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Phytotaxa 307 (1): 023–035
http://www.mapress.com/j/pt/
Copyright © 2017 Magnolia Press Article PHYTOTAXA
ISSN 1179-3155 (print edition)
ISSN 1179-3163 (online edition)
Accepted by Jeffery Saarela: 26 Apr. 2017; published: 19 May 2017
https://doi.org/10.11646/phytotaxa.307.1.2
23
Dichanthelium multiglandulosum (Paniceae, Panicoideae, Poaceae), a new
species from Jalisco, Mexico, and the reestablishment of Panicum transiens as
Dichanthelium transiens
J. GABRIEL SÁNCHEZ-KEN1
1Instituto de Ecología, A.C., Centro Regional del Bajío, 61600 Pátzcuaro, Michoacán, México.
Email: gabriels@hotmail.co.uk
Abstract
A new species, Dichanthelium multiglandulosum, from northwestern Jalisco, Mexico, is described and illustrated. Panicum
transiens, an incorrectly synonymized name lost in history, is here proposed as D. transiens, with the rarely used name D.
macrospermum treated as its synonym. Relationships of both species are discussed, and both are classified within Dichanthe-
lium section Macrocarpa. A key and a table of differences and similarities among the new species and related species are
provided.
Key words: Panicum multiglandulosum, northeastern Mexico, cane-like species, lemma micromorphology
Introduction
Dichanthelium (Hitchcock & Chase 1910: 20) Gould (1974: 59) is a large New World genus that has been neglected
greatly through history due to difficulties in species delimitation. Currently, the genus is classified within the subfamily
Panicoideae, tribe Paniceae and subtribe Dichantheliinae Zuloaga et al. (2015: 1697). Because of the difficulty in
defining boundaries at the specific level, the number of recognized species for the genus has varied greatly, from
42 (Gould (1978) for the Canadian and United States species, plus Zuloaga et al. (1993) for the Mesoamerican, the
West Indies and South American species), 72 (Freckmann & Lelong 2003) to up to 109 species (Zuloaga et al. 2003).
Such variation in species number is often due to different species concepts used by different authors. For example,
Thomas (2015), who used phenetic analyses to circumscribe species, recently reinstated to species level the varieties
of D. acuminatum (Swartz 1788: 23) Gould & Clark (1978: 1121), which differ in the morphology of the ligule and
pseudoligule. Half the species of the genus are found in Canada and the United States (Freckmann & Lelong 2003),
whereas the rest are distributed from Mexico to South America and a few in the Caribbean (Zuloaga et al. 1993).
Preliminary phylogenetic analyses confirmed the monophyly of the genus and the polyphyletic nature of some species
(Neubig et al. 2015, Majure et al. 2016). Many authors have considered Dichanthelium as a subgenus of Panicum
Linnaeus (1753: 55) (e.g., Zuloaga et al. 1993, Beetle et al. 1999, Clayton and Renvoize 1986, Clayton et al. 2006
onwards), whereas Gould (1974) elevated it to the genus category. Recognition of the taxon as a genus is supported by
phylogenetic analyses of molecular data and morphological traits (Aliscioni et al. 2003, Neubig et al. 2015, Majure
et al. 2016). Dichanthelium was first recognized as a subgenus of Panicum by Hitchcock & Chase (1910), based
on its species having winter and autumnal, or primary and secondary, growth phases with a somewhat recognizable
intermediate phase. The winter phase has a rosette of short, broad leaves, with simple culms that produce well-exposed
and terminal synflorescences with chasmogamous spikelets. The autumnal phase (which probably starts growth in
the summer) has synflorescences terminating in secondary branches, sometimes hiding among the fascicled leaves
or included in the sheaths, with cleistogamous spikelets (Hitchcock & Chase 1910). In the intermediate phases, the
synflorescences terminate in primary branches shorter than the winter phases with intermediate-sized leaves. Although
these characters are present in most North American species and some species that reach Central America, the basal
rosette and other growth stages are absent in some species from Mexico, and most species from South America
(Zuloaga et al. 1993). Other characters that contribute to the definition of the genus are leaf anatomy, presence of C3
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24 • Phytotaxa 307 (1) © 2017 Magnolia Press
photosynthetic pathways, ploidy level and fertile floret micromorphology (Brown & Smith 1975, Clark & Gould 1975,
1978, Gould 1980).
The subdivisional classification of Dichanthelium has varied through time. Hitchcock & Chase (1910) proposed
a classification of 17 informal groups of Panicum subgenus Dichanthelium, mostly for North American species. Later,
Hsu (1965) merged these groups into three sections. More recently, Freckmann & Lelong (2002) updated Hitchcock
& Chase´s classification by merging groups and segregating sections; they recognized 13 sections based solely on
morphological features. This classification treated only the North American species, including the majority of Mexican
species, leaving most South American species without any section affiliation.
Throughout history, the number of Mexican Dichanthelium species, whether recognized in Dichanthelium or
Panicum, has varied from 11 to 16, with several infraspecific taxa also recognized. The following authors recognized
different numbers of species and infraspecific taxa (in parentheses) in Mexico: Hitchcock & Chase (1910) (11/1),
Hitchcock & Chase (1915) (15), Gould (1980) (15/9), Zuloaga et al. (1993) (12/6), Beetle (1987) (20/13), Beetle et al.
