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Phylogenetic Relationships in Senegalia (Leguminosae-Mimosoideae) Emphasizing
the South American Lineages
Author(s): Vanessa Terra, Flávia C. P. Garcia, Luciano P. de Queiroz, Michelle van der Bank, and Joseph
T. Miller
Source: Systematic Botany, 42(3):458-464.
Published By: The American Society of Plant Taxonomists
URL: http://www.bioone.org/doi/full/10.1600/036364417X696122
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Systematic Botany (2017), 42(3): pp. 458–464
© Copyright 2017 by the American Society of Plant Taxonomists
DOI 10.1600/036364417X696122
Date of publication August 25, 2017
Phylogenetic Relationships in Senegalia (Leguminosae-Mimosoideae) Emphasizing the South
American Lineages
Vanessa Terra,
1,2,7
Fl´avia C. P. Garcia,
1
Luciano P. de Queiroz,
3
Michelle van der Bank,
4
and Joseph T. Miller
5,6
1
Departamento de Biologia Vegetal, Universidade Federal de Viçosa, P. H. Rolfs sn, 36.570-000, Viçosa, Minas Gerais, Brasil
2
Instituto de Ciˆencias Agr´arias, Universidade Federal de Uberl ˆandia, Campus Araras, 38.500-000, Monte Carmelo, Minas Gerais,
Brasil
3
Departamento de Ciˆencias Biol ´ogicas, Universidade Estadual de Feira de Santana, Herb´ario, Km 03 BR 116, Campus UEFS,
43031-460, Feira de Santana, Bahia, Brasil
4
Molecular Systematics Laboratory, Department of Botany and Plant Biotechnology, University of Johannesburg, APK Campus,
P. O. Box 524, Auckland Park 2006, Johannesburg, South Africa
5
Centre for Australian National Biodiversity Research, CSIRO Division of Plant Industry, Canberra, ACT 2601, GPO Box 1600,
Australia
6
Office of International Science and Engineering, National Science Foundation, Arlington, Virginia 22230, U. S. A.
7
Author for correspondence (vanessaterrab@gmail.com)
Communicating Editor: Martin Wojciechowski
Abstract—Senegalia is a genus of the legume family (Leguminosae: Mimosoideae) that has a pantropical distribution with centers of diversity in
Brazil, Mexico and southern Africa. The genus is characterized by plants having bipinnate leaves, presence of petiolar nectaries, prickles on the
branches, and pollen grains arranged in polyads with 16 grains. Morphology is an important tool for identification of Senegalia species, but it is not
sufficient to resolve all taxonomic issues and elucidate the evolutionary history of this genus. Prior molecular analyses of Mimosoideae have lacked
breadth of sampling within Senegalia, leaving many relationships uncertain, particularly the relationship among Brazilian species and other members
of the genus. The aim of this study was to identify Senegalia s. s. lineages that contain Brazilian species, and to investigate the relationship of these
species with non-Brazilian Senegalia species. We present the first comprehensively sampled phylogeny of American and African Senegalia, however
Asian species are not sampled. We sequenced four plastid and one nuclear DNA (ITS) regions for 125 samples of 59 Senegalia and one Parasenegalia
species. Both Bayesian and maximum likelihood analyses were performed. Neither the American or African species form monophyletic lineages. The
lack of monophyly of these groups suggests a more complicated evolutionary history of the genus than previously considered, including probable
transatlantic dispersal events.
Keywords—Acacieae, Brazilian flora, Fabaceae, molecular biology.
Senegalia Raf. was originally described in 1838 by Rafinesque
by the type Senegalia triacantha Raf., an illegitimate name based
on Mimosa senegal L. and currently combined to Senegalia
senegal (L.) Britton. The pantropical genus contains about 200
species which are distributed in the Americas (ca. 100 spp),
Africa (69 spp.), Asia (43 spp.) and Australia (2 spp.) (Orchard
and Maslin 2003). Eight species occur in two or more areas
(Seigler et al. 2006).
