Mitogenomic Phylogenetics of Fin Whales (Balaenoptera physalus spp.): Genetic Evidence for Revision of Subspecies

Abstract

There are three described subspecies of fin whales (Balaenoptera physalus): B. p. physalus Linnaeus, 1758 in the Northern Hemisphere, B. p. quoyi Fischer, 1829 in the Southern Hemisphere, and a recently described pygmy form, B. p. patachonica Burmeister, 1865. The discrete distribution in the North Pacific and North Atlantic raises the question of whether a single Northern Hemisphere subspecies is valid. We assess phylogenetic patterns using ∼16 K base pairs of the complete mitogenome for 154 fin whales from the North Pacific, North Atlantic - including the Mediterranean Sea - and Southern Hemisphere. A Bayesian tree of the resulting 136 haplotypes revealed several well-supported clades representing each ocean basin, with no haplotypes shared among ocean basins. The North Atlantic haplotypes (n = 12) form a sister clade to those from the Southern Hemisphere (n = 42). The estimated time to most recent common ancestor (TMRCA) for this Atlantic/Southern Hemisphere clade and 81 of the 97 samples from the North Pacific was approximately 2 Ma. 14 of the remaining North Pacific samples formed a well-supported clade within the Southern Hemisphere. The TMRCA for this node suggests that at least one female from the Southern Hemisphere immigrated to the North Pacific approximately 0.37 Ma. These results provide strong evidence that North Pacific and North Atlantic fin whales should not be considered the same subspecies, and suggest the need for revision of the global taxonomy of the species.

Demography or selection on linked cultural traits or genes? Investigating the driver of low mtDNA diversity in the sperm whale using complementary mitochondrial and nuclear genome analyses

“…Among globally‐distributed large whales, most baleen whales exhibit high mtDNA diversity relative to toothed whales and are divided into multiple subspecies and genetically distinct populations (e.g., fin, humpback, grey and blue whales; Archer et al., ; Baker et al., ; Jackson et al., ; Lang et al., ; Leduc et al., ). Among toothed whales, however, unusually low mitochondrial DNA (mtDNA) diversity in some of the social odontocetes (e.g., sperm, pilot, killer and false‐killer whales; Alexander et al., , ; Hoelzel et al., ; Martien et al., ; Van Cise et al., ) has limited power to infer population structure, phylogeography and historical demography using traditional genetic tools.…”

“…In other species with low levels of CR diversity, complete mitochondrial genome (mitogenome) sequences have been used to detect phylogeographic structure and estimate divergence times and historical demography with higher precision (e.g., Archer et al., ; Buddhakosai et al., ; Morin et al., , ; Shamblin et al., ). Several hypotheses have been proposed to explain the extremely low mtDNA diversity in sperm whales, including a population bottleneck (Lyrholm & Gyllensten, ; Lyrholm et al., ), low mutation rate (Lyrholm et al., ; Whitehead, ), stochastic variation in maternal lineage survival (Amos, ; Tiedemann & Milinkovitch, ), cultural hitchhiking (Whitehead, , ; Whitehead, Vachon, & Frasier, ) and selective constraints on CR sequences that limit accumulation of variation and lead to saturation of sites free to vary (Alexander et al., ).…”

Distribution and Demographics of Marine Mammals in SOCAL Through Photo-Identification, Genetics, and Satellite Telemetry

“…However, these populations tend to occur in more geographically isolated seas, such as the Gulf of California and the Mediterranean Sea (Tershy et al 1993, Bérubé et al 2002, so the presence of a distinct population within the continuous waters that Bp use along the west coast seems more unusual. Genetic data has also suggested a population boundary may exist for fin whales in Southern California (Archer et al 2013).…”

Population Structure and Dynamics

“…Archer et al 2013). The complete genome of the California sea lion(Edwards et al 2013), minke whale(Yim et al 2014), baji (Lipotes vexillifer)(Zhou et al 2013), and the partial genome of the bottlenose dolphin have been sequenced, and the genomes of other marine mammal species (e.g., finless porpoise, Neophocaena phocaenoides) are in the process of being sequenced.…”

“…The complete genome of the California sea lion(Edwards et al 2013), minke whale(Yim et al 2014), baji (Lipotes vexillifer)(Zhou et al 2013), and the partial genome of the bottlenose dolphin have been sequenced, and the genomes of other marine mammal species (e.g., finless porpoise, Neophocaena phocaenoides) are in the process of being sequenced. The applications of genomic studies are highly varied and include population genetics and speciation that define population structure (e.g.,Morin et al 2010;Archer et al 2013); explore evolution and adaptation (i.e., selection studies,Nery et al 2013;Zhou et al 2013;Welch et al 2014); nervous system genes(McGowen et al 2011(McGowen et al , 2012; stress-resistance genes(Yim et al 2014); and extend to conservation genetics, including gene function in the health of marine mammals and in the diagnosis of disease (e.g.,Hoffman et al 2013). The efficiency and cost effectiveness of genomic analyses is likely going to result in these techniques leading to much greater genomic coverage and phylogeographic resolution than has been possible previously among marine mammals(Hancock-Hanser et al 2013).…”