A peer-reviewed open-access journal
PhytoKeys 194: 123–133 (2022)
doi: 10.3897/phytokeys.194.80967
RESEARCH ARTICLE
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A phylogeny of the Triraphideae including Habrochloa
and Nematopoa (Poaceae, Chloridoideae)
Paul M. Peterson1, Konstantin Romaschenko1, Yolanda Herrera Arrieta2
1 Department of Botany MRC-166, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013-7012, USA 2 Instituto Politécnico Nacional, CIIDIR Unidad Durango-COFAA, Durango,
C.P. 34220, Mexico
Corresponding author: Paul M. Peterson (peterson@si.edu)
Academic editor: Clifford Morden | Received 21 January 2022 | Accepted 21 March 2022 | Published 18 April 2022
Citation: Peterson PM, Romaschenko K, Herrera Arrieta Y (2022) A phylogeny of the Triraphideae including Habrochloa
and Nematopoa (Poaceae, Chloridoideae). PhytoKeys 194: 123–133. https://doi.org/10.3897/phytokeys.194.80967
Abstract
To investigate the evolutionary relationships among species of the tribe Triraphideae (including two
monotypic genera, Habrochloa and Nematopoa), we generated a phylogeny based on DNA sequences
from nuclear ribosomal (ITS) and four plastid markers (rps16-trnK, rps16 intron, rpl32-trnL, and ndhA
intron). Habrochloa and Nematopoa form a clade that is sister to Neyraudia and Triraphis. Member of the
Triraphideae have paniculate inflorescences, 3-veined, marginally ciliate lemmas, usually with hairy lateral
veins, that are apically bifid and awned from between a sinus. A description of the Triraphideae and key to
the genera is provided, and the biogeography is discussed, likely originating in Africa.
Keywords
Classification, Habrochloa, molecular phylogenetics, Nematopoa, Neyraudia, Triraphideae, Triraphis
Introduction
Clayton and Renvoize (1986) pointed out that Neyraudia R. Br. was perhaps an ally
of Triraphis R. Br. since both genera possess slender microhairs and the two have
keeled lemmas that are villous on the lateral veins (Watson and Dallwitz 1992).
Based on DNA sequence studies Bouchenak-Khelladi et al. (2008) were first to show
strong support for Neyraudia and Triraphis as being sister in the subfamily Chloridoideae Kunth ex Beilschm. Hilu and Alice (2001) and Bouchenak-Khelladi et al.
Copyright Paul M. Peterson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC
BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
124
Paul M. Peterson et al. / PhytoKeys 194: 123–133 (2022)
(2008), using the same matK sequence marker placed these two genera in the subtribe Uniolinae Clayton, now a member of tribe Eragrostideae Stapf. Another DNA
sequence study supported the placement of the Neyraudia–Triraphis clade as being
sister to remaining species in the Chloridoideae and, subsequently, the tribe Triraphideae P.M. Peterson [based on subtribe Triraphidinae Stapf (1917)] was erected to
include these two genera (Peterson et al. 2010). Using unpublished DNA sequence
phylogenies (Peterson and Romaschenko, unpubl.), the monotypic Habrochloa C.E.
Hubb., was added to the Triraphideae in the classification of all genera within the
Poaceae (Soreng et al. 2015, 2017).
Hubbard (1935, 1957a, b) transferred Triraphis longipes Stapf & C.E. Hubb. to
Crinipes Hochst. (Arundinoideae) since it possessed a bearded callus, then later moved
it to a new monotypic genus, Nematopoa C.E. Hubb. Nematopoa was included in
the Arundinoideae by Clayton and Renvoize (1986). In more recent classifications
(Soreng et al. 2015, 2017), Nematopoa longipes (Stapf & C.E. Hubb.) C.E. Hubb.
was placed as a synonym of Triraphis as originally described. Based on unpublished
DNA sequence phylogenies (Peterson and Romaschenko, unpubl.), Soreng et al.
(2022) and Gallaher et al. (2022) placed Nematopoa in the Triraphideae. Therefore, the
current concept of the Triraphideae consists of four genera, Habrochloa, Nematopoa,
Neyraudia, and Triraphis.