(1999) (15), Zuloaga et al. (2003) (15/8), and Dávila et al. (2006) (16/9).
As part of a revision of Dichanthelium in Mexico, I encountered an undescribed species that had been previously
recognized as distinct and proposed under the name of Panicum, but not validly published. Even though the name of
this species is not valid, it has been cited in the literature (Vázquez-García, 1998, Dávila-Aranda et al. 2004). I here
describe the species under Dichanthelium and discuss its classification in the genus. I also clarify the taxonomy of
Panicum transiens Swallen (1931: 436), a name that was wrongly synonymized with D. pedicellatum (Vasey 1889: 28)
Gould (1974: 60) by Gould (1980). After reviewing the morphology of these and related species, I found the supposedly
rare D. macrospermum Gould (1980: 358) is a synonym of P. transiens, an earlier name for this Dichanthelium species.
A new name is proposed for the species, which is also discussed and illustrated.
Materials and methods
Specimens of Panicum and Dichanthelium from important Mexican herbaria (ENCB, IBUG, IEB, MEXU, and
XAL) were reviewed. Online databases from MO, NY, and US were also reviewed, including images of types and
representative specimens, as available.
Spikelets were removed from the type specimens of D. multiglandulosum and D. transiens and fixed on plates,
one showing the second glume and two showing only the fertile lemma. These samples were dehydrated to extract all
humidity and then coated with a fine layer of gold. The samples were observed and photographed using a scanning
electron microscope (SEM, JSM-5310LV, JEOL, Tokyo, Japan).
To verify the photosynthetic pathway temporary preparations of leaf anatomy were made from the type specimens
of D. multiglandulosum and D. transiens. Small pieces of the leaf blade were sectioned, rehydrated with tap water, and
placed on a slide with a drop of water/safranine/glycerol. The slide was placed under the stereoscope and cross sections
were made with a double edged razor blade. Thin sections were soaked in the stain for several minutes, transferred
to a clean slide with a drop of water, covered with a cover glass, sealed with nail polish and examined under light
microscopy (Berlyn & Miksche 1976).
Taxonomic treatment
Dichanthelium multiglandulosum Sánchez-Ken, sp. nov. (Fig. 1).
“Panicum multiglandulosum Sánchez-Ken & Dávila in Dávila et al. (1998: 204), nom. nud.”
Typ e :— MEXICO. Jalisco. Mpio. Talpa de Allende: 3 km adelante de Cuale por la brecha a Talpa de Allende, Bosque de Pinus oocarpa
y P. ayacahuite, sobre laderas húmedas, 2100 m, 31 January 1983, F. J. Santana-Michel 1219 (holotype IBUG-40043!, isotypes
IBUG-32535!, IEB!).
Plants perennial, 120–140 cm tall, rhizomatous, rhizomes short, scaly, nearly as wide as the culms, apparently not
forming a basal rosette, only one phase of growth recognized, culms cane-like, erect, branching above; internodes
10–14, 2.7–5 mm diameter, glabrous, with glandular spots at or near the apex; nodes glabrous to short-pilose upwards.
Leaf sheaths shorter than the internodes, usually with glandular spots, the lower ones glabrous, the upper ones short-
DICHANTHELIUM MULTIGLANDULOSUM Phytotaxa 307 (1) © 2017 Magnolia Press • 25
FIGURE 1. Dichanthelium multiglandulosum. A. Cane-like habit. B. Ligular area (arrow pointing to the ligule) showing the adaxial
surface of the leaf. C. Synflorescence branching pattern. D. Spikelet, first and second glume view. E. Fertile floret, fertile lemma and fertile
palea view. (Based on the type)
pilose with rigid hairs becoming glabrous in age, the margins short-pilose with rigid hairs; ligules 0.2–0.3 mm long,
membranous, the apex barely provided with minute hair, mostly glabrous and slightly irregular; collar densely short-
pilose; leaf blades 16–26 cm × 13–23 mm, the lower ones shorter to almost reduced, lanceolate, flat, ascending, both
SÁNCHEZ-KEN
26 • Phytotaxa 307 (1) © 2017 Magnolia Press
surfaces glabrous to short-pilose to hirtellous, densely pilose at the base, the margins scabrellous, densely short-pilose
at the base, the base rounded to slightly cordate on the uppermost leaves, the apex attenuate, foliar dimorphism lacking.
