Principles of Plant Systematics

• The Phylogenetic Approach emphasizes evolutionary relationships between groups.

• Uses morphological, genetic, and chemical characters to construct a phylogenetic tree, also called a “cladogram.”

• What about other approaches– Cronquist, Thorne, etc? Phylogenetic Approach builds on the previous systems.

Charles Darwin (1809-1882)

Evolution Descent with modification.

Darwin’s Orchid

Angraecum sesquipedale (native to Madagascar)

Darwin's hawk moth, Xanthopan morgani praedicta

A good classification system should be PREDICTIVE

What is a “Plant” ?

• Plants all contain photosynthetic pigments chlorophyll a & b.

• Plants all store carbohydrates, usually in the form of starch.

• Plants all have the presence of two anterior whiplash flagella at some stage of the life cycle, often modified or sometimes lost.

• ???????????????!!!!!!!!!!!!!Footnote: all oxygenic (oxygen produced during light reactions of photosynthesis) photosynthetic organisms use Chlorophyll a.

Chlorophyll a

Chlorophyll b

Starch

Polysaccharide composed of many glucose molecules in alpha 1-4 linkage

OK…what is cellulose?

Chlamydomonas– a green alga with two anterior whiplash flagella.

OK…then what is “Systematics” ?

• Systematics is easier to define than “plant.” • Systematics is the science of organismal

diversity and the relationships between organisms.

• Systematics is the study of the “biological diversity that exists on Earth today and its evolutionary history.

Carolus Linnaeus (before Darwin was born)

What About Linnaean Ranks?

About Linnaean Ranks

• Plants initially grouped mostly by morphology.• Basket groups were made up of plants that didn’t

morphologically seem to fit anywhere else.• Did not at least initially include genetic data which

hadn’t been discovered yet.• Linnaean ranks of same level are not of same

evolutionary age. • We will use Linnaean ranks when they reflect

what we see, but discard them when they do not.

The Phylogenetic Approach is based on Monophyly

• A monophyletic group is a “group composed of an ancestor and all of its descendants”

• Synonyms: monophyletic group= Clade.• A monophyletic group can be removed from

the evolutionary tree with a single cut.• Closest relatives on the evolutionary tree (also

called “cladogram”) are called Sister Groups.

What Does a Cladogram Look Like?

What Does a Cladogram Look Like?

“Dicots” – a Clade?

AsterAles

euro

sids i

i

Bixaceae Malvaceae (incl. Bombacaceae, Sterculiaceae, Tiliaceae) Cistaceae Cytinaceae Muntingiaceae Sarcolaenaceae Dipterocarpaceae Neuradaceae Thymelaeaceae

Angiosperm Phylogeny Flowering Plant Systematics

© Th

eodo

r C.H

. Cole

(Heid

elberg

) and

Hart

mut H

. Hilg

er (B

erlin)

2010

________________________________________________________________________________________- hypothetical tree based on molecular phylogenetic data (Jan 2010); branch lengths deliberate, not expressing actual time scale; position of many characters on tree unclear; if a character is marked as being a potential synapomorphy at a node/for a clade, this does not mean that all members of that clade possess that character; * orders added as of APG III (2009)- this poster depicts only the largest and most important of the currently accepted approx. 450 families (according to APweb 2010); for family characteristics see: Kubitzki K, ed. (1990 ff). - References: APG III (2009); Judd W et al. (2007); Simpson M (2005); Soltis DE et al. (2005); Stevens PF (2010) APweb – www.mobot.org/MOBOT/research/APweb; Watson/Dallwitz (2009) delta-intkey.com/angio/ - Thanks to Christoph Dobeš, Ray F. Evert, Peter H. Raven, Douglas E. Soltis, Peter F. Stevens, Maximilian Weigend, Michael Wink

bark fibrous; hairs often stellate; flw K often valvate,

petals contorted, A often ∞; mucilage, cyclopropenoid fatty acids, flavones

flw often monosymmetric, plunger pollination (long style);

nodes trilacunar; inulin, sesquiterpenes, secoiridoids

Asteraceae Goodeniaceae Pentaphragmataceae Calyceraceae Menyanthaceae Rousseaceae Campanulaceae (incl. Lobeliaceae) Stylidiaceae

