Intraspecific morphological variability of the invasive mosquito Aedes koreicus in Europe: genetic characterisation and population-level insights

BackgroundThe invasive mosquito Aedes koreicus has established populations in several European countries during the past decade, raising increasing public health concerns due to its potential role as a vector of pathogens. While species identification is primarily based on morphological characters, Ae. koreicus exhibits distinct morphological variants originating from mainland Korea and Jeju Island, which complicates surveillance and may lead to misidentification, particularly in regions where closely related species co-occur. To date, the genetic basis and population-level relevance of these morphological forms in Europe remain poorly understood. MethodsWe investigated the co-occurrence of two morphological forms of Ae. koreicus in Hungary, representing the first confirmed European location where both forms were detected sympatrically and even within the same breeding sites. Adult mosquitoes were morphologically characterised using diagnostic traits, and individuals representing both morphotypes were subjected to comprehensive genetic analyses. We sequenced multiple mitochondrial markers (COX1, COX2, COX3, ATP6, ND1, ND3) and the nuclear ITS2 region using Oxford Nanopore long-read sequencing. Phylogenetic reconstructions and haplotype network analyses were applied to assess genetic differentiation between morphotypes and to compare them with Aedes japonicus as a closely related reference species. ResultsAcross all analysed mitochondrial and nuclear markers, no genetic differentiation was detected between specimens identified as the "mainland" or "Jeju-do" morphological forms of Ae. koreicus. Phylogenetic and haplotype network analyses consistently grouped individuals independently of their morphotype, indicating a shared genetic background at the population level. In contrast, Ae. japonicus formed a clearly distinct genetic lineage, confirming the robustness of the applied markers for interspecific discrimination. ConclusionsOur results demonstrate that the observed morphological variability in Ae. koreicus populations are not underpinned by detectable genetic differentiation using commonly applied mitochondrial and genomic markers. These findings highlight the limitations of using morphology alone to infer population origin or structure and emphasise the need for heightened awareness of intraspecific variability in routine surveillance. Accurate morphological identification remains critical, particularly in citizen science-based monitoring programmes and AI-based automatization platforms, such as Mosquito Alert, to avoid confusion with morphologically similar invasive species. Further studies integrating genomic and ecological approaches are required to elucidate the mechanisms underlying morphological variability in this emerging vector species.