Synflorescence 16–22 × 14–22 cm, open, diffuse, terminal, paniculate, branches alternating, spreading, branchlets
spreading; peduncle up to 20 cm long, sparsely short-pilose, with glandular spots; axes somewhat angular, glabrous
or sparsely short-pilose toward the base, with glandular spots; axils short-pilose, the upper ones glabrous; pedicels
(0.5–)1.5–8(–11) mm long, capillary, spreading, glabrous, with glandular spots. Spikelets 3.5–4.3 × 1.3–1.4 mm,
elliptic, acuminate, purple, green-tinged, wrinkled at the base of the glumes, apparently forming a gland; first glume
1.4–2.4 mm long, up to one-half as long as the spikelets, ovate-elliptic, 1-nerved or nerveless, glabrous; second glume
3–4.1 mm long, 9-nerved, the 2 lateral nerves of the midnerve not prominent, nearly wanting, glabrous; lower floret
sterile; sterile lemma 3.2–4.2 mm long, 9-nerved, glabrous, similar to the second glume; sterile palea 3–3.5 mm
long, 0.5–0.8 mm wide, slightly shorter than the fertile lemma, linear, membranous, 2-keeled, the keels minutely
scabrellous, unwinged, puberulent; fertile lemma 3.1–3.8 × 1.3–1.5 mm, elliptic, smooth to slightly rugulose, lustrous,
yellowish to stramineous, apex acute, umbonate, usually with some minute antrorse hairs at the apex, 7-nerved but
appearing 5-veined because the 2 veins adjacent to the central ones are incomplete, visible only towards the apex,
with a germination flap, falling with the glumes; fertile palea smooth, lustrous, similar to the fertile lemma; stamens
3; anthers ca. 2 mm long; caryopsis oblong, embryo ca. one half as long as the caryopsis, hilum oblong, one fourth as
long as the caryopsis.
Additional specimen examined:—MEXICO. Jalisco. Mpio. Talpa de Allende: Minas de Zimapan por la brecha
a Cuale, bosque de pino y encino, 1620 m, 12 December 1981, F.J. Santana-Michel 889 (IBUG, XAL).
Etymology:—The specific epithet refers to the presence of glandular spots throughout the plant (internodes,
sheaths, inflorescence and spikelets).
Distribution, habitat, and ecology:—Dichanthelium multiglandulosum is endemic to the area of Talpa de
Allende, in the northwestern part of Jalisco (Fig. 4). It occurs on humid slopes in oak-pine forest, at elevations between
1620 and 2100 m.
Phenology:—Flowering in December and January.
Diagnostic characters:—Cane-like habit, plants 120–140 cm tall, glandular spots throughout the plant (internodes,
sheaths, inflorescence and spikelets, Fig. 2), and glabrous spikelets 3.5–4.3 mm.
Spikelet micromorphology:—The micromorphology of the bracts and fertile floret is simple: the glumes and
sterile lemma are glabrous and at the base of both glumes there is a wrinkled area, which may represent a gland. The
fertile lemma is smooth and shiny all over, although at high magnification (120×) tiny papillae can be seen (Fig. 3).
The apex is acute and umbonate with few tiny antrorse hairs.
Photosynthetic pathway:—Leaf blade cross sections confirm a “non-Kranz” anatomy associated with a C3
photosynthetic pathway (Brown & Smith 1975, Zuloaga et al. 1993). As described by Zuloaga et al. (1993) the midrib is
a large first order vascular bundle followed by a tandem array of several secondary vascular bundles and a smaller first
order vascular bundle up to the margin of the leaf blade. The secondary vascular bundles have an outer bundle sheath
with extensions to both surfaces, without specialized chloroplast as shown by Zuloaga et al. (1993). The mesophyll is
semiradiate around the vascular bundles, adaxially the cells are in a palisade-like arrangement, and abaxially the cells are
in a spongy-like tissue. Vascular bundles are separated by more than five chlorenchymatous mesophyll cells (Fig. 2).
FIGURE 2. Photographs showing the glandular spots on internodes (A), and synflorescence (axis, branches and pedicels) (B) and leaf
blade cross section (C) of Dichanthelium multiglandulosum.
DICHANTHELIUM MULTIGLANDULOSUM Phytotaxa 307 (1) © 2017 Magnolia Press • 27
FIGURE 3. Micromorphology of the spikelet and fertile lemma of Dichanthelium multiglandulosum (A. Spikelet second glume view. B.
Fertile lemma. C. Fertile lemma apex) and D. transiens (D. Spikelet second glume view. E. Fertile lemma. F. Fertile lemma apex).
Related species and section affiliation:—The new species was first recognized as “Panicum multiglandulosum”
in a revision of Flora Novo-Galiciana (McVaugh 1983), but was never formally published; the name was also included
in a checklist (Dávila et al. 1998). Based on the anatomy indicating a C3 photosynthetic pathway, habit, blade shape and
spikelet morphology, this species belongs in the genus Dichanthelium. Based on observations and literature (Zuloaga
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28 • Phytotaxa 307 (1) © 2017 Magnolia Press
et al. 1993), this species resembles some other Mexican and South American species lacking a basal rosette and foliar
dimorphism. The diagnostic character for which the new species is named is the presence of glandular spots throughout
the plant (internodes, sheaths, inflorescence, spikelets). Other species from Mexico and South America have glandular
spots on only some organs, not all of them. Other characters, such as the size of the plant and its cane-like habit, further
support recognition of the new species. This species, like some Mexican species and most South American species,
apparently has only one phase of growth.
FIGURE 4. Distribution of Dichanthelium transiens (¡) and D. multiglandulosum (●).