Habrochloa bullockii C.E. Hubb. is a small, delicate, African annual (culms 10–
25 cm tall) with a fringe of hairs for a ligule and delicate panicles bearing 3–5-flowered spikelets, each including awned, apically bifid, marginally ciliate lemmas that
bear trigonous caryopses, whereas Nematopoa longipes is a caespitose, southern African perennial (culms 30–80 cm tall) with ciliate, membranous ligules and capillary
panicles bearing 4–7-flowered spikelets, each including awned, apically bifid, marginally ciliate lemmas (Clayton et al. 2016). Neyraudia consists of four reedlike perennials [culms (0.8–) 1–5 m tall], a cartilaginous ridge with a line of hairs apically for
a ligule, and plumose panicles bearing 3–8-flowered spikelets, each including awned,
apically bifid lemmas that are ciliate marginally and along lateral veins; three species
in tropical and temperate Asia and one species in Africa (Watson et al. 1992; Filgueiras and Zuloaga 1999; Guala 2003; Clayton et al. 2016). Triraphis consists of eight
annual or perennials (culms 4−140 cm tall) with membranous ligules or a fringe of
hairs and open or contracted (rarely spiciform) panicles bearing 4−24-flowered spikelets, each including apically 3-lobed and 3-awned lemmas that are ciliate marginally
and villous along the lateral veins, and trigonous caryopses; six species in Africa, one
in Australasia and one in South America (Watson et al. 1992; Nightingale and Weiller
2005; Clayton et al. 2016).
In the present phylogenetic study, using DNA sequences from nuclear ribosomal (ITS) and four plastid markers (rps16-trnK, rps16 intron, rpl32-trnL, and ndhA
intron), we include for the first time Habrochloa bullockii, Nematopoa longipes, and
Neyraudia arundinacea (L.) Henrard with two other species of Neyraudia and five species of Triraphis. In addition, we include a description of the Triraphideae, key to the
genera in the tribe, and hypothesize its biogeographical history.
Phylogeny of the Triraphideae
125
Materials and methods
Detailed methods for DNA extraction, amplification, and sequencing are given in
Romaschenko et al. (2012) and Peterson et al. (2010, 2014a, b, 2015a, b, 2016). We
used Geneious Prime 2020 (Kearse et al. 2012) for contig assembly of bidirectional sequences of ndhA intron, rpl32-trnL, rps16 intron, rps16-trnK and ITS regions, and implemented in Geneious Muscle algorithm (Edgar 2004) to align the sequences and adjust the final alignment. The maximum likelihood parameters for each region were estimated with GARLI 2.0 (Zwickl 2006) and were used as priors in Bayesian calculations
to infer overall phylogeny. The Bayesian tree was constructed using MrBayes v3.2.7
(Huelsenbeck and Ronquist 2001; Ronquist et al. 2012). All compatible branches
were saved. The Bayesian analysis was initiated with random starting trees sampling
once per 100 generations and continued until the value of the standard deviation of
split sequences dropped below 0.01 indicating convergence of the chains. The effective sample size (ESS) value for all the parameters was greater than 200 and the first
25% of the sampled values were discarded. Maximum likelihood bootstrap analyses
(Felsenstein 1985) were performed using GARLI with 1000 repetitions. The resulted
file containing 1000 trees from the bootstrap analysis was then read into PAUP* v.5.0
(Swofford 2000) to compute the majority rule consensus tree.
Our study was designed to test relationships among species residing in four genera
(Habrochloa, Nematopoa, Neyraudia, and Triraphis) attributed to the Triraphideae. Representative species from all remaining tribes (Centropodieae P.M. Peterson, N.P. Barker
& H.P. Linder, Cynodonteae Dumort., Eragrostideae Stapf, and Zoysieae Benth.) in
the Chloridoideae have been included to test the monophyly of the tribe (Peterson et
al. 2010). In addition, the phylogeny includes two species from the Danthonioideae,
Danthonia compressa Austin and Merxmuellera drakensbergensis (Schweick.) Conert,
and one species from the Panicoideae, Chasmanthium latifolium (Michx.) H.O. Yates,
which was used as an outgroup.
