The Phylogenetic Affinities of Two Mysterious Monotypic Mimosoids from Southern South America

585

Systematic Botany (2005) 30(3) pp 585ndash602q Copyright 2005 by the American Society of Plant Taxonomists

The Phylogenetic Affinities of Two Mysterious Monotypic Mimosoids fromSouthern South America

MELISSA LUCKOW14 RENEE H FORTUNATO2 SILVANA SEDE3 and TATYANA LIVSHULTZ1

1L H Bailey Hortorium 228 Plant Sciences Cornell University Ithaca New York 148532Consejo Nacional de Investigaciones Cientıficas y Tecnicas (CONICET) at Instituto de Recursos Biologicos

INTA Castelar 1712 Buenos Aires Argentina3Laboratorio de Citogenetica y Evolucion Departamento de Ecologıa Genetica y Evolucion

Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires Ciudad UniversitariaPabellon II Piso 4 C1428EHA Buenos Aires Argentina

4Author for correspondence (MAL8cornelledu)

Communicating Editor Matt Lavin

ABSTRACT Two monotypic genera of Mimosoideae from southern South America Mimozyganthus and Piptadeniopsishave been particularly difficult to classify and there has been disagreement about their relationships to other legume generaWe undertook a phylogenetic study based on molecular data from the chloroplast and nucleus and synthesized it with newdata from morphology cytology and palynology in order to determine where these genera belong in the mimosoid phy-logenetic tree Mimozyganthus an enigmatic genus whose unique morphology led workers to consider it transitional betweenthe subfamilies Mimosoideae and Caesalpinioideae is instead nested among the higher mimosoids on the molecular treeCareful evaluation of the characters that were considered to be caesalpinioid-like reveals that they are not identical and areindependently derived Piptadeniopsis is most closely related to Prosopidastrum a primarily Argentinian genus with lomen-tiform fruits This is in close agreement with most morphological characters although the pollen is different in the twogenera Piptadeniopsis Mimozyganthus and Prosopidastrum form a monophyletic group on all molecular trees a result consis-tent with vegetative and fruiting morphology but not floral characters Although the relationship of this group to other taxais unresolved in the individual molecular analyses a combined analysis of all molecular data for a subset of the taxa revealsthat the three taxa are more closely related to the Leucaena group than to Prosopis We hypothesize that the unique floralcharacters of Mimozyganthus may have evolved in response to pollinator selection and a pollination study is needed to testthis hypothesis

There are two monotypic genera of Mimosoideae(Leguminosae) from southern South America whoserelationships to other taxa have been controversial andsubject to differing interpretations Mimozyganthus is ashrub confined to the Chaco Phytogeographic Region(Cabrera and Willink 1973) of Bolivia Paraguay andArgentina Piptadeniopsis is likewise a shrub of this sea-sonally dry region but restricted to central Paraguay(Fig 1) Both genera have a number of specializationsthat have made their placement within the mimosoidsdifficult to determine and Mimozyganthus in particularhas such a unique combination of characters that it hasbeen hard to ascertain its affinities with any other ge-nus in either the Mimosoideae or Caesalpinioideae

Burkart (1939) was the first to discuss the uniquefeatures of Mimozyganthus carinatus (Griseb) Burkartwhich he placed in its own monotypic tribe Mimoz-ygantheae in the Mimosoideae He considered the veg-etative features of Mimozyganthus to be most like thoseof Prosopis as both genera have spinescent stipules butnoted that Mimozyganthus has a number of featuresthat are rare or unusual in the Mimosoideae For ex-ample a defining character of the Mimosoideae hasbeen that the aestivation of sepals and petals is valvateHowever the petals of Mimozyganthus are valvateabove but not necessarily below and aestivation of thesepals is imbricate (Fig 2B D) a characteristic seenelsewhere in the Mimosoideae only in Parkia and Pen-

taclethra In addition the tip of the style of most mi-mosoids ranges from tubular to porate (Lewis and Eli-as 1981) but the stigma of Mimozyganthus is massiveand peltate (Fig 3A) Because imbricate sepals arecommon in the Caesalpinioideae Burkart argued thatMimozyganthus was probably intermediate between theCaesalpinioideae and Mimosoideae possessing a mo-saic of characters from both subfamilies In a subse-quent publication Burkart (1943) related Mimozygan-thus to the Amazonian mimosoid genus Dinizia basedon imbricate sepals and indehiscent fruits and trans-ferred the latter into tribe Mimozygantheae Diniziaand Mimozyganthus (the latter reported by Ancibor1969) each have a nectary in a distinct hypanthium asseen in some genera of Caesalpinioideae eg Dimor-phandra (Elias 1981) More recent treatments (Hutch-inson 1964 Schultz-Menz 1964 Elias 1981 Polhill1994) have treated the Mimozygantheae as monospe-cific but have retained Burkartrsquos hypothesis that itmight be an intermediate link between the Caesalpi-nioideae and Mimosoideae

Piptadeniopsis lomentifera Burkart although clearly amember of the Mimosoideae has also been difficult toclassify Burkart (1944) in discussing his reasons forgeneric distinction pointed out that although the an-ther glands and exalbuminous seeds of Piptadeniopsiswere similar to those of Piptadenia the valves of thefruits were more like those of Prosopidastrum (Fig 4F)

586 [Volume 30SYSTEMATIC BOTANY

FIG 1 Map of the distributions of Mimozyganthus Piptadeniopsis and Prosopidastrum in southern South America

He postulated a relationship with the Niopa group ofPiptadenia (now the segregate genus Anadenanthera) asboth Piptadeniopsis and Anadenanthera have capitate in-florescences Lewis and Elias (1981) placed Piptadeniop-sis in their informal Prosopis group with the generaProsopis Xerocladia and Prosopidastrum rather than inthe Piptadenia group but noted that it might be moreclosely related to Piptadenia based on pollen data Pol-len of members of the Prosopis group is in tricolporatemonads whereas Piptadenia and allies have porate po-lyads Sorsa (1969) reported polyads in Piptadeniopsisand considered the pollen to be most like that of AcaciaGuinet (1981) agreed that pollen of Piptadeniopsis wasmost similar to that of Acacia ss (A subgenus Acacia)according to Guinet both have columellate polyadswith three distally fused colpori Based on these pollendata he assumed that Acacia ss (and Piptadeniopsis)shared a common ancestor with the Piptadenia groupof Mimosoideae Thus we have a number of conflictinghypotheses for the affinities of Piptadeniopsis floralcharacters relate it to the Piptadenia group pollen char-

acters to Acacia ss and fruit and vegetative charactersto the Prosopis group

Not one of the hypotheses of relationships for eithertaxon has been tested using modern methods of phy-logenetic analysis For this reason we undertook mor-phological and molecular studies to answer the follow-ing questions

1 Is Mimozyganthus more closely related to the Cae-salpinioideae Mimosoideae or intermediate be-tween the two What do the morphological featuresreconsidered in the context of the available phylog-eny reveal about character evolution in Mimozygan-thus

