Data from: Fin whale (Balaenoptera physalus) mitogenomics: a cautionary tale of defining sub-species from mitochondrial sequence monophyly

The advent of massive parallel sequencing technologies has resulted in an
increase of studies based upon complete mitochondrial genome DNA sequences
that revisit the taxonomic status within and among species. Spatially
distinct monophyly in such mitogenomic genealogies, i.e., the sharing of a
recent common ancestor among con-specific samples collected in the same
region has been viewed as evidence for subspecies. Several recent studies
in cetaceans have employed this criterion to suggest subsequent
intraspecific taxonomic revisions. We reason that employing
intra-specific, spatially distinct monophyly at non-recombining, clonally
inherited genomes is an unsatisfactory criterion for defining subspecies
based upon theoretical (genetic drift) and practical (sampling effort)
arguments. This point was illustrated by a re-analysis of a global
mitogenomic assessment of fin whales, Balaenoptera physalus spp.,
published by Archer et al. (2013), which proposed to further subdivide the
Northern Hemisphere fin whale subspecies, B. p. physalus. The proposed
revision was based upon the detection of spatially distinct monophyly
among North Atlantic and North Pacific fin whales in a genealogy based
upon complete mitochondrial genome DNA sequences. The extended analysis
conducted in this study (1,676 mitochondrial control region, 162 complete
mitochondrial genome DNA sequences and 20 microsatellite loci genotyped in
358 samples) revealed that the apparent monophyly among North Atlantic fin
whales reported by Archer et al. (2013) to be due to low sample sizes. In
conclusion, defining sub-species from monophyly (i.e., the absence of
para- or polyphyly) can lead to erroneous conclusions due to relatively
“trivial” aspects, such as sampling. Basic population genetic processes
(i.e., genetic drift and migration) also affect the time to the most
recent common ancestor and hence the probability that individuals in a
sample are monophyletic.