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Genetic Differentiation in Salamanders of the Desmognathus ochrophaeus Complex (Plethodontidae)

Stephen G. Tilley, Robert B. Merritt, Barbara Wu and Richard Highton
Evolution
Vol. 32, No. 1 (Mar., 1978), pp. 93-115
DOI: 10.2307/2407413
Stable URL: http://www.jstor.org/stable/2407413
Page Count: 23
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Genetic Differentiation in Salamanders of the Desmognathus ochrophaeus Complex (Plethodontidae)
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Abstract

Genetic variation at 12 loci was investigated electrophoretically in southern Appalachian populations of salamanders of the Desmognathus ochrophaeus species complex. Levels of heterozygosity and allele frequencies varied markedly among the 31 populations sampled. The electrophoretic results indicate that two reproductively isolated forms are broadly sympatric in the Great Smoky Mountains. Cryptic species were not encountered at any of the 29 localities sampled in other mountain ranges. The two forms of the Great Smokies are genetically quite divergent, but extremely similar in morphology and color pattern. At some localities they are easily distinguished in the field while at others they are not. One is clearly the form described in 1926 as Desmognathus fuscus imitator Dunn; it is here treated as D. imitator, a form endemic to the Great Smoky Mountains. The two forms differ in altitudinal distribution and microhabitat preference. They and four other species of Desmognathus (D. wrighti, D. 'fuscus,' D. monticola, and D. quadramaculatus) are now known to inhabit the Great Smoky Mountains. Some populations outside the Great Smoky Mountains are genetically divergent from one another. Levels of divergence are usually highest among populations of different mountain ranges. D. imitator appears to be genetically quite distinct from any of the other populations analyzed. The other form of the Great Smokies is electrophoretically quite similar to some allopatric populations, which can resemble either or both forms in color pattern. Populations outside the Great Smokies polymorphic for colored cheek patches are electrophoretically much more similar to the form in the Great Smokies that lacks them. The form sympatric with imitator is treated as D. ochrophaeus, together with all the populations outside the Great Smokies analyzed here. This form is thus viewed as a complex of populations among which levels of genetic similarity may be rather low. The electrophoretic distinctness of D. imitator relates to questions concerning the acquisition of reproductive isolation and the genetics of speciation. It also suggests that in genera such as Desmognathus, where traditional taxonomic characters are few and poorly reflect overall genetic divergence, electrophoretic data may generate otherwise indistinguishable taxa.

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