endo- sperm scanty

dipsAcAles Adoxaceae Diervillaceae Linnaeaceae

Caprifoliaceae Dipsacaceae Morinaceae Valerianaceae

AmborellAles*

ApiAles Apiaceae Griseliniaceae Pennantiaceae

Araliaceae Myodocarpaceae Pittosporaceae

AquifoliAles Aquifoliaceae Cardiopteridaceae Stemonuraceae

GArryAles

GentiAnAles

lAmiAles

solAnAles Convolvulaceae (incl. Cuscutaceae) Solanaceae (incl. Nolanaceae) Hydroleaceae Montiniaceae Sphenocleaceae

Apocynaceae (incl. Asclepiadaceae) Loganiaceae Gentianaceae Gelsemiaceae Rubiaceae Acanthaceae Lamiaceae Orobanchaceae Plantaginaceae

Bignoniaceae Lentibulariaceae Paulowniaceae Scrophulariaceae Byblidaceae Martyniaceae Pedaliaceae Stilbaceae Gesneriaceae Hydrostachyaceae Oleaceae Phrymaceae Verbenaceae

Eucommiaceae Garryaceae (incl. Aucubaceae)

ericAles

cornAles Cornaceae Grubbiaceae Loasaceae Curtisiaceae Hydrangeaceae Nyssaceae Actinidiaceae Ericaceae Polemoniaceae Sarraceniaceae

Balsaminaceae Fouquieriaceae Primulaceae Styracaceae Clethraceae Lecythidaceae Roridulaceae Theaceae Ebenaceae Myrsinaceae Sapotaceae Theophrastaceae

Ast

erid

s

mAlvAles

brAssicAles

core

eudic

ots

cucurbitAles

rosAles

fAbAles

oxAlidAles

mAlpiGhiAles

celAstrAles

myrtAles

GerAniAles

crossosomAtAles

euro

sids i

cAryophyllAles

cAnellAles

piperAles

lAurAles

mAGnoliAles

sAbiAles

proteAles

vitAles*

sAxifrAGAles

sAntAlAles

GunnerAles

Bataceae Caricaceae Limnanthaceae Salvadoraceae Brassicaceae Cleomaceae Moringaceae Tovariaceae Capparaceae Koeberliniaceae Resedaceae Tropaeolaceae

fAGAles

rosid

s

Betulaceae Fagaceae Myricaceae Rhoipteleaceae Casuarinaceae Juglandaceae Nothofagaceae Ticodendraceae

Anisophyllaceae Coriariaceae Cucurbitaceae Begoniaceae Corynocarpaceae Datiscaceae

nymphAeAles*AustrobAileyAles

rAnunculAles

trochodendrAles*

buxAles*

ZyGophyllAles*

dilleniAles

berberidopsidAles*

Brunelliaceae Connaraceae Elaeocarpaceae Oxalidaceae Cephalotaceae Cunoniaceae Huaceae

Fabaceae Polygalaceae Quillajaceae Surianaceae

Barbeyaceae Elaeagnaceae Rosaceae Cannabaceae Moraceae Ulmaceae Dirachmaceae Rhamnaceae Urticaceae (incl. Cecropiaceae)

Celastraceae Lepidobotryaceae (incl. Hippocrateaceae, Brexiaceae) Parnassiaceae Achariaceae Euphorbiaceae Ochnaceae Podostemaceae

Chrysobalanaceae Hypericaceae Passifloraceae Rhizophoraceae Clusiaceae Linaceae Phyllanthaceae Salicaceae Erythroxylaceae Malpighiaceae Picrodendraceae Violaceae

Krameriaceae Zygophyllaceae

Combretaceae Myrtaceae Penaeaceae (incl. Oliniaceae) Lythraceae (incl. Punicaceae, Sonneratiaceae, Trapaceae) Melastomataceae (incl. Memecylaceae) Onagraceae Vochysiaceae

