Plate morphs in freshwater samples of Gasterosteus aculeatus from Arctic and Atlantic Canada: Complementary comments on a recent contribution

Abstract

Additional analyses of museum samples for plate morphs in the freshwater threespine stickleback from Arctic and Atlantic Canada confirm the scarcity of the low morph in mainland Atlantic Canada as shown by Hagen and Moodie (D. W. Hagen and G. E. E. Moodie. 1982. Can. J. Zool. 60: 1032–1042). Insular Newfoundland samples show evidence that populations containing the low morph are not uncommon and this agrees well with Hagen and Moodie's climatic explanation for plate morph distribution. This climatic explanation does not, however, account for the high frequencies of low morph populations shown here to occur in Arctic Canada. Two populations are identified which may be monomorphic for the low morph, and a monomorphic partial population is reported from an inland stream. Both these types of populations are rare in eastern North America.