of the mosquito species present in Ireland possess vector capacities, populations have not been extensively surveyed since 1991. A follow-up investigation into Irish mosquito species presence was performed in 2024. At that time of the 1991 study, species identification relied on morphological examination, a method that even then was recognised as inadequate for differentiating certain species within complexes; the 2024 follow-up study employed both morphological and genetics methods for species identification. In this study we conduct the first investigation of Irish mosquito populations using DNA barcoding of two genetic regions to confirm species presence. Our results confirmed the presence of species recently and not previously recorded from Ireland, including Culex torrentium and Culex pipiens s.s. (sensu stricto). We demonstrate that barcoding with Cytochrome C Oxidase Subunit 1-based primers is suitable for most species-level identifications. However, additional primer sets targeting the Internal Transcribed Spacer regions 1 and 2 were necessary to differentiate species within the Culex pipiens complex, although we found that researchers should be cautious relying on genetic reference databases such as GenBank for this purpose. Nevertheless, the multi-locus approach employed in this study can enhance national surveillance efforts, especially in monitoring mosquitoes that may transmit vector-borne diseases, and in recognising increased species diversity from a biodiversity perspective.