Aim Our aim was to test for transoceanic dispersal in direct‐developing species of Onchidella (Mollusca: Gastropoda). As these slugs are ecologically associated with buoyant bull‐kelp ( Durvillaea ), and are known to raft, we predicted that they would show evidence of recent genetic connectivity among isolated landmasses. Location Cool‐temperate and subantarctic coasts of the Southern Hemisphere (New Zealand and its subantarct...