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

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.

Source: Biological Journal of the Linnean Society - October 25, 2016 Category: Research Authors: William P. Goodall ‐Copestake Tags: Research Article Source Type: research