Genetic analyses on stock structure of fin whales in the Indo Pacific region of the Antarctic feeding grounds
Mutsuo Goto and Mioko Taguchi
The stock structure of fin whales in the Indo Pacific region of the Antarctic feeding grounds was investigated using 478bps mitochondrial (mtDNA) control region sequences and genotypes at sixteen microsatellite loci for a total of 108 genetic samples collected in Areas III-VIW under the JARPA, JARPAII, NEWREP-A and SOWER cruises. The observed haplotype diversity was extremely high (0.993 across all samples) with large number of singletons, and mtDNA diversities represented by haplotype (0.984-1.000) and nucleotide (0.0111-0.0115) diversities were comparable among three sample populations, i.e., POP1 (-70Â°E), POP2 (70Â°E-160Â°E) and POP3 (160Â°E) which were defined based on the genetic analyses without a prior population grouping, i.e., STRUCTURE, PCA and geographic cline of genetic variations. In addition, insignificant departures from Hardy-Weinberg equilibrium and FIS estimates observed in each sample population and across all samples suggested a lack of genetic structure of this species. This was supported by hypothesis tests, i.e., heterogeneity tests and pairwise FST estimates, among the sample populations using both markers. This inference was also consistent with the haplotype network with no distinct clusters of samples corresponding to sampling localities. On the other hand, the geographical cline of FIS estimates gradually shift to the positive in the east of 130Â°E, which implied a mixing of different stocks in the eastern part of the present survey area. Taking this observation together with the findings suggesting a lack of genetic structure of this species, further consideration with a greater number of samples, particularly in Areas I, V and VI, will be needed to conclude the genetic structure of the Antarctic fin whales.