Urban–rural structuring of mosquito assemblages in Moyen-Ogooué, Gabon reveals widespread dominance of Aedes albopictus

Mosquito-borne arboviruses such as dengue, chikungunya, Zika, yellow fever, West Nile and Rift Valley fever circulate widely in Central Africa, yet vector ecology, especially outside major cities, remains poorly characterized. Between March 2023 and January 2025, we conducted bimonthly entomological surveys to investigate the ecological patterns of mosquito communities across an urban (Lambaréné), peri-urban and rural gradient in Moyen-Ogooué province, central Gabon. Larvae were sampled with WHO ovitraps, and adult mosquitoes were collected using light traps and Prokopack aspirators. In total, 22,216 mosquitoes were collected, representing 21 species from 8 genera. Aedes (57.2%) and Culex. (23.3%) predominated, alongside Mansonia. (16.3%) and lower abundances of Anopheles, Lutzia, Coquillettidia, Uranotaenia and Erethmapodites. Three species dominated overall: Ae. albopictus (52.5%), Ma. uniformis (16.2%) and Cx. quinquefasciatus (11.3%). Six species have been firstly reported in Gabon including Ae. argenteopunctatus, Ae. opok, Cx. bitaeniorhynchus, Cx. giganteus, Cx. poicilipes, and Cx. tritaeniorhynchus. Rural areas harboured the highest richness (up to 21 species), including numerous rare and functionally specialized taxa. Urban communities were species-poor and strongly dominated by Ae. albopictus and Cx. quinquefasciatus. Diversity indices and NMDS ordination showed clear, seasonally modulated assemblages across landscapes, with peri-urban sites forming ecological transition zones with intermediate species richness and dominance levels. These findings validate and extend evidence for an Aedes and Culex. species shift and reveal a highly structured, seasonally dynamic mosquito community in Gabon. Crucially, the coexistence of dominant vectors with a broad array of less common species shows that arboviral transmission potential in central Gabon is shaped by the entire mosquito community. Biodiversity-wide surveillance, not only of major vectors, is therefore essential for understanding and anticipating arbovirus circulation in this ecologically complex region.