Results and discussion
Thirty-five new sequences (16%) from five species (nine individuals) are newly reported
in GenBank, along with all other sequences for 48 individuals and 41 species included
in this study (Table 1). Total aligned characters, numbers of sequences, proportion of
invariable sites, and other parameters are noted in Table 2. The resulting plastid and
ITS topologies were inspected for conflicting nodes with ≥ 95% posterior probabilities. No supported conflict was found so plastid and ITS sequences were combined.
The Bayesian tree from the combined plastid and ITS regions is well resolved
(Fig. 1). Most clades have posterior probabilities equal to 1.00 and additional bootstrap
values of 90% or greater. There is strong support for Habrochloa bullockii + Nematopoa
longipes sister to a monophyletic Neyraudia with three individuals of N. reynaudiana
(Kunth) Keng ex Hitchc. sister to one individual of N. arundinacea (type of the genus)
Voucher
Country
1
2
3
4
5
Centropodia glauca (Nees) Cope
Centropodia mossamedensis (Rendle) Cope
Chasmanthium latifolium (Michx.) H.O. Yates
Chloris barbata Sw.
Cottea pappophoroides Kunth
South Africa
South Africa
USA, Maryland
Mexico, Sinaloa
Peru, Ancash
JF729075
JF729076
GU360517
GU360514
GU360600
–
JF729182
GU360438
GU360435
GU360456
JF729175
JF729176
GU359891
GU359873
GU359842
6
7
8
9
Danthonia compressa Austin
Eleusine indica (L.) Gaetrn.
Eleusine poiflora (Chiov.) Chiov.
Ellisochloa rangei (Pilg.) P.M. Peterson & N.P.
Barker
Enneapogon scaber Lehm.
Entoplocamia aristulata (Hack. & Rendle) Stapf
Eragrostis kennedyae F. Turner
Eragrostis wiseana (C.A. Gardner & C.E. Hubb.)
R.L. Barrett & P.M. Peterson
Gouinia virgata var. robusta J.J. Ortíz
Gymnopogon grandiflorus Roseng., B.R. Arill. &
Izag.
Habrochloa bullockii C.E. Hubb.
Davidse 6367 (US)
Schweickerdt 2250 (US)
Peterson 22463 (US)
Peterson 22255& Saarela (US)
Peterson 21463, Soreng, LaTorre & Rojas
Fox (US)
Peterson 21986 & Levine (US)
Peterson 21362, Saarela & Flores Villegas (US)
Burger 2915 (US)
Barker 960 (BOL)
ndhA
ITS
intron
JF729164 JF729164
–
–
GU359379 GU359319
GU359377 GU359320
GU359363 GU359237
USA, North Carolina
Mexico, Mexico
Ethiopia
Namibia
GU360521
GU360496
GU360601
JF729079
GU360483
GU360472
GU360457
JF729184
GU359865
GU359797
GU359843
–
GU359370 GU359345
GU359473 GU359338
–
GU359236
JF729166 JQ345167
Sachse 008 (MO)
Seydel 187 (US)
Latz 13486 (MO)
Peterson 14345, Soreng & Rosenberg (US)
South Africa, Western Cape
South Africa
Australia
Australia, Western Australia
JQ345237
GU360492
JQ345238
GU360703
JQ345279
GU360468
JQ345281
GU360288
JQ345322
GU359793
JQ345323
GU359986
JQ345208 JQ345168
GU359469 GU359342
JQ345209 JQ345169
GU359533 GU359137
Reeder 4714 & Reeder (US)
Peterson 16642 & Refulio-Rodriguez (US)
Mexico, Zacatecas
Peru, Apurimac
KF827775
GU360581
KF827710
GU360383
KF827639
GU359816
KF827584 KF827521
GU359436 GU359200
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Leptocarydion vulpiastrum (De Not.) Stapf
Leptochloa digitata (R.Br.) Domin
Leptothrium senegalense (Kunth) Clayton
Merxmuellera drakensbergensis (Schweikerdt)
Conert
Monelytrum luederitzianum Hack.
