Nestmate recognition as an inbreeding avoidance mechanism in bumble bees (Hymenoptera: Apidae)

In flight cages containing field-reared virgin gynes and males, bumble bees Bombus frigidus and possibly B. bifarius avoided mating with nestmates. In contrast, bumble bees B. californicus and B. rufocinctus mated indiscriminately with nestmates and non-nestmates. Nonrandom mating apart from the context of the natal nest indicates that nestmate recognition occured via individually-borne cues. Bees of both sexes, except female B. rufocinctus, commonly mated more than once. Mating duration differed significantly among species, and was strongly positively correlated with the average number of gyne matings in that species. The ability of bumble bees to discriminate among potential mates via individually borne recognition cues may depend on the likelihood that female and male nestmates encounter one another in a mating context. The mate searching strategy of B. frigidus and B. bifarius males, which differs from that of B. californicus and B. rufocinctus males, may favor nestmate recognition as inbreeding avoidance mechanism.