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
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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)
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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
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J. Phycol. Feb. 2009
Heterokonts
*
Brown
Algae
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Kawai et al. 2003 Protist
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
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Wynne & Loiseaux 1976
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
Molecular Phylogeny
De Reviers et al. 2007
Basal Lineages
“Crown” group
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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. 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
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