Francoaceae Geraniaceae Ledocarpaceae Melianthaceae

Crossosomataceae Stachyuraceae Strasburgeriaceae Geissolomataceae Staphyleaceae

Vitaceae

mAGnoliids

eudi

cots

euAs

teri

ds i

woody; parasites or semiparasites; without mycorrhiza; lvs margin entire; flw A epipetalous,

perianth often simple, valvate, persisting; polyacetylenes, triterpene sapogenins, silicic acid

Altingiaceae Daphniphyllaceae Hamamelidaceae Cercidiphyllaceae Grossulariaceae Paeoniaceae Crassulaceae Haloragaceae Saxifragaceae

Balanophoraceae Misodendraceae Opiliaceae Loranthaceae Olacaceae Santalaceae (incl. Viscaceae) Aizoaceae Caryophyllaceae Molluginaceae Polygonaceae

Amaranthaceae Didiereaceae Nepenthaceae Portulacaceae [incl. Chenopodiaceae] Droseraceae Nyctaginaceae Simmondsiaceae Basellaceae Drosophyllaceae Phytolaccaceae Talinaceae Cactaceae Frankeniaceae Plumbaginaceae Tamaricaceae

Dilleniaceae

Aextoxicaceae Berberidopsidaceae

Gunneraceae Myrothamnaceae

Buxaceae (incl. Didymelaceae) Haptanthaceae

Trochodendraceae

Nelumbonaceae Platanaceae Proteaceae

Berberidaceae Eupteleaceae Menispermaceae Ranunculaceae Circaeasteraceae Lardizabalaceae Papaveraceae Sabiaceae

Amborellaceae

Austrobaileyaceae Schisandraceae (incl. Illiciaceae) Trimeniaceae

Cabombaceae Hydatellaceae Nymphaeaceae

Canellaceae Winteraceae

Annonaceae Eupomatiaceae Magnoliaceae Degeneriaceae Himantandraceae Myristicaceae

Calycanthaceae Hernandiaceae Monimiaceae Gomortegaceae Lauraceae Siparunaceae

Aristolochiaceae Piperaceae Hydnoraceae Saururaceae

woody, vessels lacking; dioecious; flw T5–8, A∞, G5–8; 1 ovule/carpel; embryo sac 9-nucleate; 1 species (New Caledonia)

aquatic, herbaceous; cambium absent; aerenchyma; flw T4–12, A3–∞; embryo sac 4-nucleate; seeds operculate, perisperm; mucilage; alkaloids (no benzylisoquinolines)

woody, vessels solitary; flw T>10, A∞, G ca.9; embryo sac 4-nuceate; tiglic acid, aromatic terpenoids

woody; pollen uniporate; aromatic terpenoids

± herbaceous; lvs two-ranked, leaf base sheathing; single adaxial prophyll; swollen nodes

woody; pith septate; lvs two-ranked; ovules with obturator; endosperm ruminate

woody; lvs opposite; flw with hypanthium, staminodes frequent, often valvate anthers; carpels with 1 ovule; embryo large

euAs

teri

ds ii

lvs often divided; flw whorled, P single or multiple whorls, G apocarpous/paracarpous, superior;

berberines

mostly woody; flw tepals often 4-merous, A epitepalous, connectives sometimes with apical appendage

mostly herbaceous; without mycorrhiza; G often unilocular with central placentation,

pollen copate, surface spiny; betalains or anthocyanins (latter, e.g., in Caryophyllaceae)

lvs with glandular teeth; often hypanthium, apically unfused carpels, stigma decurrent; fr mostly dry, dehiscent;

myricetin, flavonols

flw pentacyclic, parts alternating,

G connate,K + C (free),

(A polyandrous), pollen tricolporate;

trihydroxyl-flavonoids

lvs with glandular teeth; flw A obdiplostemonous, nectary on filament;

stems jointed at nodes; ethereal oils, ellagic acidlvs opposite, colleters (glandular hair on adaxial surface of petiole base),

stipules small (if any); cork deep seated; flw K valvate, persisting, A incurved in bud, ovary inferior; ovules many;

endosperm scanty; scaly bark; flavonols, myricetin

flw small, G often 3-merous, nectary: intrastaminal disk; seeds often with aril (red-orange);

