A series of reintroduction programs have reestablished fisher (Martes penna
nti) populations to a large part of their former range. Horizontal starch-g
el electrophoresis of 20 presumptive gene loci was used from 1996 to 1998 t
o investigate gene dynamics in 4 remnant fisher populations (sources) and 4
reintroduced fisher populations from the northeastern and Great Lakes regi
ons of the United States. Mean multilocus heterozygosities, mean number of
alleles per locus, and percentage polymorphic loci were 0.027-0.090, 1.2-1.
6, and 10.0-30.0, respectively, in the 8 populations surveyed. Significant
allelic frequency differentiation was detected among the 4 source populatio
ns and among the 4 reintroduced populations, but a significant proportion o
f the genetic variance was partitioned only among the 4 reintroduced popula
tions. Pairwise comparisons between each source and its associated reintrod
uced population indicated that only older reintroductions have attained sig
nificant differentiation of allelic frequency from their sources. Significa
nt heterozygotic deficiencies were detected for statewide populations and r
egional populations within states, suggesting that breeding biology of the
fisher, presumably among females, is creating levels of fine-scale genetic
structure within populations.