Mitochondrial DNA sequence data reveal the origins of postglacial marine macroalgal flora in the Northwest Atlantic
Trevor T. Bringloe*, Gary W. Saunders
*Corresponding author: trevor.bringloe(at)unb.ca
October 25, 2018: Substantial corrections have been made throughout the article.
The time estimates in our study should have been double those originally reported. This is owing to a calculation error when estimating the COI-5P substitution rate in brown macroalgae. The F84 distance calculated between Fucus spiralis Linnaeus and Ascophyllum nodosum (Linnaeus) Le Jolis should have been divided by two in the process of calculating the substitution rate, as we are interested in the amount of change in a given lineage upon the moment of divergence (i.e. half the genetic distance, not the total sum of change between the two lineages). In failing to do this we inadvertently used sequence divergence, but the program we used to scale isolation time estimates, IMa2, requires substitution rates (Hey 2010). As such, our reported isolation times in brown macroalgae are corrected by doubling the values. Upon investigating the literature further, we also uncovered that our COI-5P clock estimates for red macroalgae were impacted. We used the isolation times reported by Li et al. (2015) to calculate the COI-5P clock rate for red algae, but their isolation times were similarly estimated in IMa2 using sequence divergence rather than substitution rates. Consequently, our red algal isolation times also need to be doubled. In light of this change, we have updated some figures (Fig. 2 & S19) and tables (Tables 1 & S3), the methods text, and the values at several points in the text.
The above corrections do not change any of the individual biogeographic interpretations for each species, and as such, do not change the fundamental conclusions of the study. A significant proportion of the Northwest Atlantic marine flora is distinct from populations in the Northeast, suggesting the Northwest flora largely survived the Last Glacial Maximum.