Figure 4. Genetic structure of the strains of Pseudo-nitzschia multistriata within each sample, as defined by Structure.

Samples are presented in ranking order (1–22) along the x-axis. Each vertical bar represents one strain. The y-axis indicates the proportion of a strain’s genotype assigned by Structure to a population (i.e., K-cluster); the two populations identified by Structure are indicated POP_A (green), POP_B (red). Strains in each sample are ranked along the x-axis based on their assignment probabilities. Strains not assignable to any of the two populations above the 0.9-probability-level, are indicated to the right side of each sample. Samples have been grouped by year of collection: samples 1–7 in 2008, samples 8–15 in 2009, samples 16–21 in 2010 and sample 22 in 2011.