New record of a Southeast Asian mosquito species in Korea
Based on the morphological identification and molecular analysis, the collected specimen was identified as Ae. laniger, a Southeast Asian mosquito species, representing a new record in the ROK. We readily identified the collected specimen as belonging to the subgenus Mucidus due to their distinctive wing pigmentations and the scaling patterns observed across their bodies. Furthermore, molecular phylogeny also supported the position of the specimens within the Mucidus clade, distinct from previously recorded subgenera in Korea. These results confirmed the presence of a new nonnative subgenus and species in the ROK. Thus, we report that a total of 60 species, 11 genera, and two subfamilies of mosquitoes have been recorded in the ROK.
This study also suggests that even in the absence of COI sequence, commonly used as a DNA barcode, the application of multigene phylogeny could facilitate the detection of non-native species at the genus or subgenus levels for pest control purposes. Specifically, for poorly studied species with limited morphological and molecular data, the workflow used in this study enables the identification for non-native species without relying on COI sequences.
Invasion pathway scenarios for Ae. laniger and their importance
Ae. laniger occurs in subtropical or tropical regions of Southeast Asia, Australia, and Africa; it is not native to East Asia [38, 40, 41, 42]. For this perspective, the occurrence of Ae. laniger suggests that subtropical or tropical mosquitoes have the potential to expand their habitats to the ROK. In same context, it showed that more vector species, such as Aedes aegypti, which can transmit viruses responsible for dengue fever, Zika, and yellow fever, could invade the Korean Peninsula, increasing the risk of mosquito-borne diseases in future. Lee et al. [98] also reported that the strain of Ae. albopictus on Jeju Island is genetically closely related to specimens from Southeast Asia, which have a high transmission capability for dengue fever, thereby raising concerns regarding its potential risks.
The confirmation of Southeast Asian mosquito species on Jeju Island aligns with predictions reported in prior studies, as well as with reports of other non-native species. However, the results of the species distribution modeling do not indicate a strong propensity for Ae. laniger to inhabit the Korean Peninsula; this discrepancy may be due to the lack of species occurrence data. Nevertheless, on the basis of the available data, a discernible pattern emerged, indicating that Ae. laniger is likely to be predominantly found in coastal areas or on islands characterized by high humidity and temperature. Given these characteristics and the recognition that Jeju Island has coastal areas with a subtropical climate, it is plausible that Ae. laniger could establish breeding populations on this environment.
Furthermore, there was a recent outbreak of love bugs, Plecia longiforceps, in the ROK [99], and the nonnative species A. horsfieldii was identified on Jeju Island in 2019 [36]; these species are distributed mainly in southern China, Taiwan, and the Okinawa archipelago. These cases suggest the potential for provisional or temporary spread of nonnative species to the ROK. The species distribution models of Ae. laniger revealed a range extending from southern China to Taiwan under both the current and future climate conditions. Jung et al. [100] also suggested the potential emergence of Ae. aegypti in the coastal areas of Jeju Island starting in 2040 due to climate change using species distribution modeling.
In addition to climate factors, invasion can be influenced by ‘wind'. In the ROK, Nilaparvata lugens and Spodoptera frugiperda are known to spread to the island by riding westerlies in the spring or tropical cyclones in the summer [37, 101, 102]. Typhoons typically affect the Korean Peninsula to the greatest extent in July and August [103]. The two specimens captured in this study were collected in August, suggesting that their presence on the island may have been influenced by wind patterns in that period. Studies have shown that mosquitoes can spread through various means, including winds, airplanes, or watercraft, indicating the potential for provisional spread of the species [3, 6].
Notably, Jeju Island has also been identified as a bridgehead for the introduction of tropical or subtropical insects into the Korean Peninsula [37, 104, 105]. The results of this study and those of other investigations suggest that there is potential for the continued presence of Southeast Asian mosquito species on Jeju Island in the future.
Limitation and future works
The species distribution models applied in this study did not yield strong predictions for Ae. laniger to East Asia. The constraints imposed by the limited availability of occurrence data, along with the concentration of coordinates in Southeast Asia, probably led to nonsignificant outcomes [106, 107]. Given the tropical and subtropical climates in Taiwan and the Okinawa archipelago, further investigations to confirm the habitat of Ae. laniger in these regions would enhance the resolution of our analysis.
This study was confined to a limited area of Jeju Island, and further investigations across various regions are needed to expand our understanding of the broader ecological implications and potential range of Ae. laniger. The Dongbaek-dong wetland is characterized by a distinctive hot and humid environment, with numerous swampy areas and temporary pools, consistent with the habitat characteristics of Ae. laniger [41, 42]. The presence of this species in the Dongbaek-dong wetland suggests its potential to inhabit similar habitats on Jeju Island.
Additionally, it remains unclear whether the presence of Ae. laniger on Jeju Island is temporary or if it has established a breeding population on the island. To determine whether permanent populations of Ae. laniger have been established, multiyear monitoring surveys seem to be needed. Most subtropical or tropical mosquitoes face challenges in surviving cold winters; therefore, it is recommended that both adult and larval collections be conducted in subsequent monitoring surveys.
The key outcome of this study is the initial identification of mosquitoes adapted to the Southeast Asian climate in the ROK. Despite the uncertainty of the vector competence of Ae. laniger, this finding is significant, as it indicates the potential for future occurrences of vector species capable of transmitting the viruses responsible for dengue fever and Zika virus on the Korean Peninsula.