infl cymose

lvs margins toothed; flw G often tricarpellate

lvs often compound, pulvini (sleep movement); flw A5 or multiple, branched style common;

mucilage cells; oxalates

flw often “papilionaceous”: wing, standard, keel, mostly G1, mostly A10; fr a pod; symbiosis with root nodule bacteria;

diverse alkaloids, NP amino acids, lectins (in Fabaceae)

lvs mostly simple with stipules; flw K valvate (and hypanthium) persisting,

carpels with 1 ovule, stigma dry; dihydroflavonols

lvs mostly alternate; flw often unisexual, G mostly inferior,

parietal placentation; cucurbitacins

lvs undivided; flw small, unisexual, anemophilous, thus T reduced or lacking, G mostly inferior;

infl spikes or catkins; fr 1-seeded, mostly nuts; ectomycorrhiza; tannins, dihydroflavonols

lvs alternate; flw often 4-merous, often clawed petals, A often many, 2×K;

hypogynous (often gynophore); infl racemose; myrosin cells, glucosinolates

mostly woody; lvs mostly undivided, hydathode teeth; flw often 4-merous, K much smaller than C, persisting,

intrastaminal disk, G inferior; fr drupaceous; diverse iridoids

mostly sympetalous, nectary gynoecial, ovules unitegmic,

endosperm cellular; iridoids common

lvs teeth, theoid; nodes unilacunar; flw 5-merous, pentacyclic;

nonhydrolyzable tannins, ellagic acid, hydroquinones

lvs opposite, colleters; flw corolla convolute in bud;

indole alkaloids; iridoidslate sympetaly

lvs opposite; nodes 1:1; flw mostly monosymmetric, A often 2(+2); ethereal oils in gland-headed hairs;

6-oxygenated flavones, rosmarinic acid, oligosaccharides: cornoside, verbascoside (acetoside)

lvs spiral, simple; nodes unilacunar; flw petals plicate; K persisting;

diverse alkaloids, no iridoids

woody; lvs serrate; flw 1-2 ovules/carpel, C± free, K slightly connate;

fr drupe with broad stigma

woody (except Apiaceae); lvs often divided; nodes usu. multilacunar;

infl mostly umbel; drupe or schizocarp (Apiaceae: mericarp/carpophore)

lvs opposite, often basally connate; nodes 3:3; buds with scales;

flw often monosymmetric; K persistent in fruit; secoiridoids

earlysympetaly

fl small embryo short

G inf

erior

woody; flw 4–5-merous, nectary: disk, A epipetalous, G syncarpous; pollen colporate; endosperm helobial; triterpenoids

woody; vessels lacking; idioblasts in cortex; flw tepals missing, A∞, G>5 laterally connate with abaxial nectaries; fr aggregate of follicles

mostly woody; unisexual, dioecious; lvs evergreen, stomata cyclocytic; flw tepals ± uniform or missing; pregnan pseudoalkaloids

unisexual, dioecious; lvs toothed, sec. veins palmate;flw tepals small to lacking;

ellagic acid

often tendrillar vines; lvs often divided and with glandular teeth; A epipetalous, 2 ovules per carpel; raphides, pearl glands;

berries

woody; K + C, stylodia free;

hypanthium, nectary disk

cork origin deep-seated; endosperm lacking;

resinous, lignans/neolignans, harman alkaloids

woody; dioecious; flw small, C valvate, G unilocular; fruit indehiscent;

iridoids (aucubin), gutta

mostly woody; lvs veins proceed to apex & teeth; flw K5–∞, persisting; mostly A∞, G mostly slightly connate;

seeds often with aril; fr often both ventrally/dorsally dehiscent

pollen tricolpate; flw K/C/P opp A;

filaments rather narrow, anthers basifixed; nodes trilacunar;

stomata anomocytic; ethereal oils absent

features as in “Early Angiosperms”

borAGinAles Boraginaceae (incl. Codon) Ehretiaceae (incl. Lennoaceae) Hydrophyllaceae

Cordiaceae Heliotropiaceae Wellstediaceae ?

