Molecular evidence for historical and recent population size reductions of tiger salamanders (Ambystoma tigrinum) in Yellowstone National Park
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Population declines caused by natural and anthropogenic factors can quickly erode genetic diversity in natural populations. In this study, we examined genetic variation within 10 tiger salamander populations across northern Yellowstone National Park in Wyoming and Montana, USA using eight microsatellite loci. We tested for the genetic signature of population decline using heterozygosity excess, shifts in allele frequencies, and low ratios of allelic number to allelic size range (M-ratios). We found different results among the three tests. All 10 populations had low M-ratios, five had shifts in allele frequencies and only two had significant heterozygosity excesses. These results support theoretical expectations of different temporal signatures among bottleneck tests and suggest that both historical fish stocking, recent, sustained drought, and possibly an emerging amphibian disease have contributed to declines in effective population size.
KeywordsAmbystoma tigrinum amphibian declines bottlenecks M-ratio Yellowstone National Park
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This project was supported by the University of Wyoming-National Park Service Research Station, the Idaho State University Graduate Student Research and Scholarship Committee, the Idaho State University Department of Biological Sciences and NSF IBN-0213851 to A.S. G. Elrod, T.␣Elrod, D. Jochimsen, A.A. Spear, A.M Spear, B. Spear and K. Spear helped collect tissue samples. K. Lew provided assistance with the laboratory work. We thank C. Hendrix and the National Park Service for granting permission to work in Yellowstone National Park. This research was approved by the Animal Welfare Committee at Idaho State University (#02-10-463).
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