Genetic (mtDNA) evidence of a subantarctic source for beach-cast bull kelp specimens found on mainland New Zealand. (a,b): Left panels: map of the southern New Zealand region including subantarctic islands. Haplotype distributions and proportions for COI for (a) bull kelp, D. antarctica, and (b) the isopod Limnoria are shown as pie charts emerging from each site (site codes for mainland New Zealand: Kai, Kaikoura; BP, Banks Peninsula; Br, Brighton). Minimum-distance rafting trajectories from the Snares and the Auckland islands to St Clair Beach, New Zealand, are shown by dashed lines, with distances indicated. The approximate location of the subtropical convergence is shown. Right panels: phylogeographic relationships based on COI data for (a) bull kelp, D. antarctica and (b) the isopod Limnoria. Node support values of the major, well-supported branches are shown, with Bayesian PP values above and ML bootstrap values (in grey) below. Outgroups have been trimmed for clarity. Scale bars, (a,b) 200 km.