High skew in the Caucasus: functional monogyny in the ant Leptothorax scamni
Animal societies vary considerably concerning how reproductive rights are partitioned among individual group members (“reproductive skew”). Nestmate queens of most polygynous species contribute more or less equally to the brood, but queens of a few species of the genus Leptothorax form dominance hierarchies in which only the top ranking queen lays eggs (“functional monogyny”). As predicted by optimal skew models, high skew appears to be associated with habitat patchiness. Here, we document functional monogyny in the Caucaso-Anatolian ant Leptothorax scamni (Ruzsky 1905). Similar to related species, young female sexuals mate on the ground near their natal nests and thereafter either disperse to found new colonies solitarily or in groups or return into their natal nest, where only one of several co-occurring queens reproduces. A phylogeny of Leptothorax species based on partial CO I sequences corroborates the view that functional monogyny has evolved convergently in several taxa of Leptothorax. It thus is a relatively labile trait that can rapidly adapt to habitat changes.