the evolution of cam in the subfamily pitcairnioideae (bromeliaceae)

Biological Journal of the Linnean Society

, 2003,

80

, 261–268. With 2 figures

© 2003 The Linnean Society of London,

Biological Journal of the Linnean Society,

2003,

80

, 261–268

261

Blackwell Science, LtdOxford, UKBIJBiological Journal of the Linnean Society0024-4066The Linnean Society of London, 2003? 2003802261268Original Article

CAM IN PITCAIRNIOIDEAEF. REINERT

ET AL.

*Corresponding author. E-mail: [email protected]

The evolution of CAM in the subfamily Pitcairnioideae (Bromeliaceae)

FERNANDA REINERT

1

, CLAUDIA A. M. RUSSO

2

* and LEANDRO O. SALLES

3

1

Departamento de Botânica, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

2

Departamento de Genética, Instituto de Biologia, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21541–570, Brazil

3

Departamento de Vertebrados, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

Received 28 August 2002; accepted for publication 7 March 2003

A molecular phylogeny for the subfamily Pitcairnioideae was inferred to examine the distribution of crassulaceanacid metabolism in the subfamily. For this purpose, a neighbour-joining tree with p-distances was built using a

MatK

chloroplast gene data set. The phylogenetic results of our analysis confirmed the monophyletic condition of most gen-era examined:

Brocchinia

,

Dyckia

,

Encholirium

,

Fosterella

,

Hechtia

and

Puya

. A paraphyletic basal sequence showed

Hechtia

branching off from the basal node, followed by

Brocchinia

,

Cottendorfia

+

Navia phelpsiae,

and

Puya

. Theremaining taxa were divided into two groups: (a)

Deuterocohnia meziana

,

Dyckia

,

Encholirium

;

Fosterella

;

Deutero-cohnia

spp.

+

Pitcairnia heterophyla

; (b)

Pepinia

,

Pitcairnia

spp. and

Navia igneosicola

. The basal placement of theCAM genera

Hecthia

indicates that CAM may be a ‘primitive condition’ in Pitcairnioideae and that C

3

species mayhave lost the ability to induce CAM. In this molecular tree, CAM metabolism appeared scattered throughout the tree.Current knowledge, however, does not exclude the possibility that CAM arose only once and it has been switchingon and off in various lineages. Further detailed studies on photosynthetic metabolisms and the phylogenetic distri-bution of characters will provide a better basis on which to evaluate photosynthetic origins. © 2003 The LinneanSociety of London,

Biological Journal of the Linnean Society

, 2003,

80

, 261–268.

ADDITIONAL KEYWORDS:

chloroplast gene

MatK

– molecular systematics – photosynthetic metabolic

pathways – plant phylogeny.

INTRODUCTION

Crassulacean acid metabolism (CAM) is a metabolicpathway found in the photosynthetic tissues of someplants. At night CAM plants take up CO

2

which isfixed into malate via phosphoenolpyruvate carboxy-lase (PEPC). During the day, malate is decarboxylatedand the CO

2

is used in the C

3

pathway (photosyntheticcarbon reduction cycle). CAM-type PEPC is quite dif-ferent from C

3

and C

4

types. For instance, the V

max

ofCAM-type PEPC is C

4

-like but its relatively low K

m

isC

3

-like (Leegood, 1993). Furthermore, CAM-typePEPC is a tetramer whereas the C

4

type is a dimer,

which may account for its lower sensitivity to malateinhibition and to pH variation (Wedding, Black &Meyer, 1990).

During CAM circadian cycles, PEPC is activated bykinase phosphorylation while higher levels of PEPCand PEPC-mRNA regulate CAM metabolism duringtransition from C

3

to CAM in intermediate plants(Ting

et al.

, 1993). CAM plants minimize water lossthrough evaporation by opening their stomata mostlyat night, differing from C

3

and C

4

species. Thus, when-ever water supply is low or day-time temperatures arehigh, CAM plants have an enormous physiologicaladvantage over C

3

and C

4

plants.In the plant kingdom, CAM is widely and discontin-

uously distributed. More than 10% of all vascular

262

F. REINERT

ET AL

.



2003,

80

, 261–268

plant species, including monocots, dicots and somepteridophytes (e.g.

Isoetes

and

Pyrrosia

) are constitu-tive CAM or, alternatively, they may engage CAMwhen under hydric or salinic stress (Ting, 1985; Grif-fiths, 1988; Ueno

et al.

