title: Passive rafting is a powerful driver of transoceanic gene flow.
abstract: Dispersal by passive oceanic rafting is considered important for the assembly of biotic communities on islands. However, not much is known about levels of population genetic connectivity maintained by rafting over transoceanic distances. We assess the evolutionary impact of kelp-rafting by estimating population genetic differentiation in three kelp-associated invertebrate species across a system of islands isolated by oceanic gaps for over 5 million years, using mtDNA and AFLP markers. The species occur throughout New Zealand's subantarctic islands, but lack pelagic stages and any opportunity for anthropogenic transportation, and hence must rely on passive rafting for long-distance dispersal. They all have been directly observed to survive transoceanic kelp-rafting journeys in this region. Our analyses indicate that regular gene flow occurs among populations of all three species between all of the islands, especially those on either side of the subtropical front oceanographic boundary. Notwithstanding its perceived sporadic nature, long-distance kelp-rafting appears to enable significant gene flow among island populations separated by hundreds of kilometres of open ocean.
authors.affiliation: Allan Wilson Centre for Molecular Ecology and Evolution, Department of Zoology, University of Otago, Dunedin, New Zealand. raisa.nikula@otago.ac.nz
authors.forename: Raisa
authors.initials: R
authors.lastname: Nikula
authors.forename: Hamish G
authors.initials: HG
authors.lastname: Spencer
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Waters
mesh_terms: D033304:Amphipoda / Q000235:genetics* / Q000502:physiology; D054458:Amplified Fragment Length Polymorphism Analysis; D063147:Animal Distribution; D000818:Animals; D000864:Antarctic Regions; D004272:DNA, Mitochondrial / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics; D051456:Gene Flow; D055106:Genome-Wide Association Study; D006239:Haplotypes; D008969:Molecular Sequence Data; D008974:Mollusca / Q000235:genetics* / Q000502:physiology; D009520:New Zealand; D011110:Polymorphism, Genetic; D025341:Principal Component Analysis; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV