Pygmy killer whales (Feresa attenuata) have historically been a poorly studied species. They are typically found in the open ocean as well as around oceanic islands. However, they are naturally rare, cryptic, and often elusive, making them difficult to sample. Photo-identification and satellite telemetry data suggest the existence of an island-associated population around the main Hawaiian Islands. There are also reports that they are highly vulnerable to artisanal fisheries bycatch in some areas. Beyond that, little is known about the life history and population structure of this species. To investigate the global genetic structure of these animals, we sequenced a 960 bp section of the mitochondrial control region of 57 globally distributed samples. Overall haplotypic diversity is h=0.91 ± 0.020, while nucleotide diversity is Ï=0.65 ± 0.35%. We detected strong genetic differentiation (Fst = 0.42, p-value < 0.001, Φst= 0.58, p-value <0.001) between Hawai’i (n=20) and the Eastern Tropical Pacific (ETP; n=12), the only two areas with high enough sample sizes to allow comparison. Our results suggest very little gene flow between these two regions. A global median joining network indicates strong phylogeographic structure, with all haplotypes from the ETP being closely related to each other in a cluster distinct from all other samples. The most striking result is that the animals from the Philippines, represented by two haplotypes, appear to be very different from all other samples. We identified five fixed nucleotide differences between the Philippines samples and all other pygmy killer whales. Furthermore, the net nucleotide divergence between Philippines animals and the other animals (dA = 0.009) is higher than that between many recognized cetacean subspecies. The population differentiation among pygmy killer whales appears to be sufficient to warrant continued genetic study, especially given that information about this species is sparse, and that their conservation status is unknown.
Citation:
Hancock-Hanser, Brittany L., K. M. Robertson, R. W. Baird, K. K. Martien. 2015. Examining the global phylogeography of a little known species: the pygmy killer whale (Feresa attenuata). Abstract (Proceedings) 21st Biennial Conference on the Biology of Marine Mammals, San Francisco, California, December 14-18, 2015.