Kin recognition and the paradoxical patterns of aggression between colonies of a Mojave desert Pheidole ant

• Published in: Insectes sociaux Vol. 53; no. 2; pp. 127 - 135
• Main Authors: TRIPET, F, FOURNIER, D, NONACS, P, KELLER, L
• Format: Journal Article
• Language: English
• Published: Basel Springer 01.05.2006
• Subjects: Animal ethology; Biological and medical sciences; Formicidae; Fundamental and applied biological sciences. Psychology; Pheidole; Protozoa. Invertebrata; Psychology. Psychoanalysis. Psychiatry; California; United States; North America; America; Mojave Desert; Formicidae; Acceptance; exogenous cues; Insecta; Kin recognition; Social insect; Formicoidea; Population genetics; endogenous cues; Arthropoda; Intraspecific competition; Nestmate recognition; Colony; Models; common label acceptance model; Hymenoptera; Invertebrata; Aculeata; Agonistic behavior
• ISSN: 0020-1812; 1420-9098
• DOI: 10.1007/s00040-005-0846-5

Populations of the desert seed-harvesting ant Pheidole xerophylla are often characterized by high nest density leading to competitive interactions between foragers from different nests. We investigated the inter-nest aggression, spatial distribution and genetic structure of a P. xerophylla population of the Mojave Desert in Southern California. Inter-nest aggression was quantified by standardized staged encounters in a neutral arena. Genetic relatedness within nests and relatedness between nests were calculated using al-lelic frequencies at four microsatellite-DNA loci. We found a bimodal distribution of inter-colony aggression levels with a first mode at low aggression levels and another mode at much higher aggression levels. Inter-colony aggression levels were largely non-transitive. No effect of geographical distance on inter-nest aggression levels was detected. Despite high amounts of variation in inter-colony relatedness (-0.24 to 0.37) this variable did not correlate with the level of aggression between nests. Intra-nest relatedness ranged from 0.40 to 0.75 and close inspection of worker genotypes within colonies revealed a high proportion of polygynous colonies or a mixture of polygyny and polyandry. Aggression levels among nests was found to decrease with increasing intra-nest relatedness. These results do not support the idea that aggression is modulated by a nestmate recognition mechanism based on overall genetic similarity. Instead, the absence of transitivity found in inter-colony aggression and bimodal distribution of aggression levels are compatible with a common label acceptance model of nestmate recognition and suggest that label diversity may be encoded by a limited number of loci.