Figure 1.

Two main genetic groups of S. paradoxus are found in northeastern North America. (a) Assignment of S. paradoxus strains to the main genetic groups found in North America. The tree was drawn from 1458 nucleotide positions in 118 strains of S. paradoxus and four relatives as out-groups (not shown). Symbols indicate sample locations of American strains (see legend). The three American groups A, B and C are coloured in green, blue and red, respectively. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test is shown next to the branches (10 000 replicates, values lower than 90% are not shown). (b) Distribution of S. paradoxus groups in sampling area. The occurrence of genetic groups A, B and C is indicated by green squares, red circles and blue circles, respectively. The dotted lines indicate the limit between climatic areas.