8/2/2019 2 2 Introduction Classification Green Algae 2

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IntroductiontotheClassificationofIntroductiontotheClassificationof

GreenAlgaeGreenAlgae

BrianWysor,Ph.D.

Ro er Williams Universit

8/2/2019 2 2 Introduction Classification Green Algae 2

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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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ThispresentationisacontributionoftheThispresentationisacontributionofthe