Size, not temperature, drives cyclopoid copepod predation of invasive mosquito larvae

During range expansion, invasive species can experience new thermal regimes. Differences between the thermal performance of local and invasive species can alter species interactions, including predator-prey interactions. The Asian tiger mosquito, Aedes albopictus, is a known vector of several viral diseases of public health importance. It has successfully invaded many regions across the globe and currently threatens to invade regions of the UK where conditions would support seasonal activity. We assessed the functional response and predation efficiency of the cyclopoid copepods Macrocyclops albidus and Megacyclops viridis from South East England, UK against newly-hatched French Ae. albopictus larvae. First, we assessed the functional response of each copepod species at 15, 20, and 25°C. We then examined the predation efficiency of both copepod species at the same three temperatures, holding the density of mosquito larvae prey constant. Predator-absent controls were included in all experiments to account for background prey mortality. We found that temperature was not a significant driver of predator-prey interactions over temperatures likely to be experienced in UK larval mosquito habitats. Both copepod species exhibited type II functional responses across all three temperature treatments and there was no significant change in predation efficiency due to temperature. We did observe differences between predator species. The predation efficiency of M. viridis was approximately 7.5 percentage points higher than that of M. albidus. Furthermore, there was a significant positive relationship between the body masses of the copepods and their predation efficiencies, and copepod body mass explained more of the variability in predation efficiency than copepod species. The type II functional responses indicated that both M. albidus and M. viridis would be suitable biocontrol agents in the event of an Ae. albopictus invasion in the UK, but our analysis of predation efficiency suggests that M. viridis would be a slightly superior predator due to its larger size. More research is needed to quantify how well the conditions of artificial container mosquito habitats can support the long-term stability of different copepod populations. This work highlights the importance of size relationships in predicting interactions between invading prey and local predators.