MATERNALLY INHERITED MALE-KILLING MICROORGANISMS MAY CONFOUND INTERPRETATION OF MITOCHONDRIAL-DNA VARIABILITY

Variation in mitochondrial DNA is often used to trace the evolutionary history of populations and species. We here discuss the effect of inf ection with cytoplasmically inherited male-lethal symbionts on mitocho ndrial genome evolution. Male-lethal symbionts spread when killing mal e hosts increases the lifetime reproductive success of sibling female hosts. This increase in the survivorship of daughters from individuals bearing a male-killer will produce a concomitant increase in the freq uency of mitotypes associated with the male-killer. If horizontal tran smission of the microoorganism is rare and population sizes not very s mall, then linkage disequilibrium between microorganism and particular mitotypes will result in a reproduction of within-population mitochon drial variability both because of a selective sweep during the spread of such a micro-organism, and also at equilibrium. Male-killing symbio nts may thus confound the use of mtDNA variability in estimation of po pulation parameters. We discuss the differences between the effects of male-killers and the cytoplasmic incompatibility-inducing symbiont Wo lbachia, and the possibility that estimation of gene flow between popu lations may also be confounded by symbiont presence. (C) 1996 The Linn ean Society of London