Publication Date:
2022-05-25
Description:
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute Of Technology and the Woods Hole Oceanographic Institution May 1994
Description:
I sequenced mitochondrial DNA (mtDNA) from 59 long-finned pilot whales
(Globicephala melas) that stranded on the coasts of Cape Cod, Newfoundland, Nova
Scotia, Scotland, and England or were caught by commercial fisheries operating in the
western North Atlantic, to determine if there is more than one genetic stock in the North
Atlantic. Samples from 11 Atlantic and 2 Pacific short-finned pilot whales (G.
macrorhynchus) and 11 bottlenose dolphins (Tursiops truncatus) were also analyzed.
Sequences were obtained from 400-bp of the D-loop, a non-coding region involved in
replication, and from 303-bp of the protein gene coding for cytochrome b.
The D-loop sequences determined from 55 of the long-finned pilot whales were
completely identical. Only the 2 sequences from Canadian whales showed some
variability, differing from the other sequence by 0.25 - 0.50% (pairwise sequence
divergence). All of the Atlantic short-finned pilot whales had identical D-loop
sequences, and this sequence differed from the long-finned pilot whale sequences by 3.25
- 3.75%. The two Pacific short-finned pilot whale sequences differed from each other
by 0.25%, from the Atlantic short-finned pilot whale sequence by 0.25 - 0.50%, and from
the long-finned pilot whale sequences by 2.75 - 3.50%. D-loop nucleotide diversity in
long-finned pilot whales was 0.03% and in short-finned pilot whales was 0.05%. The
cytochrome b gene sequences determined for 16 long-finned pilot whales from all
sampled locations, 4 Atlantic short-finned pilot whales, and two Pacific short finned pilot
whales were all identical within each group, and differed from each other by 0.33 -
0.99%. Finally, D-loop sequences were also determined from 11 bottlenosed dolphins.
All of the individuals had distinct D-loop sequences that differed by 0.25 - 4.25%, and
the nucleotide diversity was 1.25%. Two dolphins were caught together, and the
sequence divergence within this pair was 3.50%.
These results suggest that long-finned pilot whales from the eastern and western North
Atlantic are not genetically isolated from each other and that mtDNA variability in pilot
whales may be unusually low. This might be a result of a slow rate of sequence evolution
or metapopulation dynamics resulting from the social system of pilot whales.
To examine the effect of social structure, I used an individual-based model designed to
study the effect of sub-population extinction on mitochondrial genetic diversity in a pilot
whale population which is subdivided as a result of this species' social system. MtDNA
diversity was monitored in a population of pilot whales when extinction rates, mutation
rates, and pod dynamics were altered. The results of the simulations indicate that if a
pilot whale population experienced a moderate level of pod extinctions, it could undergo
large fluctuations of mtDNA heterozygosity over time and frequently have the low
heterozygosity observed in the North Atlantic pilot whale population.
Description:
My research was funded by a New Initiative grant through NOAA National Sea
Grant (grant no. NA86-AA-D-SG090) and by an Ocean Ventures Fund grant through
the Education Office. Tuition and stipend support were supplied by a National Science
Foundation Graduate Fellowship and by a research assistantship through the Education
Office.
Keywords:
Globicephala
;
Mitochondrial DNA
;
Dolphins
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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