title: Evolution of the Northern Rockweed, Fucus distichus, in a Regime of Glacial Cycling: Implications for Benthic Algal Phylogenetics.
abstract: Northern hemisphere rockweeds (Fucus) are thought to have evolved in the North Pacific and then spread to the North Atlantic following the opening of the Bering Strait. They have dispersed and widely speciated in the North Atlantic and its tributary seas. Fucus distichus is likely near the ancestral member of this genus, and studies have shown that there are several species/subspecies in this complex (i.e. F. evanescens and F. gardneri). We used phylogenetic and haplotype analyses to test the phylogenetic relationships and biogeography of F. distichus. Our data and subsequent analyses demonstrate that, unlike previous studies that lacked samples from an extensive geographical area of the Arctic and Subarctic, there is a distinct Arctic haplotype that is the source of subspecies in both the North Pacific and North Atlantic. Fucus distichus occupies a low tide zone habitat, and in Arctic/Subarctic regions it is adapted to the severe stress of sea ice coverage and disturbance during many months per year. We hypothesize that the very large geographic area of Arctic and Subarctic rocky shores available to this species during interglacials, supported by large Arctic/Subarctic fringe areas as well as unglaciated refugia during glacial cycles, provided a robust population and gene pool (described by the Thermogeographic Model). This gene pool dilutes that of the more fragmented and area-limited Temperate/Boreal area populations when they are brought together during glacial cycles. We suggest that similar subspecies complexes for a variety of Arctic/Subarctic shore biota should be examined further in this context, rather than arbitrarily being split up into numerous species.
authors.affiliation: Department of Botany, MRC-166, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013-7012, United States of America.
authors.forename: Haywood Dail
authors.initials: HD
authors.lastname: Laughinghouse
authors.affiliation: Department of Biology, University of Waterloo, Waterloo, ON, N2T 2T4, Canada.
authors.forename: Kirsten M
authors.initials: KM
authors.lastname: Müller
authors.affiliation: Department of Botany, MRC-166, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013-7012, United States of America.
authors.forename: Walter H
authors.initials: WH
authors.lastname: Adey
authors.affiliation: Centre for Protein Engineering, University of Liège, Sart-Tilman, B-4000 Liège, Belgium.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Lara
authors.affiliation: Department of Biology, University of Waterloo, Waterloo, ON, N2T 2T4, Canada.
authors.forename: Robert
authors.initials: R
authors.lastname: Young
authors.affiliation: Department of Botany and Laboratories of Analytical Biology, Smithsonian Institution Museum Support Center, Suitland, MD 20746 United States of America.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Johnson
mesh_terms: D001110:Arctic Regions; D048028:DNA, Algal / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D019143:Evolution, Molecular; D044645:Fucus / Q000145:classification / Q000235:genetics*; D014644:Genetic Variation; D009792:Oceans and Seas; D010802:Phylogeny; D058974:Phylogeography; D013045:Species Specificity
chemical_list: D048028:DNA, Algal; D004272:DNA, Mitochondrial; D021903:DNA, Ribosomal Spacer