Mosdenia leptostachys (Ficalho & Hiern) Clayton
Muhlenbergia japonica Steud.
Peterson 23927b, Soreng, Romaschenko &
Tanzania, Ruvuma
Abeid (US)
Peterson 24238, Soreng & Romaschenko (US)
Tanzania
Risler 476 & Kerrigan (MO)
Australia, Northern Territory
Belsky 336 (MO)
Kenya
Mafa 4 (GRA)
South Africa
Smook 10031 (US)
Schweickerdt 1542 (US)
Soreng 5240, Peterson & Sun Hang (US)
South Africa
South Africa
China, Yunnan
rps16-trnK rps16 intron rpl32-trnL
ON012448 ON012442
ON012427 ON012435 OM980631
KF827792
JQ345246
KF827795
JF729078
KF827660
JQ345331
KF827663
–
KF827725
JQ345289
KF827728
JF729183
KF827595
JQ345213
KF827597
JF729165
KF827539
JQ345178
KF827542
–
GU360682 GU360421 GU359969 GU359459 GU359158
GU360681 GU360420 GU359967 GU359458 GU359159
HM143667 HM143571 HM143183 HM143388 HM143081
Paul M. Peterson et al. / PhytoKeys 194: 123–133 (2022)
Taxon
126
Table 1. Taxon voucher (collector, number, and where the specimen is housed), country of origin, and GenBank accession for DNA sequences of rps16-trnK, rps16
intron, rpl32-trnL, ndhA intron, and ITS regions; bold indicates new accession; a dash (–) indicates missing data, an asterisk (*) indicates sequences not generated
in our lab.
24
25
26
27
28
29
30
41
42
43
Country
Neesiochloa barbata (Nees) Pilg.
Nematopoa longipes (Stapf & C.E. Hubb.) C.E.
Hubb.
Neyraudia arundinacea (L.) Henrard
Swallen 4491 (US)
Simon 2353
Brazil
Africa
Peterson 23991, Soreng, Romaschenko &
Abeid (US)
Neyraudia reynaudiana (Kunth) Keng ex Hitchc.
Columbus 5302 (RSA)
Neyraudia reynaudiana (Kunth) Keng ex Hitchc.
Soreng 5318, Peterson & Sun Hang (US)
Neyraudia reynaudiana (Kunth) Keng ex Hitchc. Srisanga 97923, Norsaengsri, Unwin, Rodda,
Schuettpelz, Tin Tin Mu & Ling Shein Man
(US)
Pappophorum pappiferum (Lam.) Kuntze
Peterson 21689, Soreng, La Torre & Rojas
Fox (US)
Perotis indica (L.) Kuntze
Peterson 23880, Soreng & Romaschenko (US)
Psilolemma jaegeri (Pilg.) S.M. Phillips
Peterson 24247, Soreng & Romaschenko (US)
Sporobolus virginicus (L.) Kunth
Peterson 15683 & Soreng (US)
Tragus berteronianus Schult.
FLSP 457 (US)
Tridens flavus var. chapmanii (Small) Shinners
McCauley 438 (MO)
Triplasis americana P. Beauv.
Kral 12065 (MO)
Triraphis andropogonoides (Steud.) E. Phillips
Mennell s.n. (US)
Triraphis mollis R. Br.
Lazarides 046 & Palmer (US)
Triraphis mollis R. Br.
Peterson 14344, Soreng & Rosenberg (US)
Triraphis mollis R. Br.
Saarela 1608, Peterson, Soreng & Judziewicz
(US)
Triraphis mollis R. Br.
Saarela 1615, Peterson, Soreng & Judziewicz
(US)
Triraphis mollis R. Br.
Saarela 1648, Peterson, Soreng & Judziewicz
(US)
Triraphis mollis R. Br.
Saarela 1656, Peterson, Soreng & Judziewicz
(US)
Triraphis purpurea Hack.
