title: Abandoning aggression but maintaining self-nonself discrimination as a first stage in ant supercolony formation.
abstract: An ant supercolony is a very large entity with very many queens. Although normal colonies of small extent and few queens remain distinct, a supercolony is integrated harmoniously over a large area [1, 2]. The lack of aggression is advantageous: Aggression is costly, involving direct and indirect losses and recognition errors [3, 4]. Indeed, supercolonial ants are among the ecologically most successful organisms [5-7]. But how supercolonies arise remains mysterious [1, 2, 8]. Suggestions include that reduced within-colony relatedness or reduced self-nonself discrimination would foster supercolony formation [1, 2, 5, 7, 9-12]. However, one risks confusing correlation and causality in deducing the evolution from distinct colonies to supercolonies when observing established supercolonies. It might help to follow up observations of another lack of aggression, that between single-queened colonies in some ant species. We show that the single-queened Lasius austriacus lacks aggression between colonies and occasionally integrates workers across colonies but maintains high within-colony relatedness and self-nonself discrimination. Provided that the ecological framework permits, reduced aggression might prove adaptive for any ant colony irrespective of within-colony relatedness. Abandoning aggression while maintaining discrimination might be a first stage in supercolony formation. This adds to the emphasis of ecology as central to the evolution of cooperation in general [13].
authors.affiliation: School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia.
authors.forename: Florian M
authors.initials: FM
authors.lastname: Steiner
authors.forename: Birgit C
authors.initials: BC
authors.lastname: Schlick-Steiner
authors.forename: Karl
authors.initials: K
authors.lastname: Moder
authors.forename: Christian
authors.initials: C
authors.lastname: Stauffer
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Arthofer
authors.forename: Alfred
authors.initials: A
authors.lastname: Buschinger
authors.forename: Xavier
authors.initials: X
authors.lastname: Espadaler
authors.forename: Erhard
authors.initials: E
authors.lastname: Christian
authors.forename: Katrin
authors.initials: K
authors.lastname: Einfinger
authors.forename: Eberhard
authors.initials: E
authors.lastname: Lorbeer
authors.forename: Christa
authors.initials: C
authors.lastname: Schafellner
authors.forename: Manfred
authors.initials: M
authors.lastname: Ayasse
authors.forename: Ross H
authors.initials: RH
authors.lastname: Crozier
mesh_terms: D000374:Aggression; D000818:Animals; D001000:Ants / Q000235:genetics* / Q000502:physiology; D005075:Biological Evolution; D017753:Ecosystem; D005260:Female; D005838:Genotype; D008297:Male; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data