woody; lvs stomata cyclocytic, petiole bundles annular; fr fleshy;

calcium oxalate as crystals

lvs roughly hairy; nodes unilacunar; infl scorpioid; mostly 4 ovules;

isokestose, higher inulins, pyrrolizidine alkaloids

A=C, epipetalous polyandry

rare, G(2)

AcorAles

AlismAtAles

petrosAviAles*

dioscoreAles

pAndAnAles

liliAles

ArecAles

poAles

commelinAles

ZinGiberAles

AspArAGAles

monocots

commelinids

Alstroemeriaceae Corsiaceae Melanthiaceae Philesiaceae Colchicaceae Liliaceae Petermanniaceae Smilacaceae

Bromeliaceae Eriocaulaceae Poaceae Restionaceae Xyridaceae Cyperaceae Juncaceae Rapateaceae Typhaceae (incl. Sparganiaceae)

Arecaceae

Commelinaceae Haemodoraceae Pontederiaceae

Cannaceae Heliconiaceae Marantaceae Strelitziaceae Costaceae Lowiaceae Musaceae Zingiberaceae

Amaryllidaceae (incl. Agapanthaceae, Alliaceae) Asparagaceae (incl. Agavaceae, Hyacinthaceae, Ruscaceae) Hypoxidaceae Iridaceae Lanariaceae Orchidaceae Xanthorrhoeaceae (incl. Asphodelaceae, Hemerocallidaceae)

Cyclanthaceae Pandanaceae Velloziaceae

Burmanniaceae Dioscoreaceae Nartheciaceae Taccaceae

Alismataceae (incl. Limnocharitaceae) Juncaginaceae Ruppiaceae Aponogetonaceae Butomaceae Posidoniaceae Scheuchzeriaceae Araceae Hydrocharitaceae Potamogetonaceae Zosteraceae

Petrosaviaceae

Acoraceae

atactostele (scattered bundles), no secondary thickening;

mostly herbaceous; pollen monosulcate;

sieve tube plastids with protein crystals;

sympodial branching; vascular bundles in stem scattered;

lvs parallel-veined, entire, no glandular teeth;

flw pentacyclic, P 3-merous, A opp. P, filaments narrow,

anthers broadly attached, septal nectary; single cotyledon;

adventitious roots

infl spadix with spathe; lvs axils with mucilaginous intravaginal squamules; ovules atropous, with epidermal perisperm and copious endosperm; idioblasts with ethereal oils

mostly herbs and aquatics; rhizomatous; hydrophilous; intravaginal squamules; flw G apocarpous; placentation often laminal; endosperm helobial; embryo large/green

often geophytes; anomalous sec. growth; flw nonspotted tepals, septal nectaries; capsule or berry;

seed coat obliterated or with phytomelan

often geophytes (bulbs, tubers, rhizomes); flw tepals sometimes spotted, nectaries at tepals; many seeds, seeds coat (testa) cellular;

phytomelan lacking; fructans in stems, chelidonic acid, steroid saponins

often twining vines; lvs often reticulate; ovary often inferior, style short, branched; steroid sapogenins/alkaloids

some woody (with terminally tufted leaves), flw spadix

monopodial, woody; lvs pinnately pseudocompound, reduplicate-plicate; intense primary growth, large apical meristem;

infl with spathe; alkaloids

mostly herbaceous; epidermis siliceous; mostly mycorrhiza absent; lvs grassy; flw often anemophilous, minute, chaffy, without nectaries

flw often irregular; few fertile stamens; infl thyrsus of scorpioid cymes;

phenylphenalenones

rhizomatous, large-leafed herbs; pseudostem: central infl; flw irregular/monosymmetric, septal nectaries, G inferior, A often strongly modified/reduced;

seeds arillate; silicic acid

stem with ring of bundles; fr a follicle; East Asia

UV-fluorescing cell walls (ferulic/coumaric acids);

silicic acid in leaves; cuticular waxes often in rodlets

aggregated into scallops

cerAtophyllAles Ceratophyllaceaeaquatic, herbaceous; lvs whorled, no pellucid dots; vessels lacking; monoecious;

flw T9–10, A∞, G1, 1 apical ovule/carpel, pollen inaperturate, pollen tube branched; hydrophilous

