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Open Access Highly Accessed Research article

The dynamics of male-male competition in Cardiocondyla obscurior ants

Sylvia Cremer12*, Masaki Suefuji1, Alexandra Schrempf1 and Jürgen Heinze1

Author Affiliations

1 Evolution, Behaviour & Genetics, Biology I, University of Regensburg, Regensburg D-93040, Germany

2 Present address: Evolutionary Biology, IST Austria (Institute of Science and Technology Austria), Klosterneuburg A-3400, Austria

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BMC Ecology 2012, 12:7  doi:10.1186/1472-6785-12-7

Published: 15 June 2012

Abstract

Background

The outcome of male-male competition can be predicted from the relative fighting qualities of the opponents, which often depend on their age. In insects, freshly emerged and still sexually inactive males are morphologically indistinct from older, sexually active males. These young inactive males may thus be easy targets for older males if they cannot conceal themselves from their attacks. The ant Cardiocondyla obscurior is characterised by lethal fighting between wingless (“ergatoid”) males. Here, we analyse for how long young males are defenceless after eclosion, and how early adult males can detect the presence of rival males.

Results

We found that old ergatoid males consistently won fights against ergatoid males younger than two days. Old males did not differentiate between different types of unpigmented pupae several days before emergence, but had more frequent contact to ready-to-eclose pupae of female sexuals and winged males than of workers and ergatoid males. In rare cases, old ergatoid males displayed alleviated biting of pigmented ergatoid male pupae shortly before adult eclosion, as well as copulation attempts to dark pupae of female sexuals and winged males. Ergatoid male behaviour may be promoted by a closer similarity of the chemical profile of ready-to-eclose pupae to the profile of adults than that of young pupae several days prior to emergence.

Conclusion

Young ergatoid males of C. obscurior would benefit greatly by hiding their identity from older, resident males, as they are highly vulnerable during the first two days of their adult lives. In contrast to the winged males of the same species, which are able to prevent ergatoid male attacks by chemical female mimicry, young ergatoids do not seem to be able to produce a protective chemical profile. Conflicts in male-male competition between ergatoid males of different age thus seem to be resolved in favour of the older males. This might represent selection at the colony level rather than the individual level.

Keywords:
Sexual selection; Male-male competition; Fighting; Cuticular hydrocarbons; Detection abilities; Cardiocondyla ants