2 Is Piptadeniopsis most closely related to the Pipta-denia group the Prosopis group or Acacia ss

METHODS AND MATERIALS

We collected data from morphology pollen cytology and chlo-roplast and nuclear DNA for Mimozyganthus and PiptadeniopsisHerbarium specimens seeds pickled material and leaves in silicagel were collected in the field in Paraguay and Argentina Mor-

2005] 587LUCKOW ET AL MYSTERIOUS MIMOSOIDS

FIG 2 Mimozyganthus carinatus A Habit with Renee Fortunato for scale B Imbricate aestivation of the sepals Note thatthe bract is at the bottom and the median sepal (arrow) is adaxial C Spinescent stipules and terete branchlet D Valvateaestivation of the petals E Anther with terminal appendage but no gland F Flower Note imbricate free sepals and capitatestigma (arrow)


FIG 3 Mimozyganthus carinatus A Convexly peltate capitate stigma from flower at anthesis B Stigma in bud Note hairscovering the stigmatic surface C Seeds of Mimozyganthus (3 upper) and Piptadeniopsis (lower) Note the wing-like rim and lackof pleurogram on each seed F Fruits of Mimozyganthus showing the flattened ventral suture (arrow)

phology of all species referenced in this paper was studied fromthe newly collected specimens as well as from specimens at thefollowing herbaria BAB BH CORD CTES IZAC LIL MO NYPY SI and US For scanning electron microscopy (SEM) flowerswere reconstituted in hot water dehydrated in ethanol and criti-cal-point dried in a Bal-tec CPD 030 Specimens were sputter-coat-ed with gold palladium in a Bal-tec SCD 050 and observed on aLeo DSM 960 or Hitachi S-4500 SEM at Cornell Integrated Mi-croscopy Center or a JEOL JSM-35CF at Instituto de NeurobilogıaCONICET Pollen was mounted fresh on stubs and the same pro-cedures implemented for sputter coating and scanning electronmicroscopy as described above Polyads of Piptadeniopsis were sep-arated by immersing the material in ethyl-cellosolve (3ndash4 ml) thenin 50 glycerine and ultrasonicated for 4ndash5 min (methodologyfrom J Gamerro) The separated polyads were stained with fuch-sin and observed with a Leitz Dialux 20RB microscope

Chromosomes of Piptadeniopsis were counted using root tips andflower buds but only mitotic counts were made of MimozyganthusFor mitotic counts root tips were pretreated for 35 hours in 0002M 8- hydoxyquinoline at 208 C fixed in 3 parts absolute ethanolto 1 part acetic acid After 30 min of hydrolysis in 5 N HCl at 208

C root tips were stained in Feulgen solution (Lillie 1951) andsquashed in 2 propionic haematoxylin with ferric citrate as amordent (Nunez 1968) For meiotic counts flower buds were fixedin 6 parts absolute ethanol 3 chloroform 1 acetic acid and theanthers squashed in 2 acetic haematoxylin Squashes were ob-served using a Leitz Westlar microscope equipped with a Leicacamera

Molecular phylogenetic studies were based on previously pub-lished data sets for the Mimosoideae (Luckow et al 2000 2003Hughes et al 2003) to which we added sequences from multipleaccessions of Mimozyganthus and Piptadeniopsis For the chloroplasttree we added three caesalpinioid legumes (three species of Par-kinsonia sl[5 Parkinsonia 1 Cercidium]) that we thought based onmorphology might be related to Mimozyganthus Sequences for oneor more of the gene regions were missing in the original data setand we included new data for them as well (Table 1) BecausePiptadeniopsis had been put in the Prosopis group by some workerswe also sequenced additional species of Prosopis

The chloroplast data set consists of three gene regions trnL-trnFtrnK and matK nuclear data is drawn from the nrDNA 58S andflanking internal transcribed spacer regions (ITS1 and ITS2) DNA


FIG 4 Piptadeniopsis lomentifera A Habit with Fatima Mereles for scale B Leaves with a single pair of pinnae C Anthergland D Dissected flower showing stamens with anther glands stipitate ovary and porate stigma Note how anther gland isinserted on the abaxial side of the anther E Porate non-papillate stigma F Loment pods


TABLE 1 Voucher specimens for molecular sequences and chromosome counts Genbank accession numbers are included for the newsequences See Luckow et al (2003) and Hughes et al (2003) for accession numbers for other taxa in the analyses NA 5 not applicable

Vouchers for molecular analyses with Genbank numbers for trnL matKtrnK and ITS Calpocalyx dinklagei HarmsmdashF JBreteler 15461(WAG) Luckow et al (2003) AY944551 NA Cercidium andicola GrisebmdashR Fortunato 7638 (BAB BH) AY944536AY944552 NA Cojoba catenata (Donn Sm) Britton amp RosemdashM Alford 3017 (BH) AY944538 AY944554 NA Mimosa albida varwildenowii Humb amp Bonpland ex WilldmdashBB Klitgaard 648 (K) Luckow et al (2003) AY944555 NA Mimozyganthus carinatus(Griseb) BurkartmdashM Luckow 4484 (BAB BH) AY944540 AY944557 AY944569 R Fortunato 7575 (BAB BH) AY944539AY944556 AY944570 Parkinsonia aculeata LmdashR Fortunato 7570 (BAB BH) Luckow et al (2003) AY944558 NA Parkinsoniapraecox (Ruiz amp Pavon) HawkinsmdashR Fortunato 7566 (BAB BH) AY944537 AY944553 NA Piptadeniopsis lomentifera BurkartmdashM Luckow 4505 (BAB BH) AY944542 AY944560 AY944567 M Luckow 4476 (BAB BH) AY944541 AY944559 NA Prosopidastrumangusticarpum R A Palacios amp HocmdashDesert Legume Project M Luckow sn (BH) AY944543 Luckow et al (2003) AY944568Prosopis elata (Burkart) BurkartmdashM Luckow 4485 (BAB BH) AY944544 AY944561 NA Prosopis nigra (Griseb) HieronmdashRFortunato 7564 (BAB BH) AY944545 AY944562 NA Prosopis rojasiana BurkartmdashM Luckow 4486 (BAB BH) AY944546 AY944563NA Stryphnodendron porcatum D A Neill amp Occhioni fmdashD Neill 14001 (MO) AY944547 AY944564 NA Xylia hoffmannii (Vatke)DrakemdashM Luckow 4144 (BH) AY944548 Luckow et al (2003) NA Zapoteca formosa (Knuth) H M HernandezmdashR W Jobson1046 (BH) AY944549 AY944565 NA Zygia lathetica Barneby amp J W GrimesmdashD Neill 14002 (MO) AY944550 AY944566 NA

