GENETIC DIFFERENTIATION OF LAMPREY POPULATIONS WITHIN THE GENUS LAMPETRA AS DETERMINED BY MTDNA CONTROL REGION SEQUENCE DIVERGENCE AND ALLOZYMES
Summary
Allozyme allele frequencies and mtDNA sequence data were used to differentiate seven populations of lamprey from the Columbia, Klamath, and Sacramento River basins as well as two coastal streams in California. Allozyme genotypic data from ten polymorphic enzymes were scored in 166 lamprey specimens and mtDNA control region nucleotide sequences were obtained from nine individuals. Of 31 comparisons of observed genotypic frequencies at polymorphic loci to those expected under Hardy- Weinberg equilibrium, 9 (29%) deviated significantly (p<0.05). Log likelihood statistics were used to test for heterogeneity of allele frequencies calculated from the ten polymorphic loci and there were significant allele frequency differences among all seven [...]
Summary
Allozyme allele frequencies and mtDNA sequence data were used to differentiate
seven populations of lamprey from the Columbia, Klamath, and Sacramento River basins
as well as two coastal streams in California. Allozyme genotypic data from ten
polymorphic enzymes were scored in 166 lamprey specimens and mtDNA control region
nucleotide sequences were obtained from nine individuals. Of 31 comparisons of
observed genotypic frequencies at polymorphic loci to those expected under Hardy-
Weinberg equilibrium, 9 (29%) deviated significantly (p<0.05). Log likelihood statistics
were used to test for heterogeneity of allele frequencies calculated from the ten
polymorphic loci and there were significant allele frequency differences among all seven
populations. Approximately 560 base pairs were sequenced from the lamprey
mitochondrial genome, including 51 base pairs of the ND6 gene, 21 base pairs of the
tRNA-Thr gene and 490 base pairs (bp) at the 5′ end of the control region. This 490 bp
segment of the control region, referred to as non-coding region I, is homologous to that of
other fishes and includes conserved sequence blocks 2 and 3 and variable numbers of a
39 bp tandem repeat. Neighbor-joining trees constructed from both data sets produced
the same primary distinction between two groups of lampreys. The genetic distance
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between these two clades on the allozyme tree was 0.93 and the arrangement of them is
supported on the mtDNA tree by bootstrap values of 86% and 100 %. Both these
primary clades contain “brook” lampreys characterized as non-migratory and nonpredatory
and which are found within the range of anadromy of Lampetra tridentata,
suggesting polyphyletic origins of this life history type. These analyses support previous
conclusions about the systematics of these groups, particularly concerning the
observation of local populations of resident lampreys that exist in sympatry with a
predatory form and that appear to have arisen at different times. However, fine resolution
of closely related taxa remains problematic as evidenced by data suggesting Lampetra
tridentata was more distinct from a sympatric congener, Lampetra similis, than from its
upstream, geographically isolated relative, Lampetra lethophaga. Finally, two coastal
populations of “brook” lampreys in California (Prairie and Freshwater Creeks), appear to
be closely allied to Lampetra richardsoni from the Columbia River.
