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CSIRO PUBLISHING
© CSIRO 2003 10.1071/SB02008 1030-1887/03/010001
www.publish.csiro.au/journals/asb Australian Systematic Botany 16, 1–18
Overview of the generic status of Acacia (Leguminosae: Mimosoideae)
B. R. Maslin
A,D
, J. T. Miller
B
and D. S. Seigler
C
A
Department of Conservation and Land Management, Locked Bag 104, Bentley Delivery Centre,
WA 6983, Australia.
B
Centre for Plant Biodiversity Research, CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia;
Present address: Department of Biological Sciences, University of Iowa, Iowa City, IA 52242, USA.
C
Department of Plant Biology, University of Illinois, Urbana, Illinois 61801, USA.
D
Corresponding author; email: brucem@calm.wa.gov.au
Abstract. The systematic treatment and circumscription of the group of plants presently recognised as the genus
Acacia has a complex history. The genus was first described by Philip Miller in 1754 and until 1842, when George
Bentham clearly defined it’s generic limits (by restricting the name Acacia to mimosoid plants having numerous
free stamens), a number of species which are now referable to genera within tribes Ingeae and Mimoseae had been
referred to it. As presently defined, Acacia is a cosmopolitan genus containing in excess of 1350 species and
together with the monotypic genus Faidherbia Chev. (which occurs in Africa and the Middle East), comprises tribe
Acacieae within subfamily Mimosoideae. The current classification of Acacia views the genus as comprising three
large subgenera, namely subg. Acacia (c. 161 species, pantropical), subg. Aculeiferum Vassal (235 species;
pantropical) and subg. Phyllodineae (DC.) Seringe (syn. subg. Heterophyllum Vassal) (960 species, largely
confined to Australia). In 1986, Pedley proposed that these three subgenera be attributed generic rank, namely
Acacia, Senegalia Rafinesque and Racosperma C.Martius, respectively, but this proposal was not widely adopted.
Subsequently, the results of monographic and floristic works have greatly expanded knowledge, not only of Acacia,
but also of its presumed relatives in tribes Ingeae and Mimoseae. Cladistic analyses of chloroplast genes have been
especially informative in developing a better understanding of phylogenetic relationships of the group. The new data
clearly show that the genus as presently defined (i.e. Acacia sens. lat.) is not monophyletic. Furthermore, five
separate monophyletic groups can be recognised within Acacia sens. lat. and it is recommended that these each be
recognised as a distinct genus. The five genera correspond to those recognised by Pedley, except that Senegalia sens.
lat. is now regarded as comprising three genera, namely Senegalia sens. str., Acaciella Britton & Rose [based on
Acacia subg. Aculeiferum sect. Filicinae (Benth.) Pedley] and an undescribed genus based on a group of species
related to Acacia coulteri Benth. Acacia subg. Acacia appears to be located in tribe Mimoseae. The relationships of
subg. Phyllodineae, subg. Aculeiferum sens. str., sect. Filicinae, the ‘Acacia coulteri’ group and Faidherbia are not
fully resolved, although in all studies these groups are shown to be monophyletic. Although it is appropriate that
each be recognised as a distinct genus, the application of the names Acacia and Racosperma is currently under
consideration and it is therefore not appropriate to use these names until this matter is resolved.
SB02008
Ov e rview of the gene ric s tat us of
Ac acia
B. R. Maslin
et
al .
Introduction
As presently defined, Acacia Miller is a cosmopolitan genus
containing in excess of 1350 species (Table 1). This genus,
together with the monotypic Faidherbia Chev. (which occurs
in Africa and the Middle East), comprises tribe Acacieae
within subfamily Mimosoideae. The current classification of
Acacia views the genus as comprising three large subgenera,
namely subg. Acacia (c. 161 species, pantropical), subg.
Aculeiferum Vassal (235 species; pantropical) and subg.
Phyllodineae (DC.) Seringe (960 species, largely confined to
Australia). As discussed below, uncertainties exist not only
with the tribal status of Acacieae, especially in relation to the
closely related Ingeae and to a lesser extent Mimoseae, but
also with the definition, classification and phylogeny of
Acacia.
Pedley (1986) proposed that Acacia be divided into three
genera, namely Acacia, Senegalia Rafinesque and
Racosperma C.Martius, corresponding to Acacia subg.
25 March 2003
2 Australian Systematic Botany B. R. Maslin et al.
Acacia, subg. Aculeiferum and subg. Phyllodineae, respec-
tively. Although this proposal was not taken up by the
botanical community, it was recognised that differences did
exist within Acacia and that more comprehensive
information was needed in order to make informed decisions
concerning the status of the genus (Maslin 1988). In recent
years, there has been an accumulation of much new data
derived from both morphological and molecular genetic
studies and this has led to a better understanding of the
classification and phylogeny of Acacia. It is our purpose here
to review this new evidence in the light of previous studies
and to reassess the generic status of this large cosmopolitan
genus.
Nomenclatural and taxonomic history
Details of the nomenclatural and taxonomic history of Acacia
will be presented elsewhere (B. R. Maslin, A. E. Orchard and
J. G. West, unpubl. data). A synopsis of this work is presented
here to provide a context for the discussions of classification
and phylogeny that follow below.
When Acacia was first formally adopted by Miller
(1754), its generic delimitation was very broad and many of
the 24 African and American species that he described are no
longer referable to the genus as presently defined. Until
about the middle of the 19th century the circumscription of
the genus remained unclear, despite attempts to clarify its
definition through the description of 14 segregate genera. It
was George Bentham, in a series of publications between
1840 and 1875, who clearly defined not only Acacia but also
the tribes of subfamily Mimosoideae. When Bentham began
his studies, the tribe Acacieae was an agglomeration of many
disparate genera. Although he initially included 10 genera in
Acacieae, by 1865 he had reduced these to just one, namely
Acacia, and had constructed a new tribe, the Ingeae, to
accommodate the other nine. Bentham restricted the name
Acacia to plants having numerous, free stamens, thus clearly
defining its generic limits. Within Acacia, the six series that
Bentham (1842a) recognised were, until recently, accepted
by most taxonomists as the primary divisions of the genus,
although there has been some disagreement as to their
appropriate rank.
None of the 29 genera segregated from Acacia since the
genus was first described, except Faidherbia, is currently
accepted. These genera may be ascribed to Pedley’s (1978)
classification and are the following:
subg. Acacia—Vachellia (Wight and Arnott 1834),
Farnesia (Gasparrini 1838), Aldina (Meyer 1836), Gumifera
and Poponax (Rafinesque 1838), Delaportea (Gagnepain
1911), Pithecodendron (Spegazzini 1923), Nimiria (Craib
1927: 393), Acaciopsis, Bahamia, Fishlockia, Feracacia,
Lucaya, Myrmecodendron and Tauroceras (Britton and Rose
1928);
subg. Aculeiferum—Senegalia (Rafinesque 1838),
Manganaroa (Spegazzini 1923), Acaciella (Britton and Rose
1928), Dugandia (Britton and Killip 1936);
subg. Phyllodineae—Phyllodoce (Link 1831),
Racosperma (Martius 1835), Cuparilla, Drepaphyla,
Hecatandra and Zigmaloba (Rafinesque 1838),
Chithonanthus and Tetracheilos (Lehmann 1848),
Phytomorula (Kofoid 1914).
The only comprehensive challenge to Bentham’s generic
concept of Acacia was that of Pedley (1986) who proposed
that the genus be divided into three genera, Acacia,
Senegalia and Racosperma, corresponding to Vassal’s
T
a
bl
e
1
.
N
um
b
ers o
f
d
escr
ib
e
d
spec
i
es o
f
A
cac
i
a sens.
l
at. wor
ld
w
id
e
The generic names used here are those that would apply by the application of currently designated types
Taxon New World Africa
A
Asia Australia–Pacific Total no. of species
Faidherbia albida — 0011 — 1
Acacia sens. str. c. 60 073 36 (incl. c. 15 also 007 c. 161
(syn: Acacia subg. Acacia; found in Africa
A
)
Vachellia)
Senegalia 97 069 43 (incl. 7 also 2 (incl. 1 also 203
(syn: Acacia subg. Aculeiferum found in Africa) found in Asia)
sens. str.)
Acaciella 15 — — — 15
(syn: Acacia subg. Aculeiferum.
sect. Filicinae)
Genus ‘X’ 13 — — — 13
(‘Acacia coulteri’ group)
‘Racosperma’ — 002
B
10 (incl. 7 also 955
C
960
(syn: Acacia subg. Phyllodineae) found in Australia)
Total no. of spp c. 185 145 90 (incl. c. 29 occurring 964 (incl. 1 also c. 1353
also outside the region) found in Asia)
A
Includes Madagascar, Reunion and Mauritius.
B
Two species in Madagascar, Reunion and Mauritius.
C
948 species in Australia; seven species in the Pacific.
Overview of the generic status of Acacia Australian Systematic Botany 3
(1972) subgenera, Acacia, Aculeiferum and Phyllodineae
(syn. subg. Heterophyllum), respectively. The relationship
between Pedley’s (1986) classification, his earlier (1978)
scheme and those of Vassal (1972) and Bentham (1875) are
shown in Table 2. Although it was generally recognised in
1986 that Acacia was probably polyphyletic, Pedley’s
classification was not widely adopted, principally because
many considered that there was insufficient evidence to
support changes that had such far-reaching and worldwide
nomenclatural implications. A call for more study to acquire
critical information on which informed decisions could be
made concerning the generic status of Acacia went out. More
information on groups within Acacia, especially subg.