Schweickerdt 2115 (US)
Triraphis ramosissima Hack.
Seydel 4278 (US)
Triraphis schinzii Hack.
Smook 1933 (US)
Uniola condensata Hitchc.
Peterson 9342 & Judziewicz (US)
Zoysia macrantha subsp. walshii M.E. Nightingale
Loch 435 (US)
rps16-trnK rps16 intron rpl32-trnL
ndhA
ITS
intron
GU360724 GU360279 GU360005
–
GU359122
MF035992* MF035992* MF035992* MF035992*
–
Tanzania, Njomba
ON012449 ON012443
ON012428 ON012436 OM980632
China, Yunnan
China, Myanmar
KF356392* KF356392*
GU360272
–
–
–
KF356392* KF356392*
–
GU360003 GU359397 GU359124
ON012429
–
OM980633
GU360700
GU360276
GU359996
GU359402 GU359128
Tanzania
Tanzania
Chile, Region I
Peru
USA, Missouri
USA, Georgia
South Africa, Cape Province
Australia, Uluru National Park
Australia, Western Australia
Australia, Northern Territory
KF827801 KF827734
KM011122 KM010919
GU360610 GU360362
GU360616 GU360370
KF827817 KF827751
KF827818 KF827752
GU360654 GU360335
–
–
GU360669 GU360336
ON012450 ON012444
KF827669
KM010695
GU359892
GU359898
KF827689
KF827690
GU359949
ON012430
GU359933
ON012431
KF827601
KM010535
GU359502
GU359503
KF827615
KF827616
ON012437
–
GU359539
ON012438
Australia, Northern Territory
ON012451 ON012445
ON012432 ON012439 OM980636
Australia, Northern Territory
ON012452 ON012446
ON012433 ON012440 OM980637
Australia, Northern Territory
ON012453 ON012447
ON012434 ON012441 OM980638
GU360652
GU360651
GU360650
GU360649
GU360642
GU359932
GU359931
GU359930
GU359927
GU359922
Peru, Ancash
Namibia
Namibia
South Africa
Ecuador, Chimborazo
Australia
GU360337
GU360338
GU360339
GU360340
GU360345
KF827546
KM010326
GU359215
GU359224
KF827568
KJ768887
–
OM980634
GU359187
OM980635
GU359549
–
GU359541 GU359188
–
–
GU359534 GU359191
GU359548 GU359197
127
44
45
46
47
48
Voucher
Phylogeny of the Triraphideae
31
32
33
34
35
36
37
38
39
40
Taxon
128
Paul M. Peterson et al. / PhytoKeys 194: 123–133 (2022)
plus a monophyletic Triraphis. The Triraphis clade includes six individuals of T. mollis
R. Br. (type of the genus as treated by Burbidge 1946 and Peterson et al. 2022) sister to
T. schinzii Hack. and T. ramosissima Hack. sister to T. andropogonoides (Steud.) E. Phillips + T. purpurea Hack. Our molecular data clearly support independent recognition
of Nematopoa since it is sister to Habrochloa and not a member of the Triraphis clade.
Habrochloa bullockii and Nematopoa longipes are clearly aligned within the Triraphideae, and together with Neyraudia and Triraphis, share the following salient morphological features: paniculate inflorescences, 3-veined, marginally ciliate lemmas, usually
with hairy lateral veins, and lemmas that are apically bifid and awned from between the
sinus (Watson and Dallwitz 1992; Watson et al. 1992; Peterson et al. 2010; Clayton
et al. 2016). Another probable synapomorphy for these four genera is possession of
panicoid-type bicellular microhairs (long, narrow basal and terminal cells; Amarasinghe and Watson 1988). Watson et al. (1992) verified the presence of panicoid bicellular microhairs for Habrochloa, Nematopoa, and Triraphis but indicate that they are
absent in Neyraudia arundinacea. However, Clayton and Renvoize (1986) previously
indicated that Neyraudia possesses slender microhairs similar to those in Triraphis.