Dichanthelium multiglandulosum and a few other species (D. assurgens (Renvoize 1982: 325) Zuloaga in Aliscioni
et al. (2003: 816), D. commutatum (Schultes in Roemer & Schultes 1824: 242) Gould (1974: 59), D. davidsei (Zuloaga
& Morrone 1991: 158) Zuloaga in Aliscioni et al. (2003: 816), D. itatiaiae (Swallen (1966: 81) Zuloaga (2003: 816))
distributed from Mexico to South America are the most robust species of the genus that grow like a cane. In Mexico,
plants of D. multiglandulosum are the tallest of the genus. Of these, Dichanthelium commutatum (at least the Mexican
specimens) is the only species that seems related to D. multiglandulosum, based on the robustness of the plants,
lack of winter rosette, sometimes with glandular spots on the sheaths, the lack of indumentum of the synflorescence
axis and the wrinkled and possibly glandular base of the spikelets. Following the classifications of Hitchcock &
Chase (1910) and Freckmann & Lelong (2003) plus characters such as the habit, the lack of both basal rosette and
foliar dimorphism (in the Mexican plants) as well as characters of the spikelets, D. commutatum is placed in section
Macrocarpa Freckmann & Lelong (2002: 165)
Placing
D. multiglandulosum in section Macrocarpa or any of the other recognized sections of the genus, however,
is difficult, because the species does not agree completely with any current sectional circumscription following
Freckmann & Lelong (2003). A phylogenetic classification of the genus does not yet exist, but is currently being
studied (Neubig et al. 2015, Majure et al. 2016). The new species may be related to sections including species with
membranous-ciliate ligules (Table 1). Several of these sections, however, such as Nudicaulia Hitchcock & Chase (1910:
142) ex Freckmann & Lelong (2002: 165), Sphaerocarpa (Hitchcock in Robinson & Fernald (1908: 113)) Freckmann
& Lelong (2002: 166) and Strigosa Freckmann & Lelong (2002: 165) can be excluded from consideration because
their species are smaller plants, form a basal rosette and have much smaller spikelets, even though the species may
be glabrous like in D. multiglandulosum. This leaves as the possible groups for the new species sections Pedicellata
(Hitchcock & Chase (1910: 142) ex Freckmann & Lelong (2002: 165)), Clandestina Freckmann & Lelong (2002: 164)
and Macrocarpa, which have species that may or may not develop a basal rosette.
DICHANTHELIUM MULTIGLANDULOSUM Phytotaxa 307 (1) © 2017 Magnolia Press • 29
TABLE 1. Morphology of Dichanthelium sections with membranous-ciliate and sometimes pilose ligules, according to
Freckmann & Lelong (2003), complemented with personal observations and descriptions from Hitchcock & Chase (1910).
1 Most specimens branch at the base and above; many D. pedicellatum specimens are branched at the base and above the
middle in a fascicled or bushy way.
Pedicellata Macrocarpa Clandestina Nudicaulia Sphaerocarpa Strigosa
Rhizomes sometimes knotty often knotty,
sometimes
caudices
thick absent? with
caudices
absent? with
caudices
absent?
Corm-like
rhizomes
present absent absent absent absent absent
Culm habit “slender”,
erect becoming
decumbent
“stout”, ascending
to erect
robust or stout,
erect
slender, weakly
ascending
slightly fleshy or
thickened, erect,
spreading to
ascending
slender erect to
spreading
Culm
branching
divaricately
above1
scarcely above densely above rarely at the base sparsely at the
base
extensively at the
base
Winter rosette absent usually well-
differentiated
well differentiated somewhat
differentiated
well differentiated poorly
differentiated
Ligule membranous-
ciliate, hairs
longer than
membranous part
or pilose
membranous-
ciliate, hairs
longer than
membranous part
membranous-
ciliate, cilia or
hairs minute or
pilose
membranous-
ciliate
absent, sometimes
a few hairs,
sometimes
membranous-
ciliate
membranous-
ciliate, cilia or
hairs longer than
the membranous
part
Spikelet length
(mm)
3.2–4.4 (2.2–)2.9–5.2 2.2–3.6 2.4–3.2 1–1.8 1.1–2.3
Spikelet shape obovate to
pyriform
elliptic to obovate elliptic to ovate narrowly elliptic
to ovate
spherical to
obovate
elliptic to obovate
Spikelet base
shape
attenuate wide wide wide wide wide
Spikelet
pubescence
papillose-pilose pilose to
papillose-pilose,
hairs sometimes
sparse
glabrous to pilose glabrous glabrous or pilose glabrous or pilose
TABLE 2. Comparison of taxonomically important characters among Dichanthelium multiglandulosum, D. commutatum
and D. transiens from section Macrocarpa.
D. multiglandulosum D. commutatum D. transiens
Height (cm) 120–140 50–120 30–100
Habit cane-like cespitose cespitose, ~cane-like
Internode number 10–14 5–10 5–9
Internode pubescence glabrous short-pilose to glabrous papillose-pilose becoming
glabrescent
Glandular spots presence internodes, sheaths, peduncle
synflorescence axis, branches,
pedicels, spikelets base
sometimes sheaths, spikelets
base
spikelets base
Ligule membranous, eciliate membranous-ciliate, the cilia
longer than membranous part
membranous-ciliate, the
cilia equal or shorter than
membranous part
Synflorescence axis
indumentum
glabrous or sparsely short-
pilose toward the base
glabrous hirtellous, rarely glabrous
Spikelet length (mm) 3.5–4.3 (2.1–)2.7–3.3 (2.9–)3–4
First glume length (mm) 1.4–2.4 0.8–1.8 1.8–2.6
Second glume veins (no.) 9 7–9 9
Second glume indumentum glabrous short-pilose papillose-hirtellous
Sterile lemma veins (no.) 9 7–9 9
Sterile lemma indumentum glabrous short-pilose papillose-hirtellous, hairs all
over or sparsely
Sterile palea length (mm) 3–3.5 1.3–2 1.4–1.8
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The new species is probably not part of section Pedicellata, which includes D. nodatum and D. pedicellatum.