Aculeiferum, and broad-based comparative studies involving
genera from tribes Ingeae and Mimoseae were needed. For
discussions outlining the reasons why Pedley’s classification
was not accepted, see Maslin (1987– 1989); see also Pedley
(1987, 1989) where he defends his scheme.
Recent molecular and phylogenetic studies
Since Pedley’s (1986) publication, a number of studies have
been undertaken to reassess the taxonomic and phylogenetic
status of Acacia and tribe Acacieae. These studies, using
either morphological or molecular data, varied in sampling
strategy and focused primarily on either tribe Ingeae (Grimes
1999) or tribe Acacieae (Chappill and Maslin 1995; Bukhari
et al. 1999, Clarke et al. 2000; Miller and Bayer 2000, 2001,
2003; Robinson and Harris 2000). The diagrammatic results
of these studies are given in Fig. 1. The results of cladistic
analyses based on a synthesis of chloroplast DNA sequence
data that have been thoroughly sampled for both tribes
(Miller and Bayer 2000, 2001, 2003) and the entire
subfamily (Luckow et al., 2003) are presented in Fig. 1A.
These collaborative analyses increase the number of species
sampled and the number of DNA bases sequenced, which in
turn has improved phylogenetic resolution.
There are several reasons, including taxonomic sampling
and the amount of character information, for the differences
evident among phylogenies presented in Fig. 1. Different
sampling strategies used in these studies prevent simple
comparison of results (Fig. 1, Table 3). Insufficient sampling
increases the likelihood that species will be artificially
placed together on the basis of random chance, rather than
shared similarities, a phenomenon known as long-branch
attraction. Sampling of additional species helps to stabilise
phylogenetic relationships. The choice of outgroup and the
method of rooting also have profound effects on the
phylogenetic trees obtained. For example, the study of
Luckow et al. (2003) increased the sampling of the basal
members of the subfamily, which resulted in the
identification of a close relationship between Acacia subg.
Acacia and certain members of tribe Mimoseae. Rooting a
Table 2. Main classifications of Acacia from Bentham (1875) to Pedley (1986)
Sect. = section, Ser. = series, subg. = Subgenus, Sser. = subseries
Bentham (1875) Vassal (1972) Pedley (1978) Pedley (1986)
Acacia Acacia Acacia Acacia
Ser. Gummiferae Subg. Acacia Subg. Acacia
Ser. Vulgares Subg. Aculeiferum Subg. Aculeiferum Senegalia
Sect. Monacanthea
Sect. Aculeiferum Sect. Spiciflorae Sect. Senegalia
Ser. Filicinae Sect. Filicinae
A
Sect. Filicinae Sect. Filicinae
Subg. Phyllodineae Subg. Phyllodineae Racosperma
(syn. subg. Heterophyllum)
Ser. Botrycephalae Sect. Botrycephalae
Ser. Phyllodineae
Sser. Uninerves Sect. Uninervea Sect. Phyllodineae Sect. Racosperma
Sser. Continuae
Sser. Alatae Sect. Alatae
Sser. Pungentes
Sser. Calamiformes Sect. Plurinerves
Sser. Plurinerves Sect. Heterophyllum Sect. Juliflorae Sect. Plurinervia
Sser. Juliflorae
Sser. Brunioideae
B
Sect. Lycopodiifoliae Sect. Lycopodiifolia
Ser. Pulchellae Sect. Pulchelloidea
C
Sect. Pulchellae Sect. Pulchella
A
Formalised in Guinet and Vassal (1978).
B
The type of subseries Brunioideae is referable to sect. Phyllodineae; however, most taxa that Bentham
included in this group are referable to sect. Lycopodiifoliae; none of these species was included in Vassal’s
classification.
C
Sect. Pulchelloidea included species from Bentham subseries Pulchellae, Alatae, Continuae, Calamiformes,
Plurinerves and Uninerves.
4 Australian Systematic Botany B. R. Maslin et al.
(A)
(D)
(E)
(B)
(C)
(F)
Fig. 1. (A–F) Schematic diagrams of recent molecular and morphological cladistic studies in pruned form. These are simplified figures
based on the strict consensus cladograms of the given study. The original figures have been pruned to represent the relationships among the
major lineages. In particular, the figures represent the monophyly, polyphyly or paraphyly of various lineages as indicated in the relevant
study. See individual diagrams for references. (A) Chloroplast DNA sequence data. This overview tree was prepared using data from Miller
and Bayer (2000, 2001, 2003) and Luckow et al. (2003). (B) Bukhari et al. (1999), cpRFLP, focus on Acacia. (C) Robinson and Harris
(2000), cpRFLP, focus on Acacieae. (D) Chappill and Maslin (1995), morphology, focus on Acacieae. (E) Grimes (1999), inflorescence
morphology, focus on Ingeae. (F) Clarke et al. (2000), cpRFLP, focus on Acacieae.
Overview of the generic status of Acacia Australian Systematic Botany 5
Table 3. Number of species of respective Acacieae groups and close relatives studied in two morphological and six chloroplast DNA studies
Taxon
Number of Chappill and Grimes (1999), Bukhari et al. . Robinson and Clarke et al. Miller and Bayer Luckow et al. Miller and Bayer
species Maslin (1995),
morphology
inflorescence
morphology
(1999), cp RFLP Harris (2000), cp
RFLP
(2000), cp
RFLP
(2001), cp DNA (2003), cp DNA (2003), cp DNA
Caesalpiniodeae 4 — — — 1 0 5
Mimoseae/Parkieae 650–725
A
9 8 — 1 — 1 65 1
Ingeae 950–1000
B
23 31 — 7 2 8 29 2
Faidherbia 11
11 1 —1 11
Acacia subg. Acacia (Acacia) 161 3 2 10 32 13 11 9 22
Acacia subg. Aculeiferum, 203 7 1
3
51767714
sens. str. (Senegalia)
Acacia subg. Aculeiferum.15 1 — — 4 1 1 1 1
sect. Filicineae (Acaciella)
Acacia ‘coulteri group’ 13 — — — — 1 — 1 2
Acacia subg. Phyllodineae 960 67 1
C
65—18162
(Racosperma)
No. of informative charcters 233 95 176 245 212 203 931 228
Consistency Index Not reported 0.29 0.80 0.55 0.58 0.62 0.49 0.53
Retention Index 0.58 0.64 0.76 0.84 0.85 0.83 0.72 0.81
A
Nielsen (1981).
B
Lewis and Elias (1981).
C
A composite scoring system was used; this assumes that the group is monophyletic and may allow scoring of polymorphic character states for the taxa.
6 Australian Systematic Botany B. R. Maslin et al.
Table 4. Distribution of characters considered important in defining major groups within Acacieae (Ingeae included for comparison)
See text for further details. Much of the data presented here are derived from information given in Vassal (1981) and Pedley (1986)
Character Tribe Acacieae Tribe Ingeae
Acacia Faidherbia
Subg. Phyllodineae Subg. Aculeiferum. Sect. Filicinae ‘Acacia coulteri’ Subg. Acacia
sens. str group
Phyllodes Present Absent Absent Absent
A
Absent Absent Absent
Bipinnate leaves Present Present Present Present Present Present Present. Simply pinnate leaves also occur in Inga
and in one species of Cojoba.
Stipular spines Present or absent Absent Absent Absent
B
Present, Present Present in Albizia p.p., Calliandra p.p.,
rarely absent Havardia, Ebenopsis, Sphinga, Painteria &
Pithecellobium. Absent in 19 genera. Spinescent
peducles, oftem confused for stipular spines, occur
in Cathormion and Chloroleucon.
Prickles Absent Present, sometimes absent Absent Absent Absent Absent Present in Albizia p.p. Absent in remainder of taxa.
Involucre on peduncle Absent
C
Absent
C
Absent Absent Present
D
Present
E
A true involucre absent. However, peduncular bracts
(found from near the base to near the apex of the
peduncle) occur sporadically in several genera.
Pollen aperture type
F
Extraporate, infrequently porate Porate Porate Porate, extraporate Colporate Porate Colporate (Calliandra type
F
sens. str.). Porate in
remainder, except extraporate in some sp. of
Cojoba, Oboling, Zygia and Macrosamanea.
Pollen columellae Absent Absent Absent Absent Present Present Present in Calliandra sens. str. Absent in remainder
Pollen exine ornamentation Reticulate (rarely areolate) Smooth Smooth Smooth Smooth Faintly areolate Areolate or sometimes smooth
Pods Dehiscent, rarely indehiscent Dehiscent or indehiscent Dehiscent Dehiscent Dehiscent or
indehiscent
Indehiscent Dehiscent or indehiscnt
Seed endosperm Rare and vestigial Absent Absent Absent Sometimes
endospermous
Absent Sometimes endospermous
Seed aril Present, less commonly absent or
remedial
Present or remedial (sect.
Aculeiferum), absent
(sect. Monocanthea)
Absent Absent Absent Absent Present only in Pithecellobium, otherwise absent
Free amino acids in seeds
G
2(3) 3, 4 5 1 3
H
Present (Grimes, unpubl. data; Tim Morton, pers.
comm.)
Gums Low molecular weight, low positive
optical rotation
Intermediate molecular weight, low
positive optical rotation
Apparently not examined Apparently not
examined
High molecular
weight, highly
positive optical
rotation
Apparently not
examined
Unknown
Rust pathogens Uromycladium & Uromyces Ravenelia Unknown Unknown Ravenelia,
infrequently
Uromyces
Unknown Unknown
A
The petiole and rachis of leaves of Acacia willardiana after dehiscence of pinnae under arid conditions has been interpreted by some (Vassal and Guinet 1972) as a phyllode.
