Figure 1.

(a) Gracilaria vermiculophylla attached to hard substratum in a tide pool in the native range. Photographic credit: S.A. Krueger‐Hadfield. (b) Geographic distribution of the mitochondrial SNP frequency among sampled sites of G. vermiculophylla in the native range (Northwest Pacific) and non‐native range (WNA = western North America; EUSA = eastern United States; EU = British Isles, continental Europe, and northwestern Africa). At most sites, thalli were either “C” (blue) or “T” (red) at the 945th bp of the sequenced cox1 gene from Kim et al. (2010). At five sites, both “C” and “T” SNPs were detected and relative frequencies are shown by pie charts. Sampling information is provided in Table S1, and mitochondrial sequencing and genotyping data are provided in Figure S1 and Table S2