general introduction and characterization of the marine brown algae part i n.
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General Introduction and Characterization of the Marine Brown Algae: Part I

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  1. General Introduction and Characterization of the Marine Brown Algae:Part I Notes by Naomi Phillips Arcadia University Edited by Suzanne Fredericq University of Louisiana at Lafayette and Brian Wysor Roger Williams University

  2. Brown Algae: General *Primarily marine class with 19 orders, >50 families, 270+ genera, 2500 species *All are multicellular *Range from simple filamentous forms to large complex plants (kelps)

  3. Brown Algae: General *Rich in terms of biodiversity • *Inhabiting great array of • habitats *Critical primary producers in pelagic and coastal environments and in both temperate and tropical regions around the world

  4. Pelagic brown algae *Pelagic beds in Sargasso sea, Gulf of Mexico *Support host of creatures, from crustaceans, fish to young turtles

  5. Economic importance • Food, secondary products • Sources of alginates • Emulsifiers in everything from paint to ice cream • From kelp beds on US West Coast

  6. Brown Algae: General • Pigments • Chl a & c & fucoxanthin • Cell wall • Cellulose and mucilage • Plant body e.g., holdfast, stipe and blades • Reproduction/meiosis/life history • Most: sporic (haplodiplontic) • One order: gametic (diplontic)

  7. Life history: alternation of generations Sporic meiosis: haplodiplontic: Laminariales

  8. Life Histories Gametic meiosis: Diplontic: Fucales

  9. Survey of Protistan assemblage *Dinoflagellates *Euglenophytes *Crytomonads The Heterokonts-Stramenopiles • Oomycota • Diatoms • Brown algae ----------------------------------------- *Red algae *Green algae

  10. Heterokonts-Stramenopiles • Large heterogeneous group characterized by two heterokont flagella • One smooth, one tinsel • Includes a variety of groups: • Oomycetes • Diatoms • Brown algae • Golden brown algae

  11. Endosymbiosis events J. Phycol. Feb. 2009

  12. Heterokonts Brown Algae * Kawai et al. 2003 Protist

  13. Current Taxonomic Treatment Classifications historically emphasizes four features: *Life history traits • sporic to gametic *Gamete types • isogamous to oogamous *Growth mode • diffuse, meristems, trichothallic, apical *Thallus morphology • filamentous to parenchymatous

  14. Gamete types

  15. Growth mode Diffuse Apical Meristems

  16. Evolutionary Relationships among Orders -Traditional hypotheses make a variety of assumptions regarding primitive and derived character states -Generally “simple to complex”: *Relationships among brown algal orders were proposed to reflect this progression *Basal groups have “simple” features *Derived lineages have more “complex” features

  17. Traditional Hypothesis Wynne & Loiseaux 1976

  18. From simple to more complex • Is not a new concept • Central theme in evolutionary thinking • Common premise to our thinking of how many things • have evolved from land plants to animal systems

  19. Land Plant Evolution Evolution of the seed Vascular tissue Gametophyte protection and retention

  20. Molecular Phylogeny -Molecular data have been used to test the “simple to complex” paradigm -Molecular data provides a very distinct picture of brown algal evolution: *“Simple” lineages are nested with more complex groups *Some early divergences involved “complex” lineages *Fucales nested within other lineages Basal in most traditional taxonomies

  21. De Reviers et al. 2007

  22. Molecular Phylogeny “Crown” group Basal Lineages De Reviers et al. 2007

  23. Questions • What are the relationships among basal lineages and the “crown” group? • Did brown algal evolution generally follow a “simple to complex” pattern? • Pattern must be more complex than just “simple to complex” • General pattern still needs to be established

  24. Phylogeny from Phillips et al. (2008) J. Phycol.44:394 • Lineages with ESTs (or genomic data) available (or expected) are in purple • Libraries that we have produced and sequenced are: • Schizocladia, Choristocarpus, Desmarestia