Ongoing human-mediated spread and hybridization of two major invasive termite species

Human-mediated biological invasions can lead to introgressive hybridization events between lineages that have evolved independently, with potential for evolutionary, ecological, economic and social impacts. This study provides evidence for the ongoing spread and hybridization between two major invasive and destructive termite pest species, Coptotermes gestroi and C. formosanus in Florida. Heterospecific courtship behaviour between alates (winged reproductive caste) of the two species has led to the establishment of F1 hybrid colonies in the field, which have matured and produced F1 hybrid alates. Laboratory backcross attempts confirmed the possibility for F1 hybrid female alates to establish viable F2 colonies with males of either parental species. With the recent documentation of introgressive hybridization between the two species in Taiwan, the current study confirms its independent occurrence in Florida, demonstrating that both Coptotermes species can hybridize in areas where their distributions overlap. In Florida, the proximity of field-established hybrid colonies to the large leisure boat industry implies that Florida populations of C. gestroi, C. formosanus and their hybrids will continue to serve as a bridgehead source of propagules for further dispersal beyond their current distribution, with a potential for F1 hybrids to spread outside of Florida.