An optimisation approach to increase DNA amplification success of otter faeces
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Faeces have proved to be a suitable non-invasive DNA source for microsatellite analysis in wildlife research. For the success of such studies it is essential to obtain the highest possible PCR amplification success rate. These rates are still relatively low in most carnivorous species, especially in the otter (Lutra lutra). We therefore optimised the entire microsatellite genotyping process by combining our findings with results from previous studies to gain a high rate of reliable genotypes. We investigated the influence of otter faecal quality in relation to the quantity of slimy secretions and three levels of storage periods at −20°C on amplification success. Further, we tested the cost-effective and time-saving Chelex extraction method against the profitable QIAamp® DNA Stool Kit (Qiagen), and compared three PCR methods - a standard single-step PCR protocol, a single-locus two-step PCR procedure and a multiplex two-step PCR procedure - regarding success rate and genotyping errors. The highest amplification success rate (median: 94%; mean: 78%) was achieved using faecal samples consisting only of jelly extracted with the QIAamp® DNA Stool Mini Kit (Qiagen) immediately after collection and amplified following the time and cost efficient multiplex two-step PCR protocol. The two-step procedure, also referred to as pre-amplification approach, turned out to be the main improvement as it increases amplification success about 11% and reduces genotyping errors about 53%, most notably allelic dropouts.
KeywordsFaecal DNA Lutra lutra Microsatellites Non-invasive samples Pre-amplification
We would like to thank R. Klenke for helpful discussions and pertinent knowledge about the otter biology. A. Vallentin and U. Hempel are thanked for collecting faecal samples. Thanks to E. Küster and the Department of Bioanalytical Ecotoxicology and also to W. Durka and the Department of Community Ecology for giving access to the laboratories. We are grateful to the members of the Institute of Applied Ecology, University of Canberra for proof-reading the manuscript and to the anonymous reviewers who have greatly contributed to improve a first version of this paper. We kindly acknowledge private landowners for their permission to access the ponds.
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