Population structure of nuclear and mitochondrial DNA variation among humpback whales in the North Pacific |
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| Authors: | C S BAKER L MEDRANO-GONZALEZ J CALAMBOKIDIS A PERRY F PICHLER H ROSENBAUM J M STRALEY J URBAN-RAMIREZ M YAMAGUCHI & O VON ZIEGESAR |
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| Institution: | School of Biological Sciences, University of Auckland, PO Box 92019, Auckland, New Zealand,,;Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Mexico City 04510 D.F. Mexico,,;Cascadia Research Collective, Waterstreet Building, West Fourth Avenue, Olympia, WA 98501 USA,,;American Museum of Natural History, Central Park West at 79th Street, New York, NY, 10024–5192 USA,,;University of Alaska South-east,1332 Seward Avenue, Sitka, Alaska 99835 USA,,;Departamento de Biologia Marina, Universidad Autonoma de Baja California Sur, Apdo. Postal 19-B, 23081, La Paz, B.C.S. Mexico,,;Ogasawara Marine Center, Byobudani, Chichijima, Ogasawara-mura, Tokyo, 100–21, Japan,,;North Gulf Oceanic Society, PO Box 15244, Homer, Alaska 99603 USA |
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| Abstract: | The population structure of variation in a nuclear actin intron and the control region of mitochondrial DNA is described for humpback whales from eight regions in the North Pacific Ocean: central California, Baja Peninsula, nearshore Mexico (Bahia Banderas), offshore Mexico (Socorro Island), southeastern Alaska, central Alaska (Prince Williams Sound), Hawaii and Japan (Ogasawara Islands). Primary mtDNA haplotypes and intron alleles were identified using selected restriction fragment length polymorphisms of target sequences amplified by the polymerase chain reaction (PCR–RFLP). There was little evidence of heterogeneity in the frequencies of mtDNA haplotypes or actin intron alleles due to the year or sex composition of the sample. However, frequencies of four mtDNA haplotypes showed marked regional differences in their distributions (ΦST = 0.277; P < 0.001; n = 205 individuals) while the two alleles showed significant, but less marked, regional differences (ΦST = 0.033; P < 0.013; n = 400 chromosomes). An hierarchical analysis of variance in frequencies of haplotypes and alleles supported the grouping of six regions into a central and eastern stock with further partitioning of variance among regions within stocks for haplotypes but not for alleles. Based on available genetic and demographic evidence, the southeastern Alaska and central California feeding grounds were selected for additional analyses of nuclear differentiation using allelic variation at four microsatellite loci. All four loci showed significant differences in allele frequencies (overall FST = 0.043; P < 0.001; average n = 139 chromosomes per locus), indicating at least partial reproductive isolation between the two regions as well as the segregation of mtDNA lineages. Although the two feeding grounds were not panmictic for nuclear or mitochondrial loci, estimates of long-term migration rates suggested that male-mediated gene flow was several-fold greater than female gene flow. These results include and extend the range and sample size of previously published work, providing additional evidence for the significance of genetic management units within oceanic populations of humpback whales. |
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| Keywords: | control region intron microsatellite management stocks gene flow |
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