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Morphological and Genetic Variation in Northwestern Longnose Suckers, Catostomus catostomus: The Salish Sucker Problem
J. D. McPhail and E. B. Taylor
Vol. 1999, No. 4 (Dec. 17, 1999), pp. 884-893
Stable URL: http://www.jstor.org/stable/1447964
Page Count: 10
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The Salish sucker is a distinctive longnose sucker found in southwestern British Columbia (the lower Fraser Valley) and western Washington. Although there is some overlap, Principal Component Analysis indicates that Salish suckers differ in their morphometry from other northwestern North American longnose suckers (i.e., those in Bering Sea, upper Mackenzie, Fraser and Columbia drainage systems). We also investigated variation in the mitochondrial DNA genome of Catostomus catostomus by sequencing PCR-amplified fragments from two genes: a 360 bp region of the cytochrome b gene and a 510 bp region of the NADH subunit 2 (ND2) gene. These data suggest that British Columbia was colonized postglacially by longnose suckers from three sources: the Bering, Great Plains, and Pacific refugia. We found no diagnostic haplotypes in either the Fraser (excluding a few lower Fraser tributaries) or Columbia River systems. These drainages contain a mixture of typical western North American haplotypes. In contrast, Salish suckers possess unique haplotypes that distinguish them from all other northwestern longnose suckers. Thus, both the morphometric and molecular data indicate that Salish suckers have diverged from typical northwestern longnose suckers. Our molecular data also hint at divergence between "western" and "eastern" North American longnose suckers; however, the sample sizes are too small to be certain. Although both "typical" western longnose suckers and Salish suckers occur in the Fraser system, they are separated by about 60 km of unobstructed river, and there is no evidence of gene-flow between the two forms. Thus, we conclude that the Salish sucker constitutes an evolutionarily significant unit within the longnose sucker genome and as such warrants protection in both British Columbia and Washington State.