Fig 2.

Glacial re-colonization patterns of Picea glauca, P. engelmannii and their hybrids from 21 000 to 14 000 years before present based on climate niche modelling (CCM1 model) and palaeoclimate data. Years before present are in bold at the top of the graph. P. engelmannii is in green, P. glauca is in blue and the hybrid zone is in brown. Species frequency levels were divided equally by thirds: 0.33 (Low), 0.66 (Med), 1.00 (High). Laurentian and Cordilleran ice sheets are shown as inserts in each of the maps (Dyke et al. 2002).