Measurements of Inbreeding and Average Relatedness in a Termite Population

Colonies of the termite Reticulitermes flavipes are inbred and genetically isolated from nearby colonies. Termites were sampled in a hierarchical manner and subjected to starch-gel-protein electrophoresis; the genotypic frequencies were used to determine population structure. The regression estimate of relatedness within colonies, and its standard error, was b = 0. 57 0. 111. These data were also analyzed via F statistics, each presented with a standard error. The correlation between the alleles of an individual relative to its colony, F₈₂, was shown to be 0. 26 0. 089. The correlation between alleles of different individuals in the same colony, relative to the others in the sample, was F₂ₓ = 0. 48 0. 125. The correlation of alleles of different individuals in the same site relative to the entire sample, Fₒₓ, was indistinguishable from zero. F₈₂ represents the degree of inbreeding within a colony; F₂ₓ represents the genetic isolation of colonies near one another. These results differ somewhat from published accounts of the eusocial Hymenoptera, in that measurements of population structure in the Hymenoptera do not generally suggest the action of inbreeding. In addition, the values of relatedness presented for the eusocial Hymenoptera often fall below 0. 5. Population structure, as determined in the present study of a termite, R. flavipes, and in studies of the eusocial Hymenoptera, may provide another example of similarities between these phylogenetically diverse orders of social insects, in that the estimate of relatedness for R. flavipes does not fall outside the range of variation exhibited by the eusocial Hymenoptera. Although information regarding population structure in the termites has been lacking (Crozier 1980), it is essential to the understanding of the general nature of eusociality.