Disease risk as a cost of outbreeding in the termite Zootermopsis angusticollis.

The effect of the sibship of primary reproductives on mate mortality and the survivorship and growth of incipient colonies was studied in the dampwood termite Zootermopsis angusticollis. Males and females paired with nonsibling mates had higher mortality during the first 10-40 days after pairing, although male and female reproductives showed similar patterns of mortality after colony establishment. The source of mortality appeared to be fungal and/or bacterial pathogens. There were no overall differences in the number of eggs and larvae produced by sibling and nonsibling pairs, and no differences in colony size and biomass 4 years after colony establishment. We therefore could not identify any negative effect of inbreeding in the early phases of colony development. Our results suggest that the risk of exposure to pathogens and the ability of termites to locally adapt to disease could influence the genetic identity of primary reproductives and the extent of inbreeding in termite populations.