UNUSUAL POPULATION GENETICS OF A PARASITIC NEMATODE: mtDNA VARIATION WITHIN AND AMONG POPULATIONS.

Very little is known about the distribution of genetic variance within and among populations of parasitic helminths. In this study we used mitochondrial DNA (mtDNA) restriction fragment analysis to describe the population genetic structure of Ostertagia ostertagi, a nematode parasite of cattle, in the United States. Estimates of within-population mtDNA diversity are 5 to 10 times greater than typical estimates reported for species in other taxa. Although populations are genetically differentiated for a key life-history trait, greater than 98% of the total genetic diversity is partitioned within populations, and the geographic distribution of individual mtDNA haplotypes suggests high gene flow among populations. © 1992 The Society for the Study of Evolution.