Adaptation, isolation by distance and human-mediated transport determine patterns of gene flow among populations of the disease vector Aedes taeniorhynchus in the Galapagos Islands.

The black salt-marsh mosquito (Aedes taeniorhynchus) is the only native mosquito in the Galapagos Islands and potentially a major disease vector for Galapagos wildlife. Little is known about its population structure, or how its dynamics may be influenced by human presence in the archipelago. We used microsatellite data to assess the structure and patterns of A. taeniorhynchus gene flow among and within islands, to identify potential barriers to mosquito dispersal, and to investigate human-aided transport of mosquitoes across the archipelago. Our results show that inter-island migration of A. taeniorhynchus occurs frequently on an isolation by distance basis. High levels of inter-island migration were detected amongst the major ports of the archipelago, strongly suggesting the occurrence of human-aided transport of mosquitoes among islands, underlining the need for strict control measures to avoid the transport of disease vectors between islands. The prevalence of filarial nematode infection in Galapagos flightless cormorants is correlated with the population structure and migration patterns of A. taeniorhynchus, suggesting that A. taeniorhynchus is an important vector of this arthropod-borne parasite in the Galapagos Islands. Therefore mosquito population structure in Galapagos may have the potential to influence mosquito-borne parasite population dynamics, and the subsequent impacts of such pathogens on their host species in the islands.