Chemical profiles in Iberoformica subrufa and Formica frontalis , a new example of temporary host–parasite interaction

The aim of this paper is to describe the relationship between two ant species, Formica frontalis and Iberoformica subrufa, found together in shared nests. Therefore, we obtained data from dug nests and outdoor activity in two sympatric populations and investigated the cuticular hydrocarbons (CHCs) in both sympatric populations and in 10 I. subrufa allopatric populations to unravel whether the relationship becomes tuned between both species. We also determined the CHCs of two sympatric Serviformica species (F. cunicularia and F. lemani). Our results showed that the ant F. frontalis is a temporary parasite of I. subrufa which facultatively forms mixed colonies complying with a loose form of the Emery’s rule. Alkanes and methylalkanes are the most abundant compounds found in F. frontalis and I. subrufa CHCs, respectively, but esters were only abundant in I. subrufa. As far as the CHC similarity is concerned, the sympatric free-living hosts were chemically closer to the parasite, albeit not identical, whereas the allopatric I. subrufa populations always maintained a separate CHC composition. We provide different potential hypotheses to explain this similarity of cuticular profiles only in the two geographically distant sympatric populations.