These species have slender habits, do not form a basal rosette and have large, obovate to pyriform, papillose-pilose
and attenuate-based spikelets, with ligules in one species pilose and in the other membranous-ciliate. The section
Clandestina is also ruled out, because in its species the basal rosette is well differentiated, the spikelets are smaller,
the rhizomes are thick and the plants are densely branched above. Macrocarpa is the section that shares the most
characters with D. multiglandulosum, but differs by having a “usually well differentiated rosette” and pubescent
spikelets (Table 1). The more robust species of the genus in North America are classified in sections Macrocarpa,
which includes previously recognized groups such as Commutata Hitchcock in Robinson & Fernald (1908: 113) and
Latifolia Hitchcock in Robinson & Fernald (1908: 116), and section Clandestina. I propose to include the new species
in section Macrocarpa, with the caveat the circumscription of the section needs to be expanded to include species
without a basal rosette and with glabrous spikelets, otherwise the species would remain unclassified as the South
American species. Molecular data are needed to test this hypothesis of relationship.
In Mexico, section Macrocarpa was previously represented by two species, Dichanthelium commutatum and
D. macrospermum. The latter species is discussed in the next section and is proposed as a synonym of the new name
D. transiens. These two species and D. multiglandulosum now make up section Macrocarpa in Mexico. In Table 2
differences and similarities among these three species are summarized.
Dichanthelium transiens (Swallen) Sánchez-Ken, comb. nov. (Fig. 5).
Basionym: Panicum transiens Swallen (1931: 436).
Typ e :—MEXICO. Tamaulipas: Mpio. San Carlos: Sierra de San Carlos, Mesa de Tierra, vicinity of San José, 3500 ft, 19 July 1930, H.H.
Bartlett 10454 (holotype US-00148063!; isotypes MEXU-3882!, MICH-1108749!, NY-00381779!, US-00148064!).
Dichanthelium macrospermum Gould (1980: 358).
Typ e :—MEXICO. San Luis Potosi: 30 mi E San Luis Potosi, along highway 86 to Rio Verde, 6900 ft, 13 July 1963, R.L. McGregor, L.J.
Harms, A.J. Robinson, R. del Rosario & R. Segal 618 (holotype US-00133537!).
FIGURE 5. Dichanthelium transiens. A. Slender cane-like habit showing a multi-flowered synflorescence. B. Collar area. C. Ligule area.
D. Few flowered synflorescence. E. Spikelet showing the first glume. F. Spikelet showing the second glume. G. Fertile lemma. (Based on
Díaz & Carranza 6662 (IEB)).
DICHANTHELIUM MULTIGLANDULOSUM Phytotaxa 307 (1) © 2017 Magnolia Press • 31
Plants perennial, 30–100 cm tall, knotty rhizomatous, with a corm-like base (not always evident), basal rosette lacking,
only one phase of growth recognized, culms cespitose, slightly cane-like, commonly erect, but rarely ascending and
rooting at lower nodes, scarcely branching at the base and above, eglandular; internodes 5–9, 1.5–2.5 mm diameter,
papillose-pilose becoming glabrescent, rarely glabrous; nodes densely short pilose or glabrescent. Leaf sheaths shorter
or longer than the internodes, eglandular, papillose-hirsute becoming glabrescent, margins pilose; collar densely short
pilose; auricles sometimes present, as long as the ligule; ligules 0.1–0.3 mm long, membranous-ciliate, with the hairs
or cilia shorter than the membrane; leaf blades (6–)9–17 cm × (8–)9–20 mm, the lowermost reduced, lanceolate, flat,
spreading, hirtellous on both surfaces, sometimes glabrescent, throat densely short pilose behind the ligule without
forming a pseudoligule, margins scabrous, sparsely short to long pilose at the base, base cordate, apex attenuate,
foliar dimorphism lacking. Synflorescence (4–)10–20 cm long, lowermost branches 3–10 cm long, diffuse, terminal
or lateral when the plant is branched, paniculate, branches alternating, spreading, ascending, sparsely hirtellous to
glabrescent; peduncle 7–25 cm long, normally hirtellous rarely glabrous, eglandular; axis hirtellous glabrescent toward
the apex; axils glabrous, yellowish to brown; pedicels 1–10 mm long, the terminal ones much longer to 2 cm long,
scabrellous, capillary, appressed, rarely spreading eglandular. Spikelets (2.9–)3–4 × 1.2–1.5 mm, elliptic to slightly
obovate, acuminate, base attenuate, light green, rarely purple tinged, glandular at the base, papillose hirtellous, always
with few hairs, the hairs spreading to nearly glabrous; first glume 1.8–2.6 mm long, ca. half as long as the spikelets,
ovate to lanceolate, 1–3-nerved, glabrescent, with at least 1–2 hairs towards the margins distally; second glume 2.8–3.9
mm long, leaving the fertile floret exposed at maturity, 9-nerved, shortly papillose-hirtellous, the hairs distributed all
over or sparse; lower floret sterile; sterile lemma 2.8–3.9 mm long, 9-nerved, texture and pubescence similar to the
second glume; sterile palea 1.4–1.8 mm long, ca. half as long as the fertile floret, ovate, membranous, 2-keeled on
lower half, glabrous or puberulent; fertile lemma 2.9–3 × 1.1–1.2 mm, elliptic to slightly obovate because of the stipe,
smooth to apparently slightly rugulose depending on age, lustrous, yellowish to stramineous, 7-nerved but appearing
5-veined because the two veins adjacent to the central one are incomplete and visible only towards the apex, with a
germination flap, apex acute, umbonate with tiny antrorse hairs on and around the umbo, falling with the glumes;
fertile palea smooth, lustrous, similar to the fertile lemma but the papillae more evident; stamens 3; anthers 1–1.1 mm
long; caryopsis oblong, embryo ca. half as long as the caryopsis, hilum oblong, one third as long as the caryopsis.