, 1988; Cushman & Bohnert,1997). Given the wide and discontinuous distributionof CAM, it has been hypothesized that independentevolutionary events are responsible for the multipleappearances of CAM in land plants (Medina, 1974;Winter & Smith, 1996; Guaralnick & Jackson, 2001);likewise this has been reported for the C

4

pathway(Ehleringer, Cerling & Helliker, 1997; Kellog, 2000;Guaralnick & Jackson, 2001).

In a recent study based on molecular phylogeneticanalyses, various independent appearances of theCAM pathway in the family Portulacaceae werereported (Guaralnick & Jackson, 2001). It remainsunclear, however, if independent appearances arewidespread in plants and, if so, how such a complexmetabolism reappeared so many times in the course ofplant evolution.

The family Bromeliaceae is of major ecologicalimportance in the neotropics and comprises about2600 species divided into 56 genera (Horres

et al.

,2000). Based on floral, fruit and seed characters, thesegenera are assigned to three subfamilies: Pitcairnio-ideae, Tillandsioideae and Bromelioideae. Interest-ingly, several seemingly related bromeliacean generashow considerable variation in their photosyntheticmetabolism, which makes this family particularlyappropriate for a case study on CAM evolution(Medina, 1974). We started our study on the evolutionof CAM metabolism in Bromeliaceae with the subfam-ily Pitcairnioideae.

MATERIAL AND METHODS

We were primarily concerned with the distribution ofCAM in the Pitcairnioideae subfamily. For this, weselected the

MatK

(chloroplast maturase) genesequences available at GenBank (http://www.ncbi.nlm.nih.gov) for members of this bromeliad sub-family. Eleven pitcairnioid genera were included in theanalysis. Most of these were represented by more thanone species, allowing their monophyly to be tested andbringing the total to 35 pitcairnioid species sampled.Since monophyly of Pitcairnioideae has been ques-tioned previously (Terry, Brown & Olmstead, 1997;Horres

et al.

, 2000), we decided to select an outgroupfrom the Rapateaceae Family,

Epidryos,

for our phylo-genetic analysis. The 36 species along with their Gen-Bank accession numbers are listed in Table 1.Photosynthetic pathways were determined from pre-viously published literature (Martin, 1994). When thespecies metabolism was not described, the photosyn-thetic metabolism assigned for the genus was assumed.

Multiple sequence alignments were performed byClustalW available at web site http://www.ebi.ac.uk/clustalw (Higgins

et al.

, 1994). The phylogeneticanalysis of molecular data was carried out withMEGA 2.1, available at http://www.megasoftware.net (Kumar

et al.

, 2001). All base positions thatshowed indels (insertion/deletion events) in thealignment were excluded from the entire phyloge-netic analysis. The

MatK

chloroplast gene data setcomprises 848 base pairs (282 codons) of which only87 sites were variable. The GC content was consis-tently low among species (T: 38%; C: 17%; A: 31%;G: 14%).

Table 1.

GenBank accession numbers for species of thefamily Bromeliaceae used in this study

Family Species nameAccessionno.

Bromeliaceae (Pitcairnioideae)