Vouchers for chromosome counts Mimozyganthus carinatus R Fortunato 7353 (BAB) Piptadeniopsis lomentifera M Luckow 4505(root tips) 4476 (root tips) 4475 (flower buds) all BH BAB

was isolated from leaves that were preserved in silica gel in thefield Total DNA was isolated using DNeasy Plant Mini Kit (QIA-GEN Hilden Germany) For the chloroplast genes the PCR re-action mix consisted of 10 mL of 10X buffer with diluted concen-trations of 67 mM tris (pH 80ndash88) 2mM magnesium chloride2mgmL BSA and 1mM dNTPs (Paabo 1990) 6 mL of 10 mMforward and reverse primers 1 U of taq polymerase and 1 mL ofundiluted DNA extract in a final volume of 100 mL DNA frag-ments of the trnL-trnF IGS and trnL intron were amplified usingthe primers lsquolsquocrsquorsquo and lsquolsquofrsquorsquo of Taberlet et al (1991) The temperatureprofile for amplication consisted of a 3 min initial heating at 948C followed by 35 cycles of 1 min at 948 C 1 min at 558 C and 1min at 728 C ending with 7 min at 728 C Because of the presenceof large homopolymer regions fresh PCR products were clonedwith the TOPO TA Cloning Kit (Invitrogen Carlsbad CA) andOne-Shot competent cells (Invitrogen Carlsbad CA) Positive col-onies were identified via PCR with primers c and f Plasmids fromone positive colony per accession were purified with the QIAquickPlasmid Prep Kit (QIAGEN) Nucleotide sequences were deter-mined from portions of both strands using the amplification prim-ers and internal primers lsquolsquoersquorsquo and lsquolsquodrsquorsquo The matK gene and the 39end of the trnK intron were amplified with primers Ac12F andAc1707R (Miller and Bayer 2003) substituting a 528 C annealingtemperature and 2 min extension time in the amplification pro-gram Amplified products were separated on 07 agarose TBEgels purified using the QIAquick Gel Extraction Kit (QIAGEN)and sequenced with primers Ac12F Ac1104F and Ac1145R ITSwas sequenced following the protocols described in Hughes et al(2003) Automated sequencing was done by the Cornell Biotech-nology sequencing facility using Applied Biosystems ABI373 andABI377 machines All sequences have been deposited in GenbankGenbank accession numbers for the new sequences are listed inTable 1 all other Genbank accession numbers are listed in Luckowet al (2003) or Hughes et al (2003)

Chromatographic traces were edited in Sequencher 30 (GeneCodes Corporation Ann Arbor Michigan) to produce contiguoussequences Sequences were added to the existing data sets andedited manually in Winclada ver 0999 (Nixon 2001) to minimizegaps and base substitutions Because identical sequences can biasbootstrap results and slow computation time multiple accessionsof Mimozyganthus and Piptadeniopsis were each fused into one ter-minal as they were identical for informative cpDNA charactersAll other taxa in the cpDNA analysis had unique combinations ofinformative characters ITS sequences from three samples repre-senting two accessions of Mimozyganthus were found to be iden-tical and were fused prior to analysis Ten sequences of Leucaena

were likewise fused (Fig 8) all were sister taxa in the original ITStree published by Hughes et al (2003) The presenceabsence ofindels was scored as independent binary characters except in ho-mopolymer regions or where homology assessment was deemedarbitrary (Buroker et al 1990 Golenberg et al 1993)

A third matrix was constructed for a simultaneous analysis ofnuclear and chloroplast genes This matrix represents only a sub-set of the taxa from each individual data set as taxa were prunedfrom the ITS data set to correspond to those in the chloroplasttree In order to improve sampling density different but relatedspecies were combined as a single terminal for a few samples ofMimosa Prosopis and Alantsilodendron These amalgamated taxaare indicated in the data set and in Fig 9 A small morphologicalmatrix of 16 characters that have been considered important in thetaxonomy of Mimozyganthus and Piptadeniopsis was also scored forthis subset of taxa to allow discussion of the evolution of thesecharacters in a phylogenetic context Characters and states are list-ed in Fig 9 All aligned matrices are available in TREEBASE(study accession number S1250 matrix accession numbers M2178ndash2180)

Parsimony analyses were done spawning Nona ver 20 (Golo-boff 1993) from Winclada and employed a heuristic search strat-egy Tree searches were performed with 1000 replicates holding20 trees in each search and branch swapping with a maximumof 50000 most parsimonious trees to be held overall Additionalsearches for islands of most parsimonious trees were conductedusing the Parsimony Ratchet feature of Winclada (Nixon 1999)with five independent analyses of 200 iterations holding 5 treesper replicate and randomly reweighting 50 characters with eachiteration Strict-consensus bootstrap values were computed inWinclada and Nona with 1000 replicates and 10 tree bisection-reconnection searches and holding one tree per replicate (Davis etal 1998 Soreng and Davis 1998) and were rounded to percentagesand mapped to the strict consensus tree in Winclada

RESULTS

Morphology The morphology of Mimozyganthus isas described by Burkart (1939) It is a large shrub withhorizontal spreading branches (Fig 2A) and spines-cent stipules (Fig 2C) The flowers are small andgrouped in capitate inflorescences Sepals are imbri-cate at anthesis with the median sepal adaxial (Fig 2Barrow) In contrast petals have valvate aestivation (Fig


2D) There are 10 free stamens and the anthers bear asmall terminal appendage (Figs 2E F) The gynoeci-um is short-stipitate The stigma is convexly peltateand in older flowers becomes broadly expanded andpentagonal (Fig 3A) The stigma is wet-papillate (Figs3A B) a type commonly found in the Caesalpinioi-deae and Papilionoideae (Owens and Lewis 1996 Shi-vanna and Owens 1989) The fruits are samaroid 1ndash2seeded with the ventral suture flattened into a smallwing-like structure (Fig 3D arrow) The valves arechartaceous The seeds are dorsiventrally flattenedwith a winglike rim and lack both endosperm and apleurogram (Fig 3C) Pollen is simple in tricolporatemonads and the exine is verrucate and the colpusmembranes are granulate (Fig 5A)

Piptadeniopsis is similar to Mimozyganthus in manyvegetative features It is a large much-branched shrub(Fig 4A) with spinescent stipules The leaves consis-tently have a single pair of pinnae (Fig 4B) The flow-ers have typical mimosoid features aestivation of thecalyx and corolla are both valvate the anthers areequipped with a stipitate gland (Fig 4C) the gynoe-cium is stipitate and villous and the stigma is of thewet non-papillate type (Owens 1990) and porate (Figs4D E) The fruits are lomentiform (Fig 4F) with char-taceous valves and each segment breaks off separatelyat maturity The seeds are quite similar to those ofMimozyganthus they lack a pleurogram are exalbu-minous and are dorsiventrally flattened with a wing-like rim (Fig 3C) As previously reported by Guinet(1969) pollen is in 8ndash12- or 16-grained polyads the 8-grained polyad was most common in our sample (Fig5B) Guinet described the grains as having 3ndash4 colpiand 3 pores per grain We observed only pores in oursample (Fig 5C E) although there appears to be agranular central portion on each grain (Fig 5C D)Our observations are most consistent with those ofSorsa (1969) who described the apertures as porate

