Abstract
Cooperative breeding may be selected for in animals when, on average, it confers greater benefits than solitary breeding. In a number of eusocial insects (i.e., ants, bees, wasps, and termites), queens join together to co-create new nests, a phenomenon known as colony co-founding. It has been hypothesised that co-founding evolved because queens obtain several fitness benefits. However, in ants, previous work has suggested that co-founding is a random process that results from high queen density and low nest-site availability. We experimentally examined nest-founding behaviour in the black garden ant, Lasius niger. We gave newly mated queens the choice between two empty nesting chambers, and compared their distribution across the two chambers with that expected under random allocation. We found that queens formed associations of various sizes; in most instances, queens group together in a single chamber. Across all experiments, the frequency of larger groups of queens was significantly higher than expected given random assortment. These results indicate colony co-founding in ants may actually be an active process resulting from mutual attraction among queens. That said, under natural conditions, ecological constraints may limit encounters among newly mated queens.
Highlights
Cooperative breeding may be selected for in animals when, on average, it confers greater benefits than solitary breeding
We show that newly mated queens actively formed groups when given the choice between two empty nesting chambers. This suggests that colony co-founding in L. niger is an active process that results from mutual attraction among queens
Our results contrast with those from the few previous studies that have examined colony co-founding in ants, which assumed that the phenomenon resulted from queens being drawn to the safety of an enclosed nesting place rather than being drawn by the presence of other queens [see “Introduction”42,46,48,49]
Summary
Cooperative breeding may be selected for in animals when, on average, it confers greater benefits than solitary breeding. The frequency of larger groups of queens was significantly higher than expected given random assortment These results indicate colony co-founding in ants may be an active process resulting from mutual attraction among queens. Several adults engage in social behaviours that benefit both themselves individually and the group as a whole This system may be selected for when ecological constraints (e.g., nest-site limitation, predation, parasitism, unpredictable resource availability) and competition greatly diminish the expected fitness payoff of solitary breeding. In the tree-nesting ant Crematogaster scutellaris, the number of groups formed by queens under natural conditions did not differ from that expected based on random allocation[46], suggesting that newly mated queens were not actively co-founding colonies. This study did not take into account spatial variation in nest-site availability or the density of newly mated queens
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