Brocchinia acuminata

AF162228

Brocchinia micrantha

AF162229

Cottendorfia florida

AF162230

Deuterocohnia longipetala

AF162231

Deuterocohnia lotteae

AF162232


AF162233

Deuterocohnia

sp. AF162226

Dyckia dawsonii

AF162234

Dyckia ferox

AF162235

Dyckia

sp. AF162236

Encholirium irwinii

AF162237

Encholirium inerme

AF162239

Encholirium

sp. AF162238

Fosterella elata

AF162240

Fosterella penduliflora

AF162241

Fosterella petiolata

AF162242

Hechtia glabra

AF162244

Hechtia glomerata

AF162245

Hechtia guatemalensis

AF162246

Hechtia lindmanioides

AF162247

Navia igneosicola

AF162248

Navia phelpsiae

AF162249

Pepinia beachiae

AF162251

Pepinia corallina

AF162252

Pepinia sprucei

AF162253

Pitcairnia heterophylla

AF162254

Pitcairnia orchidifolia

AF162255

Pitcairnia recurvata

AF162256

Pitcairnia rubronigriflora

AF162257

Pitcairnia smithiorum

AF162258

Pitcairnia squarrosa

AF162259

Puya aequatorialis

AF162260

Puya humilis

AF162261

Puya laxa

AF162262

Puya werdermannii

AF162263Rapateaceae

Epidryos allenii

AF162225

http://www

http://www.ebi.ac.uk/

http://www.megasoftware

CAM IN PITCAIRNIOIDEAE

263



2003,

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, 261–268

The neighbour-joining method of Saitou & Nei(1987) was used to build the phylogenetic tree. Dis-tance methods, such as neighbour-joining, use a spe-cific statistical model to estimate the number ofdifferences between sequences (Russo, Miyaki &Pereira, 2001). Whenever p-distances (i.e. number ofbase differences divided by total number of bases com-pared) are high, there can be a serious underestima-tion of the true evolutionary distance betweenlineages (Nei & Kumar, 2000 and references therein).In such cases, a proper correction model must beapplied so that unbiased estimates are used to con-struct an accurate tree (Rzhetsky & Nei, 1993). How-ever, in our data set, p-distances were small (

<

0.05)and, thus we decided to use them since they have thesmallest variance (Russo, Takezaki & Nei, 1996;Russo

et al.

, 2001). The robustness of the molecularphylogenetic tree was tested with the confidence prob-ability (Rzhetsky & Nei, 1992) test for the neighbour-joining tree. This test has been shown to be a reliableindicator of the accuracy of the tree (Sitnikova,Rhzetsky & Nei, 1995; Russo, 1997).

RESULTS AND DISCUSSION

P

ITCAIRNIOID

PHYLOGENETICS

We used a molecular data set to produce a pitcairnioidphylogeny based on the

MatK

chloroplast gene. Thepairwise p-distance matrix (Table 2) was used to con-struct the neighbour-joining tree (Fig. 1). Mostpitcairnioid genera were monophyletic, namely: Broc-chinia (represented by B. acuminata, B. micrantha),Dyckia (D. dawsonii, D. ferox, D. sp.), Encholirium(E. inerme, E. irwinii, E. sp.), Fosterella (F. elata,F. penduliflora, F. petiolata), Hechtia (H. glabra,H. glomerata, H. guatemalensis, H. lindmanioides)and Puya (P. aequatorialis, P. humilis, P. laxa,P. werdermannii).

Our phylogenetic analysis also showed that the fol-lowing genera were not monophyletic: Deuterocohnia(D. longipetala, D. lotteae, D. meziana, D. sp.), Navia(N. igneosicola, N. phelpsiae), Pepinia (P. beachiae,P. corallina, P. sprucei) and Pitcairnia (P. hetero-phylla, P. orchidifolia, P. recurvata, P. rubronigriflora,P. smithiorum, P. squarrosa). The genus Cottendorfiawas represented by a single species. In order to makethe text more readable, we will henceforth refer to themonophyletic genera simply by the genus name; theothers will be referred to by the name of the outlierspecies and ‘Genus spp.’ will refer to the remainingspecies of the genus.

The first division in Pitcairnioideae was when Hech-tia separated from the remaining pitcairnioidean spe-cies and Brocchinia was placed inside the main group(Fig. 1). Our result contrasts with a recent phyloge-netic study in which a molecular tree shows Broc-

chinia as the basal clade and Hechtia as the second tosplit (Horres et al., 2000). In that study, pitcairnioide-ans were not grouped in a monophyletic clade, andBrocchinia appeared separately from other pitcairnio-idean species as the most basal genus for the familyBromeliaceae. Another study also placed Brocchiniaas basal among bromeliaceans (Terry et al., 1997).Unfortunately, these authors did not include Hechtiain their study, making a useful comparison betweenour study and theirs difficult.

One could argue that rooting preferences mightaccount for the differences observed among the threestudies. Nonetheless, our phylogenetic tree was rootedwith Epidryos, a member of the Rapateaceae family.Since the monophyletic status of the Bromeliaceaefamily has been ascertained (Terry et al., 1997; Horreset al., 2000), an error as a result of our rooting pref-erence is thus excluded. It should be noted that in thestudies of Terry et al. (1997), Horres et al. (2000) andhere, statistical support for the nodes were relativelylow, indicating that more data are necessary in orderto resolve this matter.

After the divergence of Hechtia, the next groupingin the tree in Figure 1 shows an unresolved trichot-omy with Brocchinia, Navia + Cottendorfia and theremaining species. Puya spp. separated basally fromthe remaining species which were, in turn, dividedinto two main groups. The first group divided intothree different subgroups: the sister genera (Dyckia,Encholirium) tightly joined (99%) with Deuterocohniameziana; Fosterella spp.; Pitcairnia heterophylla+ Deuterocohnia spp.