Cytology Chromosome numbers for Mimozygan-thus were previously reported to be 2n528 or 56 (Kra-povickas 1965) indicating both diploid and tetraploidnumbers for the genus Although these counts weretaken from a single collection it is not clear that theywere taken from a single individual We found onlydiploid cells during our investigations (Fig 5F) whichconfirms the 2n528 number for the genus No chro-mosome number has ever been reported for Piptaden-iopsis Both meiotic (n514 Fig 5G) and mitotic(2n528 Fig 5H) squashes reveal a haploid number ofn514

Molecular Phylogenies The complete cpDNA ma-trix had 153 terminals and 1172 potentially informativecharacters Phylogenetic analysis was stopped at50000 trees of 3508 steps CI 5 048 RI 5 073 Theparsimony ratchet added another 1188 equally parsi-monious trees none of which affected resolution in the

strict consensus from the initial analysis A summaryof the strict consensus of all trees is shown in Fig 6and complete sampling in the area of interest in Fig7 The details not shown in Fig 6 do not differ fromthe complete cladogram of Luckow et al (2003) and acladogram of all taxa not shown in Fig 6 can be seenin Luckow et al (2003) and Luckow et al (in prep)The three species of ParkinsoniaCercidium are nestedat the base of the tree among all the other caesalpi-nioids (Fig 6) Dinizia is also part of the basal poly-tomy that includes members of the CaesalpinioideaeMimozyganthus and Piptadeniopsis form a weakly sup-ported (bs 5 66) clade with Prosopidastrum (Fig 7)which in turn is weakly (bs5 49) supported as sisterto the Leucaena group (Leucaena Schleinitzia Desman-thus Kanaloa) The genus Neptunia recently excludedfrom the Dichrostachys group by Luckow (1997) is sis-ter to the entire clade Although the Prosopis groupconsisting of Prosopis Prosopidastrum Piptadeniopsisand Xerocladia (not included here) is not demonstratedto be monophyletic on the tree the Dichrostachys andLeucaena groups are strongly supported as monophy-letic Relationships among the Prosopis Dichrostachysand Leucaena groups are unresolved

The ITS data set lacks the breadth of taxon samplingof the cpDNA data primarily because alignment be-comes problematic over a wider taxonomic span(Hughes et al 2003) However this data set has moreintensive sampling of taxa in the area of interest Thefinal matrix had 103 terminals and 446 potentially in-formative characters Analysis of ITS data alone re-sulted in 243 trees of 1382 steps CI 5 045 RI 5 085the strict consensus is shown in Figs 8A B Many re-sults from the cpDNA analysis are confirmed by theITS data For example Mimozyganthus Piptadeniopsisand Prosopidastrum form a clade in both analyses withPiptadeniopsis and Prosopidastrum as sister taxa al-though bootstrap support for the Mimozyganthus cladeis higher (bs581) in the ITS tree than with thecpDNA data (bs 5 66) The Leucaena and Dichro-stachys groups are monophyletic with high bootstrapsupport in both analyses and relationships withinthese groups are largely congruent There are how-ever a number of differences between the nuclear andchloroplast trees most notably in the placement ofNeptunia It is sister to the Mimozyganthus clade plusthe Leucaena group in the chloroplast tree (bs 5 60)but weakly (bs 5 46) supported as sister to the Di-chrostachys group 1 Leucaena group 1 Mimozyganthusclade in the ITS tree (Fig 8A) The ITS tree also addsresolution in some parts of the phylogeny Prosopis un-resolved relative to the Dichrostachys group and theLeucaenaMimozyganthus clade in the chloroplast treeis weakly supported as outside these groups with ITSA number of probable pseudogene sequences were de-tected among Desmanthus and Leucaena species ac-


FIG 5 AndashE Pollen A Tricolporate monad of Mimozyganthus carinatus with verrucate exine and granular colpi BndashE Pollenof Piptadeniopsis lomentifera B 8ndash12- or 16-grained polyads C SEM view of 8-grained polyad showing lack of syncolpi on thegrains D Light microscopic view of 8-grained polyad E Single grain dissected from a polyad showing the porate aperaturesNote also collumellate exine FndashH Chromosome counts F Mitotic cell of Mimozyganthus carinatus 2n528 G Metaphase I cellof Piptadeniopsis lomentifera with 14 bivalents H Mitotic cell of Piptadeniopsis lomentifera 2n 5 28


FIG 6 Summary of the strict consensus of 51188 most parsimonious trees for the Mimosoideae of 3508 steps CI 5 048RI 5 073 Phylogeny is based on chloroplast genes trnL-trnF matK and trnK Members of the Caesalpinioideae are in italicsBootstrap values are above the nodes


FIG 7 Detail of the consensus tree in Fig 6 showing the position of Mimozyganthus and Piptadeniopsis relative to the Leuceanagroup and Neptunia


counting for the polyphyletic occurrence of some spe-cies (eg Desmanthus bicornutus) on the tree (seeHughes et al 2003 for discussion)

Because the analyses were largely congruent thechloroplast and nuclear data were pruned to includeonly the shared taxa and the data were combined Theresultant matrix of 37 taxa and 578 potentially infor-mative characters returned a single most parsimoni-ous tree length 5 1300 CI 5 057 RI 5 075 Theoutstanding feature of this tree (Fig 9) is that it pro-vides reasonable support (bs 5 83) for the hypoth-esis that the Mimozyganthus clade is sister to the Leu-caena group It also places Neptunia as sister to the Di-chrostachys group 1 Leucaena group 1 Mimozyganthusclade albeit with weak support (bs551) The samesubset matrix but with the 16 morphological charac-ters added increased the number of equally parsimo-nious trees from one to four length 5 1339 CI 5 057RI 5 075 In the strict consensus the position of Nep-tunia is unresolved (Fig 9)

DISCUSSION

Is Mimozyganthus Intermediate Between the Cae-salpinioideae and Mimosoideae Our phylogeneticanalyses show that Mimozyganthus is not intermediatebetween Caesalpinioideae and Mimosoideae but in-stead is part of a clade of mostly South American high-er mimosoids This result calls for reevaluation andreinterpretation of the morphological characters thatseem more typically caesalpinioid than mimosoid inparticular imbricate aestivation of the sepals a peltatepapillate stigma and absence of a pleurogram Imbri-cate aestivation is found among the mimosoids only inParkia and Pentaclethra where the sepals are connaterather than free Dinizia considered by Burkart (19431952) to be closely related to Mimozyganthus because ithas free imbricate sepals was reported by Lewis andElias (1981) to have valvate sepals but imbricate petalsOur study of herbarium specimens revealed that thesepals of Dinizia are reduced and it was difficult todetermine their aestivation without a developmentalseries of the flowers In any case independent datashow that sepal initiation in Mimozyganthus is not iden-tical to that in the caesalpinioids Tucker (1989) re-ported that the median sepal in Caesalpinioideae isabaxial whereas in Mimosoideae it is adaxial (but seeHerendeen et al 2003 for exceptions in the Caesalpi-nioideae) The median sepal of Mimozyganthus is ad-axial (Fig 2B) as in most other mimosoids and con-sistent with its placement on the molecular trees

