Population genetic structure of tailed frogs (Ascaphus truei) in clearcut and old-growth stream habitats in south coastal British Columbia

Ascaphus truei Stejneger, 1899 relies on cool, fast-flowing, forested mountain streams, which receive little protection from logging activities. During recovery of post-logging habitats, local extirpation of Ascaphus is a concern because their recolonization may be slow. In British Columbia, Oregon, and California, coastal Ascaphus populations are designated as "at risk". To infer fragmentation impacts from patterns of genetic structure, we used RAPD molecular markers and compared population genetic structures of Ascaphus larvae in an old growth with an adjacent clearcut stream located in coastal British Columbia. In the clearcut, larvae were less genetically diverse than in the old growth and exhibited no relationship between physical distance and genetic relatedness, whereas in the old growth, genetic similarity decreased with physical distance. Patterns of gene flow between the clearcut and old-growth streams were significantly different. The clearcut population went through a bottleneck/founding event, but also exhibited greater dispersal. The frogs were perhaps searching for new habitat (which would lower isolation by distance) and suffering mortality (which would decrease diversity). Most problems in conservation will require genetic and ecological data, and future research should aim to incorporate methodologies from both fields.