MTDNA RECOMBINATION IN A NATURAL-POPULATION

Variation in mtDNA has been used extensively to draw inferences in phy logenetics and population biology, In the majority of eukaryotes inves tigated, transmission of mtDNA is uniparental and clonal, with genotyp ic diversity arising from mutation alone. In other eukaryotes, the tra nsmission of mtDNA is biparental or primarily uniparental with the pos sibility of ''leakage'' from the minority parent, In these cases, hete roplasmy carries the potential for recombination between mtDNAs of dif ferent descent. In fungi, such mtDNA recombination has long been docum ented but only in laboratory experiments and only under conditions in which heteroplasmy is ensured, Despite this experimental evidence, mtD NA recombination has not been to our knowledge documented in a natural population, Because evidence from natural populations is prerequisite to understanding the evolutionary impact of mtDNA recombination, we i nvestigated the possibility of mtDNA recombination in an organism with the demonstrated potential for heteroplasmy in laboratory matings, Us ing nucleotide sequence data, we report here that the genotypic struct ure of mtDNA in a natural population of the basidiomycete fungus Armil laria gallica is inconsistent with purely clonal mtDNA evolution and i s fully consistent with mtDNA recombination.