Unexpectedly slow homogenisation within a repetitive DNA family shared between two subspecies of tsetse fly.

Repetitive DNA families in sexual species are subject to a variety of turnover mechanisms capable of homogenising newly arising mutations. Very high levels of homogeneity in DNA families in some species of Drosophila indicate that the rate of turnover is fast relative to that of mutation. To gauge the generality of such phenomena, we cloned and sequenced individual members of homologous repetitive DNA families from two subspecies of tsetse fly, Glossina morsitans centralis and G. morsitans morsitans. Unexpectedly high levels of variation were found within each subspecies, averaging 24% and 31%, respectively. Contiguous repeats and repeats cloned at random were comparably divergent. Nevertheless, it was possible to identify three instances of apparent homogenisation, each being, remarkably, of an insertion/deletion nature. We conclude that the rate of turnover in the tsetse families is comparable to that of most mutations, and discuss the possible parameters affecting flux in these families.