Dominance hierarchy and reproductive conflicts among subordinates in a monogynous queenless ant

In insect societies lacking morphologically specialized breedersandhelpers, reproduction is often restricted to behaviorallydominantindividuals. Such societies occur in about 100 speciesof ants that havesecondarily lost the queen caste. All females,who are morphologicallyworkers, can potentially mate and layeggs but only a few do so, and wedemonstrate in Dinoponeraquadriceps that this is regulated by adominance hierarchy.Six types of agonistic interactions allowed the rankingof 5-10workers in the hierarchy (n = 15 colonies). In particular,alphaand beta had characteristic behavioral profiles and were easilyrecognized.Only alpha mated, and workers ranking beta to delta sometimesproducedunfertilized, male-destined eggs. Natural replacements (n =19)and experimental removals (n = 15) of alpha demonstrated thatbetawas the individual most likely to replace alpha, although gammaand morerarely delta sometimes did, and we discuss the conflictthat occurs amonghigh-ranking individuals over who should replacealpha. After suchreplacements, the new alpha behaved more aggressivelythan the overthrownalpha. Newly emerged workers tended to reachhigh ranks and displaced olderhigh-ranking individuals downthe hierarchy. Low-ranking subordinates oftenprevented high-rankingindividuals from replacing alpha by biting and holdingtheirappendages (worker policing), which is consistent with the patternofrelatedness associated with monogyny and monandry in D. quadriceps.Weinvestigated the relative importance of chemical communicationanddominance interactions to regulate reproduction. Alpha,beta, and sterileworkers have different signatures of cuticularhydrocarbons, and these mayprovide honest information whichunderpins worker policing by low-rankingindividuals.