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Mitochondrial DNA Sequence Variation and Population Structure
of Cetaceans around Taiwan
Abstract:
Cetaceans have been abundant and distributed widely around
Taiwan in the past.
However, there were only few research on cetacean and only in
taxonomy and population estimation at the southwest coastal area
so far.
The purpose of my thesis is to investigate (1) the phylogeny
relationship among different species, and
(2) population structure of few common species around Taiwan to
check the correlation with geographical and morphological
variation.
Dr. L.-S. Chou''s research team has collected cetacean carcasses
from stranding or fishery activity since 1993.
In total, there were 16 species. I selected one to three muscle
samples from each species for the first part of my thesis and
about 10 muscle samples of three common species here, Stenella
attenuata, Stenella longirostris, and Tursiops truncatus,
from both east and west coasts of Taiwan for my second part of
thesis. All these muscle samples were executed mt DNA sequence
analysis on the control region.
In addition, the morphometric measurement of the later three
species was also collected for cladistic analysis.
The mt DNA control region sequence of 16 local species and 5
foreign species from published gene bank were compared and
structured into phylogeny tree by Neighbor-joining method.
I suggest that Physeteriodea is more similar as those in the
Mysticeti than other members in Odontoceti, and Ziphioidea is
separated from Delphinoidea in Odontoceti.
Further more, Ocinus orca showed obvious distance from the
Globicephalinae, which has been stated as a distinguished group
from the other species in Delphinidae.
Except the taxon Globicephalids, The genetic relationship among
other members of Dephinids not show any steady and
distinguishable pattern.According to Neighbor-joining method
and the maximum parsimony analysis of mt DNA sequence, the
phenomenon of stock separation of Stenella attenuata and S.
longirostris was not obvious, but slightly obvious among
Tursiops truncatus. The
nucleon diversity index of S. longirostris is higher than other
two species. Thus, it is suggested that the population size of
S. longirostris around Taiwan is either quite large or
distributed continuously with great variation. One special
specimen of a adult S. longirostris with the smaller body length
is speculated as a mid form collected from the continuously
distributed populations from Japan to Thailand.
Three special Tursiops truncatus with greater genetic distance
from other individuals of the same species is speculated as
immigrants near Peng-hu Island during winter migration.
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