In the second main group, the remaining Pitcairniaspp. were clustered as a paraphyletic sequence thatincluded Pepinia spp., with Navia igneosicola diverg-ing basally from them. It seems clear that Pitcairniaheterophylla should be considered as belonging to adifferent genus from the remaining species(Fig. 1), probably along with P. loki-schmidtii andP. pseudopungens (Horres et al., 2000). Another molec-ular study in Bromeliaceae with ndhF chloroplastgene sequences (Terry et al., 1997) also joins Pepiniaand Pitcairnia. In fact, Pepinia used to be assigned asa subgenus of Pitcairnia, but it was raised to genericstatus by a morphological analysis (Varadarajan &Gilmartin, 1988a). In our tree, these genera clusteredwith a relatively high CP value (86%) suggesting thatthe condition of Pitcairnia and Pepinia as separategenera must be re-evaluated. As a matter of fact, arecent review listed all Pepinia species examined here(P. beachiae, P. corallina, P. sprucei) within the genusPitcairnia (Taylor & Robinson, 1999).

Navia igneosicola was the basal species in the sec-ond major group, outside the Pitcairnia + Pepiniaclade, and was placed in a separate branch from thecongeneric N. phelpsiae. Besides Pitcairnia and Pep-

264 F. REINERT ET AL.

© 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80, 261–268

Tab

le 2

.M

atK

ch

loro

plas

t ge

ne

pair

wis

e p-

dist

ance

s (¥

1000

) fo

r al

l pi

tcar

inio

idea

n (

Bro

mel

iace

ae)

spec

ies

com

pari

son

s pl

us

the

outg

rou

p E

pid

ryos

(R

apat

acea

e)

12

34

56

78

910

1112

1314

1516

1718

1920

2122

2324

2526

2728

2930

3132

3334

3536

1B

rocc

hin

ia a

cum

inat

a2

Bro

cch

inia

mic

ran

tha

93

Cot

ten

dor

fia

flor

ida

2622

4D

eute

roco

hn

ia lo

ngi

peta

la28

2720

5D

eute

roco

hn

ia l

otte

ae27

2619

46

Deu

tero

coh

nia

mez

ian

a28

2722

1816

7D

eute

roco

hn

ia s

p.28

2420

34

188

Dyc

kia

daw

son

ii31

3024

2019

320

9D

ycki

a fe

rox

3130

2420

193

203

10D

ycki

a sp

.31

3024

2019

320

03

11E

nch

olir

ium

in

erm

e30

2823

1918

119

14

112

En

chol

iriu

m i

rwin

ii30

2823

1918

119

14

10

13E

nch

olir

ium

sp.

