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One tunic but more than one barcode: evolutionary insights from dynamic mitochondrial DNA in Salpa thompsoni (Tunicata: Salpida)

Goodall-Copestake, William P.. 2017 One tunic but more than one barcode: evolutionary insights from dynamic mitochondrial DNA in Salpa thompsoni (Tunicata: Salpida). Biological Journal of the Linnean Society, 120 (3). 637-648. https://doi.org/10.1111/bij.12915

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This article has been accepted for publication and will appear in a revised form in Zoological Journal of the Linnean Society, published by Wiley. Copyright Linnean Society of London.
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Abstract/Summary

The DNA barcode within the mitochondrial cox1 gene is typically used to assess the identity and diversity of animals under the assumption that individuals contain a single form of this genetic marker. This study reports on a novel exception from the pelagic tunicate Salpa thompsoni Foxton. Oozoids caught off South Georgia and the Antarctic Peninsula generated barcodes consisting of a single prominent DNA sequence with some additional, subtler signals of intra-individual variation. Further investigation revealed this was due to duplicated and/or minicircular DNAs. These could not simply be explained as artefacts or nuclear copies of mitochondrial DNA, but provided evidence for heteroplasmy arising from a dynamic mitochondrial genome. Genetic variation of this sort may allow S. thompsoni to ecologically benefit from asexually driven population blooms without incurring the genetic cost of an excessive mutational load. Analysis of the prominent barcode sequence data yielded low haplotype (h < 0.61) and nucleotide (π < 0.0014) diversities, and no evidence for genetic structure between sampling locations as assessed using analysis of molecular variance. These results are consistent with the impact of population blooms and the mixing effect of Southern Ocean currents on S. thompsoni genetic diversity.

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1111/bij.12915
Programmes: BAS Programmes > BAS Programmes 2015 > Ecosystems
ISSN: 0962-1083
Additional Keywords: Antarctica, cox1, cytochrome c oxidase subunitI, heteroplasmy, minicircles, recombination, salps, sublimons, tunicate
Date made live: 01 Nov 2016 14:14 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/509161

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