B
The stipules of Acacia coulteri have been interpreted as feebly spinose by some workers (Vassal 1972). In most instances these stipules are vegetative and, although sometimes persistent on very young vegetation, are scarcely spinose.
C
Bracts (presumably not homologous with an involucre) may occur on peduncle (found from near the base to near the apex of the peduncle) in some taxa.
D
The involucre is particularly well-developed in the American ‘ant acacia’ species but is absent in many other species, particularly those with spicate inflorescences. The homology of this structure remains to be established (see Notes 4 and 5 above).
E
In Faidherbia albida there is at the base of the peduncle a structure that Robberse (1974) regards as homologous with an involucre.
F
Pollen information derived from Guinet (1981); however, not all pollen characters are included here (see also Guinet 1986).
G
See Pedley (1986) for definition of biochemical Groups 1–5.
H
Faidherbia albida seeds have the ‘marker’ amino acids of Group 3, except they ± lack S-carboxyethylcysteine (see Evans et al. 1977).
Overview of the generic status of Acacia Australian Systematic Botany 7
phylogenetic tree on a single outgroup representative of the
Mimoseae (Chappill and Maslin 1995; Robinson and Harris
2000; Miller and Bayer 2001) could artificially remove
closely related taxa from the ingroup, thus obscuring
relationships. In addition to sampling issues, the datasets
used have not been sufficiently informative to determine all
phylogentic patterns. This problem can be addressed with the
addition of more phylogenetically informative characters
into the analyses. Hence, it is critical to interpret carefully
the results of phylogenetic analyses, some of which may have
been based on inadequate taxon and character sampling,
and/or on inappropriate outgroup selection.
The tribes Acacieae and Ingeae, as well as the genus
Acacia, are non-monophyletic in all molecular studies,
whereas Acacia subg. Acacia and Acacia subg. Phyllodineae
are always monophyletic. The major differences among the
investigations (Fig. 1) are whether Acacia subg. Aculeiferum
is monophyletic and the sister relationships among the major
lineages (namely Ingeae, Faidherbia and the three Acacia
subgenera).
In order to assess the phylogeny of subfamily
Mimosoideae more completely, additional data from basal
elements of the subfamily, as well as from closely related
taxa of subfamily Caesalpinioideae (Luckow et al. 2000)
will be required. On the basis of currently available data,
amalgamation of tribes Ingeae and Acacieae into a single
tribe (an amalgamated Acacieae/Ingeae), without the
removal of Acacia subg. Acacia, would result in a
paraphyletic tribe Mimoseae and a polyphyletic
Acacieae/Ingeae (Fig. 1A, Luckow et al. 2003). Lack of
phylogenetic resolution within the tribe Ingeae also hinders
recircumscription of tribal boundaries (see below).
Within tribe Acacieae, all cladistic studies agree that
Acacia subg. Acacia and subg. Phyllodineae are each
monophyletic (Chappill and Maslin 1995; Clarke et al. 2000;
Miller and Bayer 2000, 2001, 2003; Robinson and Harris
2000; Luckow et al., 2003). However, these same studies
disagree on the relationships among the three subgenera of
Acacia, Faidherbia and the tribe Ingeae. As discussed above,
differing sampling strategies employed have contributed to
the disparate interpretations of these relationships. This is
apparent in differences shown between two cladistic studies
on the basis of morphological data, each focusing on a
different tribe. Chappill and Maslin (1995), focusing on tribe
Acacieae, showed that Acacia subg. Aculeiferum and subg.
Phyllodineae constitute a monophyletic group that is basal to
the Ingeae (pro parte), whereas Faidherbia, Acacia subg.
Acacia and tribe Ingeae (pro parte) formed a derived, second
monophyletic group (Fig. 1D). On the other hand, an
inflorescence morphology study emphasising the Ingeae
(Grimes 1999) placed Acacia subg. Phyllodineae basal to the
Ingeae, whereas Faidherbia, Acacia subg. Aculeiferum and
Acacia subg. Acacia formed a derived monophyletic group
(Fig. 1E).
Three separate chloroplast DNA restriction fragment
studies of the Acacieae have been undertaken. No inferences
on monophyly of the genus Acacia or tribe Acacieae can be
made from the study by Bukhari et al. (1999), in which only
a limited number of Acacia taxa were sampled (Table 3,
Fig. 1B). In a study of New World Acacia groups (Clarke et al.
2000), taxa of Acacia subg. Phyllodineae were not included
(Table 3, Fig. 1F). In another study with more thorough
sampling of tribes Acacieae and Ingeae (Robinson and Harris
2000), the Acacieae is non-monophyletic (Table 3, Fig. 1C).
Notably, these three studies disagree on relationships among
the three subgenera of Acacia. Acacia subg. Acacia is
monophyletic in all three studies, but varies from being basal
(Clarke et al. 2000), to having a sister group relationship to
subg. Aculeiferum (Robinson and Harris 2000) or sister group
to subg. Phyllodineae (Bukhari et al. 1999).
In their extensive cp RFLP study of Acacia, Robinson and
Harris (2000) found two large clades (Fig. 1C). The first,
which comprised tribe Ingeae, Acacia subg. Phyllodineae
and the genus Faidherbia, had strong bootstrap and jackknife
support. The second clade, which lacked bootstrap and
jackknife support, comprised the other two subgenera of
Acacia, namely subg. Acacia and subg. Aculeiferum.
Robinson and Harris noted that the combined subgenera
Acacia and Aculeiferum could correspond to tribe Acacieae,
whereas Faidherbia and Acacia subg. Phyllodineae could be
subsumed into tribe Ingeae. However, it is critical to note the
low support for the Acacia–Aculeiferum clade and the
sampling of only one species from the outgroup tribe
Mimoseae. A study based on a more comprehensive
sampling of tribe Mimoseae (Luckow et al. 2003) did not
find the sister relationship of subg. Acacia and subg.
Aculeiferum (Fig. 1A).
An advantage of DNA sequencing is the ease of adding
taxa and DNA sequences to datasets to broaden the sampling
base and improve phylogenetic resolution. The development
of a collaborative dataset has led to a subfamily-level
phylogeny (Luckow et al., 2003) that has improved our
understanding of phylogenetic relationships within the
Mimosoideae. This work found (1) Acacia subg. Acacia as
monophyletic and nested deeply within tribe Mimoseae,
(2) both tribe Ingeae and Acacia subg. Aculeiferum sens. lat.
(a group comprising three lineages, see below) as
non-monophyletic, (3) Acacia subg. Phyllodineae as
monophyletic and sister to a polyphyletic Ingeae and
(4) Acacia subg. Aculeiferum sens. str. (i.e. subg.
Aculeiferum excluding sect. Filicinae and the ‘Acacia
coulteri’ group—see below) as monophyletic. These data,
however, still lack resolution for many taxa within the
Ingeae, the placement of Faidherbia and two segregate subg.
Aculeiferum lineages (namely sect. Filicinae and the ‘Acacia
coulteri’ group).
Despite recent cladistic and molecular studies, some
uncertainties remain concerning Acacia subg. Aculeiferum.
8 Australian Systematic Botany B. R. Maslin et al.
The differences in results relating to this group are
influenced not only by the disparate sampling strategies
employed, but more particularly to the dearth of
phylogenetically useful information on account of the
relatively few species that have been studied (Table 3).
Further study of this subgenus is needed. Nevertheless,
current evidence suggests that Acacia subg. Aculeiferum
sens. lat. comprises three distinct, monophyletic lineages,
namely subg. Aculeiferum sens. str., sect. Filicinae and the
‘Acacia coulteri’ group.
Acacia subg. Aculeiferum sens. str. is monophyletic in
all cladistic studies (Fig. 1) and well supported by
bootstrap values. Relationships within the group are
discussed below. The relationship of sect. Filicinae to
subg. Aculeiferum sens. str. is equivocal among studies
(Fig. 1). Molecular studies of Miller and Bayer (2000,
2001, 2003) and Clarke et al. (2000) sampled only a
single placeholder for the section. In each case, the
Filicinae was removed from the rest of subg. Aculeiferum
and was shown to be sister to the Ingeae. Chappill and
Maslin (1995), who also included only a single species of
this section in their study, placed the Filicinae sister to
subg. Aculeiferum sens. str. Robinson and Harris (2000),
who sampled four species of Filicinae, showed the group
as having a sister relationship to subg. Aculeiferum sens.
str. In this study, there was little bootstrap or jackknife
support for monophyly of subg. Aculeiferum sens. lat.;
however, there was 100% support for monophyly of the
four species of sect. Filicinae sampled. Support for
Acacia subg. Aculeiferum sens. str., with sect. Filicinae
removed, was weaker in relative terms in the study of
Robinson and Harris (2001; 53% bootstrap) than in that
of Miller and Bayer (2001; 81% bootstrap).
A group of species including, and related to, A. coulteri
has recently been monographed (Jawad et al. 2000). These
species, which have most often been considered members of
Acacia subg. Aculeiferum, are now informally called the
‘Acacia coulteri’ group. Cladistic analyses based on
molecular and morphological data suggest that the group is
of more ancient origin than other species of Acacia sect.
Aculeiferum (fide Clarke 1995; Clarke et al. 2000; C. Glass
and D. S. Seigler, unpubl. data, cited in Jawad et al. 2000).
