The influence of social cues on oviposition decisions in the mosquito Aedes aegypti

Abstract

Animals use a variety of social and non-social cues in evaluating the habitat quality of a patch. Assessing social information and incorporating it into future decisions can translate into important fitness consequences for an individual. Local adult-density, among other social cues, can heavily influence individual adult decisions. In particular, adult-density can play a crucial role in affecting maternal decisions like oviposition site-selection that can potentially set-off a cascade of responses in both the parent and the offspring. In this study, I used the mosquito Aedes aegypti as a model system to investigate the influence of adult-density on oviposition responses. Specifically, I measured oviposition responses of individual adult females to patches differing in quality when present singly (solitary) or in the presence of non-breeding adult individuals (social setting). In a series of binary choice experiments, patch quality was represented by pools differing in larval predation risk in one set of experiments and by pools differing in larval competition risk in another. My study indicates that social cues appeared to substantially modify female oviposition decisions. In response to competition risk, while social status did not influence several measures of oviposition, social females displayed great selectivity by ovipositing in pools with cues indicating high conspecific larval densities. In contrast, social females showed a higher preference and increased fecundity in predator treatments. Social females also distributed eggs more often in this treatment than solitary adults. In addition, social and solitary females alike were more likely to bet-hedge when the contrast between pools was less pronounced than when it was stark. Also, social and solitary females exhibited a large variation in egg-laying choices across varying risks of predation and competition. Overall, my study indicates that individual adult females are able to assess the presence of other individuals and in response modify their behaviour during oviposition events. Adult females seem to respond to the presence of other females by adopting a bet-hedging strategy, sometimes withholding eggs perhaps to distribute eggs further across multiple pools while exhibiting preference for riskier patches. I suggest that adult female density may favour a shift in preference of individual females towards seemingly riskier patches and discuss potential evolutionary explanations for this shift.