Are the southern feeding group of eastern Pacific gray whales a maternal genetic isolate?


RAMAKRISHNAN, U.; R. G. LEDUC; J. DARLING; B. L. TAYLOR; P. GEARIN; M. GOSHO; J. CALAMBOKIDIS; R. L. BROWNELL, JR.; J. HYDE and T. E. STEEVES. 2001. Are the southern feeding group of eastern Pacific gray whales a maternal genetic isolate? Unpublished paper to the IWC Scientific Committee. London, July 2001. (SC/53/SD8).


The managment of eastern Pacific gray whales that feed in southern waters depends on how individuals are recruited into this feeding group, which remains uncertain. Separate management is needed if recruitment is internal with mothers bringing their calves to their life-long feeding grounds. Such exclusively internal recruitment would make the southern feeding group a maternal genetic isolate. We simulate mitochondrial haplotype diversity for the southern feeding group under the assumption that it is a maternal genetic isolate and compare our results to empirical genetic data from the southern feeding group. We find that the haplotypic diversity and number of haplotypes are higher than predicted for a maternal isolate by the simulations. Other empirical data are also inconsistent with maternal genetic isolation. Comparisons with the genetics of other small populations of large whales show that both the number of haplotypes and haplotypic diversity are much higher for the southern feeding group. Also, genetic analysis shows that the sex ratio is significantly male biased, which may not be consistent with a closed population. Thus, we can reject the hypothesis that the southern feeding group is a maternal isolate. Other hypotheses remain and we discuss future directions.

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