ARISTIDAE ELUDENDAE II: A RE-EVALUATION OF THE ARISTIDA GIBBOSA COMPLEX (POACEAE: ARISTIDEAE), INCLUDING A. MARGINALIS, A. ORIZABENSIS, AND A. SORZOGONENSIS

2008·17.1 MB·English

by  Robert T Strahan

ELUDENDAE A OF THE
RE-EVALUATION GIBBOSA
ARISTIDAE AjRISTIDA
II:
COMPLEX INCLUDING
MARG1NAL1S,
(POACEAE: ARISTIDEAE),
A.
AND
SORZOGONENSIS
ORIZABENSIS,
A.
A.
and W.
Robert Strahan Allred
Kelly
T.
Range Herbarium
Science
co State University
w
LasCrulTNe
Mexico
88003,
U.S.A.
trahan@nmsi [email protected]
i.edu;
rs
Z^&bosa.AnsMarnarpnalis.ArisMaori:
am
ion morphologic,
variation
.1
ihedbyanuml
mta^osa
and
complex, spee
.determine .eeiesoftheA, hrief descripttons,
the
s
F
RESUMEN
INTRODUCTION
growing warmer,
some 250-350 worldwide
The genus comprises nearly in distribution, in
species,
Aristida
L.
Members by one-flowered
more environments characterized panicle inflorescence,
(Allred 2003). are a
arid
The by
and glumes, usually larger than the florets are characterized three
spikelets, relatively large floret.
awns, the two awns absent or much reduced in some species, and a sharp pointed callus with a tuft
lateral
some lemma body drawn an elongated beak below the divergence
of hair the base. In cases the out into
at is
Members
such groups
awns. The genus has share taxonomically species complexes. of
of the of difficult
its
commonly
and geographic distribution (Allred
only morphologically overlap in their
often
differ slightly
Longhi-Wagner
1984a, 1984b; 1990).
New
World complex by
The complex one such This characterized the
group. fol-
Aristida gibbosa is
is
lemma and
lowing two features: floret sulcate, the margins of the slightly overlapping, 2) callus short,
1)
mm
mm
New
World
and 0.2-0.3 diameter taxa
0.3-0.4 long, the attachment scar circular tiny, in (Fig.
1).
names
chronological
corresponding these features have received the following (in order):
to
Chaetaria gibbosa Nees In his ample description, Nees noted the regular branching of the
(1829):
and
culms, short lower sheaths exposing the gibbous nodes (whence the specific epithet), folded or rolled
Blade margins not thickened, the marginal veins being no wider than those inward, and the
blades. are
leaf
and
adaxial surface lacking pilose hairs except the corners of the sheath. Panicles lack pulvini are thus
at
is
name
American and was unused in North and Central
narrow and South the
This species,
contracted. a
is
American works Longhi-Wagner (1990) called attention to the sulcate lem:
until
310 Journal of the Botanical Research Institute of Texas 2(1)
MO
and US and annotated them The name was then an expanded
as applied, in
at this.
f
sense, to Meso-American plants by Pohl and Davidse (1994) to include Aristida sorzogon-
and
A. orizabensis, A. marginalis.
ensis,
Aristida sorzogonensis Erroneously believing Haenke's specimen
Presl (1830):
J.
to be from Sorsogon on the island of Luzon in the Philippines, Presl applied the specific
new
specimen
epithet sorzogonensis to his species. highly probable that the actually
is
It
came from Central America or Mexico (annotation in 1921 on the type by E.D. Merrill;
Henrard The by two both with
1928). type collection represented at least sheets, a single
is
(of
flowering culm: the holotype PR(!) has three mid- to upper blades, but lacks the base
at
the plant or any basal blades; an apparent isotype PR(!) has a culm with three upper
at
blades and two mid- to lower blades. Presl described the blades as convolute-setaceous,
upon
which the upper but the middle and lower blades are (perhaps rolled a bit
are, flat
band
wide
drying) in both specimens. Blade margins are noticeably thickened, with a of
sclerenchyma the margin; this easily visible even on the upper blades that are rolled.
