Nuclear and Mitochondrial Patterns of Population Structure in North Pacific False Killer Whales (Pseudorca crassidens)

Abstract

False killer whales (Pseudorca crassidens) are large delphinids typically found in deep water far offshore. However, in the Hawaiian Archipelago, there are 2 resident island-associated populations of false killer whales, one in the waters around the main Hawaiian Islands (MHI) and one in the waters around the Northwestern Hawaiian Islands (NWHI). We use mitochondrial DNA (mtDNA) control region sequences and genotypes from 16 nuclear DNA (nucDNA) microsatellite loci from 206 individuals to examine levels of differentiation among the 2 island-associated populations and offshore animals from the central and eastern North Pacific. Both mtDNA and nucDNA exhibit highly significant differentiation between populations, confirming limited gene flow in both sexes. The mtDNA haplotypes exhibit a strong pattern of phylogeographic concordance, with island-associated populations sharing 3 closely related haplotypes not found elsewhere in the Pacific. However, nucDNA data suggest that NWHI animals are at least as differentiated from MHI animals as they are from offshore animals. The patterns of differentiation revealed by the 2 marker types suggest that the island-associated false killer whale populations likely share a common colonization history, but have limited contemporary gene flow.

The incidence of bent dorsal fins in free‐ranging cetaceans

“…for P. crassidens from Hawaii, see Martien et al. ). The age class was based on the comparison of the relative size of individuals using photographs featuring multiple individuals as well as on field observations.…”

False killer whales and fisheries interactions in Hawaiian waters: Evidence for sex bias and variation among populations and social groups

“…These include sighting history of individuals, mitochondrial haplotypes from genetic samples obtained from some groups (Martien et al . ), the location where photographs were obtained, the proportion of individuals within an encounter that were already in the catalog, and satellite tag data (Baird et al . , ).…”

“…, , ; Martien et al . ). For the pelagic population, estimates of mortality and serious injury from interactions with the Hawai‘i‐based tuna longline fishery exceed the population's Potential Biological Removal (PBR) level (Carretta et al .…”

“…), and based on genetic analyses represent extended groups of related individuals (Martien et al . ). Satellite tagging data from two of the three social clusters (Clusters 1 and 3) indicate that, while their ranges largely overlap, each cluster has different high density areas (Baird et al .…”

Demography or selection on linked cultural traits or genes? Investigating the driver of low mtDNA diversity in the sperm whale using complementary mitochondrial and nuclear genome analyses

“…Among globally‐distributed large whales, most baleen whales exhibit high mtDNA diversity relative to toothed whales and are divided into multiple subspecies and genetically distinct populations (e.g., fin, humpback, grey and blue whales; Archer et al., ; Baker et al., ; Jackson et al., ; Lang et al., ; Leduc et al., ). Among toothed whales, however, unusually low mitochondrial DNA (mtDNA) diversity in some of the social odontocetes (e.g., sperm, pilot, killer and false‐killer whales; Alexander et al., , ; Hoelzel et al., ; Martien et al., ; Van Cise et al., ) has limited power to infer population structure, phylogeography and historical demography using traditional genetic tools. The sperm whale ( Physeter macrocephalus ) is particularly enigmatic in this respect, as it is one of the most cosmopolitan and abundant of the large odontocetes, and known to move over large ranges of up to thousands of kilometres over annual or longer time periods (Mizroch & Rice, ; Steiner et al., ; Straley et al., ), yet it exhibits low mtDNA diversity and evidence of female philopatry (Alexander et al., ; Lyrholm & Gyllensten, ; Lyrholm, Leimar, Johanneson, & Gyllensten, ; Mesnick et al., ).…”