Queen life-span and total reproductive success are positively associated in the ant Cardiocondyla cf. kagutsuchi

While reproduction and longevity are negatively correlated in a large number of animals, this fundamental trade-off appears to be absent from social insect queens. Here, we examine the distribution of the life-spans of queens and their mates and the age-trajectory of reproduction in experimental colonies of the Pacific tramp ant Cardiocondyla cf. kagutsuchi. Queens of Cardiocondyla are generally short-lived (0.5–2 years), which allows determining their lifetime reproductive success and establishing mortality tables. We show that the queen’s total number of sexual offspring is positively associated with its life-span. Regular counts of eggs, larvae, and pupae suggest that more fecund queens live longer than less fecund queens and that an early onset of sexual production does not negatively affect the queen’s life-span. This corroborates the view that the costs of reproduction are not born by the queen itself. The number of eggs present in colonies increased with queen’s age until shortly before death, indicating negligible reproductive senescence. Sex ratios were strongly affected by the origin of queens but neither by colony size nor total productivity. Several queens produced only males late in their lives, suggesting the occurrence of sperm depletion. Male life-span was not correlated with any other studied trait. Our study shows that the ant genus Cardiocondyla provides a suitable model system to investigate the evolution of life-span in social insect queens and males.