Seasonal nestmate recognition in the polydomous ant Plagiolepis pygmaea

Abstract

Nestmate recognition cues can derive from genetic and/or environmental factors and can be contextdependent rather than fixed over time. We examined the influence of genetic relatedness and environment on nestmate recognition and its seasonal variations in a natural population of the polydomous (multiple-nests per colony) ant Plagiolepis pygmaea in southern France. Recognition between colonies was measured by testing aggression levels during encounters between five workers of colony A and one of colony B and vice versa. The combination of genetic data, spatial data and aggressive behaviour data shows that nestmate recognition cues have principally a genetic component. Whereas workers from different nests of the same colony are never aggressive to each other, they are always hostile to alien conspecifics regardless of the spatial or genetic distance between the colonies. Our results also reveal significant seasonal variations in the levels of aggression among workers of different colonies, probably according to the biological cycles of the species. Surprisingly, despite the mode of colony reproduction being budding in P. pygmaea, the population of Tarabel is not genetically structured.

Sib‐mating in the ant Plagiolepis pygmaea: adaptative inbreeding?

“…These results are consistent with the weak gene flow between colonies and the high level of inbreeding previously reported in this species (Trontti et al. , 2005; Thurin & Aron, 2008). Workers are even more aggressive towards unrelated males than towards unrelated workers.…”

“…In all experiments (see below), the individuals (workers, virgin queens and males) tested were of two types: they either originated from the same colony and were considered as related, or they came from different populations and were considered as unrelated to each other. As expected from a previous study (Thurin & Aron, 2008), preliminary tests performed with individuals from different colonies of the same population gave similar results than those performed with individuals from different populations.…”

“…Genetic analyses on different populations reveal that within‐population inbreeding value F ranges from 0.29–0.39 (Trontti et al. , 2005, 2007; Thurin & Aron, 2008), which is consistent with low male dispersal, extensive mating among relatives and adoption of young queens in their natal colony (Trontti et al. , 2005).…”

“…Interestingly, despite the high level of inbreeding found in all P. pygmaea populations sampled, no diploid males were found in any of them (Trontti et al. , 2005; Thurin & Aron, 2008). Two alternative mechanisms may explain this absence.…”

“…Data on the genetic structure of the sampled populations are given elsewhere (Trontti et al. , 2005; Thurin & Aron, 2008). The ants were housed in standard laboratory nests (Passera, 1969), and fed honey and water ad libitum.…”