Based on a sample containing Nematopoa, Neyraudia, and Triraphis, Gallaher
et al. (2022) determined the crown age (10.62 Ma) and stem age (46.76 Ma) of
the Triraphideae. Although at least three species of Neyraudia include tropical and
temperate Asia in their distribution, Africa is the most likely area of origin for the
Triraphideae since all four genera in the tribe include species distributed in Africa.
In addition, the Triraphideae shares a common ancestor with Centropodieae, also
from Africa and temperate Asia (Peterson et al. 2011). Because more than half of the
genera of Chloridoideae reside in Africa and the larger tribes, i.e., the Eragrostideae
Table 2. Characteristics of the five DNA regions (rps16-trnK, rps16 intron, rpl32-trnL, ndhA and ITS)
and parameters used as priors in Bayesian analyses estimated with GARLI. 2.0.
Characteristic
Total aligned characters
Number of sequences
Number of new sequences
rps16-trnK rps16 intron rpl32-trnL ndhA intron Combined plastid data
ITS
Overall
887
1046
844
1146
3923
769
4692
45
45
46
42
178
41
219
6 (13%)
6 (13%)
8 (17%)
7 (17%)
27 (15%)
8 (20%)
35
(16%)
Likelihood score (-lnL)
3909.0
3405.6
3778.7
4281.4
7973.0
Number of substitution types
6
6
6
6
Model for among-sites rate variation gamma
Gamma
gamma
gamma
Substitution rates
1.2071
1.2951
1.0625
0.9848
–
1.1422
2.7093
1.2876
1.7914
2.5216
2.6273
0.4083
0.3028
0.3251
0.2912
1.7222
1.5405
1.1547
1.4401
1.9389
0.6568
2.9778
2.0746
1.5146
2.3679
4.5253
1.0000
1.0000
1.0000
1.0000
1.0000
Character state frequencies
0.3088
0.3779
0.3693
0.3669
–
0.2404
0.1363
0.1226
0.1380
0.1348
0.2374
0.1462
0.1743
0.1222
0.1484
0.2582
0.4084
0.3251
0.3703
0.3497
0.2641
Proportion of invariable sites
0.1666
0.3154
0.0413
0.2537
–
0.2547
Gamma shape parameter (α)
2.1848
1.0833
0.9498
1.0636
–
0.9409
Phylogeny of the Triraphideae
129
Chasmanthium latifolium (outgroup)
DAN
Danthonia compressa
.86
86
Merxmuellera drakensbergensis
Ellisochloa rangei
CEN
Centropodia glauca
Centropodia mossamedensis
Habrochloa bullockii
Nematopoa longipes
Neyraudia arundinacea
Neyraudia reynaudiana Soreng 5318
Neyraudia reynaudiana Columbus 5302
Neyraudia reynaudiana Srisanga 97923
Triraphis ramosissima
Triraphis andropogonoides
Triraphis purpurea
Triraphis schinzii
Triraphis mollis Saarela 1615
Triraphis mollis Peterson 14344
Triraphis mollis Saarela 1608
Triraphis mollis Lazarides 046
Triraphis mollis Saarela 1648
.84
Triraphis mollis Saarela 1656
.59
1
81
TRI
*
.76
50
1
86
ERA
ZOY
.75
74
1
75
CYN
NA
1
56
SA
Africa
Australia
Eastern Asia (China, Mongolia, Japan, India)
0.02
Cottea pappophoroides
Enneapogon scaber
Entoplocamia aristulata
Uniola condensata
Eragrostis kennedyae
Eragrostis wiseana
Zoysia macrantha ssp. walshii
Psilolemma jaegeri
Sporobolus virginicus
Muhlenbergia japonica
Monelytrum luederitzianum
Tragus berteronianus
Neesiochloa barbata
Pappophorum pappiferum
Tridens flavus var. chapmanii
Chloris barbata
Leptochloa digitata
Eleusine poiflora
Eleusine indica
Gouinia virgata var. robusta
Triplasis americana
Mosdenia leptostachys
Perotis indica
Leptothrium senegalense
1
Gymnopogon grandiflorus
82
Leptocarydion vulpiastrum
Figure 1. Maximum-likelihood tree inferred from combined plastid (rps16-trnK, rps16 intron, rpl32trnL, and ndhA intron) and ITS sequences. Numbers above branches are posterior probabilities; numbers
below branches are bootstrap values; thick branches indicate bootstrap ≥ 90% and posterior probabilities of
1.00; DAN = Danthonioideae; tribes within the Chloridoideae = *, include: CEN = Centropodieae, TRI =
Triraphideae, ERA = Eragrostideae, ZOY = Zoysieae, and CYN = Cynodonteae. Scale bar: 2%.
