Abstract
The abundance of butternut (Juglans cinerea L.) trees has severely declined rangewide over the past 50 years. An important factor in the decline is butternut canker, a disease caused by the fungus Ophiognomonia clavigigenti-juglandacearum, which has left the remaining butternuts isolated and sparsely distributed. To manage the remaining populations effectively, information regarding how butternut’s population genetic structure is affected by environmental and historical factors is needed. In this study, we assessed genetic structure and diversity of 161 butternut trees from 19 adjacent watersheds in the southern portion of butternut’s range using 12 microsatellite markers. We assessed the genetic diversity and genetic differentiation among trees grouped at various spatial scales. Our goal was to use historical abundance and land use data for these watersheds, which are now all a part of the Great Smoky Mountains National Park (GSMNP), to understand the ecological and evolutionary forces that challenge the conservation and management of butternut. In general, butternuts within the 19 neighboring watersheds were all part of one continuous population, with gene flow throughout. Significant genetic differentiation was detected between some groups of trees, but the differentiation was quite small and may not represent an ecologically significant distinction. The mean heterozygosity in all watersheds remained high, despite extensive mortality. Overall, genetic diversity and rare alleles were evenly distributed across all watersheds, with some variability in subpopulations containing butternut-Japanese walnut hybrids (Juglans x bixbyi or buarts). These results indicate that management of this species should focus on protection from future hybridization with Japanese walnut, promotion of regeneration, and persistence of all remaining butternut trees, which still retain high levels of genetic diversity.
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Acknowledgments
We would like to thank the employees and volunteers of Great Smoky Mountains National Park for providing invaluable support for this project, especially Tom Remaley, Janet Rock, Keith Langdon, Kristine Johnson, Glenn Taylor, Emily Darling, Emily Guss, and Paul Super for contributing their time and resources to facilitate our work in GSMNP. Field assistance was provided by H. Seiner, B. Greene, V. Meyer, B. Moehl, J. Albritton, M. Cooke, S. Simpson, J. Byrne, M. Duffy, M. Clebsch, C. Pan, M. Williams, K. Hansen, C. deGuia, L. Combs, C. Black, D. Love, D. Clabo, and K. Mann. William Beatty provided useful advice for statistical analyses. This work was supported by the Hardwood Tree Improvement and Regeneration Center (United States Department of Agriculture Forest Service Northern Research Station) and the Department of Forestry and Natural Resources at Purdue University. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the US Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that also may be suitable.
Data archiving statement
Microsatellite genotypes at all loci for all samples including hybrids, and the watershed from which the samples were obtained, are archived at TreeGenes as TGDR007. The specific locations of sampled trees are available for research purposes from Great Smoky Mountains National Park; contact Tom Remaley, Supervisory Ecologist/Inventory & Monitoring Coordinator, TOM_REMALEY@NPS.GOV.
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Communicated by G. G. Vendramin
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Parks, A., Jenkins, M., Ostry, M. et al. Biotic and abiotic factors affecting the genetic structure and diversity of butternut in the southern Appalachian Mountains, USA. Tree Genetics & Genomes 10, 541–554 (2014). https://doi.org/10.1007/s11295-014-0702-8
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DOI: https://doi.org/10.1007/s11295-014-0702-8