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Abstract

The Pacific Giant Salamander {Dicamptodon tenebrosus) is considered vulnerable to local extirpation from British Columbia by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and is red-listed by the BC Ministry of the Environment, Lands and Parks. The impacts of forest practices potentially threaten the long-term persistence of Pacific Giant Salamanders in Canada. I used microsatellite and AFLP markers to indirectly assess the impacts of forest harvesting on the population structure and colonisation potential of Pacific Giant Salamanders. Levels of genetic variation and population differentiation were compared among eight sub-populations in three coastal forest types (old-growth, secondgrowth and clear-cut) in the Chilliwack River Valley, British Columbia, and other populations across D. tenebrosus' biogeographic range. Patterns of genetic variation and heterozygosity revealed that populations at the northern extent of D. tenebrosus' range have lower allelic richness and heterozygosity than more central and southern populations. Comparisons of genetic variation among forest types in BC revealed that recently clear-cut sites have less genetic variation than secondgrowth and old-growth sites, suggesting that clear-cutting may cause genetic bottlenecks. The level of genetic variation (allelic richness and percent polymorphic loci) and heterozygosity were significantly correlated with stand age. There was no relationship between geographic distance and genetic differentiation within the Chilliwack Valley. Analyses of molecular variance (AMOVA) and estimates of population structure Fst and Φst, confirmed that there was slight to moderate differentiation among sub-populations of D. tenebrosus in BC. The colonisation potential of Pacific Giant Salamanders appears to be sufficient to re-establish locally extirpated sub-populations or to recover lost genetic variation from surrounding streams, particularly among clustered streams within drainages. However, long-term studies are required to assess whether the recovery of sub-populations is occurring faster than they are being disturbed, and whether Pacific Giant Salamanders are numerically stable in BC, or whether they are in decline. [Scientific formulae used in this abstract could not be reproduced.]