and Zoysieae have centers of diversity there, Hartley and Slater (1960) earlier concluded that the subfamily probably originated on the African continent and spread
to other parts of the world (Bouchenak-Khelladi et al. 2008; Peterson et al. 2007,
2010, 2011, 2014c).
130
Paul M. Peterson et al. / PhytoKeys 194: 123–133 (2022)
Taxonomy
Triraphideae P.M. Peterson, Molec. Phylogen. Evol. 55(2): 591. 2010 ≡ Triraphidinae Stapf, Fl. Trop. Afr. 9: 22. 1917 – Type: Triraphis R. Br., Prodr. 185. 1810.
Description (emendation). Annuals or perennials, sometimes rhizomatous or reedlike (Neyraudia) culms 4–500 cm tall, erect or decumbent; ligules membranous and
ciliate or a fringe of hairs; inflorescence a panicle, open to contracted, rarely spiciform;
spikelets 2–15 mm long, 3–24-flowered, laterally compressed; glumes usually shorter
than the spikelets or upper glume 2 × as long as adjacent lemma (Habrochloa), 0-, 1- or
3-veined, membranous, sometimes hyaline, apex entire to mucronate, rarely awned;
lemmas membranous, rarely cartilaginous, 3-veined with ciliate or pilose margins, lateral veins, if present, usually hairy and sometimes extending as awns (Triraphis), apex bifid
and awned from between the sinus; paleas 0.5 to as long as lemma, 2-veined; stamens 3;
caryopses with adherent pericarp, often trigonous to ellipsoid, sometimes linear.
Included genera. Habrochloa, Nematopoa, Neyraudia, Triraphis.
Key to the genera
1
–
2
–
3
–
Lemmas 3-awned, the lateral veins extending into awns.................Triraphis
Lemmas 1-awned, the lateral veins never extending into awns ....................2
Culms (80–) 100–500 cm tall, generally 1–1.5 cm wide at base, often woody;
plants perennial, reedlike; ligules cartilaginous at base, apically with a line of
hairs; panicles 30–80 cm long, plumose .......................................Neyraudia
Culms 10–80 cm tall, ≤ 3 mm wide at base, herbaceous; plants annual not
reedlike; ligules membranous with a fringe of hairs, not cartilaginous at base;
panicles 2–30 cm long, not plumose ...........................................................3
Spikelets 2–2.5 mm long; lemmas 1–1.3 mm long, 3-veined, awned, the
awns 4–6 mm long; upper glumes 2 × as long as adjacent lemma .................
..................................................................................................Habrochloa
Spikelets 6–10 mm long; lemmas 3.5–4.3 mm long, 1-veined, awned, the
awns 8–13 mm long; upper glumes 0.5–0.6 × as long as adjacent lemma .....
.................................................................................................. Nematopoa
Acknowledgements
We thank the National Geographic Society Committee for Research and Exploration (Grant No. 8848-10, 8087-06) for field and laboratory support; the Smithsonian
Institution’s Restricted Endowments Fund, the Scholarly Studies Program, Research
Opportunities, Atherton Seidell Foundation, Biodiversity Surveys and Inventories
Program, Small Grants Program, the Laboratory of Analytical Biology, and the United
States Department of Agriculture. We thank Neil Snow, Clifford W. Morden, and Ana
Isabel Honfi for suggesting changes to the manuscript.
Phylogeny of the Triraphideae
131
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