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.

Swarms of diversity at the gene cox1 in Antarctic krill

“…The nucleotide diversity of cox1 was also consistently high within all krill swarms (p ¼ 0.010275-0.011537, Table 1). To our knowledge, only one previous study has found consistently high nucleotide diversity across populations (Cyamus ovalis; Kaliszewska et al, 2005), whereas several studies have reported much higher nucleotide diversity for individual populations, usually from samples of cryptic species or the products of incipient speciation followed by secondary contact (for example, brittle stars, Muths et al, 2009). The high Antarctic krill diversity values reported in this study are unlikely to be an artefact of sequencing error or the presence of numts, as our sequence reproducibility assessment and tests for numts effectively ruled out these possibilities.…”

“…To model this variability, we followed the rationale and approach of Kaliszewska et al (2005), by generating a data partition from each alignment containing all third position sites augmented by the variable sites at the first position (data partitions A* and B*). DNA sequence variability in these data partitions was then evaluated for nucleotide homogeneity using tetrahedral plots and matched-pairs tests for symmetry (Ababneh et al, 2006) implemented in the software SeqVis v.1.3 (Ho et al, 2006).…”

Occurrence of whale barnacles in Nerja Cave (Málaga, southern Spain): Indirect evidence of whale consumption by humans in the Upper Magdalenian

“…Three species of right whale species are known (Rosenbaum et al, 2000;Gaines et al, 2005;Kaliszewska et al, 2005), including Eubalaena australis (Desmoulins, 1822), the southern right whale, and Eubalaena glacialis (Müller, 1776), the North Atlantic right whale.…”

Life history told by a whale-louse: a possible interaction of a southern right whale Eubalaena australis calf with humpback whales Megaptera novaeangliae

“…Right whales are known to host three species of cyamids: Cyamus ovalis Roussel de Vauzème, 1834, Cyamus erraticus Roussel de Vauzème, 1834, and Cyamus gracilis Roussel de Vauzème, 1834 [15][16][17]. Each species has a different spatial distribution on the right whale's body [12,15,18].…”