Fig 3. Two alternative host parasite associations between G. teuchis (left) and Salmo sp.

(right), whereby (A) represents the HPM-1 model allowing for some ambiguity due to shared clades within drainages, and B is the most parsimonious model based on the most frequent or presumed native lineages (see methods for details). G. teuchis lineages A-E refer to the major lineages recovered in the Bayesian analysis illustrated in Fig 2. The major lineages for Salmo sp. are abbreviated as follows: DU—Duero, AT—Atlantic, AD—Adriatic, DA—Danube, and SS—S. salar.