Genetic relatedness and partner preference in a monogamous, wood-dwelling termite

Abstract

A mate preference study on adult dampwood termites, Zootermopsis nevadensis subspeciesnuttingi , supports the hypothesis that mate-seeking adults avoid forming partnerships with nestmates. The observed proportion of nestmate pairs formed from all potential pairs was significantly less than expected. In addition, fewer pairs formed when there was a higher availability of nestmates versus non-nestmates. Genetic relatedness estimates, obtained from multilocus fingerprints of overwintering pairs, showed that relatedness between partners was not significantly different from background relatednesses of members chosen randomly from the population. Thus, nest-founding reproductive adults typically do not breed incestuously in this wood-dwelling termite. Furthermore, relatedness estimates between adult breeding males and between adult breeding females coinhabiting each log showed that there was a low probability of genetic relatedness among adults of neighbouring pairs, indicating that adults are typically dispersing in ways that minimize contact with relatives. Relatedness between laboratory-reared full siblings produced by field-collected pairs showed that relatedness was not significantly higher thanr =0.50, which is expected if sustained incestuous breeding does not occur, or if cycles of inbreeding occur with negligible frequency among breeding adults. These findings do not support arguments that selection favours inbreeding because it confers disease resistance in termites. They also indicate that the level of genetic relatedness between nest-founding adults and among siblings cannot, by itself, explain the high levels of altruism within colonies of this single-site, wood-dwelling termite. Ecological pressures and the benefits of group living, together with ordinary genetic relatedness characteristics of outbred families appear sufficient to explain the advantages of kin-based altruism in wood-dwelling termites like Zootermopsis.