Contrasting Phylogeographic Patterns Among Northern and Southern Hemisphere Fin Whale Populations With New Data From the Southern Pacific

Mjosé Pérez-Alvarez,Sebastián Kraft,Lorena Viloria-Gómora,Frederick Archer,Jorge Urbán R,Nicolás I Segovia,Maritza Sepúlveda,Rodrigo Moraga,Carlos Olavarría,Guido Pavez,Sergio Nigenda-Morales,Macarena Santos-Carvallo,Elie Poulin

doi:10.3389/fmars.2021.630233

Abstract

Four fin whale sub-species are currently considered valid:Balaenoptera physalus physalusin the North Atlantic,B. p. veliferain the North Pacific,B. p. quoyiandB. p. patachonicain the Southern Hemisphere. The last, not genetically validated, was described as a pygmy-type sub-species, found in low to mid latitudes of the Southern Hemisphere. Genetic analyses across hemispheres show strong phylogeographic structure, yet low geographic coverage in middle latitudes of the Southern Hemisphere impeded an assessment within the area, as well as evaluating the validity ofB. p. patachonica. New mtDNA sequences from the Southeastern Pacific allowed an improved coverage of the species’ distribution. Our phylogenetic analyses showed three main lineages and contrasting phylogeographic patterns between Northern and Southern Hemispheres. Absence of recurrent female mediated gene flow between hemispheres was found; however, rare dispersal events revealing old migrations were noted. The absence of genetic structure suggests the existence of one single taxa within the Southern Hemisphere. Thus, until further evidence supporting this subspecies can be produced, such as genetic, ecological, behavioral, or morphological data, we propose that all fin whales from the Southern Hemisphere, including those from middle latitudes of the Southeastern Pacific belong toB. p. quoyisubspecies. This information is important for the current assessment of fin whales, contributing to the evaluation of the taxonomic classification and the conservation of the species.

Highlights

The fin whale (Balaenoptera physalus) is a widespread mysticete that occurs in all major oceans (Mizroch et al, 1984), in middle and high latitudes (Mackintosh, 1966; Miyashita et al, 1995; Branch and Butterworth, 2001; Reilly et al, 2013) and mainly, but not exclusively, in offshore waters (Edwards et al, 2015)
We evaluate the genetic structure among fin whale populations within the Southern Hemisphere, the existence of two SH subspecies, the degree of genetic structure between North Pacific and Southeastern Pacific populations, and differentiation the Gulf of California (GoC) and the wider North Pacific
The addition of new control region sequences from the waters off of Chile to the global data set of fin whale (Balaenoptera physlaus) sequences has allowed us to contribute new insights to our growing understanding of phylogeographic structure within this species

Summary

Introduction

The fin whale (Balaenoptera physalus) is a widespread mysticete that occurs in all major oceans (Mizroch et al, 1984), in middle and high latitudes (Mackintosh, 1966; Miyashita et al, 1995; Branch and Butterworth, 2001; Reilly et al, 2013) and mainly, but not exclusively, in offshore waters (Edwards et al, 2015). Patachonica (Burmeister, 1865), which are found in the Southern Hemisphere (SH). Quoyi) subspecies was proposed in the mid twentieth century (Tomilin, 1946), primarily based on size differences between fin whales from the Northern Hemisphere (NH) and Antarctic waters. This was later verified by comparisons of body measurements and organ weights of North Atlantic and Antarctic individuals (Lockyer and Waters, 1986). Its distribution was described as being restricted to low to mid-latitudes in the SH, not extending further south than approximately 55◦S, feeding at lower latitudes than most fin whales (Clarke, 2004). Aside from the original description, there has been no further evidence supporting this subspecies

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