Miller and Bayer (2003) found members of this group,
represented by A. coulteri and A. dolichostachya, outside
Acacia subg. Aculeiferum sens. str. and placed in a polytomy
with Acacia subg. Phyllodineae, sect. Filicinae, Faidherbia
albida and certain Ingeae taxa (Fig. 1A). Clarke et al. (2000)
found A. willardiana, another member of the ‘Acacia
coulteri’ group, on a long branch and sister to subg.
Aculeiferum sens. str., suggesting divergence from other taxa
of subg. Aculeiferum.
Until relatively recently, the monotypic genus Faidherbia,
which occurs in Africa and the Middle East (Fig. 2), has been
treated as a species of Acacia. Although the independent
generic status of Faidherbia is no longer in doubt (see Maslin
and Stirton 1997), its tribal placement is equivocal [e.g.
Vassal (1981) placed it in tribe Acacieae whereas Polhill
(1994) placed it in tribe Ingeae]. Recent cladistic and
molecular studies (Fig. 1) place Faidherbia near the Ingeae
(Chappill and Maslin 1995; Robinson and Harris 2000) or
sister to Acacia subg. Acacia (Grimes 1999) or unresolved
with the Ingeae and Acacia subg. Aculeiferum lineages
(Miller and Bayer 2000, 2001; Luckow et al. 2003). In all
studies, Faidherbia is on a long branch, suggesting significant
evolutionary divergence from its nearest relatives, a finding
that supports its continuation as a monotypic lineage.
Fig. 2. Indicative distribution of Faidherbia albida.
Overview of the generic status of Acacia Australian Systematic Botany 9
Assessment of the current generic status of Acacia
On the basis of recent molecular and cladistic studies
discussed above and from consideration of previous
morphological, biochemical and other evidence, it is clear
that the genus Acacia, as currently defined, is polyphyletic
and cannot be sustained as currently defined. The data
present two alternatives for a reorganisation of Acacia:
(1) the addition of hundreds of species to form an even larger
genus Acacia, or (2) the splitting of Acacia in several genera.
The first alternative is not prudent because it would require
the amalgamation of the entire Ingeae into Acacia, or into
part of Acacia. This would only further complicate the
nomenclature of the group. With this in mind, we support the
division of Acacia as outlined below.
Available data now confirm that subg. Acacia is
monophyletic and is very distinct from the remainder of the
genus; also, subg. Phyllodineae is confirmed as being clearly
monophyletic. Pedley (1986) treated these two groups as
genera, namely Acacia and Racosperma, respectively, and
we consider that there is now sufficient justification to
accept this rank for them [but not necessarily these generic
names (see below)]. Pedley (1986) also recognised a third
genus, Senegalia, that was based on Acacia subg.
Aculeiferum. However, neither the morphological data of
Chappill and Maslin (1995) nor the molecular data discussed
above provide significant support for the monophyly of this
group (which is referred to herein as subg. Aculeiferum sens.
lat.). Instead, current evidence indicates that within subg.
Aculeiferum sens. lat. there are at least three distinct
monophyletic lineages, namely sect. Filicinae, the ‘Acacia
coulteri’ group and the remainder of the subgenus, which is
referred to here as Acacia subg. Aculeiferum sens. str.
Although it is possible to recognise Acacia subg.
Aculeiferum sens. lat. as a paraphyletic (or possibly
polyphyletic) genus, we consider that it is better to treat each
of the three major monophyletic lineages as separate genera,
thereby providing a more precise taxonomy that better
reflects known evolutionary relationships. It is recognised
that within Acacia subg. Aculeiferum sens. str., there are
several species groups that have not been included in the
cladistic and molecular studies and that subsequent
examination of these may possibly lead to the recognition of
additional monophyletic lineages worthy of generic status
(see discussion under subg. Aculeiferum sens. str. below).
In summary, we consider that the current molecular and
morphological data indicate that Acacia sens. lat. comprises
at least five major monophyletic lineages, namely subg.
Acacia, subg. Phyllodineae, subg. Aculeiferum sens. str.,
sect. Filicinae and the ‘Acacia coulteri’ group. Although the
relationships of these taxa to each other are equivocal, this
does not negate the validity of the five evolutionary lineages.
We consider it is appropriate to recognise each of these
lineages as a distinct genus; however, for nomenclatural
reasons discussed below, we will not use generic names for
the taxa here.
A synopsis of the five genera that, on the basis of the
above considerations, comprise Acacia sens. lat., follows.
For comparative purposes, the distributions of Faidherbia
and tribe Ingeae are shown in Figs 2 and 3, respectively.
Acacia subg. Acacia (Fig. 4)
A cosmopolitan group containing about 161 species
(Table 1) that are distributed as follows:
New Worl d—c. 60 species [species numbers derived from
information presented in Ebinger et al. (2000) and Clarke
et al. (2000)].
Fig. 3. Indicative distribution of tribe Ingeae.
10 Australian Systematic Botany B. R. Maslin et al.
Africa (including Madagascar)—73 species [species
numbers derived from information presented in Ross (1979),
Lock (1989), Boulos (1995), Thulin and Hassan (1996),
Thulin (1998), and Du Puy and Villiers (2002)].
Asia (including about 15 species that occur also in
Africa)—36 species [species numbers derived from
information presented in Ali (1973), Nielsen (1992),
Thothathri (1992), Lock and Simpson (1991), Lock and
Heald (1994), S. Kumar and P. V. Sane (unpubl. data) and
D. S. Seigler (unpubl. data)].
Australia—seven species [species numbers derived from
Kodela and Tindale (2001)].
The subgenus may be characterised in the following ways
(see Table 4 for further details): Trees or shrubs. Branchlets
usually lenticellate. Prickles absent. Stipules spinose, in
pairs, often being larger and more prominent on young
growth, sometimes enlarged and inhabited by ants, rarely
absent. Leaves bipinnate, with usually numerous small
pinnae (1–15 pairs); leaflets 1–50 or more pairs, from less
than 5 to 35 mm long. Petiolar glands mostly small and
non-specialised, but large (up to 10 mm in length) and
modified in some species. Inflorescence systems simple or
racemose; flowers yellow-orange or whitish-yellow,
arranged in globose to subglobose heads or cylindrical
spikes (8–20 mm in diameter), pentamerous or tetramerous.
Floral bracts linear, spatulate to peltate. Ovary sessile,
nectariferous tissue not evident. Pods rectangular in cross
section or terete, dehiscent or indehiscent, pericarpic strip
present or not. Funicle exarillate. Pleurogram large to small.
Many studies have shown subg. Acacia to be
monophyletic and clearly distinct from the other two
subgenera of Acacia, for example the cladistic results of
Chappill and Maslin (1995) based on morphological data
and molecular results of Robinson and Harris (2000), Clarke
et al. (2000), Miller and Bayer (2000, 2001, 2003) and
Luckow et al. (in press). In one of these studies (Luckow
et al., in press), Acacia subg. Acacia is shown to be nested
deeply within tribe Mimoseae, a relationship also suggested
by Guinet (1990) on the basis of pollen data. There is strong
evidence supporting recognition of subg. Acacia as a distinct
genus (i.e. Acacia). However, as discussed below, a formal
proposal will be made to retypify Acacia and, if this is
successful, the generic name Vachellia then would apply to
this group.
Currently, there is no universally accepted classification
that meaningfully subdivides the species of subg. Acacia into
subordinate groups. Bentham’s (1875) scheme, which was
based on the position of the involucre on the peduncle, is no
longer considered suitable for discriminating infra-generic
groups (Ross 1979). Vassal’s (1972) classification, which
recognised two subordinate groups (namely subsect.
Pluriseriae and subsect. Uniseriae) on the basis of the
arrangement of seeds within the pod, has not been widely
adopted. Although Ross (1979) was unable to subdivide the
African species meaningfully, a number of those in the
Americas were recently accommodated in reasonably
distinct, albeit small, informal species groups, namely the
A. rigidula group (Lee et al. 1989), A. constricta group
(Clarke et al. 1990), A. farnesiana group (Clarke et al. 1989;
Guinet 1990), A. daemon group (Clarke and Seigler 1991)
(also called the A. acuifera group), the Acacia macracantha
group and the ant acacia group (Janzen 1974; Seigler and
Ebinger 1988; D. S. Seigler, unpubl. data). These species
Fig. 4. Indicative distribution of Acacia subg. Acacia (excluding the distribution of A. farnesiana in Australia).
Overview of the generic status of Acacia Australian Systematic Botany 11
groups were supported by chloroplast data, except for the
Acacia farnesiana group (Miller and Bayer 2003) and the
Acacia macracantha group (Clarke et al. 2000). Miller and
Bayer (2003) found a strong separation between New World
and African–Asian taxa of subg. Acacia. The African
members of subg. Acacia that shared some similarities with
Acacia farnesiana formed a clade separate from American
members of the Acacia farnesiana group. These chloroplast
data (Clarke et al. 2000; Miller and Bayer 2003) also support
multiple origins of ant associations in the New World and
Africa.
Acacia subg. Aculeiferum sens. str. (Fig. 5)
A cosmopolitan group containing about 203 species
(Table 1) that are distributed as follows:
New Wo rl d —97 species (plus about another 20 as yet
undescribed) (D. S. Seigler, unpubl. data).
Africa (including Madagascar)— 69 species [species
numbers derived from information presented in Ross (1979),
Thulin and Tardelli (1988), Lock (1989), Thulin (1989),
Thulin and Hassan (1990), and Du Puy and Villiers (2002)].
Asia (including about seven species that occur also in
Africa)—43 species [species numbers derived from
information presented in Ali (1973), Lock and Simpson
(1991), Nielsen (1992), Lock and Heald (1994), S. Kumar
and P. V. Sane (unpubl. data), and D. S. Seigler (unpubl.
data)].
