General Introduction and Characterization of the Marine Brown Algae: Part I

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General Introduction and Characterization of the
Marine Brown AlgaePart I

• Notes by Naomi Phillips
• Arcadia University
• Edited by Suzanne Fredericq
• University of Louisiana at Lafayette
• and
• Brian Wysor
• Roger Williams University

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Brown Algae General
Primarily marine class with 19 orders, gt50
families, 270 genera, 2500 species All are
multicellular Range from simple filamentous
forms to large complex plants (kelps)
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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

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

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

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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)

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Life history alternation of generations
Sporic meiosis haplodiplontic Laminariales
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Life Histories
Gametic meiosis Diplontic Fucales
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Survey of Protistan assemblage

• Dinoflagellates
• Euglenophytes
• Crytomonads
• The Heterokonts-Stramenopiles
• Oomycota
• Diatoms
• Brown algae
• -----------------------------------------
• Red algae
• Green algae

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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

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Endosymbiosis events
J. Phycol. Feb. 2009
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Heterokonts
Brown Algae

Kawai et al. 2003 Protist
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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

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Gamete types
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Growth mode
Diffuse
Apical
Meristems
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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
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Traditional Hypothesis
Wynne Loiseaux 1976
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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

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Land Plant Evolution
Evolution of the seed
Vascular tissue
Gametophyte protection and retention
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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
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De Reviers et al. 2007
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Molecular Phylogeny
Crown group
Basal Lineages
De Reviers et al. 2007
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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

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• Phylogeny from Phillips et al. (2008) J. Phycol.
  44394
• Lineages with ESTs (or genomic data) available
  (or expected) are in purple
• Libraries that we have produced and sequenced
  are
• Schizocladia, Choristocarpus, Desmarestia