Spatially interpolated predicted 0.1 northern-allele frequency contours for the locus WW1 from the GAM logistic regression geographic model overlaid on elevation background.

<p>The 0.5 isocline represents the center of the cline. The background represents a hill-shade digital elevation model (DEM). The map has a 30 arc-second resolutions and is projected using the Swedish RT 90 0 gon Mercator projection.</p

Parameter estimates for the GAM cline model examining geographical (i.e., latitude, longitude, and their interaction) and altitude variation in the northern-allele frequency for the AFLP marker WW1.

<p>Parameter estimates for the GAM cline model examining geographical (i.e., latitude, longitude, and their interaction) and altitude variation in the northern-allele frequency for the AFLP marker WW1.</p

Parameter estimates for the GAM model examining variation in the northern-allele frequency for the AFLP-WW1, where insignificant terms were removed using stepwise regression evaluating the reduction in deviance and significance.

<p>Final model variables include the mean monthly maximum temperature for May and mean annual potential evapotranspiration (PET).</p

Maps of Scandinavia with backgrounds representing a digital elevation model (DEM) with Sample site locations.

<p>Sample sites within the willow warbler contact zone have square symbols, while those outside triangles. The maps have a 30 arc-second resolutions and is projected using the Swedish RT 90 0 gon Mercator projection.</p