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

Abstract

32During range expansion, invasive species can experience new thermal regimes. Differences between the thermal 33 performance of local and invasive species can alter species interactions, including predator-prey interactions. 34The Asian tiger mosquito, Aedes albopictus, is a known vector of several viral diseases of public health 35 importance. It has successfully invaded many regions across the globe and currently threatens to invade regions 36 of the UK where conditions would support seasonal activity. We assessed the functional response and predation 37 efficiency of the cyclopoid copepods Macrocyclops albidus and Megacyclops viridis from South East England, 38UK against newly-hatched French Ae. albopictus larvae. First, we assessed the functional response of each 39 copepod species at 15, 20, and 25°C. We then examined the predation efficiency of both copepod species at the 40 same three temperatures, holding the density of mosquito larvae prey constant. Predator-absent controls were 41 included in all experiments to account for background prey mortality. We found that temperature was not a 42 significant driver of predator-prey interactions over temperatures likely to be experienced in UK larval mosquito 43 habitats. Both copepod species exhibited type II functional responses across all three temperature treatments and 44 there was no significant change in predation efficiency due to temperature. We did observe differences between 45 predator species. The predation efficiency of M. viridis was approximately 7.5 percentage points higher than 46 that of M. albidus. Furthermore, there was a significant positive relationship between the body masses of the 47 copepods and their predation efficiencies, and copepod body mass explained more of the variability in predation 48 efficiency than copepod species. The type II functional responses indicated that both M. albidus and M. viridis 49 would be suitable biocontrol agents in the event of an Ae. albopictus invasion in the UK, but our analysis of 50 predation efficiency suggests that M. viridis would be a slightly superior predator due to its larger size. More 51 research is needed to quantify how well the conditions of artificial container mosquito habitats can support the 52 long-term stability of different copepod populations. This work highlights the importance of size relationships in 53 predicting interactions between invading prey and local predators. 54 55 Keywords 56 cyclopoid copepods, predation efficiency, functional response, invasion, biocontrol, public health, range 57 expansion, vector-borne 58 59 60 61 62

No impact of biocontrol agent’s predation cues on development time or size of surviving Aedes albopictus under optimal nutritional availability

“…Previous work has shown that M. viridis exhibits a type II functional response curve and a relatively high predation efficiency against Ae. albopictus prey at temperatures representative of UK larval habitats [46]. This study builds on recent work and further supports the use of M. viridis as a biocontrol agent for Ae.…”

“…Due to the suitability of some areas in southeast England for Ae. albopictus populations [45], we used Megacyclops viridis , a likely copepod species for future biocontrol applications [46], collected from Longside Lake in Egham, UK, and Ae. albopictus that were originally collected in Montpellier, France.…”

Quantifying predator functional responses under field conditions reveals interactive effects of temperature and interference with sex and stage

“…Therefore, the lower density of females at high temperatures may free up males and juveniles to forage at high temperatures. Our results on the temperature dependence of space clearance rates contrast with experimental examinations of temperature effects on functional responses in which individuals are often exposed to a uniform temperature and are typically in homogeneous arenas with no potential temperature refuges (Archer et al, 2019; Broom et al, 2021; Islam et al, 2021; Russell et al, 2021) This difference has potentially strong implications for the general way in which we conceive of temperature altering predator-prey interactions and thus food web dynamics given changing climates. Using more realistic temperature regimes and arenas in experiments will allow us to understand whether our result is unique to zebra jumping spiders or potentially more widespread in terrestrial ectotherms.…”

How can the copepod Mesocyclops longisetus (Thiébaud, 1912) be used to control mosquito production effectively in pots, plates, and slabs?

“…Copepods preyed upon Culicidae more intensively, even when chironomids were abundant. Russel et al (2019) highlighted the importance of size relationships in determining predation efficiency among copepods in laboratory experiments. Früh et al (2019) also found results showing that copepods preferred to prey on the smallest culicid larvae.…”

“…Beserra et al (2014) found that the population fluctuations of A. aegypti larvae did not show a correlation with climatic variables in the South of Brazil, since there are no optimal temperature conditions for establishing this species annually. Russel et al (2019), working in the United Kingdom, discarded the temperature effect and pointed to prey size as the dominant factor.…”