Wet papillate stigmas although common in the Cae-salpinioideae and Papilionoideae (Owens 1989 Owensand Lewis 1996) have not been previously reported inany mimosoid There are a number of caesalpinioidswith stigma morphology similar to that of Mimozygan-thus (eg Gleditsia see Owens and Lewis 1996 their

fig 1 D) but the protruberences on the stigma of Mi-mozyganthus (Fig 3B) are more hairlike and less tuber-culate than those in the Caesalpinioideae The peltatestigma of Mimozyganthus is not dissected by a stylargroove unlike many caesalpinioids in which the stig-mas are bilobed due to the stylar groove (Owens andLewis 1996)

Absence of a pleurogram is also characteristic of theCaesalpinioideae but is seen occasionally in the mi-mosoids where it is highly correlated with wind-dis-persal In mimosoids either seeds or fruits can bewind-dispersed and lack of a pleurogram is foundmost often in taxa with wind-dispersed seeds For ex-ample members of the Newtonia group (Newtonia Cy-licodiscus Indopiptadenia Piptadeniastrum) the Piptad-enia group (Parapiptadenia Pseudopiptadenia) and Fil-laeopsis all have winged seeds that lack a pleurogram(Gunn 1984) Wind-dispersed fruits in which the seedslack a pleurogram are less common found only in thegenera Aubrevillea Piptadeniopsis and MimozyganthusSeeds of the latter two taxa are anatomically similar tothe winged seed they are highly dorsiventrally flat-tened lack endosperm and have a thin testa Therimmed edges are reminiscent of wings (Fig 3C) Theseeds of Prosopidastrum and Anadenanthera althoughhaving a pleurogram may also have rimmed edgesalthough this varies within the genus ProsopidastrumLack of a pleurogram can thus best be viewed as aninnovation that Mimozyganthus shares with Piptadeniop-sis and possibly Prosopidastrum (Fig 9 char 11)

In summary some of the morphological charactersof Mimozyganthus that have been used as evidence ofintermediacy between the two subfamilies are uncom-mon but not unknown in other mimosoids and so donot necessarily conflict with a molecular phylogeny inwhich Mimozyganthus is nested among the higher mi-mosoids Furthermore there is evidence that somecharacters are not identical and so probably not ho-mologous with the similar state in the Caesalpinioi-deae However it is unusual to find such a confluenceof distinctive characters in a single monotypic taxonand the combination of the three characters (imbricatesepals peltate stigma and lack of a pleurogram) hasbeen more powerful than any one character might beif considered individually

What do Morphological Features Reconsidered inthe Context of the Available Phylogenies Reveal aboutCharacter Evolution in the Mimozyganthus CladeThe sister-group relationship of Mimozyganthus to Pip-tadeniopsis and Prosopidastrum also requires a reevalu-ation of morphology primarily because the three gen-era differ in so many floral traits (Table 2 Fig 9) Pip-tadeniopsis and Prosopidastrum have a typical mimosoidflower with valvate aestivation of calyx and corollaanther glands and a porate stigma This contrasts withthe imbricate sepals and papillate peltate stigma (Fig


FIGS 8A B Strict consensus of 243 most parsimonious trees of 1382 steps CI 5 045 RI 5 085 Phylogeny is based thenrDNA 58S and flanking internal transcribed spacer regions (ITS1 and ITS2) most of the sequences are from Hughes et al(2003) Strict consensus bootstrap values are above the nodes Putative pseudogenes were detected and may explain the po-lyphyly of some species on the tree (eg Desmanthus bicornutus)

9 char 6) of Mimozyganthus In addition Mimozygan-thus lacks an anther gland but instead has an extendedapiculate connective (char 5) The calyx is free in Mi-mozyganthus (char 4) and connate in Piptadeniopsis andProsopidastrum The pollen is also variable Mimozygan-thus (Fig 5A) and Prosopidastrum (Palacios and Hoc2001) have tricolporate monads Piptadeniopsis has por-ate polyads (Fig 5B C Fig 9 chars 14 15) Overall

the flowers of Mimozyganthus and Piptadeniopsis areabout as distinct from one another as any in the Mi-mosoideae

What the three taxa share are some vegetative andfruit characters as well as geographic proximity anda long history in arid regions They all have a shrubbyhabit although Prosopidastrum has distinctive photo-synthetic often leafless spinose stems These stems



FIG 9 Phylogenetic tree from combined data for a subset of taxa The fully resolved tree is the single most parsimonioustree of 1300 steps CI 5 057 RI 5 075 from the combined nuclear and cpDNA sequence data Bootstrap values are the largernumbers below the nodes Dashed branches are those that collapse in the strict consensus of four MPTs of 1339 steps CI 5057 RI 5 075 that result when 16 morphological characters are added Taxa have been fused and pruned from the originalmolecular data sets to provide maximum overlap Fused terminals are indicated with a slash between species epithets the firstepithet is the source of the ITS sequence the second epithet applies to the cpDNA data Morphological character changes arerepresented by black (uncontested synapmorphy) or white (homoplastic changes) boxes Numbers above the boxes correspondto the characters as shown in the legend and discussed in the text small numbers below the boxes are the character statechanges


TABLE 2 A comparison of key characters among Mimozyganthus Piptadeniopsis and their hypothesized relatives Chromosome numbersfor the Piptadenia group Acacia ss and the Prosopis group taken from Goldblatt 1981 Prosopidastrum from Lewis and Elias 1981 Seetext for discussion

Taxon Stipular spines Sepal aestivation Pollen Pleurogram Chromosome number

Mimozyganthus Present Imbricate Monads tricolporatecollumellate

Absent 2n514 28 prob x5 14

Piptadeniopsis Present Valvate Polyads porate col-lumellate

Absent x514

Prosopidastrum Present Valvate Monads tricolporatecollumellate

Present Faint 2n514 28 prob x5 14

Acacia ss Present Valvate Polyads colporatecollumellate

Present x513

Dinizia Absent Tetrahedral tetradscolporate collu-mellate

Absent x5

Leucaena group Absent Valvate Polyad or monadstricolporate orporate collumel-late

Present x514

Piptadenia group Present (InPart)

Valvate Polyads porategranular

Present (Except 2Genera WithWinged Seeds)

x513

Prosopis group Present Valvate Monads tricolporatecollumellate

Present x514

are angled with golden corky ridges very similar tothose of Neptunia Young stems of Piptadeniopsis arelikewise photosynthetic with less pronounced corkyridges whereas those of Mimozyganthus are terete Alltaxa have spinescent stipules (Fig 9 char 1) and thoseof Prosopidastrum are equipped with glands at the base(Palacios and Hoc 2001) Fruits of the three taxa arealso similar they have chartaceous pericarps and dor-siventrally flattened rimmed seeds (char12) Theseeds of Prosopidastrum mexicanum (Dressler) Burkarthave very little endosperm and are quite similar mor-phologically to those of Mimozyganthus and Piptaden-iopsis although still retaining a faint pleurogram Incontrast seeds of the Argentine species of Prosopidas-trum are lsquolsquotypicalrsquorsquo mimosoid seeds with abundant en-dosperm and thicker seed coats Prosopidastrum is alsovariable in fruit type although most species have lo-ments (char 9) the fruit of P dehiscens dehisces onlyalong the ventral suture (Palacios and Hoc 2001)