3635

3026

248

268

118

77

14F

oste

rell

a el

ata

3028

2322

2018

2220

2020

1919

2615

Fos

tere

lla

pen

du

lifl

ora

4238

3127

2628

2731

3131

3030

3623

16F

oste

rell

a pe

tiol

ata

2827

2019

1818

1920

2020

1919

265

2017

Hec

hti

a gl

abra

2824

1822

2023

2226

2626

2424

2822

3019

18H

ech

tia

glom

erat

a24

2013

1816

1918

2222

2220

2024

1826

154

19H

ech

tia

guat

emal

ensi

s24

2013

1816

1918

2222

2220

2024

1826

159

520

Hec

hti

a li

nd

man

ioid

es28

2418

2220

2322

2626

2624

2428

2230

190

49

21N

avia

ign

eosi

cola

2627

2016

1518

1620

2020

1919

2622

3019

2218

1822

22N

avia

ph

elps

iae

2624

1219

1820

1923

2323

2222

2822

3219

1915

1519

1923

Pep

inia

bea

chia

e24

2319

1816

1818

2020

2019

1926

1831

1820

1616

2012

1624

Pep

inia

cor

alli

na

2423

1918

1618

1820

2020

1919

2618

3118

2016

1620

1216

025

Pep

inia

spr

uce

i24

2319

1816

1818

2020

2019

1926

1831

1820

1616

2012

160

026

Pit

cair

nia

het

erop

hyl

la27

2718

1615

2016

2323

2322

2228

2230

1922

1818

2218

1918

1818

27P

itca

irn

ia o

rch

idif

olia

2423

1918

1618

1820

2020

1919

2319

3118

1813

1318

1216

55

518

28P

itca

irn

ia r

ecu

rvat

a26

2420

1918

1919

2222

2220

2027

2032

1920

1618

2013

187

77

197

29P

itca

irn

ia r

ubr

onig

rifl

ora

2423

1918

1618

1820

2020

1919

2618

3118

2016

1620

1216

00

018

57

30P

itca

irn

ia s

mit

hio

rum

2423

1915

1318

1520

2020

1919

2619

3118

2016

1620

1216

33

315

57

331

Pit

cair

nia

squ

arro

sa23

2218

1513

1515

1818

1816

1623

1828

1619

1515

199

154

44

164

54

432

Pu

ya a

equ

ator

iali

s22

1811

1211

1312

1616

1615

1522

1523

1212

88

1212

1211

1111

1211

1211

119

33P

uya

hu

mil

is22

2013

1211

1312

1616

1615

1522

1526

1215

1111

1512

1211

1111

1211

1211

119

334

Pu

ya l

axa

2218

1112

1113

1216

1616

1515

2215

2312

128

812

1212

1111

1112

1112

1111

90

335

Pu

ya w

erd

erm

ann

ii20

1912

119

1211

1515

1513

1320

1324

1113

99

1311

119

99

119

119

98

11

136

Epi

dry

os a

llen

ii90

9086

9089

8890

9090

9089

8993

8892

8684

8080

8489

8485

8585

8984

8585

8582

8284

8282

CAM IN PITCAIRNIOIDEAE 265


inia, other pitcairnioidean taxa have consistentlyappeared as sister groups in phylogenetic analyses todate. For instance, the genera (Navia + Cottendorfia)and (Encholirium + Dyckia) are always grouped inmolecular- (Terry et al., 1997; this study) and morphol-ogy-based trees (Varadarajan & Gilmartin, 1988b;Robinson & Taylor, 1999). The generic status of Navia,Pepinia, Pitcairnia and Deuterocohnia should be care-fully reconsidered given that their morphological diag-nostic characters may prove to be convergences ratherthan homologies.

Plant-specific features such as polyploidization, aninstant speciation agent, may facilitate convergentevolution, starting at the molecular level. For thisreason, major events in plant evolution are nowstarting to be re-investigated and molecular tools

are playing a central role in this process (for reviewssee Soltis & Soltis, 2000; Daly, Cameron & Steven-son, 2001). This is happening not only at lower butalso at higher taxonomic levels, whenever homologyhypotheses are difficult to confirm. Obviously, iflower level taxonomy is not well-established, even inimportant families such as Bromeliaceae, there islittle hope for higher level taxonomy in plants. Forinstance, our phylogenetic tree (Fig. 1) does not rein-force tribal subdivisions previously suggested forPitcairnioideae into two (Robinson & Taylor, 1999) orthree (Varadarajan & Gilmartin, 1988a) tribes. Rig-orous statistical tests in molecular systematics, suchas the bootstrap and the confidence probability tests,have proven reliable both in simulations (Sitnikovaet al., 1995) and in empirical tests (Russo, 1997).

Figure 1. Neighbour-joining tree with p-distances for 35 pitcairnioid species for MatK gene sequences. Epidryos (FamilyRapataceae) was used as the outgroup.

Dyckia dawsonii

Dyckia sp.

Dyckia ferox

Encholirium sp.

Encholirium inerme

Encholirium irwinii


CAM

Fosterella penduliflora

Fosterella elata

Fosterella petiolata

C3

C3 Pitcairnia heterophylla

Deuterocohnia lotteae

Deuterocohnia longipetala

Deuterocohnia sp.

CAM

Navia igneosicola

Pitcairnia squarrosa

Pitcairnia orchidifolia

Pitcairnia recurvata

Pitcairnia smithiorum

Pepinia beachiae

Pitcairnia rubronigriflora

Pepinia corallina

Pepinia sprucei

C3

Puya humilis

Puya werdermannii

Puya laxa

Puya aequatorialis

CAM/C3

Cottendorfia florida

Navia phelpsiaeC3

Brocchinia acuminata

Brocchinia micranthaC3

Hechtia guatemalensis

Hechtia glomerata

Hechtia glabra

Hechtia lindmanioides

CAM

Epidryos allenii

99

92

68

73

65

99

69

92

96

85

86

80

99

76

67

86

79

71

68

57 68

70

51

69

64

63



Such tests are known to distinguish between noiseand phylogenetic signals, and we strongly encour-age their use in plant phylogenetics. Molecular andstatistical tools have great potential to unravel plantphylogenetic relationships, contributing to a betterunderstanding of the origin of the photosyntheticpathways, such as the evolution of CAM.