Plants from southern locations are more robust and more glabrescent than northerly-distributed plants, and most
have many-flowered synflorescences.
Additional specimens examined:—MEXICO. Nuevo León: Mpio. Galeana, Sierra Madre Oriental, Mesa de la
Camisa, about 15 mi SW of Galeana, 22 July 1934, C.H. Mueller & M.T. Mueller 1171 (F, MEXU); Mpio. General
Zaragoza: Sierra Madre Oriental, 0.5 mi NE Dulces Nombres, and just E of border into Tamaulipas, 1850 m, 18
June 1948, F.G. Meyer & D.J. Rogers 2574 (MO); Mpio. Monterrey: Sierra Madre, 7 April 1933, C.H. Mueller &
M.T. Mueller 166, 408 (MEXU); Mpio. San Pedro Garza García: Parque Ecológico Chipinque, vereda El Empalme,
1266–1291 m, 6 October 2005, J.A. Encina, F.J. Encina & I. Ramírez 1540 (MEXU); Mpio. Santiago: delante de San
Juan Bautista, rumbo a Laguna de Sánchez, 1600 m, 19 May 2004, E. Estrada et al. 16125 (MEXU). Querétaro: Mpio.
Arroyo Seco: 4–5 km WNW de La Florida, 1300 m, 29 July 1991, E. Carranza G. 3322 (IEB); 2 km W de El Jardín,
1400–1500 m, 7 June 1991, H. Díaz B. & E. Carranza G. 6662 (IEB); Mpio. Jalpan, 5–6 km NE de San Antonio
Tancoyol, 1000–1200 m, 6 March 1991, E. Carranza G. 3073 (IEB); 3 km SE de El Lobo, 1780 m, 7 December 1987,
L. M. Chávez 139 (IEB); 5 km al W de El Lobo, sobre el camino a Landa, 1600 m, 26 June 1959, J. Rzedowski 10925
(ENCB); 4 km S de Valle Verde (La Parada), sobre el camino a Landa, 1200 m, 2 June 2005, V.W. Steinmann & E.
Pérez C. 5092 (IEB); ca 2 km from Valle Verde (La Parada) along the trail to La Cercada, 1350 m, 24 September 2002,
V. W. Steinmann & S. Zamudio 2798 (IEB); Mpio. Landa, Hoyo del Lodo, 5 km N de Acatitlán de Zaragoza, 1780 m,
2 October 1989, E. González P. 1085 (IEB); 2 km SW de El Madroño, 1900 m, 23 May 1990, E. Carranza G. 2499
(IEB); 6–7 km NE de la Lagunita de San Diego, vertiente SE del Cerro Grande, 2300 m, 2 August 2000, G. Ocampo
& E. Pérez C. 895 (IEB); 1.5 km NE de El Sabinito, 1500, 16 June 1990, H. Rubio 1728 (IEB); 1 km SW de El Lobo,
1600 m, 1 August 1987, J. Rzedowski 44033 (IEB). San Luis Potosí: Mpio. El Naranjo, 21.1 mi W of SLP-Tamaulipas
border on MEX 80 from Antiguo Morelos, 4000 ft, 14 August 1989, J.F. Utley & K. Utley 8470 (MEXU); about 18 mi
E of Ciudad del Maiz on Mex 70 near pueblo of El Naranjo, 4000 ft, 27 May 1974, G. McPherson, T. Duncan & R.
