Graduate Thesis Or Dissertation
 

Geographic variation in Dunn's salamander Plethodon dunni Bishop (Amphibia:Caudata:Plethodontidae)

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/2801pk22r

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  • Life history attributes and apparent distributional patterns suggest that Plethodon dunni exists as small, semi-isolated populations throughout its range. Isozyme and morphological variation in this species was examined to determine any possible geographic trends. Starch gel electrophoresis was utilized to examine genetic variation at 24 isozyme loci in 287 individuals from 12 populations to determine the genetic structure of populations of this species. Low total genetic variability was observed. However, this variability is partitioned into relatively low genetic heterozygosity within populations and proportionally high diversity between populations. It is concluded that this geographically restricted species is characterized by small local populations with little gene flow. Comparisons with previous reports of Plethodon species indicate that the high genetic divergence between local populations is apparently general for species in this genus. There is marked reduction in heterozygosity with peripheral populations of P. dunni, which may result from the reduction in genetic exchange from surrounding populations in peripheral as ccmpared to central populations. No indication of additional structural genes associated with the increased DNA in P. dunni was found. Morphological variation in 10 populations was examined via stepwise discriminant analyses. Considerable overlap of individuals' canonical scores and only moderately correct classifications into groups indicate that phenotypic expression in this species is exceedingly similar. However, on a fine scale there is significant heterogeneity between all populations. Generalized distance values (D²) between the P. dunni populations are high, particularly when compared to those of Aneides ferreus, a wider-ranging, more ubiquitous sympatric species. Clinal variation in morphological divergence was observed and was highly correlated with a similar cline in allele frequencies of EST-2. It is concluded that the phenotypic structuring of populations of P. dunni is consistent with the structuring observed via electrophoresis and that this species is characterized by small, localized populations throughout its range.
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