Senegalia s. l. along with Vachellia Wight & Arn., and Acacia
Mill, albeit with different names, are the three subgenera of
Acacia s. l. (see Maslin et al. 2003). Acacia s. s. and Vachellia have
proven to be robust monophyletic groups. Senegalia s. l. is non-
monophyletic (Luckow et al. 2003; Miller et al. 2003b; Seigler
et al. 2017). The paraphyly of Senegalia s. l. has resulted in the
recognition of several groups that have been segregated as the
genera Mariosousa, Acaciella, Parasenegalia, and Pseudosenegalia
(Fig. 1).
The resulting Senegalia s. s., i.e. the genus Senegalia excluding
Acaciella,Mariosousa, Pseudosenegalia, and Parasenegalia, has
been shown in all studies to be monophyletic (Fig. 1; Luckow
et al. 2003; Miller and Bayer 2003; Bouchenak-Khelladi et al.
2010; Miller and Seigler 2012; Kyalangalilwa et al. 2013;
Boatwright et al. 2015; Miller et al. 2017), and is the subject of
this investigation.
The species belonging to Senegalia s. s. are shrubs, trees, or
lianas, with branches armed with prickles scattered on the
branches or forming longitudinal series on the ribs of the
branches. Senegalia s. s. species lack the stipular spines that are
found in Vachellia. The leaves are bipinnate, never phyllodes,
and the petiole and primary rachis have sessile or stipitate
glands that vary in position. Paraphyllides are usually present.
Flowers are pentamerous, usually with a stipitate ovary and
many free stamens. Inflorescences are capitate or spicate, often
grouping into complex terminal inflorescences. Pods are de-
hiscent, separating into two valves at maturity, or less com-
monly indehiscent or separating into indehiscent one seeded
articles. The seeds are uniseriate (Cialdella 1984; Seigler et al.
2006; de Queiroz 2009).
Senegalia s. s., the focus of the present work, is related to the
other segregate Senegalia s. l. genera as well as the genus
Vachellia and also to tribe Ingeae (Miller and Seigler 2012;
LPWG 2013). The relationships within Senegalia s. s. are not
well understood because there has been insufficient data to
clarify relationships within the genus. In phylogenetic studies
performed to date (Miller and Bayer 2000, 2001, 2003; Miller
et al. 2003a, b; Luckow et al. 2003; Bouchenak-Khelladi et al.
2010; Miller et al. 2011; Miller and Seigler 2012; Kyalangalilwa
et al. 2013; Boatwright et al. 2015), of the 52 Senegalia species
known to exist in Brazil, only S. polyphylla,S. tenuifolia (both
species with an extensive Neotropical distribution) and S.
bonariensis, of the Cono Sur of South America, have been in-
cluded (Terra et al. 2014).
The American Senegalia species are distributed in rain-
forests, thorn-scrub, Caatinga vegetation, and in deserts (de
Queiroz 2009). The liana growth form is more common in
Brazilian Senegalia species that in extra-Brazilian species.
Another uncommon characteristic found in some South
American species is the presence of large leaflets measuring
about 4–7 cm long and 2–4 cm wide. These attributes em-
phasize the importance of the sampling these Brazilian species
in order to understand the evolution and systematics of
Senegalia.
458
The aim of this study was to identify Senegalia s. s. lineages
that contain Brazilian species, and to investigate the re-
lationship of these species with non-Brazilian Senegalia
species.
Materials and Methods
Taxon Sampling—Sampling consisted of 125 samples of 59 Senegalia
species (including Senegalia senegal, the type species of the genus) and two
samples of Parasenegalia muricata as outgroups (Supplemental Appendix
S1; Terra et al. 2017).
The sampling within Senegalia s. s. includes 32 samples of 12 Brazilian
species, 50 samples of 25 American species not endemic to Brazil, and 37
samples of 23 African species. Leaf samples were collected in the field and
dried in silica gel and, where no other material was available, from her-
barium specimens. Details of source material and provenance, and Gen-
bank accession numbers used, are listed in Appendix S1. Reference
vouchers for collections used in this study are housed at VIC, HUEFS,
CANB, PRE, MO and ILL.