Sanders 915 (NY); Mpio. Xilititla, Potrerillos, 1400 m, 28 February 1959, J. Rzedowski 10020 (ENCB). Tamaulipas:
Mpio. Guémez, El Chiue, 1800 m, 19 August 1981, J.L. Ramos 18 (MEXU); La Ventanita, 1250 m, 4 November 1982,
G. Villegas 538 (MEXU); Mpio. Hidalgo, 1 km al S de Puerto Purificación, rumbo a Conrado Castillo, 13 July 1988, F.
González M., I. Díaz & D. Corona 17045 (MEXU); 5 km al N de los Caballos, May 1984, F. González M., L. González,
V. Juárez, D. Baro & L. Hernández 14029, 14042 (MEXU); Aserradero Galindo, a 6 km de Puerto Purificación, 5 June
1990, F. González M., V. Juárez & P. Tenorio 17430 (MEXU); Mpio. Jaumave, La Trementina, 1940 m, 21 April 1994,
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32 • Phytotaxa 307 (1) © 2017 Magnolia Press
G. Galván 453 (MEXU); Mpio. San Carlos: Sierra de San Carlos, La Vegonia, vicinity of San José, 975 m, 5 July 1930,
H.H. Bartlett 10090 (US); Mina La Homogénea San José, 900–1000 m, 28 September 1985, O.L. Briones V. 2048
(MEXU); Mpio. Victoria, camino al Molino, 800 m, 10 November 1986, M.H. Cervera 191ª (MEXU); Altas Cumbres,
1240 m, 19 October 1982, P. Moya 14 (MEXU).
Distribution, habitat, and ecology:—This species has a restricted distribution in Mexico in the Sierra Madre
Oriental mountains in the states of Queretaro, San Luis Potosi, Nuevo León and Tamaulipas (Fig. 3). Found in cloud
forest, oak or oak-pine forest, or sometimes secondary grasslands, at elevations from 800 to 2300 m.
Phenology:—Flowering from February to December.
Diagnostic characters:—Plants with a corm-like base, slight cane-like habit, basal rosette lacking, scarcely
branching below and above, eglandular, collar densely short-pilose, ligules 0.1–0.3 membranous-ciliate, and spikelets
(2.9–)3–4 mm, elliptic to slightly obovate, papillose-hirtellous, the hairs spreading to glabrescent but always with few
hairs.
Spikelet micromorphology:—The glumes and sterile lemma are papillose-hirtellous and at the base of both
glumes there is a wrinkled area, which may represent a gland. The fertile lemma is smooth and shiny all over, although
at high magnification (120×) papillae are evident. The fertile lemma apex is acute and umbonate, with a few tiny
antrorse hairs on and around it (Fig. 3).
Photosynthetic pathway:—Leaf blade cross sections confirm a “non-Kranz” anatomy associated with a C3
photosynthetic pathway (Brown & Smith 1975, Zuloaga et al. 1993). The anatomy of the leaf blade of D. transiens is
similar to D. multiglandulosum but the former has more cells between vascular bundles.
Related species and section affiliation:—Panicum transiens was described by Swallen (1931), who placed it in
the Pedicellata group sensu Hitchcock & Chase (1910) with the two other members of the group, P. pedicellatum Va sey
(1889: 28) and P. nodatum Hitchcock & Chase (1910: 293). The inclusion of P. transiens in this group was based on the
lack of a basal rosette, corm-like culms and attenuate papillose-pilose spikelets. It differs from the two other species by
having longer spikelets (4 mm long), a longer subacute first glume, and larger plants, with culms scarcely branching
below and above and much longer and wider blades without foliar dimorphism. In the original description the author
stated “ligule densely ciliate, about 0.5 mm”, but he was probably referring to a membranous-ciliate ligule. The isotype
(Bartlett 10454, MEXU) has a membranous-ciliate ligule with the membranous portion longer than the cilia. On the
other hand, D. pedicellatum and D. nodatum have pilose ligules sensu Hitchcock & Chase (1910), although in the
section sensu Freckmann & Lelong (2003), the authors mentioned membranous-ciliate ligules for D. pedicellatum.
Based on my observations, the latter authors are correct, although the membranous portion of the ligule is very short,
which makes it look like a line of hairs, contrary to P. transiens in which the membranous portion is longer than the
cilia or hairs. The specimens A.F. Skutch 524 (probably US) and J.A. Steyermark 43443 (F) were included under the
name Panicum transiens in Flora of Guatemala by Swallen (1955), although he was doubtful about their identity and
assigned them to this species with the possibility they might be a different species. According to the Swallen´s (1955)
key, these specimens have glabrous spikelets. Most specimens of P. transiens from throughout its known distribution
range have papillose-pilose spikelets, although some specimens have nearly glabrous spikelets, with a few scattered
hairs. Later, Zuloaga et al. (1993) identified the specimen A.F. Skutch 524 as Panicum divergens Kunth in Bonpland et
al. (1816: 102), a name now considered a synonym of D. commutatum, and the specimen J.A. Steyermark 43443 (F)
was identified as D. pedicellatum by Davidse in Davidse et al. (1994).
In a treatment of the Mexican species of Dichanthelium, Gould (1980) placed P. transiens in the synonymy of
D. pedicellatum without comment. Possibly Gould (1980) did not see the type of P. transiens, because he did not
cite it, and he probably followed Swallen´s assumption that it belonged to the Pedicellata group sensu Hitchcock &
Chase (1910). In a Mexican grasses checklist, Beetle (1987) recognized P. transiens as a distinct species, but later as
a synonym of D. pedicellatum (Beetle et al. 1999). After reviewing an isotype of P. transiens and comparing it with
specimens of D. pedicellatum and D. nodatum I concluded the name was wrongly synonymized by Gould (1980) and
should be recognized as a species in the genus Dichanthelium.
