The Queen Charlotte Islands are the most isolated islands in
British Columbia and are populated by eight species of indigenous land
mammals, all except one of which are represented by at least one endemic
form. Geological and botanical evidence lend strong support to the
hypothesis that the Islands could have been a refuge to most of these
mammals during the last (Vashon) glaciation. Their unique mammal fauna
could be the product of insular evolution, or due to the fact that it is
of geographical relicts. Absence of fossil material prohibits a final
solution to this problem, but circumstantial evidence suggests that the
mammals have evolved their unique characteristics as a result of living
in an insular environment. This conclusion is reached after the study
of the most common mammals living on the Islands; the deer mice
(Peromyscus maniculatus keeni and P. sitkensis prevostensis) and the
dusky shrews (Sorex obscurus elassodon and S. o. prevostensis), and
after a wide literature survey of mammals found on other islands. The
most important evidence favouring the insular evolution theory is the
uniformity displayed when the characteristics of insular birds and
mammals are compared with relatives living on the nearby mainland.
Birds living on islands often possess longer tarsi and culmens;
artiodactyls, lagomorphs and carnivores tend to be smaller on islands,
while rodents are usually larger, live longer and possess shorter tails.
A corollary of the relict hypothesis holds that a large reliot rodent
can not survive active competition with the smaller form and is
displaced by the latter when they come into contact. This theory could
not be substantiated by the present study; on the contrary, the two would
likely interbreed. The differences between the insular populations of
large Peromysous are greater than one would expect if they owed their
similarity to a common origin. Finally, the relict hypothesis would
hold that such a characteristic as large size is conservative, whereas
evidence indicates that this is not generally true. Reasons are
suggested for the characteristics which are commonly found in insular
mammals and herein lies the most interesting area for future work. / Science, Faculty of / Zoology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/42414 |
| Date | January 1963 |
| Creators | Foster, J. Bristol |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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