Supplementary Material

Figure S1. Null allele frequency for all loci for (A) Fucus spiralis, (B) F. guiryi and (C) F. vesiculosus. Dots correspond to the mean frequency across populations for each locus calculated using Estimator 1 from Brookfield (1996). Vertical bars represent the standard deviation for the estimated values.

Figure S2. Allelic frequencies for Fucus spiralis, F. guiryi and F. vesiculosus, for each locus and location. Dots of varying diameter represent the frequency of the allele classes indicated below. Codes correspond to locations in Table 1.

Figure S3. Magnitude of ΔK as a function of K for F. vesiculosus. The modal value of ΔK that is based on the rate of change in the log probability of data between successive K values is considered as the highest level of population structuring.

Table S1. PCR conditions. Mixture and program for the microsatellites amplified following Engel et al. (2003) for L20, L38, L58, L78, L94; Wallace et al. (2004) for F26II; Coyer et al. (2009) for F42. (⁎) indicates a touchdown step: decrease in 0.2 °C per cycle.

Table S2. Pairwise genetic differentiation for (A) Fucus spiralis, (B) F. guiryi and (C) F. vesiculosus. Mean values of F_ST with the estimator θ are reported above the diagonal, while mean D_Jost values are reported below the diagonal. 95% confidence intervals are in brackets. Codes correspond to locations in Table 1.

© EDP Sciences 2017