DNA Isolation, Amplification and Sequencing—Genomic DNA was
extracted from 10–100 mg of silica gel-dried leaf tissue, or from herbarium
material, using the DNeasy Plant Mini Kit (Qiagen, Hilden Germany)
either individually or in the 96-well plate format. Five regions were am-
plified. Four plastid loci were sequenced: psbA-trnH intergenic spacer, trnL-
Fintron and intergenic spacer, rpl32-trnL intergenic spacer and a portion of
the matK intron. All amplifications were performed using the PCR profile
outlined in Shaw et al. (2005). The primers used were as follows: psbA-trnH
intergenic spacer (Sang et al. 1997); trnL-F intron (Taberlet et al. 1991); rpl32-
trnL intergenic spacer (Shaw et al. 2005); matK 59R/6 (Johnson and Soltis
1994). The complete sequences of nuclear ribosomal DNA internal (ITS)
transcribed spacers were amplified and sequenced using the primers and
protocols in Murphy et al. (2010).
Phylogenetic Analyses—Contiguous sequences were edited using
Sequencher
TM
v. 3.0 (Gene Codes Corporation, Ann Arbor) and aligned in
MUSCLE (Edgar 2004) using default parameters. Sequence alignments
were lodged in TreeBASE (ID 16218).
Alignment of fast evolving DNA sequences across broad phylogenetic
depths,suchasgenera,canoftenresultintheinsertionoflargegapsand
sections of alignment that are non-homologous across all terminals. One
method of reducing the impact of poor homology on the phylogenetic
signal is to exclude ambiguous alignments before tree construction. This
is often accomplished visually without regard to specific consistent
metrics. To alleviate the problem of phylogenetic homoplasy in our
datasets we applied the program GBlocks (Castresana 2000) to assess and
exclude potentially non-homologous sequences as used by Soria-
Carrasco and Castresana (2012) and Igea et al. (2013). We applied the
default GBlocks parameters on each Muscle derived multiple sequence
alignment individually for each gene for the Senegalia dataset. These
settings include: minimum number of sequences for a conserved position
(b1 550%); minimum number of sequences for a flank position (b2 5
0.85); maximum number of contiguous non-conserved positions (b3 58);
minimum length of a block blank position (b4 510); and allowed gap
positions (b5 5h, half). These settings identified regions of misaligned or
non-homologous alignment and excluded these sites from the alignment.
This generally included uncertain base positions, generally located close
to priming sites, and highly variable regions with uncertain sequence
homology., In addition, indels with mostly missing data were excluded
from phylogenetic analysis. Potentially informative insertions/deletions
(indels) were manually coded as additional binary characters. Modeltest
v. 1.1 (Posada and Crandall 1998) determined that the GTR1I1gamma
model was the best-fit model for rpl32-trnL intergenic spacer, trnL-F
intron, and ITS, while GTR1I1invgamma was the best model for the
matK intron and psbA-trnH intergenic spacer; these models were applied
to each DNA sequence partition. Indel characters were included as a
separat e partition a nd a standard (morphology) discrete state model with a
gamma shape parameter was applied to this partition. The Incongruence
Length Difference (ILD) test (Farris et al. 1994) was carried out to determine
whether there was congruence between the nuclear and plastid data and was
implemented using PAUP* v. 4.02 (Swofford 2002). No significant in-
congruence was found, enabling phylogenetic analyses to be performed on
the combined datasets.
Bayesian analyses were performed using MrBayes v. 3.1.2. (Ronquist
and Huelsenbeck 2003). The Markov chain Monte Carlo search was run for
20 million generations with trees sampled every 5,000 generations.
MrBayes performed two simultaneous analyses starting from different
random trees (Nruns 52), each with four Markov chains (Nchains 56).
The first 20% of the trees were discarded from each run. A Bayesian
consensus phylogram with posterior probability values plotted was cal-
culated in MrBayes.
