Table 1.
Sampling information and genetic diversity for mtDNA (COI) and microsatellite markers for the barnacle B. improvisus.
Fig 1.
Distribution of haplotypes in the different populations of B. improvisus.
The twelve most common haplotypes (represented by five or more individuals) are colour-coded and the “white proportion” contains all the haplotypes represented by five or less individuals including unique haplotypes.
Fig 2.
A minimum spanning haplotype network based on a 694 bp fragment of the mtDNA COI gene in B. improvisus.
Each node represents one mutational step and the size of each circle represents the frequency of a haplotype. The pie chart colours represent different geographical groupings of populations; PU = Pacific US, AU = Atlantic US (North Carolina and Chesapeake Bay combined), AR = Argentina, FR = France, BS = Baltic South (including Kiel, Torhamn, Estonia and Saltö), BN = Baltic North (Öregrund and Umeå), CA = Central Asia (Caspian Sea and Black Sea) and JP = Japan. Small empty circles (nodes) represent non-sampled haplotypes.
Fig 3.
Mismatch distributions based on COI sequences from B. improvisus populations.
Observed mismatch distribution (bars) and expected mismatch distributions under the sudden expansion model (solid line) of mtDNA COI sequences for each population. D = Tajima’s D, FS = Fu’s FS, R = raggedness value. Significance is presented as *: P = 0.01–0.05, **: P < 0.01. The populations are sorted according to the pattern of mismatch distribution, with populations displaying more diverged haplotypes (2–4 mismatches) to the left, and populations with less differentiated haplotypes (1–2 mismatches) to the right.
Table 2.
Pairwise population genetic differentiation between populations of the barnacle B. improvisus, based on mtDNA and microsatellites.
Fig 4.
Non-metric multidimensional scaling plot (MDS) based on Slatkin’s linearized distances among populations of B. improvisus.
A) MDS based on mtDNA (ΦST): stress: 0.064; B) MDS based on microsatellites (FST): data including all four loci with null allele correction, stress: 0.11 (stress values over 0.2 suggest that the precision in representing the relationships among populations is limited).
Fig 5.
Correlating pairwise genetic distances between B. improvisus populations to geographical distance and oceanographic connectivity.
Pairwise genetic distance (ΦST, COI) for populations of B. improvisus in the Baltic Sea plotted as a function of (a) closest geographical shipping distance (km) (Mantel test: R = 0.46, p = 0.075); (b) minimum oceanographic connectivity between sampling sites; (c) standardised and null allele corrected pairwise genetic distance ((FST/1-FST) in microsatellites plotted as a function of minimum oceanographic connectivity between sampling sites.