Mechanisms of inbreeding avoidance in the Chilean termite Neotermes chilensis (Isoptera: Kalotermitidae)

Inbreeding depression refers to a decrease in some fitness components of the offspring produced by mating of a closely related sexual pair. Given the disadvantage of inbreeding depression, it is of interest to study the mechanisms involved in its avoidance, particularly in social insects. Termites show a reproductive behavioral repertoire consisting in the production of alates of both sexes inside the colony, their emergence during a swarming event, their landing and loss of wings (dealates), the encounter of both sexes in a tandem behavior (the male walks behind the female touching her abdomen), the construction of a bridal chamber and finally, their mating to found a new colony (primary reproductive pair). Two mechanisms have been proposed for inbreeding avoidance: indirect mechanisms that occur before the landing of alates (monogeny, biased sex dispersal and dilution effect during swarming), and an active mechanism (kin recognition) that occurs when alates come into contact after landing. We studied the mechanisms of inbreeding avoidance in Neotermes chilensis through: i) genetic analysis of individuals within a colony,  swarming alates and primary reproductive pairs; ii) observation of the emergence of alates from individual colonies; iii) differential sex dispersal distances of swarming alates; iv) behavioral bioassays involving dealates from the same or different colonies; v) analysis of semiochemicals and genetic analysis of bioassayed individuals; and vi) mating and egg production in artificial colonies started with single male and female dealates from the same or different colonies. This is the first time that indirect and active mechanisms of inbreeding avoidance have been studied in the same termite species, and through the complete reproductive period. Our results demonstrate that the dilution effect during a swarming event is the main indirect mechanism of inbreeding avoidance while kin recognition can be discarded as an active mechanism of inbreeding avoidance. The reason why kin recognition is not involved in inbreeding avoidance in termites will be discussed.

Funding statement: This work was financially supported by CONICYT fellowship for PhD studies and MECESUP’s internship program to DAO, FONDECYT grant 1120210 to HMN, CONICYT grant 79100013 to LF-P, and CONICYT PFB-23 and ICM P05-002 grants to DV.

Keywords: inbreeding avoidance, kin recognition, dispersal, termite, microsatellite markers.