at is
A
The adaxial surface has prominent pilose hairs upwards from the throat region. close
examination of the panicle branches and pedicels reveals small (perhaps young) pulvini
in nearly the with the resultant spreading of the axes, a feature not noted
axils, slight
all
^
name
any The has been
for this species in previous works. Aristida sorzogonensis largely
unknown
ignored or by nearly North American botanists, even though Henrard recog-
all
Sulcate
Fig. 1. nized in both his Revision and Monograph of Aristida (Henrard 1929, 1932). Pohl and
it
Day and
over
idse (1994) rightly called attention to the priority of sorzogonensis orizabensis
attachment
circular
we
marginalis, but believe they misinterpreted the typification in tentatively applying the
scar (arrow).
name
with than
sorzogonensis to plants rolled, rather blades.
flat,
Aristida liebmanii E. Fourn. (1886): Fournier's description came from a collection
by Liebmann (whence the specific epithet) and noted the following distinctive features: basal blades are
flat
and upper (much and glumes than
the blades are rolled as in the type of A. sorzogonensis), are longer
first
He an beak on lemma,
the second. did not attention the nearly complete absence of elongated the
call to
the awns immediately diverging from the apex, but was stressed by Henrard easily observ-
this (1927),
is
An
able in the type, and was re- emphasized by Pohl and Davidse (1994). isotype at MO(!) contains three
flowering shoots and one basal portion. The margins of the blades are noticeably thickened, and the lower
panicle branches are naked the base and somewhat flexuous. Panicles are non-pulvinate. Pohl and Davidse
at
and
with
(1994) called attention to similarity A. succedeana Henr., a species of Bolivia Brazil that also
its
may
has sulcate lemmas, blades, and sub-flexuous panicle branches, with the suggestion that the two
flat
be conspecific. However, because of the scarcity of specimens further analysis and conclusions concerning
must more
this species await the availability of material.
Aristida orizabensis Fourn. (1886): Fournier's description, though short, mentions blades
E. flat
(rolled upon drying), somewhat unequal glumes, and a narrow lemma that was slightly shorter or longer
came
than the glumes. Material from "Valle de Orizaba," Veracruz, Mexico (whence the specific epithet),
with Fournier citing two specimens, which are considered syntypes. Isosyntypes at NY(!) and US(!) have
curling blades with thickened margins and with long pilose hairs on the adaxial surface near the ligule,
flat,
and Henrard with Vasey and
panicles lacking pulvini. (1927) contrasted A. orizabensis A. arizonica A. appressa
two excluded from complex lemmas.
Vasey, species this that lack sulcate
Ekman named
Aristida marginalis This species was from material collected along the dry,
(1911):
woods whence
grassy edges of forests or ("in margine silvulae," the specific epithet) in Matto Grosso, south-
new
The by Ekman.
ern Brazil. species very well described In type material (isotypes G!, US!), sheaths
is
are about half as long as the numerous internodes with gibbous nodes; lower blades are curling, and
flat,
thick-margined with pilose adaxial surfaces; the panicle obscurely and incompletely pulvinate with
is (i.e.,
poorly developed pulvini in the axils of some branchlets and pedicels); and the lemmas are sulcate with a
Strahan and Re-evaluation of the gibbosa complex 311
Alfred, Aristida
name
subsumed under comparisons
Longhi-Wagner using
A. of
short, circular callus. (1990) this gibbosa,
name
spikelet features such as beak length and relative glume length. The A. marginalis has been applied to
numerous Mexican specimens with curling blades and well-developed pulvini.
flat,
among and
This study investigates the relationships Aristida gibbosa, A. sorzogonensis, A. orizabensis,
from herbarium specimens
using morphological characters scored
A. marginalis multivariate analysis of to
assess species boundaries and determine the usefulness of certain traits used to distinguish them.
AND METHODS
MATERIALS
For analysis of taxonomic relationships, specimens identified as Aristida gibbosa, A. sorzogonensis, A. oriz-
NMCR,
MO,
and WIS.
abensis, and A. marginalis were obtained from the following herbaria: F, G, US, All
lemma them members
specimens were examined for a sulcate to distinguish as of the A. gibbosa complex.
A OTUs
complete examination of specimens yielded 90 (operational taxonomic units) for the analysis,
all
and The specimens used
specimens
including type of A. gibbosa, A. sorzogonensis, A. orizabensis, A. marginalis.
represented the geographic distribution of the species complex from northern Mexico through Central
full
A
upon Roughly specimens
and South America. complete data available request. two-thirds of the
set
is
and
received that were identified in herbaria as A. orizabensis were actually A. appressa, not included in this
study. In addition to not having a sulcate lemma, A. appressa develops a thicker beak (0.2-0.3 mm), usu-
mm)
longer lemma (7-16 mm), and longer callus (0.6-1 with a longer, elongated (rather than circular)
ally
attachment
scar.