Maximum likelihood (ML) analyses were conducted on RAxML
(Randomized Axelerated Maximum Likelihood) using ‘RAxML-HPC
BlackBox’via the CIPRES Science Gateway (www.phylo.org) under the
GTR 1G model of sequence evolution (as recommended by the RAxML
manual). Nodal support values for the ML topology were estimated using
the rapid bootstrap algorithm implemented in RAxML employing 100
replicates (Stamatakis et al. 2008).
The supplemental materials for this article are available from the Dryad
Digital Repository (Terra et al. 2017).
Results
The alignment of the ITS sequences comprised 914 bp. The
analysis of this alignment with the default parameters of
Gblocks resulted in an alignment of 607 bp. No indels were
scored. The final alignment contained 162 parsimoniously
informative characters. The aligned length of the plastid
sequences rpl32-trnL intergenic spacer, trnL,matK intron
and psbA intergenic spacer sequences were 806, 1,162, 890,
and 545 bp, respectively. The analysis of these alignments
with the default parameters of Gblocks resulted in align-
ments of 571, 895, 751, and 410 bp for rpl32-trnL intergenic
spacer, trnL,matK intron, and psbA intergenic spacer, re-
spectively. There were 10, 13, seven, and three indels scored
for rpl32-trnL intergenic spacer, trnL, matK intron and psbA
intergenic spacer, respectively. The final concatenated
plastid alignment consisted of 2,659 bp, 33 scored indels,
and 327 parsimony-informativecharacters.Thefinalcon-
catenated dataset of the combined plastid and ITS dataset
Fig. 1. Schematic knowledge of evolutionary relationships of Acacia s. l.
and related taxa based on Miller and Seigler (2012) and Miller et al. (2017).
The present work focuses on Senegalia s. s.
TERRA ET AL.: PHYLOGENETIC RELATIONSHIPS IN SENEGALIA 4592017]
consisted of 3,266 bp, 33 scored indels, and 389 informative
characters.
ITS Phylogeny—The Bayesian analysis of the ITS data of
73 specimens resulted in a phylogenetic tree with two
major lineages each with PP 5100% (Bayesian posterior
probabilities (PP) expressed as percentages) support (Fig.
2). The ML phylogeny of the same dataset (not shown)
was congruent to the Bayesian phylogeny for these two
lineages with BS 5100 (bootstrap values expressed as
percentages).
One clade (Fig. 2, Clade A) contained most but not all of the
African species and no American species. Of the seven species
in this clade that were sampled multiple times, four were
recovered as monophyletic. This suggests that the markers do
not resolve at the species level, specimens are identified to
species incorrectly, or the species descriptions are not sufficient
to differentiate taxa. Within clade A, the clade of S. ataxacantha
and S. macrostachya was sister (PP 5100; BS 5100) to a
strongly supported clade (PP 5100; BS 596) containing S.
caffra, one accession of S. macrostachya, S. hereroensis, S. burkei,
S. erubescens, S. galpinii, S. goetzei subsp. goetzei, S. montis-usti,
S. nigrescens, S. robysiana, S. senegal var. leiorachis and S. senegal
var. rostrata. One strongly supported subclade (Fig. 2, Clade
A1; PP 5100; BS 5100) included all specimens sampled of
S. senegal varieties. Other strongly supported relation-
ships include S. galpinii and S. montis-usti (Fig.2,Clade
A2; PP 5100; BS 593) as well as a clade (Fig. 2, Clade A3;
PP 5100) containing S. burkei,S. goetzei subsp. goetzei,and
S. nigrescens.
The second major lineage (Fig. 2, Clade B) contains all the
American species as well as four African species. Of the 12
species that were sampled multiple times eight were mono-
phyletic. The main clade (Fig. 2, Clade B; PP 5100; BS 574) is a
polytomy containing two small clades of North American
species and a large well-supported clade (Fig. 2, Clade C; PP 5
100; BS 585). One clade (PP 599; BS 581) contains
S. macilenta, S. picachensis, and S. interior and the other (PP 552;
BS 582) contains S. occidentalis, S. roemeriana, S. greggii, and
S. berlandieri.
CladeChastwosubclades.Onesubclade(Fig.2,CladeD;
PP 5100; BS 5100) contains climbing shrubs or liana species.
