The role of mandible morphology in termite inquilinism

In heterospecific termite-termite (Blattodea, Isoptera) cohabitation, defensive morphologies are more evident in inquiline soldiers than in the workers. Nevertheless, these latter are prone to present defensive adaptations as well. After all, by living and feeding inside the nest of other species, such workers would suffer less pressure from building and foraging, but more demand for defensive adaptations. Interestingly, these three functions - building, foraging, and defense - can be exerted by a single structure, the mandibles. Providing that, in inquilines, defensive needs may prevail over building and foraging, it seems adaptive for inquiline termite workers to have mandibles modified for defense. Here we report on a significant correlation between mandibular modifications in termite workers and their propensity to inquilinism. Using behavioral assays, we show these adaptations to play relevant roles in the defense/attack dynamics of guests and hosts. We show that, in termite workers, the size and position of the apical tooth relative to the marginal teeth may arm termite hosts and termite inquilines with an effective defensive weapon. Hosts may also use it as a weapon to attack inquilines. The latter, however, are unable to do so, confirming previous reports on peaceful behavior as a typical strategy for termite inquilines. We argue that mandibular patterns in termites (as measured by the left mandible index, LMI), more than a product of feeding habit selective pressure, may also serve to mediate nest heterospecific cohabitation.

Automated summary

In heterospecific termite-termite cohabitation, defensive morphologies are more evident in inquiline soldiers than in the workers. The mandibular modifications in termite workers show a significant correlation with their propensity to inquilinism. These adaptations play relevant roles in the defense/attack dynamics of guests and hosts, suggesting that the mandibles may mediate nest heterospecific cohabitation.