Table 4. IMa estimates of effective population sizes, migration, and divergence time between regional groups of Littorina saxatilis.
| Pairwise model | IMa parameter results | Divergence time, ka | |||||
| θ1 | θ2 | θA | m1→2/μ | m2→1/μ | 2% per Ma | 4% per Ma | |
| NEA+ISL vs NWA | 50 (32–67) | 45 (27–62) | 36 (12–60) | 0.21 (0.01–0.40) | 0.12 (0.01–0.22) | 178 (46–334) | 89 (23–167) |
| NEA vs NWA | 41 (24–60) | 45 (26–66) | 38 (12–63) | 0.22 (0.01–0.41) | 0.14 (0.01–0.27) | 182 (48–320) | 91 (24–160) |
| NEA vs ISL | 68 (33–158) | 6 (3–33) | 33 (10–58) | 3.12 (0.01–7.69) | 3.97 (0.36–7.36) | 59 (6–121) | 30 (3–61) |
| NEA(S) vs ISL | 29 (20–75) | 7 (2–33) | 17 (5–45) | 3.66 (0.01–7.74) | 2.07 (0.01–6.02) | 24 (3–91) | 12 (1–45) |
| NWA vs ISL | 46 (23–68) | 16 (7–25) | 20 (5–40) | 0.20 (0.10–0.46) | 0.32 (0.01–0.56) | 68 (22–200) | 34 (11–100) |
| NWA(S) vs ISL | 20 (2–28) | 14 (5–23) | 29 (5–57) | 1.79 (0.01–4.76) | 3.29 (0.01–6.67) | 45 (4–172) | 23 (2–86) |
| NEA(MAIN) vs BI | 15 (7–24) | 26 (11–40) | 24 (10–50) | 1.91 (0.17–3.53) | 0.74 (0.01–1.64) | 51 (14–231) | 26 (7–115) |
| NEA(MAIN) vs SPAIN | 18 (9–30) | 7 (3–17) | 22 (5–60) | 0.28 (0.01–0.63) | 0.10 (0.01–0.23) | 92 (30–498) | 46 (15–249) |
| NEA(MAIN) vs CAN | 18 (7–37) | 13 (6–33) | 26 (1–55) | 1.07 (0.23–1.91) | 0.16 (0.01–0.37) | 76 (14–231) | 38 (16–156) |
| NEA(MAIN) vs USSOUTH | 18 (8–40) | 25 (11–48) | 18 (1–60) | 0.16 (0.01–0.36) | 0.13 (0.01–0.28) | 160 (40–326) | 80 (21–163) |
| NEA+ISL vs VENICE | 100 (60–150) | 0.2 (0.1–1.6) | 34 (16–56) | 4.12 (0.01–8.31) | 7.15 (0.03–13.62) | 5 (0.8–10) | 3 (0.4–5) |
| EUROPE(S) vs VENICE | 38 (8–88) | 0.1 (0.02–0.3) | 25 (15–35) | 18 (6–30) | 13 (0.02–26) | 3 (1–5) | 1 (0.6–2) |
θ is effective population size (θ = 4Nμ) for first (θ1) and second (θ2) populations in the model and their ancestral population (θA); migration rates m1→2/μ and m2→1/μ are from first to second and second to first population in the model, respectively; divergence time is converted to thousands years (ka) using mutation rates of 2 and 4% per Ma. Values in parentheses represent 90% HPD confidence intervals for each parameter (see Table S3 for probability analysis of significant differences between parameters).
Groups of populations are as following (see map in Fig. 1):
NEA – Northeast Atlantic; ISL - Northeast Atlantic islands; NWA – Northwest Atlantic; NEA(S) includes NEA sites grouped in SAMOVA with North Atlantic islands (Ireland-1, Norway, Barents Sea, White Sea, Sweden-2, Germany, Belgium and France); NWA(S) includes NWA populations grouped in SAMOVA with North Atlantic islands (Cape Breton in Nova Scotia and Newfoundland); NEA(MAIN) includes mainland sites in Europe; BI includes all British Isles sites; CAN includes all Maritime Canada sites; USSOUTH includes southern US sites below 43°N; EUROPE(S) includes European sites (British Isles and Sweden) that formed a group with Venice in SAMOVA analyses; SPAIN is the site in Galicia; VENICE is the Venetian lagoon site.