Australia (including A. pennata subsp. kerrii, which
extends to Asia) – 2 species (species number from Ross
2001).
If treated as a distinct genus, the name Senegalia would
apply to this subgenus.
Acacia subg. Aculeiferum sens. str. may be characterised
in the following ways (see Table 4 for further details): Trees
or shrubs, often scandent. Prickles usually present, recurved
or straight, scattered or 1–3 at nodes. Stipules normally
present and scarious, not spinose, often early deciduous.
Leaves bipinnate, with 1–50 pairs of pinnae; leaflets 1–80
pairs, 3–80 mm long. Petiole nearly always glandular; glands
single or multiple, usually small, not specialised, but
occasionally modified. Inflorescence systems racemose,
paniculate, fasciculate or simple; flowers arranged in
globular or obloid heads or cylindrical spikes,
cream-colored, pentamerous. Floral bracts linear to
spatulate. Ovary on gynophore (0.4–2 mm long), with a
nectariferous disk at the base of the ovary. Pods mostly
dehiscent, chartaceous, some coriaceous, a few articulate.
Funicle often arillate.
As discussed above, the exclusion of sect. Filicinae and
the ‘Acacia coulteri’ group from subg. Aculeiferum sens. lat.
leaves a core group, subg. Aculeiferum sens. str., which is
shown to be monophyletic in all cladistic studies and which
is well-supported by bootstrap values.
Subgenus Aculeiferum sens. str. comprises two sections,
sect. Aculeiferum (which appears to be confined to Africa
and Asia) and sect. Monacanthea (which is pantropical).
There are several characters that distinguish these two
relatively large sections (Vassal 1972), including the number
and placement of prickles and the nervation of stipules.
Species of sect. Aculeiferum have prickles near the nodes,
whereas those of sect. Monacanthea have prickles scattered
along the stem. Recent evidence, however, suggests that
these two sections are non-monophyletic, with a few taxa not
Fig. 5. Indicative distribution of distribution of Acacia subg. Aculeiferum sens. str. (excludes sect. Filicinae and the ‘Acacia coulteri group’).
12 Australian Systematic Botany B. R. Maslin et al.
grouping according to their sectional classification. These
exceptions include A. chariessa, A. riparia, A. gaumeri,
A. persiciflora and A. ataxacantha (Robinson and Harris
2000), A. ataxacantha (Chappill and Maslin 1995) and
A. eriocarpa (Miller and Bayer 2003). Vassal (1972)
considered A. ataxacantha to be a member of sect.
Monacanthea and A. galpinii to belong to sect. Aculeiferum.
Although Vassal did not include A. riparia, A. gaumeri,
A. chariessa or A. eriocarpa in his treatment, on the basis of
their overall characters, they should fall into sect.
Monacanthea, whereas A. persiciflora should be in sect.
Aculeiferum. Ross (1979) noted that A. eriocarpa was one of
four African species of sect. Monacanthea with spicate
inflorescences, which differed from other African species
(all of which have capitate inflorescences), in pollen, seed
and seedling characters, as well as inflorescence structure.
Chappill and Maslin (1995) showed that three African–Asian
species of Vassal’s (1972) sect. Aculeiferum (A. caffra,
A. mellifera and A. senegal), together with A. ataxacantha
(which Vassal placed in sect. Monacanthea), formed a
monophyletic group. Biochemical data from both Evans
et al. (1977) and Brain (1990) have also shown
A. ataxacantha to be atypical within sect. Monacanthea.
These independent studies suggest parallel evolution of
prickle and inflorescence type in subg. Aculeiferum sens. str.
and indicate that further investigation within sections
Aculeiferum and Monacanthea on a worldwide scale is
needed in order to reassess the boundaries between them.
It is worth repeating here that sampling within subg.
Aculeiferum sens. str. has been somewhat limited (see
Table 3). It is therefore possible that future study of this
group may identify additional monophyletic lineages that
warrant generic recognition.
Acacia subg. Aculeiferum sect. Filicinae (Fig. 6)
A New World group comprising 15 species (L. Rico-Arce,
pers. comm.) that extends from the south-central USA south
to Argentina; the highest concentration of species occurs in
Mexico. As noted above, molecular data suggest that sect.
Filicinae is a distinct evolutionary lineage. This group was
recognised by Britton and Rose as the genus Acaciella
(Britton and Rose 1928). According to Pedley (1987), the
morphological and chemical attributes of sect. Filicinae
suggest that it could well be treated as a distinct genus; a
similar view was expressed by Guinet (in Maslin 1987).
Treated as a genus, this group would be called Acaciella.
Robinson and Harris (2000) provided the only molecular
insight into relationships within the Filicinae. They found
that A. rosei and A. chamelensis had a sister group
relationship to A. tequilana, with A. angustissima
completing the well-supported clade.
The section may be characterised in the following ways
(see Table 4 for further details): Trees, shrubs or
suffrutescent perennials. Prickles absent. Stipules normally
present, never spinose. Leaves bipinnate, with 1–25 pairs of
pinnae; leaflets 3–60 pairs, 3–60 mm long. Petiolar glands
absent. Inflorescence systems simple, racemose or
paniculate; flowers arranged in globular or obloid heads,
white-cream colored, 5-merous, drying a pink-brown color.
Floral bracts linear, early deciduous. Ovary on gynophore; a
nectariferous disk at the base of the ovary. Pods small,
chartaceous, dehiscent. Funicle exarillate.
‘Acacia coulteri’ group (Fig. 7)
A New World group of 13 species that represent a distinct,
but presently undescribed, genus. This group extends from
Fig. 6. Indicative distribution of distribution of Acacia sect. Filicinae.
Overview of the generic status of Acacia Australian Systematic Botany 13
Arizona south through Mexico to Costa Rica. The ‘Acacia
coulteri’ group was segregated from Acacia subg.
Aculeiferum, partly on account of the lack of prickles and the
non-liane habit (Jawad et al. 2000). Members of this group
would presumably have been assigned to sect. Monacanthea.
The discrete nature of this group does not appear to have
previously been recognised and no generic name for it
appears in the literature.
The ‘Acacia coulteri’ group may be characterised in the
following ways (see Table 4 for further details): Trees or
shrubs. Prickles absent. Stipules normally present and
scarious, occasionally feebly spinose. Leaves bipinnate, but
in one species (A. willardiana) phyllode-like after dehiscence
of pinnae; pinnae 2–40 pairs; leaflets mostly less than 7 mm
long. Petiolar glands small, solitary, not specialised,
sometimes absent in one species. Inflorescence systems
simple or racemose, sometimes paniculate; flowers in
elongated cylindrical spikes, white, pentamerous. Floral
bracts linear. Ovary short stipitate (0.2–0.4 mm), no
nectariferous disk at the base of the ovary. Pods chartaceous
and dehiscent. Funicle exarillate. Pleurogram relatively large.
While sampling of the ‘Acacia coulteri’ group has been
small, in recent molecular work there is evidence of early
divergence of this group from subg. Aculeiferum sens. str.
Miller and Bayer (2003) found members of this group,
represented by A. coulteri and A. dolichostachya, outside
Acacia subg. Aculeiferum sens. str. and placed in a polytomy
with Acacia subg. Phyllodineae, sect. Filicinae, Faidherbia
albida and certain Ingeae taxa (Fig. 1A). Clarke et al. (2000)
found A. willardiana, another member of the ‘Acacia
coulteri’ group, on a long branch and sister to subg.
Aculeiferum sens. str., again suggesting divergence from
other taxa of subg. Aculeiferum.’
Acacia subg. Phyllodineae (Fig. 8)
This enormous group of 960 species is largely confined to
Australia (Table 1). Within Australia there are 948 described
species [species numbers derived from information presented
in Pedley (1999), Kodela and Tame (1999), McDonald and
Maslin (2000) and Maslin (2001)]. We estimate that about 100
species are yet to be described. Nineteen species of subg.
Phyllodineae occur outside Australia (fide Pedley 1975, in
addition to A. sericoflora, which occurs in Papua-New
Guinea). Seven of these species also occur in Australia; the
extra-Australian endemics are found in the Pacific region
(seven species) including Hawaii, Asia (three species) and
Madagascar and the Mascarene islands in the Indian Ocean
off the east coast of Africa (two species).
The subgenus may be characterised in the following ways
(see Table 4 for further details): Trees or shrubs. Prickles
absent. Stipules normally present and scarious, sometimes
spinose. Leaves bipinnate or more commonly modified to
polymorphic phyllodes, rarely reduced to scales or absent.
Inflorescence systems simple or racemose, sometimes
paniculate; flowers arranged in globular or obloid heads or
cylindrical spikes, very rarely with ovary on gynophore.
Funicle arillate or exarillate.
All genetic and cladistic studies since 1995 have shown
subg. Phyllodineae to be monophyletic (Chappill and Maslin
1995; Miller and Bayer 2000, 2001; Robinson and Harris
2000) and, as already noted above, we consider it now timely
that the group be recognised as a distinct genus. Pedley
(1986) proposed use of the generic name Racosperma for
subg. Phyllodineae; however, as discussed below, a proposal
is being prepared to retypify Acacia with an Australian type.
If this effort is successful, the generic name Acacia would be
retained for this group.
Fig. 7. Indicative distribution of distribution of the ‘Acacia coulteri group’.