The endemic Brazilian species (S. bahienses, S. globosa, S.
grandistipula, S. harleyi, and S. lasiophylla) are paraphyletic
as the three species with extensive distributions across the
Fig. 2. Bayesian topology tree based on ITS. Posterior probabilities (PP) shown as percentages above and bootstrap percentag es (BS) below the branches.
SYSTEMATIC BOTANY [Volume 42460
Americas including Brazil (S. riparia, S. hatschbachii and
S. multipinnata) are nested within the endemic Brazilian
species.
The second subclade (Fig. 2, Clade E; PP 590; BS 543)
contains two well-supported subclades. Clade F (PP 599;
BS 559) contains S. alemquerensis, S. altiscandens, S.
langsdorffii, S. giganticarpa, and S. polyphylla, all species
with medium to large leaflets. Clade G (PP5100; BS 597)
comprises a mix of Central American and Brazilian species
(S. tenuifolia, S paganucci, S. paraensis,S.lacerans, and S.rostrata)
that are paraphyletic to four African species. Senegalia rostrata,
a northern Brazilian species that is not commonly collected and
is the only Brazilian species with a fruit constricted between
seeds, is in a clade (clade H; PP 597; BS 576) with four African
species S. brevispica, S. schweinfurthii, S. kraussiana, and S. adenocalix)
on a long branch.
Plastid Phylogeny—The plastid partitioned analysis
(Supplemental Fig. S1) comprises 122 specimens and is less
resolved than the ITS tree. The different sampling makes
comparisons with the plastid tree difficult, however the
increased sampling allows phylogenetic placement of taxa
for which ITS sequences were not available. The ML and
Bayesian phylogeny (Fig. S1 and not shown, respectively)
recovered both clade A and B. In the plastid analysis of
CladeA(Fig.S1)onesampleofS. wrightii (JM 1377), a North
American species not represented in the ITS dataset, was
sister to Senegalia mellifera subsp. mellifera (PP 572; BS 595).
The other sample (JM 239) is in the same clade of other North
American species (Clade B). This is probably due to ex-
perimental error.
Additional African species are sampled in the plastid
analysis. Newly sampled S. modesta, along with S. wrightii and
S. melliffera subsp. mellifera, form a clade sister to the S. senegal
varieties (Clade A1).
Despite relationships within the mainly American Clade B
(Fig. S1; PP 590; BS 590) being poorly resolved and less
supported, most ITS clades are resolved in this plastid trees.
The additional plastid sampling S. painterei, S. wrightii, Sene-
galia Xemoryana, and S. gaumeri brought two clades (com-
prised of S. occidentalis, S. roemeriana, S. greggi, S. berlandieri,
S. macilenta, S. picachensis, and S. interior) into a single clade
(Fig. 2; PP 580) not found in the ITS analysis.
Clade C of the plastid analysis contains 69 of the 73 taxa
sampled from the ITS analysis. Clade D contains climbing
shrubs or liana species and is the same as the ITS but now
includes newly sampled S. lowei and S. tucumanensis. Clade E is
not recovered in the plastid analysis.
The additional sampling in the plastid analysis places S.
rhytidocarpa, S. loretensis, S. polyphylla, and S. kallunkiae in Clade
F. Senegalia kallunkiae is one of the Brazilian species that has
larger leaflets. Newly sampled S. polyphylla along with S.
loretensis and S. rhytidocarpa, species treated as varieties of
S. polyphylla in the past, appear in Clade F (PP 580) with S.
giganticarpa (another old variety of S. polyphylla) as expected.
All these species along with S. kallunkiae and S. klugii (not
sampled here) are already known as part of a complex of
species with difficult taxonomic delimitation (Rico-Arce
2007; de Queiroz 2009; Terra 2014).
