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Phylogeography, evolution, and conservation in forest-associated Pacific Northwest salamanders

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Title Phylogeography, evolution, and conservation in forest-associated Pacific Northwest salamanders
Names Wagner, R. Steven (creator)
Haig, Susan M. (advisor)
Date Issued 2000-12-01 (iso8601)
Note Graduation date: 2001
Abstract Phylogeographic studies of six Pacific Northwest forest-associated
salamanders provide insight into historical and contemporary processes on
population genetic structure. Among Larch Mountain Salamanders (Plethodon
larselli), cytochrome b mitochondrial (mtDNA) sequences (381 bp) and random
amplified polymorphic DNA (RAPDs; 34 loci) supported separate Management
Units for northern and southern populations (12 populations, N 184 individuals)
as delineated by the Columbia River. Southern populations exhibited significantly
reduced expected heterozygosity at RAPD loci, which may be a consequence of a
founder event or bottleneck. Similarly, significant population structure was found
in Oregon Slender Salamanders (Batrachoseps wrighti). Cytochrome b sequences
(744 bp) revealed two historical lineages among 22 populations (N = 339
individuals). RAPD markers further differentiated mid-range populations.
Therefore, overlapping Management Units are warranted for northern-most, mid-range,
and southern-most populations. Phylogenetic relationships, taxonomic
identity, and population differentiation was examined among four morphologically conserved Torrent Salamanders species (Family Rhyacotritonidae). Analysis of
three mitochondrial genes (cytochrome b, 16S, and 12S ribosomal RNA) indicated
each species represented a well-supported monophyletic group. Results agreed
with allozyme data (Good et. al. 1987, Good and Wake 1992) suggesting three
groups of Torrent Salamanders (Rhyacotriton variegatus, R. cascadae, and the
ancestor of R. olympicus and R. kezeri) diverged during the Miocene. A more
recent divergence appears to have occurred between R. olympicus and R. kezeri
during the late Pliocene/early Pleistocene. Populations within R. variegatus appear
to be as diverged as R. olympicus and R. kezeri, supporting conservation unit
designation within R. variegatus. MtDNA 16S ribosomal RNA sequences and
allozymes (5 loci) identified Cascade and Southern Torrent Salamanders recently
discovered in the Central Oregon Cascades. Results indicate a range extension for
both species and suggest the Middle Fork of the Willamette River may provide a
geographic barrier to dispersal. Phylogenetic analyses of Southern Torrent
Salamanders (72 localities) based upon cytochrome b sequences revealed three
divergent clades (north coast, Oregon, and California) that coincide with possible
geographic barriers to dispersal. Merging mtDNA results with previous allozyme
studies provides support for an Evolutionary Significant Unit for the California
dade and separate Management Units for the north coast and Oregon clades.
Genre Thesis/Dissertation
Topic Salamanders -- Northwest, Pacific -- Phylogeny
Identifier http://hdl.handle.net/1957/20854

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