title: Population histories of right whales (Cetacea: Eubalaena) inferred from mitochondrial sequence diversities and divergences of their whale lice (Amphipoda: Cyamus).
abstract: Right whales carry large populations of three 'whale lice' (Cyamus ovalis, Cyamus gracilis, Cyamus erraticus) that have no other hosts. We used sequence variation in the mitochondrial COI gene to ask (i) whether cyamid population structures might reveal associations among right whale individuals and subpopulations, (ii) whether the divergences of the three nominally conspecific cyamid species on North Atlantic, North Pacific, and southern right whales (Eubalaena glacialis, Eubalaena japonica, Eubalaena australis) might indicate their times of separation, and (iii) whether the shapes of cyamid gene trees might contain information about changes in the population sizes of right whales. We found high levels of nucleotide diversity but almost no population structure within oceans, indicating large effective population sizes and high rates of transfer between whales and subpopulations. North Atlantic and Southern Ocean populations of all three species are reciprocally monophyletic, and North Pacific C. erraticus is well separated from North Atlantic and southern C. erraticus. Mitochondrial clock calibrations suggest that these divergences occurred around 6 million years ago (Ma), and that the Eubalaena mitochondrial clock is very slow. North Pacific C. ovalis forms a clade inside the southern C. ovalis gene tree, implying that at least one right whale has crossed the equator in the Pacific Ocean within the last 1-2 million years (Myr). Low-frequency polymorphisms are more common than expected under neutrality for populations of constant size, but there is no obvious signal of rapid, interspecifically congruent expansion of the kind that would be expected if North Atlantic or southern right whales had experienced a prolonged population bottleneck within the last 0.5 Myr.
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Zofia A
authors.initials: ZA
authors.lastname: Kaliszewska
authors.forename: Jon
authors.initials: J
authors.lastname: Seger
authors.forename: Victoria J
authors.initials: VJ
authors.lastname: Rowntree
authors.forename: Susan G
authors.initials: SG
authors.lastname: Barco
authors.forename: Rafael
authors.initials: R
authors.lastname: Benegas
authors.forename: Peter B
authors.initials: PB
authors.lastname: Best
authors.forename: Moira W
authors.initials: MW
authors.lastname: Brown
authors.forename: Robert L
authors.initials: RL
authors.lastname: Brownell
authors.forename: Alejandro
authors.initials: A
authors.lastname: Carribero
authors.forename: Robert
authors.initials: R
authors.lastname: Harcourt
authors.forename: Amy R
authors.initials: AR
authors.lastname: Knowlton
authors.forename: Kim
authors.initials: K
authors.lastname: Marshall-Tilas
authors.forename: Nathalie J
authors.initials: NJ
authors.lastname: Patenaude
authors.forename: Mariana
authors.initials: M
authors.lastname: Rivarola
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Schaeff
authors.forename: Mariano
authors.initials: M
authors.lastname: Sironi
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Smith
authors.forename: Tadasu K
authors.initials: TK
authors.lastname: Yamada
mesh_terms: D033304:Amphipoda / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D004272:DNA, Mitochondrial / Q000235:genetics; D019143:Evolution, Molecular; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D006790:Host-Parasite Interactions; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011156:Population Density; D011157:Population Dynamics; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D014907:Whales / Q000469:parasitology*
chemical_list: D017931:DNA Primers; D004272:DNA, Mitochondrial