Mimosoid taxonomy has traditionally relied on flo-ral characters which tend to be quite conservativecompared to fruiting and vegetative characters For ex-ample until recently stamen number and connationwas used to delimit tribes and the importance of aes-tivation of the perianth as a subfamilial character hasalready been discussed Thus without a molecularphylogeny one might have hypothesized that the thinpericarps and flattened rimmed seeds lacking a pleu-rogram of Mimozyganthus Piptadeniopsis and Prosopi-dastrum were parallel adaptations to wind or water dis-persal Likewise photosynthetic stems and stipularspines are ubiquitous in the Chaco region and arefound in most of the legumes from that area (eg Par-

kinsonia Prosopis) so one might assume parallel deri-vation of these features in the Mimozyganthus cladeHowever in light of the phylogenetic analysis it seemsthat these characters are synapomorphies (Fig 9) TheMimozyganthus clade is thus highly unusual becausefloral characters are plastic and fruit and vegetativecharacters are conserved

Geography would also support a close relationshipamong the three taxa (Fig 1) Prosopidastrum has a bi-centric distribution with one species in Mexico and therest in Argentina where species are native to the Mon-te Phytogeographic Province (Cabrera 1994) in thefoothills of the Andes from Prov San Juan south toProv Santa Cruz northeast into the Rio Negro Therange of Mimozyganthus lies largely north of this in theChaco Phytogeographic Region (Cabrera 1994) fromProv San Luis in Argentina north into southwesternParaguay and southeastern Bolivia (Fortunato 1997)Although there is some range overlap with Prosopidas-trum in the northern Argentine provinces of Catamar-ca and La Rioja they inhabit different phytogeograph-ic regions Piptadeniopsis confined to central Paraguayis allopatric with Prosopidastrum but sympatric withMimozyganthus where both were found even within thesame small patch of woodland

Is Piptadeniopsis (and Therefore the Mimozygan-thus Clade) More Closely Related to the PiptadeniaGroup the Prosopis Group or Acacia ss All anal-yses indicate that Piptadeniopsis belongs in a clade withMimozyganthus and Prosopidastrum and so the relevantquestion becomes lsquolsquowhat are the affinities of the Mi-mozyganthus cladersquorsquo rather than of Piptadeniopsis per seMuch of our new evidence argues against a close re-


lationship of Piptadeniopsis andor the Mimozyganthusclade with either Piptadenia or Acacia ss The new chro-mosome count for Piptadeniopsis of n 5 14 is inconsis-tent with the x 5 13 number for both Piptadenia andAcacia (Table 2) The molecular data also consistentlylink Mimozyganthus with the Leucaena Dichrostachys orProsopis groups all of which are characterized by achromosome base number of x 5 14 Although prob-lematic rooting of the ITS tree precludes interpretationfrom nuclear data the chloroplast tree separates thePiptadenia group and Acacia ss from the polytomousnode below that includes the Mimozyganthus clade withfairly high support (bs 5 78 Fig 7)

Pollen characters especially tectal ornamentationand polyad arrangement seem to be the only remain-ing evidence for a relationship between PiptadeniopsisAcacia ss and the Piptadenia group However Piptad-eniopsis and Acacia ss have a collumellate exine (Fig5E) whereas in the Piptadenia group the exine is usuallygranular Furthermore the distal fused colporate ap-ertures that Guinet (1981) used to group Piptadeniopsiswith Acacia were not found in our study Pollen seemsto be evolutionarily unconstrained in the Mimosoideaeand it is quite common to find all possible types ofpollen within a single genus (eg Leucaena Desman-thus and Dichrostachys [Guinet 1969 Luckow 1993Hughes 1998]) so pollen heterogeneity in the Mimo-zyganthus clade is not unexpected

Unfortunately the individual molecular data setswhich have the best taxon sampling are either unre-solved or poorly supported near the Mimozyganthusclade (Figs 7 8) and it is not possible to determineconclusively that it is sister to the Leucaena group fromthese analyses The simultaneous analysis of the com-bined data (Fig 9) supports a novel hypothesis of arelationship between the Mimozyganthus clade and theLeucaena group (bs 5 83) although the higher boot-strap value may be an artifact of low taxon densityrather than strong signal from the data In commonwith the Mimozyganthus clade members of the Leucaenagroup are mostly shrubs or trees of arid regions (al-though some Desmanthus are herbaceous) with char-taceous inertly dehiscent pods and a wide array ofpollen types (Table 2) However they are unarmed andlack the specialized seeds that characterize the Mimoz-yganthus clade Although a sister relationship betweenthe Leucaena group and the Mimozyganthus clade is cur-rently our most viable hypothesis it would be pre-mature to discard the possibility that the latter is moreclosely related to Prosopis without more convincingdata

Final Considerations Overall our evidence pre-sents a new hypothesis that Mimozyganthus Piptaden-iopsis and Prosopidastrum form a monophyletic groupwhich in turn may be related to the Leucaena group Arelationship between Piptadeniopsis and Prosopidastrum

had been proposed previously by both Burkart (1944)and Lewis and Elias (1981) and is consistent with flo-ral vegetative fruiting and cytological data as well asthe molecular phylogeny The only inconsistent char-acter is the presence of polyad pollen in Piptadeniopsis

Total evidence is far less congruent for Mimozygan-thus Although Mimozyganthus shares few floral char-acters with Piptadeniopsis or Prosopidastrum it is diffi-cult to relate the unique flowers of Mimozyganthus tothose of any other mimosoid No other mimosoids areknown to have a peltate papillate stigma AlthoughMimozyganthus Parkia and Pentaclethra all have imbri-cate sepals they differ in many other features and onecould argue that even the lsquolsquoimbricate sepalsrsquorsquo are notthe same as they are free in Mimozyganthus and fusedin Parkia and Pentaclethra Pollen of Mimozyganthus is ofa generalized type found throughout the DichrostachysProsopis and Leucaena groups as well as in one of theputative sister taxa Prosopidastrum Thus although theflowers of Mimozyganthus are quite different fromthose of either Prosopidastrum or Piptadeniopsis they arenot any more congruent with some other placementon the phylogenetic tree

Given the geographic unity of the Mimozyganthusclade some might question the utility of continuing torecognize three genera two of which are monotypicThe many distinctive characters of Mimozyganthussome of them unique within the Mimosoideae certain-ly seem to merit generic status The case for maintain-ing Piptadeniopsis as distinct from Prosopidastrum is notso clear cut given their many similarities in flowersand fruits The major differences relate to habit andpollen type and continued recognition of the two gen-era is maintained primarily because of tradition andthe importance that habit can assume in field recog-nition

