Patterns and consequences of dispersal in Columbia spotted frogs (Rana luteiventris)

Ecological and evolutionary theory predicts that dispersal can have important effects on population dynamics and evolutionary trajectories. The objective of my dissertation was to estimate rates and patterns of dispersal and gene flow in Columbia spotted frogs (Rana luteiventris) in order to explore the ecological and evolutionary consequences of dispersal. I used multistate capture-recapture analysis of site-specific capture histories and allele frequency data for six microsatellite loci to characterize dispersal and gene flow among populations in western Montana and Idaho. I collected site-specific capture histories for 10,443 uniquely marked frogs from two focal low elevation basins in northwest Montana over four consecutive years of fieldwork. Although amphibians are generally considered to have low dispersal capabilities, I found exceptionally high juvenile dispersal rates of up to 53% annually. Moreover, juveniles dispersed over long distances (>5 km), large elevation gains (>750 m), and steep inclines (36° mean incline over 2 km). In contrast, adult dispersal rates and distances were very low. Microsatellite estimates of gene flow were also high for these two basins, suggesting that juvenile dispersers successfully reproduce in the populations to which they immigrate.; I collected microsatellite data from 28 sites from throughout western Montana and Idaho that provide additional insights into movement patterns among Columbia spotted frog populations. In particular, although gene flow is very high among low elevation sites, it is often low among high elevation sites and restricted between low and high elevation sites. Additionally, I observed a strong negative relationship between within population genetic variation and elevation, suggesting that historic effective population sizes are much smaller at high elevations than low elevations. High elevation populations may therefore be more susceptible to stochastic population extinction than low elevation populations. Low elevation populations may also serve as important sources of immigrants and colonists for high elevation populations. Moreover, although there is dispersal and gene flow between low and high elevation populations, gene flow does not appear to constrain local adaptation in egg size.