Mh. Murdoch et Pdn. Hebert, MITOCHONDRIAL-DNA EVIDENCE OF DISTINCT GLACIAL REFUGIA FOR BROWN BULLHEAD (AMEIURUS-NEBULOSUS) IN THE GREAT-LAKES, Canadian journal of fisheries and aquatic sciences, 54(7), 1997, pp. 1450-1460
Restriction fragment length polymorphisms were used to sun ey the mito
chondrial genome of Ameiurus nebulosus for nucleotide sequence variati
on. Two hundred and forty-nine individuals were analyzed from 12 popul
ations across the Great Lakes drainage and 3 populations in possible r
efugial drainages. Fifteen restriction endonucleases revealed 50 disti
nct haplotypes among these fish. Two major phylogenetic assemblages, A
and B, were revealed with an average 3.22% sequence divergence. Both
assemblages were themselves fragmented into two groups. Strong geograp
hic patterning was observed in the frequency of assemblages and groups
across the sampling area: assemblage A was predominant in fish from p
opulations east of Lake Erie, while western populations were dominated
by assemblage B. The distribution and phylogenetic divergence of mito
chondrial haplotypes indicate that brown bullhead in the Great Lakes o
riginated from two Pleistocene refugia and further provides genetic ev
idence of subdivision within these refugia. Pleistocene glaciations ap
pear to have had a similar influence on the geographic distribution of
mitochondrial DNA lineages of other North American fishes. In contras
t with these other species, however, much of the mitochondrial DNA var
iation and divergence was retained in brown bullhead populations livin
g south of the ice sheets and is represented in extant populations.