Clade G includes the same taxa but with the additional
sampling also includes S. serra, a Brazilian endemic species
with prickles forming longitudinal series on the ribs of the
branches, the only species occurring in Brazil with such
morphological characteristic.
The other African clade (Clade H) is recovered in the ML
analysis. However, Senegalia rostrata is not supported as the
sister taxon in either analysis of the plastid data.
Senegalia tucumanensis and S. lowei are now sampled and are
in the Clade D with other South American species (mostly
Brazilian) that have small leaflets.
Combined Phylogeny—The combined ITS and plastid
partitioned dataset comprises73specimens.Bayesian(Fig.
3) and maximum likelihood (not shown) analyses delineate
two major lineages similar in most respects to the ITS tree
(Fig. 2). The Bayesian analysis has S. brevispica and S.
kraussiana sister to all the other subclades within Clade B.
The ML analysis of the combined dataset is similar to the ITS
dataset which places these taxa with the other African taxa
in Clade B.
Discussion
Previous molecular phylogenies focused on broader
questions such as the monophyly of Acacia s. l. and included
just a couple of species of Senegalia,mostofthestudiesin-
cluding just African and/or North American species (Miller
and Bayer 2001; Luckow et al. 2003; Miller and Bayer 2003;
Bouchenak-Khelladi et al. 2010; Kyalangalilwa et al. 2013). In
these studies only three species that occur in Brazil were
sampled (S. bonariensis, S. polyphylla [5Acacia glomerosa5A.
polyphylla], and S. tenuifolia) and they also occur elsewhere in
South America. All studies lacked species endemic to Brazil,
and as mentioned by Miller and Seigler (2012), “relation-
ships of the approximately fifty Brazilian species as well as
several species in South-east Asia and northern Australia
belonging to genus Senegalia have not been sufficiently stud-
ied.”Our study expanded sampling of the Brazilian Senegalia,
showing that these species are not a monophyletic group and
neither the American or African species form a monophyletic
lineage.
African species are non-monophyletic in our study, which
disagrees with Bouchenak-Khelladi et al. (2010) that
showed that African Senegalia is a monophyletic group.
Their study included 29 specimens of African and American
species using three plastid DNA regions (trnL-F intron,
matK intron and psbA-trnH intergenic spacer) and the
bootstrap value was only 65% for this clade. They included
eight American species, 12 species endemic to Africa, and
six species that are widely distributed in America, Africa,
and Asia. The American species do not form a monophyletic
clade. On the other hand, Kyalangalilwa et al. (2013), sampling
46 African and American species and using three plastid
DNA regions (trnL-F intron, matK intron, psbA-trnH inter-
genic spacer), showed that the African Senegalia are not a
monophyletic group. Of the 46 sampled species, 31 were
sampled in our study and this non-monophyly agrees with
our results.
Clade A (Fig. 2) contained most of the African species, all
belonging to Vassal’sAcacia sect. Aculeiferum except for S.
ataxacantha and S. macrostachya. Maslin and Stirton (1997)
mentioned that S. ataxacantha has a lot of similarities with
species of Acacia sect. Aculeiferum. Both S. ataxacantha and
S. macrostachya have spicate inflorescences, as do all taxa of
Acacia sect. Aculeiferum Pedley. The second major lineage
(Clade B) contains all the American species as well as four
African species all belonging to Acacia sect. Monacanthea
Vassal.
TERRA ET AL.: PHYLOGENETIC RELATIONSHIPS IN SENEGALIA 4612017]
Many Brazilian species have unique morphological features.
Large leaflets, measuring about 4–7 cm long and 2–4 cm wide,
are not a common characteristic for the other Senegalia s. s.
species that mostly have small leaflets (3–6 mm long and about
1 mm wide). The Brazilian species S. giganticarpa,S. alem-
querensis, and S. altiscandens have these medium to large
leaflets and they are all clustered in the same clade with S.
langsdorffii (Fig. 2, Clade F). S. giganticarpa is found in the
Atlantic Forest and is a tree. On the other hand, S. alemquerensis
and S. altiscandens occur in northern Brazil (Par´aand
Amazonas states, respectively) and are lianas or climbing
shrubs that are more likely found on the edges of the Amazon
rainforest. Senegalia langsdorffii has medium size leaflets and
occurs in dry areas in South America, such as the Caatinga
Biome in Brazil.
