Genetic assessment of the effects of streamscape succession on coho salmon Oncorhynchus kisutch colonization in recently deglaciated streams

Measures of genetic diversity within and among populations and historical geomorphological data on stream landscapes were used in model simulations based on approximate Bayesian computation (ABC) to examine hypotheses of the relative importance of stream features (geomorphology and age) associated with colonization events and gene flow for coho salmon Oncorhynchus kisutch breeding in recently deglaciated streams (50–240 years b.p.) in Glacier Bay National Park (GBNP), Alaska. Population estimates of genetic diversity including heterozygosity and allelic richness declined significantly and monotonically from the oldest and largest to youngest and smallest GBNP streams. Interpopulation variance in allele frequency increased with increasing distance between streams (r = 0·435, P < 0·01) and was inversely related to stream age (r = –0·281, P < 0·01). The most supported model of colonization involved ongoing or recent (