Figure 1.

Overview of the colonization of the Durance valley by the poplar rust pathogen. (A) The Durance ecological system. The rust fungus has one round of sexual reproduction on larch trees each spring. This is followed by the annual epidemic resulting from several rounds of clonal multiplication on poplar and spread along the corridor (dark green area, larch distribution; pale green line, riparian stands of wild poplars). (B) Disease dynamics (in nine locations monitored in 2004 from early July to mid‐October). Higher incidences are represented by darker colors. (C) Network of spatial genetic structure among locations at the percolation threshold (D _p = 0.36). Nodes represent locations, whereas links represent the magnitude of genetic distance between two locations (dark blue pairwise F_ST in [0–0.1]; normal blue F_ST in [0.1–0.21]; pale blue F_ST in [0.21–0.3]; very pale blue F_ST in [0.3–0.36]).