title: Sperm whale population structure in the eastern and central North Pacific inferred by the use of single-nucleotide polymorphisms, microsatellites and mitochondrial DNA.
abstract: We use mitochondrial DNA (mtDNA) (400 bp), six microsatellites and 36 single-nucleotide polymorphisms (SNPs), 20 of which were linked, to investigate population structure of sperm whales (Physeter macrocephalus) in the eastern and central North Pacific. SNP markers, reproducible across technologies and laboratories, are ideal for long-term studies of globally distributed species such as sperm whales, a species of conservation concern because of both historical and contemporary impacts. We estimate genetic differentiation among three strata in the temperate to tropical waters where females are found: California Current, Hawai`i and the eastern tropical Pacific. We then consider how males on sub-Arctic foraging grounds assign to these strata. The California Current stratum was differentiated from both the other strata (P < 0.05) for mtDNA, microsatellites and SNPs, suggesting that the region supports a demographically independent population and providing the first indication that males may exhibit reproductive philopatry. Comparisons between the Hawai`i stratum and the eastern tropical Pacific stratum are not conclusive at this time. Comparisons with Alaska males were statistically significant, or nearly so, from all three strata and individuals showed mixed assignment to, and few exclusions from, the three potential source strata, suggesting widespread origin of males on sub-Arctic feeding grounds. We show that SNPs have sufficient power to detect population structure even when genetic differentiation is low. There is a need for better analytical methods for SNPs, especially when linked SNPs are used, but SNPs appear to be a valuable marker for long-term studies of globally dispersed and highly mobile species.
authors.affiliation: Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA 92037, USA. sarah.mesnick@noaa.gov
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Mesnick
authors.forename: Barbara L
authors.initials: BL
authors.lastname: Taylor
authors.forename: Frederick I
authors.initials: FI
authors.lastname: Archer
authors.forename: Karen K
authors.initials: KK
authors.lastname: Martien
authors.forename: Sergio Escorza
authors.initials: SE
authors.lastname: Treviño
authors.forename: Brittany L
authors.initials: BL
authors.lastname: Hancock-Hanser
authors.forename: Sandra Carolina
authors.initials: SC
authors.lastname: Moreno Medina
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Pease
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Robertson
authors.forename: Janice M
authors.initials: JM
authors.lastname: Straley
authors.forename: Robin W
authors.initials: RW
authors.lastname: Baird
authors.forename: John
authors.initials: J
authors.lastname: Calambokidis
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Schorr
authors.forename: Paul
authors.initials: P
authors.lastname: Wade
authors.forename: Vladimir
authors.initials: V
authors.lastname: Burkanov
authors.forename: Chris R
authors.initials: CR
authors.lastname: Lunsford
authors.forename: Luke
authors.initials: L
authors.lastname: Rendell
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Morin
mesh_terms: D025041:Animal Migration; D000818:Animals; D004272:DNA, Mitochondrial / Q000737:chemistry*; D005260:Female; D005843:Geography; D008297:Male; D018895:Microsatellite Repeats; D020641:Polymorphism, Single Nucleotide; D011157:Population Dynamics; D012919:Social Behavior; D050661:Sperm Whale / Q000235:genetics* / Q000502:physiology
chemical_list: D004272:DNA, Mitochondrial