The Shyest Blackfish: The Global Phylogeography of the Pygmy Killer Whale ( Feresa attenuata ) Suggests Considerable Population Structure and an Unrecognized Taxon

Abstract

Pygmy killer whales ( Feresa attenuata ) are a poorly studied, globally‐distributed species found in pelagic waters and around oceanic islands. They are naturally rare, making them difficult to study. Reports indicate that they are highly vulnerable to artisanal fisheries bycatch in some areas. To investigate the global genetic structure of these animals, we sequenced a 671 bp section of the mitochondrial control region of 89 globally distributed samples. Overall haplotypic diversity is h = 0.94 ± 0.020, while nucleotide diversity is π = 0.0088 ± 0.0035. We found statistically significant genetic differentiation between all pairs of strata ( F ST from 0.115 to 0.381, Φ ST from −0.01 to 0.876) and evidence of phylogeographic structure. The most striking result is the deep divergence between samples from the Sulu Sea ( n = 3), which are separated from all other pygmy killer whale haplotypes by four transitions and one indel. The net nucleotide divergence between the Sulu Sea haplotypes and all others ( d A = 0.013) is higher than that between many recognized cetacean subspecies and tenfold higher than that between the Pacific and western North Atlantic samples. A Bayesian phylogenetic tree indicates that the divergence between the Sulu Sea and the rest of the samples is comparable to that between other sister species from the same subfamily, suggesting the presence of an unrecognized pygmy killer whale taxon. Further study, including more extensive sampling, is needed in order to better understand and conserve the genetic diversity of this poorly‐understood species.

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