14 Australian Systematic Botany B. R. Maslin et al.
Although subg. Phyllodineae is monophyletic, its
relationships are seemingly equivocal. Chloroplast and
nuclear DNA evidence supports a non-monophyletic tribe
Ingeae as sister to subg. Phyllodineae (Miller and Bayer
2000, 2001; Robinson and Harris 2000; Luckow et al. 2003).
This strong evidence contradicts previous notions by Pedley
(1986) and Chappill and Maslin (1995) that the sister group
of the subg. Phyllodineae is subg. Aculeiferum sens. lat.
Further work within the tribe Ingeae is necessary to
determine phylogenetic relationships and which lineage is
sister to subg. Phyllodineae.
On the basis of cpDNA work, relationships within subg.
Phyllodineae appear less resolved than within either subg.
Acacia or subg. Aculeiferum (Miller and Bayer 2000, 2001;
J. T. Miller, R. Andrew and R. J. Bayer, unpubl. data). The
elucidation of infrageneric categories within subg.
Phyllodineae is hampered by the enormous size of the group,
which comprises more than 960 species contained in at least
100 informal species groups (Maslin and Stirton 1997).
Furthermore, on the basis of currently available sequence
data, the small amount of divergence within subg.
Phyllodineae will slow development of a meaningful and
well-supported infrageneric classification (Murphy et al.
2000, 2003; J. T. Miller, R. Andrew and R. J. Bayer, unpubl.
data). The low resolution in these studies may indicate that at
least many of the lineages have undergone a large, recent
morphological radiation and that hybridisation among taxa
may be a common phenomenon.
Although Pedley’s (1978) classification (Table 2)
provides a useful framework for discussing species of this
vast subgenus, this is largely an artificial scheme. Recent
cladistic, molecular and morphological studies suggest that,
with the possible exception of the relatively small sections
Lycopodiifoliae (phyllodes whorled) and Pulchellae (leaves
bipinnate), the other sections (which comprise mostly
phyllodinous species and constitute about 95% of the
subgenus) are paraphyletic or polyphyletic.
Nevertheless, recent examination of subg. Phyllodineae
shows that some general trends are beginning to emerge;
perhaps the most significant of these are the following:
(1) Bipinnate-leaved species of sect. Botrycephalae and
certain members of sect. Phyllodineae with racemose
inflorescences (e.g. A. binervata, A. microbotrya and several
additional species) form a monophyletic group. This
relationship is well supported by the results of a number of
independent studies, for example Vassal (1972), Tindale and
Roux (1974), Brain and Maslin (1996), Murphy et al. (2000,
2003), Miller and Bayer (2001) and J. T. Miller, R. Andrew
and R. J. Bayer (unpubl. data). The results of J. T. Miller,
R. Andrew and R. J. Bayer (unpubl. data) and Murphy et al.
(2003) indicate that the Botrycephalae is non-monophyletic,
suggesting that there have been multiple reversals from
phyllodes back to bipinnately compound leaves.
(2) Among the phyllode-bearing species, there appears to
be an important division between uninerved taxa (sect.
Phyllodineae) and plurinerved taxa (sect. Plurinerves and
sect. Juliflorae). The classifications of Vassal (1972) and
Pedley (1986) embody these differences. Some support for a
uninerves v. plurinerves division is seen in the results of
various recent studies, including morphology (Chappill and
Maslin 1995), immunology (Brain and Maslin 1996) and
DNA sequence data (Murphy et al. 2000, 2003; Miller and
Bayer 2001; J. T. Miller, R. Andrew and R. J. Bayer, unpubl.
data). The general trend in the morphological and DNA
Fig. 8. Indicative distribution of distribution of Acacia subg. Phyllodineae.
Overview of the generic status of Acacia Australian Systematic Botany 15
studies was for the uninerved species of sect. Phyllodineae
(together with the bipinnate-leaved species of sect.
Botrycephalae) to form a terminal monophyletic group,
whereas the plurinerved species of sections Plurinerves and
Juliflorae formed a series of basal paraphyletic groups.
(3) The two plurinerved groups (sect. Plurinerves and
sect. Juliflorae) are traditionally separated on the basis of the
shape of their inflorescences, globular in the former and
cylindrical in the latter section. However, studies by Chappill
and Maslin (1995), Murphy et al. (2000, 2003) and
J. T. Miller, R. Andrew and R. J. Bayer (unpubl. data) do not
support monophyly of either sect. Plurinerves or sect.
Juliflorae. On the basis of immunological evidence, Brain
and Maslin (1996) produced a similar result.
(4) Inflorescence structure, racemose v. non-racemose,
has traditionally been an important character for recognition
of subgroups within sect. Phyllodineae. However, the
immunological study by Brain and Maslin (1996) and DNA
studies (Murphy et al. 2000, 2003; J. T. Miller, R. Andrew
and R. J. Bayer, unpubl. data) show these two groups not to
be as closely related as once thought. In fact, these studies
showed that some of the uninerved, non-racemose species of
sect. Phyllodineae have their greatest affinities with the
plurinerved species of sect. Juliflorae and sect. Plurinerves
and practically none with the racemose species of sect.
Phyllodineae. These surprising results require further
investigation.
(5) The racemose species of sect. Phyllodineae certainly
do not form a monophyletic group. As is evident from the
results of Brain and Maslin (1996), Miller and Bayer (2001),
J. T. Miller, R. Andrew and R. J. Bayer (unpubl. data) and
Murphy et al. (2000, 2003), there are at least three main
groups of racemosae and these are centred on
A. podalyriifolia–A. microbotrya (this group is close to sect.
Botrycephalae), A. pyrifolia and A. ligulata–A. myrtifolia
(these two species are contained in the expanded
Pulchelloidea group as defined by J. T. Miller, R. Andrew
and R. J. Bayer, unpubl. data). Testing of more species will
undoubtedly reveal further racemose groups, e.g.
A. suaveolens and its allies.
(6) The results of molecular studies of Murphy et al.
(2000, 2003) and J. T. Miller, R. Andrew and R. J. Bayer
(unpubl. data) suggest support for Vassal’s small sect.
Pulchelloidea, which brings together bipinnate-leaved
species of sect. Pulchellae with a few uninerved and
plurinerved phyllodinous species. In addition, J. T. Miller,
R. Andrew and R. J. Bayer (unpubl. data) also placed sect.
Lycopodifoliae and several species of sect. Alatae into this
clade. Vassal’s Pulchelloidea was partially described by
seedling ontogenetic characters. These data show that the
first two seedling leaves appear simultaneously as a pair of
opposite, pinnate leaves in all taxa of this clade (J. T. Miller,
unpubl. data). In the majority of taxa outside this clade, the
first leaf is pinnate and the second leaf is alternate and
bipinnate, a more common pattern of subg. Phyllodineae.
However, it is noted that the results of Chappill and Maslin
(1995) did not support sect. Pulchelloidea as monophyletic;
similarly, Pettigrew and Watson (1975) found no support for
this section. Further study of this intriguing group is
warranted, particularly as to the inclusion of sect.
Lycopodifoliae within its circumscription.
(7) Most studies have shown sect. Alatae to be a
polyphyletic assemblage.
Future work
Whereas sampling within the tribe Acacieae has greatly
increased in recent years, additional taxa need to be included
in future studies. Important among these are Asian species of
both subg. Acacia (e.g. A. inopinnata and A. harmandiana)
and subg. Aculeiferum (e.g. A. pennata and A. thailandica).
Additionally, a much wider sampling of subg. Aculeiferum
sens. lat. is needed. Taxa from both the New World (e.g.
A. willardiana, A. muricata, A. visco, A. furcatispina) and
Africa (e.g. A. ataxacantha) need to be included within
future studies. Within subg. Phyllodineae, it is clear that
much more work is needed in order to elucidate the complex
patterns of relationships. The challenge for the future is to
undertake molecular and other studies of the group that
include sufficiently large numbers of ‘key’ species in order
to clarify the above-discussed uncertainties, delineate other
higher-order groups and to produce a hierarchical system
that adequately reflects the evolutionary history. Such
studies may be guided in their selection of taxa by Maslin
and Stirton (1998).
Besides the addition of more taxa, continued research in
Acacia molecular systematics will require the sampling of
more genes, especially genes residing in the nucleus. This
will allow comparisons of maternal and biparental lineages
that may allow the identification of hybridisation events that
may be confounding our present understanding. A
well-resolved molecular phylogeny will aid in the next step
of our work, which is to develop a meaningful formal
classification within Acacia sens. lat., especially subg.
Phyllodineae.
Nomenclatural implications
As discussed above, we consider that there are now sufficient
data to support the formal subdivision of the polyphyletic
genus Acacia into five genera, based on the following
infrageneric groups: Acacia subg. Acacia, Acacia subg.
Phyllodineae, Acacia subg. Aculeiferum sens. str., Acacia
subg. Aculeiferum sect. Filicinae and the informal ‘Acacia
coulteri’ group. Our decision to advocate the fragmentation
of this enormous, cosmopolitan genus is not taken lightly
because it is recognised that this action will cause
considerable nomenclatural disruption globally and will
have both economic and pragmatic repercussions.
16 Australian Systematic Botany B. R. Maslin et al.
Under the International Code of Botanical Nomenclature,
the application of names is set by the designation of types. In
Acacia, the (lecto)type is the African–Asian species,
A. nilotica (fide Britton and Rose 1928), and under normal
circumstances it would be expected that when the genus is
dismantled the name Acacia would be applied to the group
containing this species (i.e. subg. Acacia). Under this
scenario, about 161 species would retain the name Acacia
(73 species in Africa, about 60 species in the Americas, 36
species in Asia and seven species in Australia). Name
changes would then be required for the remaining 1191
species: 960 species would probably become Racosperma,
based on subg. Phyllodineae (a majority of these species are
confined to Australia); 203 species would become
Senegalia, based on subg. Aculeiferum sens. str. (69 species
in Africa, 97 species in the Americas, 43 species in Asia and
two species in Australia); 15 species would become
Acaciella, based on sect. Filicinae (all these species are
confined to the Americas); and 13 species of the ‘Acacia
coulteri’ group (confined to the Americas) will require a
new generic name.
