Abstracts (first author)
Consequences of an arms race on the cuticular hydrocarbon profiles of an insect host and its three brood parasites
Parasites and their hosts have conflicting interests – to either successfully exploit the host or to defend against the parasite attack. This situation sets the board for an evolutionary arms race between both species. The species pair then follows a trajectory through repeated cycles of fine tuning of the parasite’s attack strategies and evasive actions of the host. As a special case, brood parasites need to avoid detection by the host in order to neither be attacked while in the nest nor risk the nest to be abandoned by the host afterwards. Insect brood parasites may avoid olfactory detection by mimicking the host’s cuticular hydrocarbon (CHC) profile. In this case, the arms race would lead to optimized chemical mimicry in the parasite. The host could e.g. change the CHC composition in order to escape a mimetic match. The most straightforward parasitic associations consist of one parasite and one host. More complex variations are possible but very rare: one parasite may use several hosts or several parasites may specialize in one single host. In this study, a solitary host and its three host-specific brood parasites serve as a model of such a multi enemy / single target system. We compare the CHC profiles and predict that a brood parasite whose intrusion is detectable by the host should develop chemical mimicry. The host in return should establish counterstrategies. Competition between parasites may fuel the perfection of mimicry or the development of completely new intrusion strategies. We find two chemotypes of the host that differ greatly in their CHC composition. Evolving a second CHC profile might be the outcome of escaping a parasite’s mimicry. However, a second parasite species has evolved a close match of their CHC composition compared to the alternative chemotype. The third parasite produces its very own CHC bouquet – it has developed a new strategy for invading host nests and can no longer be fended off by the host.