OTU
Each was scored 13 characters, seven discrete and six continuous (Table All discrete
for
1).
and
characters were recorded mature vegetative features as present or absent, with without the aid of a
for
dissecting microscope depending on the nature of the character. All spikelet measurements were taken using
an ocular micrometer on dissecting microscope and were obtained from one mature spikelet from each
a
components
specimen. measurements were taken using standard metric Principal analysis
Panicle a ruler.
(PCA) of the standardized data was conducted using Kovach (2005).
AND
RESULTS DISCUSSION
An PCA OTUs 83% among
with
of indicated morphological differences of the variability speci-
initial
all
mens components due high
occurring along the three (Table This in part to variable- to -variable
is
first 2).
among and
correlations various discrete features of leaf blade pubescence, type of blade involution curling,
thickness margins, and shape of nodes (Table the high correlations render these features taxonomi-
of
3);
important.
cally
Component among OTUs, weak
60.1% mostly
accounted of the variability reflecting correlations
for
I
awn
Component and
of vegetative features. accounted for 14.9% of the variability, correlating variation in
II
glume and Component correlated with pulvini and panicle length (Table
lengths,
III 2).
OTUs was two components, with between two morpho-
Dispersion along the resolution
of greatest
first
groups occurring along component The two groups were distinguished by a combination of
logic (Fig.
2).
I
OTUs
Group by and
vegetative and spikelet features. corresponding to are characterized leaf blades folded
1
gibbous nodes lacking pilose hairs on the adaxial surface, margins not thickened
straight (Fig. (Fig.
4),
3),
OTUs
awn Group
and
(Fig. smaller glumes, shorter awns, shorter callus to lengths (Figs. 6-7). clustered in
5),
nodes
2 are characterized by contrasting features: curling leaf blades (Fig. terete (Fig. leaf blades flat
8), 9),
with thickened margins and prominent pilose hairs on the adaxial surface (Fig. larger glumes, longer
10),
and awn The within Group and
awns, longer lengths 11-12). type of Aristida gibbosa
callus to (Figs. fell
1,
the types of Aristida sorzogonensis and A. orizabensis within Group 2. The placement of the type specimen
fell
some Group
of A. marginalis between Groups and 2 a result of having features of (gibbous nodes,
1 is its 1
branching culms) and some features of Group 2 curling blades, adaxial pubescence).
(flat
members Group had been
Because of 2 previously identified as three different species {marginalis,
PCA
and second
both non-pulvinate
well including pulvinate panicles, a
as as
orizabensis, sorzogonensis),
Journal of the Botanical Research Institute of Texas 2(1)
branched
i
esstraigh
lades curling leaf blad
folded
lades leafblad es
flat
^^
MARGINS
PUBESCENCE
urfacegla
Snider
PULVINI
length (cm)
le
(mm)
2 length
-
^;:;:zss
LATAWNL
«„,
Table Factoi loadings for the three components of the nt analysis of OTUs. Loadings less that
2. first all
p
±0.250 have )een replaced by
zero.
t
Components
Component Component
2
1
*:?>
PCA
82%
OTUs
was conducted on 54 Group 2 The three components of the explained
of
all (Fig. 13). first
OTUs
component was
second Dispersion along function of
of the variability of this analysis (Table of a
4). I
awn awn Component
glume and revealed differences in
variability in lengths, lengths, callus to length. II
Component
the central awn, glume two, and panicle lengths, as well as the pulvini development. III cor-
responded to variation in panicle length and pulvini development (Table
4).
