Correction to: First monk seal from the Southern Hemisphere rewrites the evolutionary history of true seals

Proc. R. Soc. B287, 20202318. (Published 11 November 2020). (doi:10.1098/rspb.2020.2318)

Since the publication of our original paper, three errors in the total evidence phylogenetic analysis have been brought to our attention. These do not affect our main conclusions, but must be rectified to avoid potential downstream effects on studies building on our results.

• 1. The cytb gene [1] for Neomonachus tropicalis we obtained from Genbank (JX853967) actually represents Monachus monachus (S. J. Gaughran 2021, personal communication), which probably explains the unusual placement of N. tropicalis in our original analysis. A replacement record (JX170689) was uploaded to Genbank, but the original record was never taken down. Here, we instead use the replacement gene.
• 2. An alignment error, resulting from the circular nature of mitochondrial DNA, meant that the mitogenomes of Halichoerus grypus and Phoca vitulina were misaligned relative to the remaining species. To rectify this, we first replaced the mitochondrial sequence originally used for the outgroup Arctocephalus forsteri (AF513820, 15 413 base pairs) with a more complete alternative (KT693377, 16 572 bp) [2]. We then repeated our alignment in Aliview [3] using the MUSCLE algorithm [4], ensuring that the ‘start’ and ‘end’ points of the mitogenomes of Halichoerus grypus and Phoca vitulina were in the correct position. Species for which no entire mitogenome was available were aligned with more complete sequences using the FFT-NS-2 method in MAFFT v. 7 [5]. This was followed by the adjustment of poorly aligned blocks and the deletion of gap-only columns. Six hundred and thirty-seven base pairs from non-protein-coding region 10 were excluded as alignment for this section remained poor after these steps. Finally, we converted all terminal gaps to ‘?’ and re-analysed the mitochondrial data in PartitionFinder2 [6] on the Cipres Science Gateway [7]. Model selection was based on AICc, branch lengths were linked and the partition scheme set to ‘greedy’. See revised datasets for details.
• 3. For the ingroup priors, we erroneously treated the 95% quantile values for the offset exponential distributions as the mean, which risked overestimating the age of the basal nodes. We rectified this error by generating revised mean estimates in BEAUTi 2 [8]; we then repeated our phylogenetic analysis as outlined in our original paper.

Our corrected phylogeny shows slightly younger divergence times and some topological differences. Of note, the positions of Halichoerus grypus, Neomonachus tropicalis and Ommatophoca rossii are now consistent with previous molecular hypotheses [1,9–11]: H. grypus is sister to Pusa, Neomonachus is monophyletic and Ommatophoca is the earliest diverging lobodontin. DIVALIKE+J remains the best-supported biogeographical model. Despite some minor changes to the estimated ancestral ranges of some nodes, our main conclusions remain the same (figure 1). In particular, this includes (i) the identification of Eomonachus as the first monk seal from the Southern Hemisphere, (ii) the southern origin of the branch uniting monk seals and other crown monachines and (iii) the surprising frequency (10 times under our revised model) with which true seals have crossed the equator in the course of their evolution.

Figure 1.

Total evidence phylogeny (maximum clade credibility tree) of Phocidae, with DIVALIKE+J ancestral range estimation. Black lines indicate outgroup lineages, coloured lines a simplified representation of the DIVALIKE+J model, and dots on branches ancestors resolved by the fossilized birth–death model. Numbers at nodes and ancestors represent posterior probabilities above 0.5. Daggers indicate extinct species. Middle Miocene Climatic Optimum range from Song et al. [12]. Biogeographic node labels are only shown where the reconstructed range differs from the previous (basal) node. Ancestral range estimations with a probability below 50% are indicated with an asterisk. Posterior tree output and full biogeographic models are available from Figshare. (Online version in colour).