High occurrence of colony fusion in a European population of the American termite Reticulitermes flavipes

The coexistence of multiple unrelated reproductives within social insect colonies decreases the relatedness among colony members and therefore challenges kin selection theory. This study investigated the colony genetic structure of a French introduced population of the American subterranean termite Reticulitermes flavipes by analyzing genotypes at eight microsatellite loci and at one mtDNA region. Results revealed that all colonies contained numerous related secondary reproductives, and that 31% of colonies possessed more than two unrelated reproductives. The presence of several unrelated reproductives within colonies of this species is commonly assumed to result from colony fusion. Although such a high occurrence of colony fusion is the highest ever observed in a termite population, it is probable that the available methodology underestimated the detection of colony fusion in French populations. Overall, these results suggest that French colonies might differ strongly from the great majority of American colonies in their capacity to produce secondary reproductives as well as in their ability to merge. The nature and evolutionary origin of these population differences are discussed.