Queens from a unique hyper-denseLasius nigerpopulation tolerate pleometrosis better than queens from a ‘normal’ population

The claustral, monogynous ant Lasius niger often founds colonies pleometrotically (with two or more queens), but later aggression from queens or workers can result in the death of all but one queen. Recently, a hyper-dense population of L. niger was discovered, showing minimal worker-worker aggression and interconnected colonies. Here, we ask whether queens are more tolerant of conspecifics in a pleometrotic setting. We collected queens directly after a nuptial flight from both the hyper-dense population and a ‘normal’ population, maintained them in pleometrotic groups, and followed queen survival for 227 days. While queens from the ‘normal’ population showed poor survival (under 20% survival after 130 days), resulting in usually one queen per pleometrotic group, 75% of queens from the hyperdense population survived to 227 days. Mortality in the ‘normal’ population was not centered around the emergence of the first workers. While the colonies from the hyper-dense population are all monogynous, this tolerance of pleometrosis may be linked to their apparent intraspecific tolerance and may be a step towards unicoloniality.