Courtship Behavior Confusion in Two Subterranean Termite Species that Evolved in Allopatry (Blattodea, Rhinotermitidae, Coptotermes)

Congeneric species that live in sympatry may have evolved various mechanisms that maintain reproductive isolation among species. However, with the spread of invasive organisms owing to increased global human activity, some species that evolved in allopatry can now be found outside their native range and may have the opportunity to interact, in the absence of mechanisms for reproductive isolation. In South Florida, where the Asian subterranean termite, Coptotermes gestroi (Wamann), and the Formosan subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae) are invasive, the two species can engage in heterospecific mating behavior as their distribution range and their dispersal flight season both overlap. Termites rely on semiochemicals for many of their activities, including finding a mate after a dispersal flight. In this study, we showed that females of both species produce (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol (DTE) from their tergal glands as a shared sex pheromone. We suggest that both species primarily rely on an inundative dispersal flight strategy to find a mate, and that DTE is used as a short distance pheromone or contact pheromone to initiate and maintain the tandem between males and females. The preference of C. gestroi males for C. formosanus females during tandem resulted from the relatively high amount of DTE produced by tergal glands of C. formosanus females, when compared with those of C. gestroi females. This results in confusion of mating in the field during simultaneous dispersal flights, with a potential for hybridization. Such observations imply that no prezygotic barriers emerged while the two species evolved in allopatry for ~18 Ma.