Genetic variation and differentiation in parent-descendant cattle and bison populations.

Genetic variation and differentiation at 32 microsatellite loci was quantified for parent-descendant cattle populations and parent-descendant bison () populations. We compared heterozygosity () and allelic richness () for 587 cattle of four breeds and three lines derived from them, and 188 bison in three pairs of parent-descendant populations. and were less in the Line 1 Hereford inbred cattle population than in the parent Hereford breed. and were intermediate in a composite population (CGC, derived from crossing Red Angus, Charolais, and Tarentaise) compared to the three parent breeds. Crossbreeding of Line 1 with CGC resulted in an F generation with increased and relative to Line 1 and CGC, followed by decreased and in 2 backcross generations to Line1. Three transplanted wild bison populations had smaller and than their respective parent populations. These data demonstrate that genetic variation reduced from founder effects or inbreeding can be restored with crossbreeding and gene flow.