Racosperma is by far the largest genus and would therefore
require the largest number of new names (about 1100, with
infraspecific taxa included). Although Racosperma is mainly
confined to Australia, a number of its species are extensively
utilised for commercial, environmental and social purposes
in about 70 different countries (Midgley and Turnbull 2003).
Therefore, applying a new name to species of this genus will
have repercussions worldwide.
Under these circumstances, it can be argued that in the
interest of nomenclatural stability it would be better if the
name Acacia were applied to the largest group (namely,
subg. Phyllodineae, which contains 960 species), rather than
to the smaller group of 161 species represented by subg.
Acacia. To achieve this it would require that the name Acacia
be conserved with a new type, selected from subg.
Phyllodineae. This is technically possible under the
provisions of Article 14 of the International Code of
Botanical Nomenclature, which provides a mechanism for
conserving names under exceptional circumstances. The
conservation process requires that a case be prepared for
consideration by an International Botanical Committee. If
the Committee recommends in favour of the proposal, the
decision must then be ratified by the Nomenclature Session
of the International Botanical Congress.
A formal proposal to retypify Acacia is currently in
progress (B. R. Maslin, A. E. Orchard and J. G. West, unpubl.
data). If successful, it will mean that the 960 species of subg.
Phyllodineae would retain the name Acacia, whereas the 161
species of subg. Acacia would become known as Vachellia.
The names of the other three genera noted above would not
be affected by this proposal. The main arguments advanced
by B. R. Maslin, A. E. Orchard and J. G. West in support of
their case are as follows:
(1) Fewer name changes will be required worldwide;
(2) The name Acacia will be retained for the largest
group;
(3) It will cause least disturbance to international
industries and projects based on Australian acacias;
(4) In areas such as Africa, Asia and the Americas, where
subg. Acacia and subg. Aculeiferum co-occur, it might be
less confusing if all taxa change their names simultaneously,
rather than just half. (At a global level these two groups are
broadly sympatric—compare Figs 4 and 5—and in parts of
Africa and the Americas, at least, species of these two groups
can be found growing side by side.)
Until the proposal by B. R. Maslin, A. E. Orchard and
J. G. West has been assessed in accordance with the process
outlined above, we consider it inappropriate that any new
combinations involving species of subg. Phyllodineae be
made.
Acknowledgments
We acknowledge the assistance of Dr John Ebinger for
measurement and confirmation of a number of
morphological features of taxa included in the manuscript.
References
Ali SI (1973) Mimosaceae. In ‘Flora of West Pakistan, no. 36’. (Eds
E Nasir, SI Ali) pp. 1–41. (Department of Botany, University of
Karachi: Karachi)
Bentham G (1840a) Contributions towards a Flora of South
America—Enumeration of plants collected by Mr Schomburgk in
British Guiana. Journal of Botany (Hooker) 2, 127–146.
Bentham G (1840b) Acacia dentifera. Botanist 4, t. 179.
Bentham G (1842a) Notes on Mimoseae, with a synopsis of species.
London Journal of Botany 1, 318–392.
Bentham G (1842b) Notes on Mimoseae, with a synopsis of species.
London Journal of Botany 1, 494–528.
Bentham G (1844a) Notes on Mimoseae, with a synopsis of species.
London Journal of Botany 3, 82–112.
Bentham G (1844b) Notes on Mimoseae, with a synopsis of species.
London Journal of Botany 3, 195–226.
Bentham G (1845) Notes on Mimoseae, with a synopsis of species.
London Journal of Botany 4, 577–622.
Bentham G (1846) Notes on Mimoseae, with a synopsis of species.
London Journal of Botany 5, 75–108.
Bentham G (1865) Leguminosae. In ‘Genera plantarum’. (Eds
G Bentham, JD Hooker) pp. 434–600. (Lovell Reeve & Co., and
Williams & Norgate: London)
Bentham G (1875) Revision of the suborder Mimoseae. Transactions of
the Linnaean. Society of London 30, 335–664.
Boulos L (1995) Notes on Acacia Mill. Studies in the Leguminosae of
Arabia: 1. Kew Bulletin 50, 327–337.
Brain P (1990) Immunology and phylogeny II: further studies on
Acacia. Suid-Afrikaanse Tydskifvir Wetensk ap 86, 195–199.
Brain P, Maslin BR (1996) A serological investigation of the
classification of Acacia subgenus Phyllodineae (Leguminosae:
Mimosoideae). Biochemical Systematics and Ecology 24, 379–392.
Britton NL, Killip EP (1936) Mimosaceae and Caesalpiniaceae of
Colombia. Annals of the New York Academy of Sciences 35,
101–208.
Britton NL, Rose JN (1928) ‘North American flora. Vol. 23.’ (The New
York Botanical Garden: New York)
Overview of the generic status of Acacia Australian Systematic Botany 17
Bukhari YM, Koivu K, Tigerstedt PMA (1999) Phylogenetic analysis of
Acacia (Mimosaceae) as revealed from chloroplast RFLP data.
Theoretical and Applied Genetics 98, 291–298.
Chappill JA, Maslin BR (1995) A phylogenetic assessment of tribe
Acacieae. In ‘Advances in legume systematics 7: phylogeny’. (Eds
MD Crisp, JJ Doyle) pp. 77–99. (Royal Botanic Gardens: Kew,
London)
Clarke HD (1995) Systematic and evolutionary studies of Acacia series
Gummiferae (Fabaceae: Mimosoideae). PhD Thesis, University of
Illinois, Urbana-Champaign.
Clarke HD, Seigler DS (1991) The systematics of Acacia series
Gummiferae in the Caribbean. American Journal of Botany 78,
173–174.
Clarke HD, Seigler DS, Ebinger JE (1989) Acacia farnesiana
(Fabaceae: Mimosoideae) and related species from Mexico, the
southwestern US, and the Caribbean. Systematic Botany 14,
549–564.
Clarke HD, Seigler DS, Ebinger JE (1990) Acacia constricta (Fabaceae:
Mimosoideae) and related species from the southwestern US, and
Mexico. American Journal of Botany 77, 305–315.
Clarke HD, Downie SR, Seigler DS (2000) Implications of chloroplast
DNA restriction site variation for systematics of Acacia (Fabaceae:
Mimosoideae). Systematic Botany 25, 618–632.
Craib WG (1927) Contribution to the flora of Siam. In ‘Bulletin of
miscellaneous information 1927, no. 9’, pp. 374–395. (Royal
Botanic Gardens: Kew, London)
Du Puy D, Villiers JF (2002) Acacia. In ‘The Leguminosae of
Madagascar’. (Eds DJ Du Puy, JN Labat, R Rabevohitra, JF Villiers,
J Bosser, J Moat) pp. 224–242. (Royal Botanic Gardens, Kew:
London)
Ebinger JE, Seigler DS, Clarke HD (2000) Taxonomic revision of
South American species of the genus Acacia subgenus Acacia
(Fabaceae: Mimosoideae). Systematic Botany 25, 588–617.
Evans CS, Qureshi MY, Bell EA (1977) Free amino acids in the seeds
of Acacia species. Phytochemistry 16, 565–570.
Gagnepain F (1911) Notulae Systematicae (Paris) 2, 118.
Gasparrini G (1838) ‘Descrizione di un nuovo genere piante della
famiglia delle Leguminosae.’ pp. iii–x, pl.
Grimes JW (1999) Inflorescence morphology, heterochrony, and
phylogeny in the Mimosoid tribes Ingeae and Acacieae
(Leguminosae: Mimosoideae). Botanical Review 65, 317–347.
Guinet P (1981) Mimosoideae: the characters of their pollen grains, In
‘Advances in legume systematics, part 2’. (Eds RM Polhill,
PH Raven) pp. 835–855. (Royal Botanic Gardens: Kew, London)
Guinet P (1986) Geographic patterns of the main pollen characters in
the genus Acacia (Leguminosae), with particular reference to
subgenus Phyllodineae. In ‘Pollen and spores: form and functions’.
(Eds S Blackmore, IK Ferguson) pp. 297–311 (Academic Press:
London)
Guinet P (1990) The genus Acacia (Leguminosae, Mimosoideae): its
affinities as borne out by its pollen characters. Plant Systematics
and Evolution Supplement 5, 81–90.
Guinet P, Vassal J (1978) Hypotheses on the differentiation of the major
groups in the genus Acacia (Leguminosae). Kew Bulletin 32,
509–527.
Jawad JT, Seigler DS, Ebinger JE (2000) A systematic treatment of
Acacia coulteri (Fabaceae, Mimosoideae) and similar species in the
New World. Annals of the Missouri Botanical Garden 87, 528–548.
Kodela PG, Tame TM (1999) Acacia pedina (Fabaceae: Mimosoideae),
a new species fro the South Coast, New South Wales. Telopea 8,
305–309.
Kodela PK, Tindale MD (2001) Acacia subg. Acacia. In ‘Flora of
Australia, vol. 11A’. (Eds AE Orchard, AJG Wilson) pp. 196–207.
