|SREL Reprint #0951|
Biochemical Genetics of Mosquitofish.
R. McClenaghan Jr., Michael H. Smith, and Michael W. Smith
Gene frequency data from samples of Gambusia affinis
populations at 76 localities across the Savannah River drainage were used to
investigate temporal and spatial patterns in population genetic structure.
Localities in the Par Pond system on the Savannah River Plant were
sampled in 1971, 1977, and 1979. Allelic
frequencies in these populations were generally stable through time, although
significant temporal changes were observed among samples from Pond C, an
impoundment receiving thermal effluent.
Significant spatial heterogeneity in allele
frequencies was observed on both microgeographic and regional scales.
Populations within the Par Pond system were spatially subdivided at four
of the five loci surveyed (mean FST=0.051).
Subdivision was even more pronounced when samples from across the
Savannah River drainage were compared (mean F=0.196).
A hierarchial analysis of gene diversity (GST) demonstrated
that most of the genic diversity across the drainage exists as
within-subdivision diversity. Even
when populations from such contrasting habitats as rivers, creeks, ponds, and
reservoirs are compared, an average of only 13% of the total gene diversity was
attributed to between-group diversity. Greatest
between-group gene diversity was observed when reservoirs were compared with one
another. This general pattern of
low between-habitat diversity suggests that differential selection pressures are
not playing a major role in producing the observed levels of subdivision.
In the Par Pond system, neither single locus nor
multilocus genetic distances were significantly associated with geographic
distance or with its reciprocal. For
samples from over the Savannah River drainage, significant correlations between
genetic and geographic distance were observed only for the Gpi-2 and Pgm-2 loci.
Thus, there was a general lack of concordance between genetic and
Spatial autocorrelation demonstrated patterns
consistent with Wright’s isolation by distance model. Significant positive correlations in allelic frequencies
among neighboring populations were observed for five of six alleles; allelic
frequencies in more distantly separated populations were typically not
SREL Reprint #0951
McClenaghan, L.R., Jr., M.H. Smith, and M.W. Smith. 1985.
Biochemical genetics of mosquitofish. IV. Changes of allele frequencies through
time and space. Evolution 39:451-460.