An inevitable question given that flowers are oftenevolutionarily conservative in the Mimosoideae is howmight such diverse floral syndromes arise amongclosely related taxa Mimozyganthus is sympatric withPiptadeniopsis and nearly so with Prosopidastrum and itmay be that its unique morphology has been drivenby pollinator selection (Schemske and Bradshaw 1999Ippolito et al 2004) We would predict that Mimozy-ganthus is visited by a different group of pollinatorsthan its sister taxa This would be a relatively easyhypothesis to test No pollinators have yet been re-ported for any of these genera and it is not evenknown if they bloom simultaneously Although thereis currently controversy about the importance of pol-linators in driving floral divergence and speciation (Ol-lerton 1996 Waser 1998) a study of this group mightat the very least shed light on the kinds of floral char-acters associated with particular pollinators

In addition to pollination studies more phylogeneticdata are needed to confirm the results presented here


and to clarify the homology of morphological charac-ters Specifically a comprehensive morphological dataset is needed for the entire Mimosoideae given thelack of resolution in the molecular tree near the Pro-sopis group one cannot easily undertake an analysis ofa monophyletic subset of taxa near it Increased sam-pling of taxa and genes will also improve on our re-sults Nonetheless we have a much better idea ofwhere these unusual taxa belong within the Mimoso-ideae than ever before and a platform from which toundertake a more intensive study of the nearest rela-tives to the Mimozyganthus clade

ACKNOWLEDGEMENTS We are deeply indebted to Dr FatimaMereles at the Dpto de Botanica Facultad de Ciencias QuımicasUniversidad Nacional de Asuncion Paraguay for coordinating ourcollecting trip to Paraguay and for her delightful company in thefield Prof Juan C Gamerro is gratefully acknowledged for sharinghis important comments on the interpretation preparation andphotographs (light microscopy) of the pollen morphology Wethank Colin Hughes for sending us his ITS data set and for histhoughtful comments on this manuscript We also thank the cu-rators of the herbaria mentioned in the text This work was sup-ported by NSF grant DEB-0129228 to the first author and by CON-ICET and ICBG grant UO1 TW00316 to the second author

LITERATURE CITED

ANCIBOR E 1969 Los nectarios florales en Leguminosas-Mimo-soideas Darwiniana 15 128ndash140

BUROKER N E J R BROWN T A GILBERT P J OrsquoHARA A TBECKENBACH W K THOMAS and M J SMITH 1990 Lengthheteroplasmy of sturgeon mitochondria DNA an illegitimateelongation model Genetics 124 157ndash163

BURKART A 1939 Descripcion de Mimozyganthus nuevo generode Leguminosas y sinopsis preliminar de los generos argen-tinos de Mimosoideas Darwiniana 3 445ndash469

mdashmdashmdash 1943 Las Leguminosas Argentinas silvestres y cultivadasBuenos Aires Acme Agency

mdashmdashmdash 1944 Tres nuevas Leguminosas del Paraguay colecciona-das por el Senor Teodoro Rojas Darwiniana 6 477ndash493

mdashmdashmdash 1952 Las Leguminosasa Argentinas silvestres y cultivadas sec-ond edition Buenos Aires Acme Agency

CABRERA A L 1994 Regiones fitogeograficas Argentinas Pp 1ndash85 in Enciclopedia Argentina de agricultura y jardinerıa volume 2second edition ed W F Kugler Buenos Aires EditorialAcme

CABRERA A L and A WILLINK 1973 Biogeografıa de America La-tina Organizacion de los Estados Americanos MonografıaNo 13 (Serie de Biologıa) Washington Programa Regionalde Desarrollo Cientıfico y Tecnologico

DAVIS J I M P SIMMONS D W STEVENSON and J F WENDEL1998 Data decisiveness data quality and incongruence inphylogenetic analysis an example from the monocotyledonsusing mitochondrial atpA sequence Systematic Biology 47282ndash310

ELIAS T S 1981 Mimozygantheae P 154 in Advances in legumesystematics part 1 eds R M Polhill and P H Raven KewRoyal Botanic Gardens

FORTUNATO R H 1997 Tribu Mimozygantheae Pps 5ndash6 in FloraFanerogamica Argentina 34 ed A T Hunziker Cordoba Pro-grama PROFLORA (CONICET)

GOLDBLATT P 1981 Cytology and the phylogeny of the Legumi-nosae Pp 427ndash463 in Advances in legume systematics part 2eds R M Polhill and P H Raven Kew Royal Botanic Gar-dens

GOLENBERG E M M T CLEGG M L DURBIN J DOEBLEY andD P MA 1993 Evolution of a noncoding region of the chlo-roplast genome Molecular Phylogenetics and Evolution 2 52ndash64

GOLOBOFF P 1993 Nona version 20 Computer program pub-lished by the author Argentina Available on the web atwwwcladisticscom

GUINET PH 1969 Les Mimosacees etude de palynologie fonda-mentale correlations evolution Institut Francais PondicheryTravaux de la Section Scientifique et Technique 9 1ndash293

mdashmdashmdash 1981 Mimosoideae the characters of their pollen grainsPp 835ndash857 in Advances in legume systematics part 2 eds RM Polhill and P H Raven Kew Royal Botanic Gardens

GUNN C R 1984 Fruits and seeds of genera in the subfamily Mimo-soideae (Fabaceae) Washington U S Department of Agricul-ture Technical Bulletin 1681

HERENDEEN P S G P LEWIS and A BRUNEAU 2003 Floral mor-phology in caesalpinioid legumes testing the monophyly ofthe lsquolsquoUmtiza cladersquorsquo International Journal of Plant Sciences164(Supplement 5) S393ndashS407

HUGHES C E 1998 A monograph of Leucaena (Leguminosae-Mi-mosoideae) Systematic Botany Monographs 55 1ndash244

mdashmdashmdash D C BAILEY S KROSNICK and M LUCKOW 2003 Rela-tionships among genera of the informal Dichrostachys andLeucaena groups (Mimosoideae) inferred from nuclear ribo-somal ITS sequences Pp 221ndash238 in Advances in legume sys-tematics part 10 higher level systematics eds B B Klitgaardand A Bruneau KewRoyal Botanic Gardens

HUTCHINSON J 1964 The genera of flowering plants volume 1 Lon-don Oxford at Clarendon Press Amen House

IPPOLITO A G W FERNANDES and T P HOLTSFORD 2004 Polli-nator preferences for Nicotiana alata N forgetiana and theirF1 hybrids Evolution 58 2634ndash2644

KRAPOVICKAS A 1965 Recuentos cromosomicos de LeguminosaeKurtziana 2 91ndash94

LEWIS G P and T S ELIAS 1981 Mimoseae Pp 155ndash168 in Ad-vances in legume systematics part 1 eds R M Polhill and PH Raven Kew Royal Botanic Gardens

LILLIE R D 1951 Simplification of the manufacture of Schiff re-agent for use in histochemical procedures Stain Technology26 163ndash165

