Unexpected termite inquilines in nests of Constrictotermes cyphergaster (Silvestri, 1901) (Blattodea: Isoptera)

The heterospecific termite-termite cohabitation in a single termitarium, so called in-quilinism, is a common event whose basal mechanisms remain hypothetical. While some termite hosts have plenty of inquilines, others house only a few. Among these, Constrictotermes cyphergaster are frequently found cohabiting with a single obligate inquiline species but have been unknown to house any facultative inquilines. Here we present the first record of facultative inquilines (Embiratermes festivellus, Nasutitermes kemneri, Obitusitermes bacchanalis and Subulitermes) to this host, evidencing that this was unlikely to have happened fortuitously. In an attempt to pose hypotheses on the mechanisms behind such invasions, we explored likely connections between the settlement of obligate and facultative inquilines and nest wall’s physical traits. We found that nests bearing atypical external walls (moist, eroded, and partially covered by mosses) held higher richness of facultative inquilines than nests presenting walls void of such traits (χ2 = 8.3965, 1 df, n = 17, P = 0.0038). The presence of healthy host colonies in all nests, including the atypical ones, reinforces the hypothesis that the settlement of these facultative inquilines depends less on host colonies biotic status and more on abiotic features associated to the nest. In addition, the presence of obligate inquilines was not affected by the nest wall status (χ2 = 8.3965, 1 df, n = 17, P = 0.0038), implying that invasion by facultative and obligate inquilines in these nests would obey distinct restrictions. While warning that these hypotheses require further testing, we suggest that their understanding could shed light on the determinants of cohabitation not only in C. cyphergaster but in termites in general. cohabitation interspecific interaction nest invasion barriers