Female-only workers and soldiers in Schedorhinotermes intermedius are not produced by parthenogenesis

Abstract

Termites differ from hymenopteran social insects in several important respects, perhaps most significantly in their sex and caste determination systems: while hymenopteran colonies are female dominated (and sex determination is haplo-diploid), termite colonies are usually split evenly between males and females (and sex determination is through sex chromosomes). Not all termite species have an equal sex ratio—in the termite genus Schedorhinotermes, almost all workers and soldiers are females. The mechanism maintaining this sex ratio skew is unknown, but a possible mechanism (known in other termites as a mechanism for producing reproductives) is parthenogenesis. Under this scenario, soldiers and workers would be offspring of the queen only. In this study, we performed microsatellite analysis on 11 colonies of Schedorhinotermes intermedius (Isoptera: Rhinotermitidae) to investigate the parentage of workers, soldiers and alates within colonies, and to determine whether parthenogenesis is responsible for the production of female workers and soldiers. We also conducted a preliminary analysis of population and colony genetic structure. We found that females from a single colony had in some instances more than two alleles among them at a single microsatellite locus. This indicates that a single female cannot be producing these offspring, as she has a maximum of two different alleles at any locus, ruling out the possibility that the high proportion of females in this species comes about through parthenogenesis.