Progress 06/01/03 to 09/30/04
Outputs
As a case study for better understanding the utility of both genetic and acoustic variation for stock identification in vocally active, endangered baleen whale species, we characterized population subdivisions among fin whales (Balaenoptera physalus) in the North Pacific and North Atlantic through comparison of genetic and acoustic diversification within these ocean basins. To directly estimate male-mediated gene flow, we isolated Y chromosome markers from fin whales using Representational Difference Analysis (RDA). Gene flow estimated from Y-specific markers was compared directly to female-mediated gene flow estimated from mitochondrial DNA (mtDNA) to determine whether fin whale dispersal is 'sex-biased'. Geographic variation in songs produced by male fin whales in the North Pacific and North Atlantic Oceans was quantified for comparison with estimates of genetic distance based on Y chromosome DNA, mtDNA, and autosomal microsatellite loci (aDNA) to identify particular
signal features that are concordant with patterns of gene flow mediated by male fin whales, female fin whales or both. Sampled fin whale Y chromosome sequences showed seven times less nucleotide diversity than observed at the mitochondrial control region. Comparisons among multiple estimates of genetic differentiation derived from yDNA, mtDNA and aDNA support the hypothesis that, on an evolutionary timescale, male fin whales disperse more widely than females. In addition, genetic distances based on maternally, paternally, and biparentally inherited DNA show trends toward negative correlations with acoustic distance, although only significantly when the influence of geographic distance is removed. Such patterns provide preliminary evidence of character displacement between regions in which singers are sympatric, either physically, or acoustically. More generally, results of integrating data types suggest that, for the most part, significant acoustic differentiation among regions is not
reflected in estimates of genetic divergence. Patterns of male acoustic dissimilarity may therefore represent discontinuities in fin whale movement and/or social behavior that either are too recent to be reflected in the evolutionary history of genomes, or vary over relatively short periods of time (i.e. decades). Finally, the utility of the Y chromosome markers isolated from fin whales for assessing male-mediated gene flow among stocks in closely related mysticete species was addressed, and a genealogy based on Y chromosome sequences was compared to previously published phylogenetic relationships among baleen whales. Genealogies derived from yDNA and mtDNA showed significant differences, particularly in the placement of minke whales and grey whales. Both data sets showed strong support for humpbacks and fin whales (representing two different genera) as sister taxa, calling into question a role for hybridization and/or introgression among the rorqual species in generating
inconsistencies among phylogenetic analyses. Results of this research were recently published as Leila Hatch's doctoral dissertation, and are currently being prepared for publication in scientific journals.
Impacts
Information on genetic relationships among whales from different geographic areas provides an important framework for effective management of these endangered species. In this study, we used both molecular markers and quantitative measurements of whale song to define relatedness and gene flow among fin whales (Balaenoptera physalus) in the North Pacific and North Atlantic. These data allow us to assess the utility of genetic and acoustic variation for identifying local populations or 'stocks' of vocally active baleen whales.
Publications
- Hatch, L. T. 2004. Male genes and male song: integrating genetic and acoustic data in defining fin whale, Balaenoptera physalus, management units. Doctoral Dissertation, Cornell University, Ithaca, NY.
- Hatch, L. T. and Clark, C. W. 2004. Fin whale genes and song: An integrated approach to designing management units. Report of the Scientific Committee of the International Whaling Commission's 56th Annual Meeting, SC/56/SD6.
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Progress 01/01/03 to 12/31/03
Outputs
We proposed to develop Y chromosome-specific markers for endangered fin whales to estimate male-mediated gene flow among and within the North Atlantic and North Pacific populations. To date, a geographically diverse sample of male fin whales has been genotyped for a total of 8 loci on the Y chromosome, as well as 5 autosomal nuclear loci and 1 mitochondrial locus. Estimates of gene flow derived from males, females and both genders were compared. Males from an additional eight species of baleen whales have also been genotyped for Y-specific and mitochondrial loci, and maternally and paternally derived phylogenies of the baleen whale clade were compared. Finally, fin whale song from 11 geographic regions in the North Pacific and North Atlantic have been sampled and analyzed for differentiation among regions using a library of acoustic characters. Currently, analysis comparing acoustic and genetic measures of population structure among fin whales is in progress. Results
are being drafted for publication.
Impacts
Information on genetic relationships among whales from different geographic areas provides an important framework for effective management of these endangered species. Here, we have used both molecular markers on the Y chromosome and quantitative measurements of whale song to define relatedness and gene flow among fin whales (Balaenoptera physalus) in the North Pacific and North Atlantic. These data allow us to assess the utility of genetic and acoustic variation for identifying local populations or 'stocks' of vocally active baleen whales.
Publications
- No publications reported this period
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