Most American Senegalia species have a typical pod (not
constricted between the seeds) but some species can have
constricted pods as in many African species. Senegalia
rostrata, a South American species, is sister (Fig. 2, Clade H;
BS 597) to one of the African Senegalia clades in our ITS
phylogeny, is the only Brazilian taxa with constricted pods.
The combined analysis places S.rostrata sister to the South
American S.lacerans. This discrepancy between the two
datasets may suggest a chloroplast capture event.
Most of the African and North American Senegalia species
are shrubs or trees, contrasting with the South American
species that are mainly lianas or climbing shrubs. Of the
Brazilian species sampled, only S. polyphylla, S. tenuifolia, and
S. riparia present only tree habit. These species have a wide
distribution as mentioned before and they can show pheno-
typic plasticity due to age of the plant or the local environ-
mental conditions (Rico-Arce 2007; de Queiroz 2009). The
other Brazilian species, as well as the South American Sene-
galia, are climbing shrubs or lianas.
Senegalia species can have either a spicate or a capitate in-
florescence (Seigler et al. 2006; de Queiroz 2009). All the species
belonging to sect. Aculeiferum have spicate inflorescences but
not all of sect. Monacanthea have capitate inflorescences (Ap-
pendix S1). Clade A is comprised of species with spicate in-
florescences and they are all African. Senegalia adenocalyx, S.
kraussiana, and S. schweinfurthii are the only three African
Senegalia species that do not have a spicate inflorescence, and
Fig. 3. Bayesian topology tree based on ITS, rpl32-trnL intergenic spacer, matK intron, trnL-F intron, psbA-trnH intergenic spacer DNA regions. Posterior
probabilities (PP) shown as percentages above and bootstrap percentages (BS) below the branches.
SYSTEMATIC BOTANY [Volume 42462
they grouped with other capitate Senegalia species in Clade B.
Most American species of Senegalia have a capitate in-
florescence. Among the species endemic to Brazil, S. lacerans
and S. lowei have spicate inflorescences, and both are lianas
that occur in the Atlantic Forest.
We present the first comprehensively sampled phylogeny
of Senegalia. Our study expanded sampling of the Brazilian
Senegalia, showing that neither the American nor African
species form monophyletic lineages, which suggests a more
complicated evolutionary history of the genus than pre-
viously thought. Morphology and geography do not map as
single origins on the phylogeny. The origin of Senegalia s. s. is
estimated from 31 MYA (20.0–41.9; Miller et al. 2013) to 21.1
MYA (16.8–27.8; Bouchenak-Khelladi et al. 2010). This
suggests one, possibly two, trans-Atlantic dispersal event
has occurred since the origin of the genus. This needs to be
clarified with better taxon sampling, especially from Asia,
better markers, and fossil data. This would further illumi-
nate character evolution and biogeography knowledge of
Senegalia.
Acknowledgments. This work is part of the Ph.D. dissertation of VT.
VT acknowledges CNPq, MCT/CNPq/MEC/CAPES/ FNDCT/
FAPs–SISBIOTA, Fapemig, PNADB/Capes and PPG-Bot ˆanica-UFV for
grants; CAPES for the Ph.D. scholarship that made it possible to work
in Canberra Australia; CSIRO Plant Industry and Centre CANBR for all the
support in Canberra. We would like to say thank you to Alexander N.
Schmidt-Lebuhn, Andrew Thornhill, and Cathy Miller for help with the
analysis, and also Ish Sharma for help in the lab work. JTM acknowledges
NSF-Systematic Biology grant DEB 04-14902. This manuscript includes
work done by JTM while serving at the National Science Foundation. The
views expressed in this paper do not necessarily reflect those of the
National Science Foundation or the United States Government.
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