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IntroductiontotheClassificationofIntroductiontotheClassificationof
GreenAlgaeGreenAlgae
BrianWysor,Ph.D.
Ro er Williams Universit
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ClassificationClassification
20+classesofgreenalgaehavebeendescribed
s nceL nnaeus
Manycriteriahavebeenusedtoestablishclasses
Morphology
Ultrastructure
, , ,
Lifehistorypatterns
Molecular
PrimarilyrRNA
genes,
rbcL
Ambiguityremains,butconsensusisemerging
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Classification:MorphologicalConceptClassification:MorphologicalConceptPrschold
Photosby
&Leliaert.2007
Hua
ngSufang.
.
Parenchymatous Siphonocladous
Evolutionofstructuralcomplexity
Premise
Primitiveunicellsevolvedstructuralcomplexityovertime
orp o og ca vergence s ngu s esgroups
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ProblemswithMorphologicalConceptProblemswithMorphologicalConcept
Selectiveenvironmentalpressuremaydriveconvergence
Charophyceae
Chlorophyceae
Ulvophyceae
Fig.16.18Grahametal.2008.
4
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MorphologicalConvergencew/inClassMorphologicalConvergencew/inClass
Class: Ulvophyceae Ulvophyceae
Order: Ulvales Ulotrichales
Genus: Ulvaria Monostroma
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Chlorophyta:MorphologicalConvergenceChlorophyta:MorphologicalConvergence
Howcangreen
algae
be
classified
if
theyexhibitboth
divergentand
convergentpatternsof
morphology?
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UltrastructuralConceptUltrastructuralConcept
Mattox&Stewart(1984)proposednewClass
eve taxonomyont e as so asa o y
orientation
unicellularflagellates
Numerousancient
flagellate
lineages
diversified
into
contemporaryformsalongdifferentevolutionary
paths,butmanywithsimilarmorphologicalresults
eren asa
o ypa erns
en e
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BasalBodyOrientationsBasalBodyOrientations
Ulvophyceae,Charophyceae,
Ancestralcondition
,DrierGreenAlgae
STREPTOPHYTACHOROPHYTA
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MolecularConceptMolecularConcept
Elucidationofgreenalgalphylogenyinmolecular
contextcommence near y1990s
Earlystudies
confirmeddistinctionbetweenChlorophyta&
Streptophytaalreadysuggestedbycellularand
ultrastructuralcharacters
elucidated
from
EM
recognized5lineages:
Prasinophyceae,Chlorophyceae,Trebouxiophyceae,
,
Subsequentstudieshaveconfirmedtheselineages,but
relationshipsamong&withinthelineages remains
unclear
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MolecularConceptMolecularConcept
moleculardatasupporttherecognitionoftwophylaandapoorlyresolvegradedofearlydivergingflagellatesinformallyknownasPrasinophyceans
V
irido
planta
eo
Streptophyta+
Chlorophyta
rChloro
DrierGreen
Algae)
bionta
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SSUrDNAMolecularConceptSSUrDNAMolecularConcept(Prschold&Leliaert2007)(Prschold&Leliaert2007)
Chlorophyta+Streptophyta
UTCclade
recovered
with
low
BSsupport(noboldlines)
Poorlyresolved
Prasinophyceangrade
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ClassUlvophyceaeClassUlvophyceae
Mostmacroscopicmarinegreenalgaebelongto
C assU vop yceae
Ulvophyceaeiscircumscribedonthebasisofa
su eo p e s omorp cc arac ers
Closedmitosis,persistentspindle,furrowing,CCW,
Theabsenceofwelldefined,sharedderived
charactershasresultedinuncertainrelations
withinthe
class
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ClassUlvophyceaeClassUlvophyceae
Generally,5(or6)ordersMcCourt&Lewis.2004.
flagellarapparatus
zoosporangial&gametangial
structures
lifehistory
Ordersare
enerall
supportedbymolecular
analysis,butrelationships
uncertain
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ptpt
onc
onc
al.200
2)
al.200
2)
la
r
la
rut
istaet
ut
istaet
lecu
lecu
(Lopez
(Lopez
BB
MM
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SubSubordinalclassificationordinalclassification
Genericandspecieslevelclassificationis
requent y ase onmorp o ogyw c can e
problematic
Morphologicalconvergence
theseproblems
startthatcanleadtotherecognitionofnovelmorphological,physiologicalorbiologicalfeatures
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ZZcladesclades &BiologicalSpeciesinferredfromITS22&BiologicalSpeciesinferredfromITS22structurestructure
(see
Coleman
2009)(see
Coleman
2009)
AsITS2differences
increase,sexual
compatibilityandzygote
productivitydecrease
Organismsthatdifferby
arecompletelyunableto
cross
Identityfor
the
entire
ITS2
correlateswithsignificant
interbreedin otential.
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LiteratureCitedLiteratureCited
Coleman,A.2009.Isthereamolecularkeytothelevelofbiologicalspecies
ineukaryotes?ADNAguide.Mol.Phylogen.Evol.50:197203.
Graham,L.E.,Graham,J.M.,&Wilcox,L.W.2008.Algae,2nd Ed.,Benjamin
Cummings,San
Francisco,
616
p.
Mattox,K.R.&Stewart,K.D.1984.Classificationofthegreenalgae:aconcept
basedoncomparativecytology.Pp.2972,In Irvine,D.E.G.&John,D.M.
(eds.),ThesystematicsofGreenAlgae.TheSystematicsAssociation,Special
Vol.
27,
Academic
Press,
London., . , . . . . .
Bot. 91:15351556.
Prschold,T.&Leliaert,F.2007.Systematicsofthegreenalgae:conflictof
classicandmondernapproaches.Pp.123153InBrodie,J.&Lewis,J.
Unravellingthe
algae:
the
past,
present
and
future
of
algal
systematics.
CRC
press,BocaRaton,376p.
vandenHoek,C.,Mann,D.G.,&Jahns,H.M.(1995)Algae.AnIntroductionto
Phycology.CambridgeUniversityPress,Cambridge.
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