Genetic Variation Assessment of Rainbow Smelt in Green Bay and Western Lake Michigan
File(s)
Date
1994-05Author
Cahill, Joseph R.
Publisher
University of Wisconsin-Stevens Point, College of Natural Resources
Metadata
Show full item recordAbstract
Collections of 60 or 22 rainbow smelt, Osmerus mordax,
were obtained from each of six spawning sites in Green Bay
and western Lake Michigan during the spawning season, April,
1991 and April, 1992. Smelt were also collected from
Crystal Lake, Michigan in June, 1990, and Lake Erie and
Green Bay in summer, 1992. The smelt were assessed with
isozyme electrophoresis and restriction fragment length
polymorphisims (RFLP) of mitochondrial DNA (mtDNA) to
determine the degree of genetic differentiation among the
collection sites. Evidence of discrete stocks among
locations was inconsistent and inconclusive
Analysis of the products.of 4 isozyme loci from the
1990 and 1991 sites provided some evidence of genetic
differentiation. Evidence consistent with the existence of
different stocks among sites was: 1) contingency chi-square
tests of allele frequency heterogeneity among all loci
indicated that the IDH-2 locus was significantly different;
2) subsequent contingency chi-square tests of allele
frequency heterogeneity at the IDH-2 locus revealed
significant differences among·several collections; 3) the
Little Bay de Noc sample was different at the IDH-2 locus
from three other Green Bay sites, Days River, Turtle Creek
and Green Island; 4) the Green Island collection was
different from one other sample, Little Bay de Noc; 5) the
Green Island collection had low genetic identity and high
genetic distance when compared to each of the other
collections; and 6) consequently, the Green Island
collection was not clustered on a dendrogram with any of the
other five sites.
Evidence that did not indicate different stocks among
sites was: 1) the mean number of alleles and average
heterozygosity per locus were similar among all collections;
2) the highest F(ST) value (IDH-2 locus) indicated only 2.5%
of the total genetic variation was due to differences among
sites; 3) coefficients of genetic similarity and distance
did not indicate existence of discrete genetic stocks among
collections; and 4) unweighted pair group method (UPGM)
clustering of genetic distances revealed no geographic
relation among collections.
Restriction fragment length polymorphisims (RFLP)
analyses of mtDNA from the 1992 samples also provided
inconsistent and inconclusive evidence of genetic
differentiation among the collections. Some evidence for
differentiation at the Green Island site was found. Green
Island clonal line frequencies differed significantly from
those of Turtle Creek and Little Bay de Noc; however,
generally low levels of genetic variation were found both
within and among collections. Unweighted pair group method
clustering of mitochondrial DNA genotypes revealed two major
clonal lines separated by a mean sequence divergence of only
1.405%. Nucleon diversity index values were low
both among collections and for pooled data from all
collections, suggesting that levels of genetic
differentiation among collections were low. With the
exception of Green Island, contingency chi-square tests of
clonal line frequency heterogeneity also indicated no
genetic difference among collections. No geographical
relation among clonal line frequencies was evident among
collections.
Analyses of pooled data did not indicate genetic
difference between Green Bay and Lake Michigan. Green Bay
and Lake Michigan allele frequencies did not differ
significantly, nor did Green Bay and Lake Michigan clonal
line frequencies. Percentage of loci polymorphic and
average heterozygosity at all loci were similar between
Green Bay and Lake Michigan. Coefficients of genetic
identity and distance between Green Bay and Lake Michigan
indicated little difference. The mean F(ST) value indicated
that ot the total variation observed at all loci, only 0.2%
was due to differences between Green Bay and Lake Michigan.