(ABRS/CSIRO Publishing: Melbourne)
Kofoid CA (1914) Phytomorula regularis, a symmetrical protophyte
related to Coleastrum. University of California Publications in
Botany 6, 35–40, pl. 7.
Lee YS, Seigler DS, Ebinger JE (1989) Acacia rigidula (Fabaceae) and
related species in Mexico and Texas. Systematic Botany 14, 91–100.
Lehmann JGC (1848) ‘Plantae Preissianae. Vol. 2.’ (Hamburg)
Lewis GP, Elias TS (1981) Mimoseae. In ‘Advances in legume
systematics, part 1’. (Eds RM Polhill, PH Raven) pp. 155–168.
(Royal Botanic Gardens: Kew, London)
Link J (1831) ‘Handbuch zur Erkennung der nutzbarsten und am
haufigsten vorkommenden Gewachse. Vol. 2.’ (Berlin)
Lock JM (1989) ‘Legumes of Africa, a check-list.’ (Royal Botanic
Gardens: Kew, London)
Lock JM, Heald J (1994) ‘Legumes of Indo-China, a check-list.’ (Royal
Botanic Gardens: Kew, London)
Lock JM, Simpson K (1991) ‘Legumes of West Asia, a check-list.’
(Royal Botanic Gardens: Kew, London)
Luckow L, White PJ, Bruneau A (2000) Relationships among the basal
genera of Mimosoid legumes. In ‘Advances in legume systematics,
9’. (Eds PS Herendeen, A Bruneau) pp. 165–179. (Royal Botanic
Gardens: Kew, London)
Luckow L, Miller JT, Murphy DJ, Little DP (2003) A molecular
analysis of the Mimosoideae. In ‘Advances in legume systematics,
10’. (Royal Botanic Gardens: Kew, London)
Martius CFP von (1835) Racosperma. Hortus regius Monacensis
seminifer.
Maslin BR (1987) Report of discussions at I. G. S. M. meeting no. 6 on
the proposal to split Acacia. Bulletin of the International Group for
the Study of Mimosoideae 15, 108–118.
Maslin BR (1988) Should Acacia be divided? Bulletin of the
International Group for the Study of Mimosoideae 16, 54–76.
Maslin BR (1989) Wattle become of Acacia? Australian Systematic
Botany Society Newsletter 58, 1–13.
Maslin BR (2001) Acacia. In ‘Flora of Australia, vol. 11A,
Mimosaceae, Acacia, part 1’. (Eds AE Orchard, AJG Wilson) p. 41.
(ABRS/CSIRO Publishing: Melbourne)
Maslin BR, Stirton CH (1998) Generic and infrageneric classification
in Acacia (Leguminosae: Mimosoideae): a list of critical species on
which to build a comparative data set. Bulletin of the International
Group for the Study of Mimosoideae 20, 22–44.
McDonald MW, Maslin BR (2000) Taxonomic revision of the
Salwoods: Acacia aulacocarpa Cunn. Ex Benth., and its allies
(Leguminosae: Mimosoideae: sect. Juliflorae). Australian
Systematic Botany 13, 21–78.
Meyer EHF (1836) Description of Aldina. In ‘Commentariorum de
plantis Africae australis’. p. 171. (Lipzig)
Midgley SJ, Turnbull JW (2003) Domestication and use of Australian
acacias: case studies of five important species. Australian
Systematic Botany 16, 89–102.
Miller JT, Bayer RJ (2000) Molecular phylogenetics of Acacia
(Fabaceae: Mimosoideae) based on chloroplast trnK/matK and
nuclear histone H3-D sequences. In ‘Advances in legume
systematics, 9’. (Eds PS Herendeen, A Bruneau) pp. 180–200.
(Royal Botanic Gardens: Kew, London)
Miller JT, Bayer RJ (2001) Molecular phylogenetics of Acacia
(Fabaceae: Mimosoideae) based on the chloroplast matK coding
sequence and flanking trnK intron spacer region. American Journal
of Botany 88, 697–705.
Miller JT, Bayer RJ (2003) Molecular phylogenetics of Acacia
subgenera Acacia and Aculeiferum (Fabaceae: Mimosoideae),
based on the chloroplast matK coding sequence and flanking trnK
intron spacer regions. Australian Systematic Botany 16, 27–33.
Miller P (1754) ‘The gardeners’ dictionary.’ (Abr. 4th edn). (London)
18 Australian Systematic Botany B. R. Maslin et al.
http://www.publish.csiro.au/journals/asb
Murphy DJ, Udovicic F, Ladiges PY (2000) Phylogenetic analysis of
Australian Acacia (Leguminosae: Mimosoideae) by using sequence
variations of an intron and two intergenic spacers of chloroplast
DNA. Australian Systematic Botany 13, 745–754.
Murphy DJ, Miller JT, Bayer RJ, Ladiges PY (2003) Molecular
phylogeny of Acacia subgenus Phyllodineae (Mimosoideae:
Leguminoseae) based on DNA sequences of the internal transcribed
spacer region. Australian Systematic Botany 16, 19–26.
Nielsen I (1981) Ingeae Benth. In ‘Advances in Legume Systematics.
Part 1’. (Eds RM Polhill and PH Raven.) pp. 173–190. (Royal
Botanic Gardens, Kew: London)
Nielsen IC (1992) Acacia. In ‘Flora Malesiana ser. I, 11.’ pp. 34–64.
(Foundation Flora Malesiana Rijksherbariun/Hortus Botanicus,
Leiden University: The Netherlands)
Pedley L (1975) Revision of the extra-Australian species of Acacia
subg. Heterophyllum. Contributions from the Queensland
Herbarium 18, 1–24.
Pedley L (1978) A revision of Acacia Mill. in Queensland.
Austrobaileya 1, 75–234.
Pedley L (1986) Derivation and dispersal of Acacia (Leguminosae),
with particular reference to Australia, and the recognition of
Senegalia and Racosperma. Botanical Journal of the Linnean
Society 92, 219–254.
Pedley L (1987) In defence of Racosperma. Bulletin of the
International Group for the Study of Mimosoideae 15, 123–129.
Pedley L (1989) Racosperma again. Australian Systematic Botany
Newsletter 59, 1–2.
Pedley L (1999) Notes on Acacia (Leguminosae: Mimosoideae) chiefly
from northern Australia. Austrobaileya 5, 307–321.
Pettigrew CJ, Watson L (1975) On the classification of Australian
Acacias. Australian Journal of Botany 23, 833–347.
Polhill RM (1994) Classification of the Leguminosae. In
‘Phytochemical dictionary of the Leguminosae, vol 1. Plants and
their constituents’. (Eds FA Bisby, J Buckingham, JB Harborne) pp.
35–36. (Chapman & Hall: London)
Rafinesque CS (1838) ‘Flora Telluriana. Part 1.’ (Philadelphia)
Robbertse PJ (1974) The genus Acacia in South Africa. II. With special
reference to the morphology of the flower and inflorescence.
Phytomorphology 24, 1–15.
Robinson J, Harris SA (2000) A plastid DNA phylogeny of the genus
Acacia Miller (Acacieae, Leguminosae). Botanical Journal of the
Linnean Society 132, 195–222.
Ross J (1979) A conspectus of the African Acacia species. Memoirs of
the Botanical Survey of South Africa 44, 1–155.
Ross JH (2001) Acacia subg. Aculeiferum. Flora of Australia 11A,
207–209.
Seigler DS, Ebinger JE (1988) Acacia macracantha, A. pennatula, and
A. cochliacantha (Fabaceae: Mimosoideae). Species complexes in
Mexico. Systematic Botany 13, 7–15.
Spegazzini CL (1923) Algunas observaciones relativas al suborden de
las Mimosoideas. Physis (Buenos Aires) 6, 308–315.
Thothathri K (1992) Nomenclatural note on Acacia minutifolia Ragu.
et al. from India. Rheedea 2, 73.
Thulin M (1989) New or noteworthy species of Leguminosae in NE
tropical Africa. Nordic Journal of Botany 8, 457–488.
Thulin M (1998) Two new species of Acacia (Leguminosae) from
north-eastern Somalia. Nordic Journal of Botany 18, 513–517.
Thulin M, Hassan AS (1990) Acacia ochracea
(Leguminosae-Mimosoideae), a new species from Somalia. Nordic
Journal of Botany 10, 477–479.
Thulin M, Hassan AS (1996) A new species of Acacia (Leguminosae)
from the Horn of Africa. Nordic Journal of Botany 16, 303–306.
Thulin M, Tardelli M (1988) A new species of Acacia (Leguminosae,
Mimosoideae) from Somalia. Willdenowia 17, 125–128.
Tindale MD, Roux DG (1974) An extended phytochemical survey of
Australian species of Acacia: chemotaxonomic and phylogenetic
aspects. Phytochemistry 13, 829–839.
Vassal J (1972) Apport des recherches ontogeniques et seminologiques
a l’etude morphologique, taxonomique et phylogenique du genre
Acacia. Bulletin de la societe d’histoire naturelle de Toulouse 108,
105–247.
Vassal J (1981) Acacieae. In ‘Advances in legume systematics, part l’.
(Eds RM Polhill, PH Raven) pp. 169–171 (Royal Botanic Gardens:
Kew, London)
Vassal J, Guinet P (1972) Un Acacia Américain à pétiole
diaphyllodinise A. willardiana Rose. Adansonia, sér. 2, 12,
421–428.
Wight R, Arnott GAW (1834) ‘Prodromus florae Peninsulae Indiae
orientalis.’ (London)
Manuscript received 8 April 2002, accepted 11 December 2002
