A difference in larval mosquito size allows a biocontrol agent to target the invasive species

Abstract

AbstractAs the global temperature rises in the coming decades,Aedes albopictusis expected to invade and establish in South East England, whereCulex pipiensis currently the most common native mosquito species. Biocontrol measures that use local cyclopoid copepods againstAe. albopictusmay be compromised if the copepods prefer alternateCx. pipiensprey. In this study, we assessed the predation efficiency ofMegacyclops viridiscopepods against FrenchAe. albopictuslarvae and larvae that hatched from egg rafts ofCx. pipienscollected in South East England. The experiments were conducted at 15°C and 25°C, which are representative of present and future summer temperatures in South East England.Ae. albopictuslarvae that survived the course of the experiment in the predator-absent controls were significantly smaller thanCx. pipienslarvae that survived in the absence of predation. The background mortality ofCx. pipienslarvae increased with the ten-degree increase in temperature, and the smaller size of survivingCx. pipienslarvae at 25°C, relative to survivors at 15°C, suggests that largerCx. pipienslarvae were more likely to die at the higher temperature setting. Across all experimental treatments, the ratio of copepod body length to mean prey length, based on larval lengths of survivors from the corresponding predator-absent controls, was a significant predictor of predation efficiency. Adding temperature setting to the predation efficiency model as a predictor did not improve model fit. Within the mixed prey treatments, the predation efficiency ofM. viridiswas 34.5 percentage points higher againstAe. albopictusprey than againstCx. pipiensprey. The higher predation efficiency thatM. viridisexhibited against invasiveAe. albopictusprey, likely due to the smaller size of these larvae, supports the future use ofM. viridisas a biocontrol agent in the UK.