Cryptic invasion of Northern Leopard Frogs (Rana pipiens) across phylogeographic boundaries and a dilemma for conservation of a declining amphibian
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Anthropogenic introduction of species is a major contributor to loss of biodiversity. Translocations within the range of a species are less frequently recognized, but have the potential for negative effects as well. Genetic mixing may lead to loss of local adaptations or further decline through outbreeding depression. These cryptic invasions may be quite difficult to recognize, but genetic tools can be used to recognize and monitor such intraspecific introductions. Conversely, translocations within species can be an important conservation tool to reduce inbreeding depression and replace lost genetic diversity. Thus, cryptic invasions can be either an aid or a hindrance to conservation efforts. We tested for the presence of non-native genotypes and assessed the extent and nature of introgression in populations of Northern Leopard Frog (Rana pipiens) in the southwestern US, where populations have declined to a few remnant populations. The most abundant and diverse complex of populations in the region contained a mitochondrial haplotype that was not native to the western US, probably resulting from the introduction of released pets, laboratory animals, or release during fish stocking. These non-native haplotypes were well integrated into a large complex of ponds and lakes, contributing to high genetic diversity in this area. Logistically, the geographic extent of non-native genetic influence within this population precludes eliminating or controlling the non-native component of this population. We recommend assessing the progress and fate of the introgression over time—along with population fitness parameters—to determine whether this introduction is beneficial or detrimental to population persistence. Meanwhile, translocations from nearby locations with similar environmental conditions have the best prospects for avoiding problems with outbreeding depression in other declining populations and will also most effectively preserve regional genetic diversity.
KeywordsCryptic invasion Population genetics Lithobates pipiens Northern Leopard Frog Introgression
Funding for this work was provided by the Heritage Fund Program of the Arizona Game and Fish Department. A Willard L. Eccles Graduate Fellowship from the Utah State University College of Science provided partial support for Ryan O’Donnell. Lisa Gelczis, Caleb Loughran, A. J. Monatesti, Dan Groebner, Diana Kimberling, Susan MacVean, and Oliver Hyman collected genetic samples. Susan MacVean of the Arizona Game and Fish Department provided assistance, advice, and insights. Jer Pin Chong, Catherine M. Culumber, and Jay Baker contributed to laboratory work. Tara Fulton and Greg Wilson of the University of Alberta provided access to primers and unpublished data. Preliminary portions of this manuscript were published as part of a peer-reviewed US Geological Survey Open-File Report, number 2011-1186.
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