First come, first served: the first-emerging queen monopolizes reproduction in the ant Cardiocondyla “argyrotricha”

Abstract

While colonies of most tropical species of the ant genus Cardiocondyla regularly contain multiple egg-laying queens (polygyny), single-queening (monogyny) evolved convergently in a Palearctic clade of Cardiocondyla and in Southeast Asian C. “argyrotricha.” In the latter species, monogyny is probably an adaptation to patchily distributed but highly stable nest sites. In experimentally orphaned colonies of C. “argyrotricha,” the first emerging queen shed its wings, began to lay eggs, and stayed mostly on the brood pile. Queens that emerged later remained in the peripheral areas of the nest without dispersing but retained their wings even after mating in the nest. Aggressive interactions among queens and between workers and queens were occasionally observed, but it appears that the order of queen emergence determines which of them will become reproductive and inherit the nest. We conclude that young queens commonly compete for nest inheritance in some species of Cardiocondyla and that queen–queen antagonism does not necessarily involve lethal fighting.