Compensatory mechanisms during development contribute to overcome intraspecific competition in a dipteran solitary ectoparasitoid with larval active host seeking behaviour

Abstract

1. Superparasitism has been rendered many times as detrimental for fitness, although there are examples in which the competing winning larvae compensate for its development. Here, we studied if, in the host-parasitoid system Cyclocephala signaticollis (Coleoptera: Scarabaeidae) – Mallophora ruficauda (Diptera: Asilidae), larvae have compensatory mechanisms during development to overcome competition. 2. Through a combination of behavioural and artificial parasitism protocols, we investigated if host instar or time between parasitism events influences the probability of a larva winning the competition. In addition, we studied the effect that superparasitism has in terms of some fitness traits like sex ratio, size, and shape. 3. Our results showed that M. ruficauda has compensatory mechanisms like differential larval survival according to host availability. In addition, we found that as the time between parasitism events increased, the second larva lowers its chance to win the competition in favour of the first arriving larva. Larvae under competition develop at a similar rate compared to larvae that had not experienced competition for hosts. Finally, our results show that wing shape is different between groups, and this could influence flight and courtship. 4. Our study suggests that superparasitism in M. ruficauda is an advantageous strategy under some circumstances although it might influence adult performance with flight related behaviours.