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Pseudogenes and DNA-based diet analyses: a cautionary tale from a relatively well sampled predator-prey system

Published online by Cambridge University Press:  28 April 2008

G. Dunshea*
Antarctic Wildlife Research Unit, School of Zoology, University of Tasmania, PO Box 252-05, Hobart, Tasmania 7005, Australia Applied Marine Mammal Ecology Group, Australian Antarctic Division, 203 Channel Highway, Kingston, Tasmania, Australia, 7050
N.B. Barros
Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236, USA
R.S. Wells
Chicago Zoological Society c/o Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236, USA
N.J. Gales
Applied Marine Mammal Ecology Group, Australian Antarctic Division, 203 Channel Highway, Kingston, Tasmania, Australia, 7050
M.A. Hindell
Antarctic Wildlife Research Unit, School of Zoology, University of Tasmania, PO Box 252-05, Hobart, Tasmania 7005, Australia
S.N. Jarman
Applied Marine Mammal Ecology Group, Australian Antarctic Division, 203 Channel Highway, Kingston, Tasmania, Australia, 7050
*Author for correspondence Fax: (+61) 36 232 3449 E-mail:


Mitochondrial ribosomal DNA is commonly used in DNA-based dietary analyses. In such studies, these sequences are generally assumed to be the only version present in DNA of the organism of interest. However, nuclear pseudogenes that display variable similarity to the mitochondrial versions are common in many taxa. The presence of nuclear pseudogenes that co-amplify with their mitochondrial paralogues can lead to several possible confounding interpretations when applied to estimating animal diet. Here, we investigate the occurrence of nuclear pseudogenes in fecal samples taken from bottlenose dolphins (Tursiops truncatus) that were assayed for prey DNA with a universal primer technique. We found pseudogenes in 13 of 15 samples and 1–5 pseudogene haplotypes per sample representing 5–100% of all amplicons produced. The proportion of amplicons that were pseudogenes and the diversity of prey DNA recovered per sample were highly variable and appear to be related to PCR cycling characteristics. This is a well-sampled system where we can reliably identify the putative pseudogenes and separate them from their mitochondrial paralogues using a number of recommended means. In many other cases, it would be virtually impossible to determine whether a putative prey sequence is actually a pseudogene derived from either the predator or prey DNA. The implications of this for DNA-based dietary studies, in general, are discussed.

Research Paper
Copyright © 2008 Cambridge University Press

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