Population structure and species relationships within Right whales (genus Eubalaena) and gray whales (genus Eschrichtius) based on molecular analysis and use of historical samples

• Main Author: Gaines, Carl Amos
• Format: Text
• Language: English
• Published: Fordham Research Commons 2008
• Subjects: Molecular biology|Oceanography; Pacific; North Atlantic
• Online Access: https://research.library.fordham.edu/dissertations/AAI3310417

Management effort directed towards modern cetacean populations are dependent on a strong estimation of current and historical estimations of molecular diversity and population sizes. Extant and extinct populations of Right whales (genus Eubalaena) and gray whales (genus Eschrichtius ) were characterized through the use of molecular markers. For right whales, species boundaries and evolutionary relationships across ocean basins were examined using DNA sequence data from 13 nuclear loci in addition to the mitochondrial (mtDNA) control region. Diagnostic characters among the nuclear and mitochondrial markers in addition to the monophyly of each group supports the hypothesis of three genetically distinct species, despite the lack of any previously documented diagnostic morphological characters. The study also demonstrated the need for the use of numerous loci when examining relationships of closely-related species as none of the nuclear markers examined independently would have provided enough support to produce a well-resolved phylogenetic history for the group. The data was combined into a total analysis and produced a strongly supported phylogenetic tree. Evolutionary relationships of right whales as well as changes in genetic diversity through time were also examined within an ocean basin using historical samples of a possibly extinct population of right whales. Of 20 historical eastern North Atlantic specimens, six were characterized by five mtDNA haplotypes previously unknown from right whales. Haplotype D, the most common haplotype among the extant western stock was the most common among the historical eastern samples. Analysis of mtDNA sequence data does not support the hypothesis that North Atlantic right whales consist of more than one distinct evolutionary lineage. However, the discovery of numerous haplotypes that are now likely extinct, suggests that North Atlantic right whales have lost a significant amount of genetic diversity since the onset of modern commercial whaling. For gray whales, archaeological bones from the North Atlantic, purported to be gray whale specimens, were characterized through the examination mtDNA control region sequence data. Analysis of the molecular data strongly supports the hypothesis that gray whales inhabited the North Atlantic as recently as 300 years ago. Of the three samples studied, two haplotypes were discovered. Both of these haplotypes are unknown among modern North Pacific gray whales, however there is no evidence to suggest the North Atlantic population consisted of a genetically distinct species. The North Atlantic haplotypes do fall within the modern haplogroup suggesting a close relationship to the North Pacific populations. While there is no evidence to suggest that North Atlantic gray whales represented a distinct species, further research is needed to determine if this group was a distinct population(s) or if they were part of the same population as modern gray whales.