When good species go bad: Evidence for recent and continuing hybridization of two neotropical termites

Sympatric neotropical termites Nasutitermes corniger and N. ephratae are clearly distinguishable based on morphology, nest architecture, and defensive secretion composition. Previous analysis has found them to be genetically distinct (“good species”). Throughout their range, they share habitat, including nesting and foraging sites. Alate production and release are synchronous. Given the extensive ecological overlap, potential for interbreeding exists unless there are strong barriers against it. To explore these possibilities, heterospecific pairs were formed experimentally. Corniger females mated to ephratae males produced significantly fewer offspring than the reciprocal cross or conspecific pairs. This was also the only pairing in which any aggression was observed. In mixed-species mate choice trials, heterospecific pairs engaged in tandem running for up to 10 minutes before forming conspecific pairs. When offered the choice of a new conspecific mate post-pairing, the original heterospecific pair simply integrated it into the founding association. Thus, species mismatch tolerance is high, as is hybrid offspring viability, indicating its adaptiveness and the likelihood of occasional natural hybridization. Mixed mono- and di-terpene signatures have been observed in field colonies. Together with lower genetic distances between the two species in an island habitat than between N. corniger populations on the island and the mainland, this suggests that genetic introgression has and continues to occur. Reproductive barriers between these two species may not yet be fully developed; hybridization could provide a rare but important source of genetic diversity, and be a strategy to ensure mating opportunities for the more abundant sex of alates in each species.