LUCKOW M 1993 A monograph of Desmanthus (MimosoideaeLeguminosae Systematic Botany Monographs 38 1ndash166

mdashmdashmdash 1997 Generic relationships in the Dichrostachys group (Le-guminosae Mimosoideae) evidence from chloroplast DNArestriction sites and morphology Systematic Botany 22 189ndash198

mdashmdashmdash P J WHITE and A BRUNEAU 2000 Relationships amongthe basal genera of mimosoid legumes Pp165ndash180 in Ad-vances in legume systematics part 9 eds P S Herendeen andA Bruneau Kew Royal Botanic Gardens

mdashmdashmdash J T MILLER D J MURPHY and T LIVSHULTZ 2003 Aphylogenetic analysis of the Mimosoideae (Leguminosae)based on chloroplast DNA sequence data Pp 197ndash220 in Ad-vances in legume systematics part 10 eds B B Klitgaard andA Bruneau Kew Royal Botanic Gardens

MILLER J T and R J BAYER 2003 Molecular phylogenetics ofAcacia subgenera Acacia and Aculeiferum (Fabaceae Mimoso-ideae) based on chloroplast matK coding sequence and flank-ing trnK intron spacer regions Australian Systematic Botany16 27ndash33

NIXON K C 1999 The parsimony ratchet Cladistics 15 407ndash404mdashmdashmdash 2001 Winclada Published by the author Ithaca NY Avail-

able at wwwcladisticscomNUNEZ O 1968 An acetic haematoxylin squash method for small

chromosomes Caryologia 21 115ndash119OLLERTON J 1996 Reconciling ecological processes with phylo-

genetic patterns the apparent paradox of plant-pollinatorsystems Journal of Ecology 84 767ndash769


OWENS S J 1989 Stigma style pollen and the pollen-stigma in-teraction in the Caesalpinioideae Monographs in SystematicBotany from the Missouri Botanical Garden 29 113ndash126

mdashmdashmdash 1990 The morphology of the wet non-papillate (WN) stig-ma form in the tribe Caesalpinieae (Caesalpinioideae Le-guminosae) Botanical Journal of the Linnean Society 104 293ndash302

mdashmdashmdash and G P LEWIS 1996 Stigma morphology in the Legu-minosae the wet papillate (WP) stima in CaesalpinioideaeKew Bulletin 51 119ndash131

PAABO S 1990 Amplifying ancient DNA Pp 159ndash166 in PCRprotocols a guide to methods and applications eds M A InnisDavid H Gelfand John J Sninsky and Thomas White SanDiego Academic Press Inc

PALACIOS R A and P S HOC 2001 Three new species of Pro-sopidastrum (Mimosaceae) from Argentina Novon 11 79ndash87

POLHILL R M 1994 Classification of the Leguminosae Pp xxxvndashlvii in Phytochemical dictionary of the Leguminosae eds F ABisby J Buckingham and J B Harbourne London Chap-man and Hall

SCHEMSKE D W and H D BRADSHAW JR 1999 Pollinator pref-erence and the evolution of floral traits in monkeyflowers

(Mimulus) Proceedings of the National Academy of Sciences 9611910ndash11915

SCHULTZ-MENZ G K 1964 Rosales Pp 193ndash242 in A Englerrsquos syl-labus der Pflanzenfamilien edition 12 ed H Melchior BerlinBorntraeger

SHIVANNA K R and S J OWENS 1989 Pollen-pistil interactions(Papilionoideae) Monographs in Systematic Botany from theMissouri Botanical Garden 29 157ndash182

SORENG R and J I DAVIS 1998 Phylogenetics and character evo-lution in the grass family (Poaceae) simultaneous analysis ofmorphological and chloroplast DNA restriction site charactersets Botanical Review 64 1ndash86

SORSA P 1969 Pollen morphological studies on the MimosaceaeAnnales Botanici Fennici 6 1ndash34

TABERLET P L GIELLY G PAUTOU and J BOUVET 1991 Universalprimers for amplification of three non-coding regions of chlo-roplast DNA Plant Molecular Biology 17 1105ndash1109

TUCKER S C 1989 Evolutionary implications of floral ontogenyin legumes Monographs in Systematic Botany from the MissouriBotanical Garden 29 59ndash75

WASER N M 1998 Pollination angiosperm speciation and thenature of species boundaries Oikos 81 198ndash201


FIG 1 Map of the distributions of Mimozyganthus Piptadeniopsis and Prosopidastrum in southern South America

He postulated a relationship with the Niopa group ofPiptadenia (now the segregate genus Anadenanthera) asboth Piptadeniopsis and Anadenanthera have capitate in-florescences Lewis and Elias (1981) placed Piptadeniop-sis in their informal Prosopis group with the generaProsopis Xerocladia and Prosopidastrum rather than inthe Piptadenia group but noted that it might be moreclosely related to Piptadenia based on pollen data Pol-len of members of the Prosopis group is in tricolporatemonads whereas Piptadenia and allies have porate po-lyads Sorsa (1969) reported polyads in Piptadeniopsisand considered the pollen to be most like that of AcaciaGuinet (1981) agreed that pollen of Piptadeniopsis wasmost similar to that of Acacia ss (A subgenus Acacia)according to Guinet both have columellate polyadswith three distally fused colpori Based on these pollendata he assumed that Acacia ss (and Piptadeniopsis)shared a common ancestor with the Piptadenia groupof Mimosoideae Thus we have a number of conflictinghypotheses for the affinities of Piptadeniopsis floralcharacters relate it to the Piptadenia group pollen char-

acters to Acacia ss and fruit and vegetative charactersto the Prosopis group

Not one of the hypotheses of relationships for eithertaxon has been tested using modern methods of phy-logenetic analysis For this reason we undertook mor-phological and molecular studies to answer the follow-ing questions

1 Is Mimozyganthus more closely related to the Cae-salpinioideae Mimosoideae or intermediate be-tween the two What do the morphological featuresreconsidered in the context of the available phylog-eny reveal about character evolution in Mimozygan-thus

2 Is Piptadeniopsis most closely related to the Pipta-denia group the Prosopis group or Acacia ss

METHODS AND MATERIALS

We collected data from morphology pollen cytology and chlo-roplast and nuclear DNA for Mimozyganthus and PiptadeniopsisHerbarium specimens seeds pickled material and leaves in silicagel were collected in the field in Paraguay and Argentina Mor-





















RESULTS


















DISCUSSION





















Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED







































































RESULTS


















DISCUSSION





















Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED





































































RESULTS


















DISCUSSION





















Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED






























































RESULTS


















DISCUSSION





















Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED




























































RESULTS


















DISCUSSION





















Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED



































































DISCUSSION





















Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED




























































DISCUSSION





















Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED


























































DISCUSSION





















Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED
























































DISCUSSION





















Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED






















































DISCUSSION





















Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED

































































Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED




























































Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED



























































Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED

























































Absent x514




Present x513


Absent x5


Present x514




x513


Present x514



















LITERATURE CITED
































































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LITERATURE CITED



































































Date post:	28-Apr-2023
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The Phylogenetic Affinities of Two Mysterious Monotypic Mimosoids from Southern South America

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