Copepods as biocontrols of an invasive mosquito in the UK

Abstract

Aedes albopictus mosquitoes are highly invasive and are capable of transmitting debilitating diseases such as dengue, yellow fever, Zika, and chikungunya to humans. Cyclopoid copepods have previously been suggested as biocontrol agents against aedine mosquitoes, but they are rarely incorporated by most vector control programs due to heavy reliance on pyrethroid insecticides. In this thesis, I conducted a series of analyses to inform future Ae. albopictus biocontrol strategies in the UK. First, I used a meta-analysis approach to investigate the existing evidence for both consumptive and non-consumptive effects of predation on mosquito populations. I found that predation generally results in smaller mosquito body size, and this non-consumptive effect can lead to lower rates of disease transmission. Since Ae. albopictus are predicted to establish throughout most of England and Wales within the next fifty years, I examined the efficacy of UK copepod species against invasive larvae at temperatures that they are likely to experience in South East England. I found that cyclopoid copepods are effective predators against newly-hatched Ae. albopictus larvae across temperatures from 15 to 25°C, and that these predators exhibit type II functional response curves, indicating their suitability as biocontrols. The invasive mosquito larvae prey were preferred by copepod predators when both invasive Ae. albopictus prey and resident Culex pipiens prey were made available. I did not find any significant change in development time or size of Ae. albopictus mosquitoes that were exposed to copepod predation during the later stages of larval development. The absence of non-consumptive effects on Ae. albopictus may be due to their lack of a shared evolutionary history with UK copepod predators. In summary, my findings support the integration of local cyclopoid copepods as biocontrols into future vector control programs that target Ae. albopictus in the UK.