Ancient DNA applications for wildlife conservation

Authors

  • JENNIFER A LEONARD

    1. Genetics Program, Smithsonian Institution, 3001 Connecticut Avenue NW, Washington, DC 20008-0551, USA and Department of Evolutionary Biology, Uppsala University, Norbyvägen 18D, 75236 Uppsala, Sweden
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  • Box 1 Ancient DNA: What? Where? When?

    Ancient DNA is DNA extracted from old biological material, including (but not limited to) teeth, bones, museum skins, naturally mummified tissue and fish scales. These materials can originate from museum skins/skeletal material, archaeological material or paleontological remains and range in age from tens of years to about a hundred thousand years old (Lindahl 1993).

    The DNA in all of these materials is degraded and is therefore more difficult to analyse than modern high quality DNA. DNA degradation leads to the three main problems: (i) reduced quantity of DNA which makes it particularly sensitive to contamination, (ii) broken DNA strands which reduce the length of fragments that can be amplified, and (iii) DNA damage which can lead to the identification of false mutations.

    DNA damage and degradation is often more influenced by preservation conditions than by time (within approximately the last hundred thousand years). Some factors that favour DNA preservation include constant temperature, low temperature and dryness. A better understanding of these factors gives us more of an idea about the precautions necessary to obtain reliable ancient DNA results, although these factors are still not fully understood (reviewed in Pääbo et al. 2004). Systematic studies of the efficiency of particular extraction methods (Rohland & Hofreiter 2007) and polymerase enzymes (Stiller et al. 2006; Shapiro 2008) as applied to ancient DNA have revealed surprising differences between common methods, and more studies like these will benefit the field as a whole.

    Isolation of ancient DNA extractions and PCR set-up from high quality DNA remains crucial. Proper negative controls in both extractions and PCRs, and appropriate replication of results are fundamental to any results based on old and/or degraded DNA. Many research groups are now overcoming these challenges and producing reliable, replicable data from ancient individuals and populations.

Jennifer A. Leonard, Fax: +46-18-471-6310; Email: jennifer.leonard@ebc.uu.se

Abstract

Ancient DNA analyses of historical, archaeological and paleontological remains can contribute important information for the conservation of populations and species that cannot be obtained any other way. In addition to ancient DNA analyses involving a single or few individuals, population level studies are now possible. Biases inherent in estimating population parameters and history from modern genetic diversity are exaggerated when populations are small or have been heavily impacted by recent events, as is common for many endangered species. Going directly back in time to study past populations removes many of the assumptions that undermine conclusions based only on recent populations. Accurate characterization of historic population size, levels of gene flow and relationships with other populations are fundamental to developing appropriate conservation and management plans. The incorporation of ancient DNA into conservation genetics holds a lot of potential, if it is employed responsibly.

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