eArl

y AnG

iosp

erms

woody; vessels absent, eustele; nodes;sieve tube plastids with starch grains; lvs simple, persistent, entire; flw parts free, strobilar, perfect, P parts varying, often in threes, weakly differentiated, stamen with broad filaments, pollen monosulcate; G apocarpous (style short in most), nectaries absent; embryo very small; aromatic terpenoids

infl cymose

ellagic acid lacking

ellag

ic ac

id tan

nins

lvs with stipules

axial nectary

common

nodes trilacunar

sesq

uiterp

enes

benz

yliso

quino

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lkaloi

ds;

embr

yo sa

c 8-nu

cleate

ethere

al oil

s in s

pheri

cal id

ioblas

ts (pe

llucid

dots)

benz

yliso

quino

lines

abse

nt

N fix

embryo large, endosperm scanty

endosperm nuclear helobial,nectaries

when present septal

Ca oxalate raphides

fr us

ually

1–

few-se

eded

chlorAnthAles* Chloranthaceaelvs opposite, interpetiolar stipules; nodes swollen;

flw small T0–3, A1–5, G1, 1 apical ovule/carpel

sApindAles Anacardiaceae Meliaceae Rutaceae Simaroubaceae

Burseraceae Nitrariaceae Sapindaceae

mostly woody (silica/silicified);lvs alternate, odd-pinnately compound;

flw often imperfect, intrastaminal disk; ethereal oils

huerteAles* Dipentodontaceae Gerrardinaceae Tapisciaceaevessel elements: scalariform perforations; mucilage cells;

lvs margins toothed, stipules cauline; flw small, A = and opposite K, ovules 1-2/carpel;

AnitA

GrAde

pArAcryphiAles* Paracryphiaceae

bruniAles* Bruniaceae Columelliaceae (incl. Desfontainiaceae)

escAlloniAles* Escalloniaceaemostly woody; infl racemose, C free,

anthers basifixed, nectary disc

woody, evergreen; nodes 1:1; flw polysymmetric, anthers basifixed

woody; infl racemose, flw 4-merous, filaments stout, capsule septicidal

picrAmniAles* Picramniaceaetrees; lvs spiral; extrafloral nectaries;

staminate flw: A = and opposite C; bark bitter, anthraquinones

embryo large

How Is a Cladogram Interpreted?

• It is not a graph, in the sense that the axes are not labeled.

• It shows relationships. • An evolutionary tree must be rooted to know

which changes are relatively recent and which occurred further in the past. Piece of string analogy.

• Rooting is done using an outgroup.An outgroup is a relative of the groups under study. The outgroup separated from the ingroup lineage before the ingroup diversified.

Outgroup Separated before the Ingroup Diversified

Determining Evolutionary History

• There is uncertainty whenever more than two lineages diverge from a single point.

• Groups that include a common ancestor but only some and not all of its descendents are called paraphyletic. Separate lineages diverging from different ancestors are without a true common ancestor are called polyphyletic.

How Is a Cladogram Interpreted?

What is a Synapomorphy?

• A synapomorphy is a shared derived character state. Synapomorphies can be used to define species and evolutionary events in a cladogram. Shown as “tic” marks on cladograms.

• A symplesiomorphy is a shared ancestral character state. Symplesiomorphies are not helpful in defining current taxa. Synapomorphies may be become symplesiomorphic over evolutionary time.

Strength of Evidence for a Clade

• Evidence is strongest for those groups that have the most synapomorphies, morphological, chemical, genetic, etc. (any kind of synapomorphy.)

• The more “tic” marks leading to a monophyletic group (clade) the stronger the evidence for it.

How Is a Cladogram Interpreted?

Asparagales

Homology

• Identity by descent• A character is homologous if the species in

question all inherited the trait from a common ancestor.

• A seal’s front fins are homologous to our arms.• Our arms are not homologous to those of a

spider.

Homoplasy

• Similarity without identity by descent.• Can be caused by parallelism (i.e., “convergent

evolution) in two unrelated lineages.• Can be caused by a reversal of a character

state within a lineage.• Homoplasies make it much harder to

determine evolutionary history (i.e., to construct an accurate cladogram.)