The culms of D. transiens are sometimes scarcely branched above (at least in a few specimens collected from
February to December) and the leaves are (6–)9–17 cm × (8–)9–20 mm and lanceolate with cordate bases, whereas
in D. pedicellatum and D. nodatum the culms are usually much branched above (in specimens collected from April to
August) and the leaf blades are 3–12 cm × 2–8 mm and linear with bases rounded, truncate or subcordate. The venation
of the leaf blades of D. transiens comprises a central thick vein and, on each side of the midvein, a tandem array of
(4–)5 areas of several tertiary veins divided by a secondary vein, contrary to the 3 to 4 tandem arrays on each side of
the central vein in the Pedicellata species. In some northern specimens of D. transiens the synflorescences are few-
flowered like those in D. pedicellatum, but in most plants the synflorescences in D. transiens are (4–)10–20 cm long,
with southern specimens multi-flowered.
DICHANTHELIUM MULTIGLANDULOSUM Phytotaxa 307 (1) © 2017 Magnolia Press • 33
In the same publication, Gould (1980) described D. macrospermum as a close ally of D. albomaculatum
(Scribner 1900: 2) Gould (1980: 357) (the latter name was later synonymized to D. commutatum) from the group
Commutata, currently recognized as section Macrocarpa (Freckmann & Lelong 2002). According to Gould (1980),
D. albomaculatum differed from D. macrospermum by its smaller spikelets, smaller first glume and glabrous axis
and branches of the synflorescence. Dichanthelium macrospermum has not been collected since its description and
was considered a rare species, known only from the three specimens reported in the protologue. Beetle (1987) and
Beetle et al. (1999) treated it in Panicum; in the former treatment it was reported for three states of Mexico (Hidalgo,
Queretaro and San Luis Potosi) and in the latter treatment only from Queretaro and San Luis Potosi. After reviewing
types of D. macrospermum and Panicum transiens, I conclude they are the same species, and because the latter name
was published first, the accepted name in Dichanthelium should be D. transiens, proposed here.
To determine the sectional placement for D. transiens all the sections with membranous-ciliate ligules and large
spikelets were compared (Table 1). The three sections sensu Freckmann & Lelong (2002, 2003) with these characters
are Pedicellata, Clandestina and Macrocarpa. Dichanthelium transiens cannot be placed in the Pedicellata section,
where Swallen (1931) included it, because of the differences among D. transiens, D. nodatum and D. pedicellatum
discussed above. The section Clandestina is excluded from consideration by having thick rhizomes, a basal well-
differentiated rosette, dense culms branching above, and elliptic to ovate spikelets. The characters of D. transiens agree
best with the circumscription of section Macrocarpa (Freckmann & Lelong 2002); in fact, D. transiens is similar to D.
commutatum and many specimens of D. transiens were wrongly identified as part of the latter species. The inclusion of
D. transiens in D. commutatum probably altered the original circumscription of the latter in publications such as Flora
Novo-Galiciana (McVaugh 1983) and Las Gramíneas de México (Beetle et al. 1999), which will need to be verified.
More recently, the D. commutatum species complex has been suggested to be polyphyletic (Majure et al. 2016, Neubig
2016). If D. transiens belongs in sect. Macrocarpa, the circumscription of the section will need to be further expanded
to include species that have corm-like bases, in addition to the characters of D. multiglandulosum also unique in
the section (described above), and corm-like bases would no longer be exclusive to sect. Pedicellata. Otherwise, D.
transiens would remain unclassified until relationships within the genus are clarified. Dichanthelium transiens is
easily distinguished from D. commutatum and D. multiglandulosum by the presence of corm-like bases of the culms,
densely pilose collars, pubescence of the internodes, pubescence of the peduncle and axis of the synflorescence, as well
as larger and papillose-hirtellous spikelets (Table 2).
KEY TO THE MEXICAN SPECIES OF DICHANTHELIUM SECT. MACROCARPA
1. Plants cane-like, 120–140 cm tall; culms 2.7–5 mm diameter; spikelets 3.5–4.3 mm long, glabrous; glandular spots on internodes,
sheaths, peduncles and synflorescence axis, branches and pedicels ................................................................ D. multiglandulosum
- Plants cespitose to slightly cane-like, up to 120 cm tall; culms < 2.7 mm diameter; spikelets 2.1–4 mm long, pubescent, sometimes
glabrescent with a few scattered hairs; glandular spots on some organs but never all of them ....................................................... 2
2. First glume 1.8–2.6 mm long; collar densely short pilose; peduncle, axils and branches of the synflorescence pubescent; spikelets
green, rarely purple tinged, attenuate at the base ........................................................................................................... D. transiens
- First glume 0.8–1.8 mm long; collar glabrous; peduncle, axils and branches of the synflorescence glabrous; spikelets usually
purple, rounded at the base ....................................................................................................................................... D. commutatum
Acknowledgments
I would like to thank L.M. González-Villarreal for kindly sending me the material of the new species. Special thanks
to M. Berenit Mendoza G. for the scanning electronic microscope (SEM) images at the Instituto de Biología, UNAM.
Thanks to my friends Drs. Christine Notis Mella and Corrinne Grover for reviewing the manuscript as well as Richard
LeBlond, an anonymous reviewer and Jeff Saarela for their suggestions.
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