CAM EVOLUTION

The basal placement of Hechtia (a CAM plant) ratherthan Brocchinia (a C3 plant) suggests that CAMmetabolism is a ‘primitive condition’ for the subfamily(Fig. 1). Clarifying the base of the tree is important ifwe are to understand how CAM has emerged in bro-meliads. If this pattern proves to be correct, it meansthat all C3 pitcairnioidean species have lost the abilityto induce CAM metabolism.

Figure 1 also shows that CAM seems to have origi-nated several times in this subfamily where it appearsscattered throughout the tree, as was reported for thePortulacaceae family (Guaralnick & Jackson, 2001).Nevertheless, if we plot the occurrence of CAM metab-olism in a morphologically based tree, surprisingly,CAM may have arisen only once (Fig. 2 – adapted fromVaradarajan & Gilmartin’s (1988b) data set). Indeed,we notice that, with the exception of Brewcaria, ofunknown photosynthetic pathway, CAM is present ina single clade. Note, however, that the genus Puya hasspecies that exhibit both types of metabolisms (C3 andCAM) and that the photosynthetic mode of some mem-bers is also uncertain.

Given that the two basal genera, namely Glomero-pitcairnia and Brocchinia, display C3 metabolism, theCAM photosynthetic pathway could well be inter-preted as a synapomorphy for the CAM clade in thismorphological analysis, contrary to the patternobserved in the molecular tree. In other words, giventhe distribution of C3 and CAM in the cladogram inFigure 2, it appears that a single evolutionary change

might have produced a shift from C3 to CAM pathwayin Pitcairnioideae. Differences between morphologicaland molecular trees regarding CAM distribution maybe explained by sampling differences in these studiesor by convergent evolution events.

The molecular tree presented here (Fig. 1) suggestsmultiple appearances of CAM in various pitcairnioidlineages. Nevertheless, a single origin of CAM in anancient plant lineage cannot be ruled out. In this sce-nario, CAM has been switching on and off in variouslineages. Biochemically, however, switches in descentlineages seem like an oversimplification because theseplants may show different ‘levels’ of CAM, such asCAM-cycling, CAM-idling and CAM-like (Ting, 1985;Monson, 1989). The expression of CAM in certainplants, such as Mesembryantheumum crystallinumand Guzmania monostachya, can be triggered eitherdevelopmentally or when they are subjected to variousstresses (e.g. water and salt stresses) (Maxwell, 2002;Ting, 1985; Winter & Ziegler, 1992; Saitou et al.,1994).

It has been proposed that all the machinery neces-sary for CAM is available in C3 plants, suggesting thata complex regulatory mechanism plays a key role inthe appearance of CAM (Cushman & Bohnert, 1997).However, the central issue still remains as to whetherCAM represents a single phylogenetic unit. More data,specifically on the promoter region of key enzymes ofCAM, is crucial.

Future avenues of research on the evolution ofphotosynthesis and the mechanisms which optimizecarbon assimilation should integrate two researchlines. The first must concentrate on a detailed andthorough study of the genetics, biochemistry andphysiology behind multiple photosynthetic com-plexes. The second should focus on the phylogeneticdistribution of such complexes. A combination ofthese approaches will provide sound empiricalgrounds for the formulation of hypotheses of photo-synthetic identities and origins.

Figure 2. Maximum parsimony tree for an ecomorphological data set (redrawn from Varadarajan & Gilmartin, 1988b).

Brewcaria Dyckia Encholirium Deuterocohnia Abromeitiella Puya Hechtia

CAM

Steyerbromelia Pitcairnia Pepinia Cottendorfia Ayensua Navia Connelia Fosterella

C3

Brocchinia Glomeropitcairnia

CAM IN PITCAIRNIOIDEAE 267


ACKNOWLEDGEMENTS

The authors wish to thank CNPq (Brazilian researchcouncil) and FAPERJ (Rio de Janeiro’s research foun-dation) for research grants, and Andrew Macrae forsuggestions about the manuscript.

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