OTUs
Group no morphological nor separation
Dispersion of 2 reveals further clear distinctions, a clear
between and being Axillary pulvini
pulvinate non-pulvinate forms, in spite of these visually distinctive.
somewhat
and appearance,
cause panicle branches pedicels spread outward, giving the panicle a diffuse
to
contrasting with the dense contracted appearance of non-pulvinate panicles (Figs. 14-17).
may
among and
In summary, spikelet features are deceptively similar the three species analyzed, lead
them though thought be
one to consider as conspecific. In contrast, vegetative features, often to of lesser
value in grass taxonomy, serve very well in distinguishing the species.
and
Strahan Re-evaluation of the gibbosa complex
Allred, Aristida
-999999
95
9
Journal of the Botanical Research Institute of Texas 2(1)
TAXONOMIC
which was
Consequent PCA, three species are recognized (in addition to A. liebmannii,
to the results of the
and
(Group OTUs),
(Group OTUs), Aristida sorzogonensis 2
not analyzed in this study): Aristida gibbosa 1
described in Table
marginalis (represented solely by the type specimen). Variation in features is 5.
Aristida
on two from problematic,
The (based the isotypes a single collection) is
recognition of Aristida marginalis
known about distinguished from the other two species by a suite of peculiar vegeta-
since so
little is It is
it.
numerous nodes and conspicuously short sheaths, about half
more culms with
robust
tive features: taller,
mix and
exposing many gibbous nodes. Other features are a of A. gibbosa A.
the
long the internodes,
as
as
and gibbous
blades with adaxial pilose hairs characteristic of A. sorzogonensis,
curling
sorzogonensis:
flat,
We
name
further
nodes and branching culms characteristic of A. gibbosa. leave the A. marginalis intact until
analyses are possible.
COMPLEX
KEY TO THE OF THE ARISTIDA GIBBOSA
SPECIES
lemma
apex
Lemma the awns almost immediately diverging from e not-twisted of the
lacking beak,
a
.
!ong^_ liebmannii
cm A.
awns 2-3
body; 1
,
cm
awns
Lemma the divergence of awns; (0.5-)1-2
with a well developed beak, often twisted prior to
1.
MO
from
We and an specimen (Burch 6143A)
have studied only two specimens: the isotype at additional
&
A
Sheaths glabrous;
Davidse provide description]:
Honduras. diagnosis follows [Pohl (1994) a fuller
brief
and
upon ends with thickened margins; collar throat glabrous;
blades (rolled drying or at the of the blades),
flat
non-pulvinate, but the lower branches somewhat flexuous and naked at the base;
narrow,
panicles elongate,
mm
mm
8-9 lemmas beak absent,
glumes 10-12 long, the second long; involute, sulcate, a
inverse, the
first
cm
lemma; awns 2-3 ± equal in length.
the awns diverging immediately at the tip of the long,
lemma and awns immediately
The long distinctive.
combination
of a sulcate is
and Honduras.
Mexico
(Veracruz)
Distribution.—
Enum.
Aristida gibbosa (Nees) Kunth, 1:189. 1833. Basionym: Chaetaria &bbosa Nees, Agrostologia Brasiliensis,
2. pi.
and
usually lacking
by glabrous,
characterized blades that are folded or rolled, stiffly erect,
Aristida gibbosa
is
with
and prominently gibbous nodes,
have
The culms branch above the base
thickened margins. regularly
narrow and
non-pulvinate.
2-6(-8) nodes above Panicles are
elevated the base.
and
South America: Venezuela, British Guiana, Brazil (Fig. 18).
Distribution.— Bolivia,
and
Strahan Allred, Re-evaluation of the Aristida gibbos;
-0.47 -0.38 -0.28 -0.19 -0.09 0.00 0.0 0.19 0.28 0.38 0.47
Component
1
Ekman,
Aristida marginalis
3. Ark. Bot. 10(17):23, 12. 1911. b
3, 2, 6, Type:
t. f. t. f.
Apr
.6
]
known
Aristida marginalis only from the type collection, and characterized as follows: culms robust,
is is
generally about twice as thick as in A. gibbosa or A. sorzogonensis, branching above the base, with numerous
nodes
(7-8) elevated above the base; sheaths short, about the length of the internode, straw-colored and
V2
contrasting with the pale greenish internode; blades curling, with thickened margins, pilose on the
flat,
adaxial surface; panicles narrow, but weakly pulvinate.
Known
Distribution.— only from Matto Grosso, Cuiba
Brazil: (Fig. 18).
The name many
has been from North America, which
Aristida marginalis applied to similar plants of
Journal of the Botanical Research Institute of Texas 2(1)
HE
7
Howard from
Gentry
reported such by Scott (1942)
conspicuously pulvinate, particularly collections as
are
Mayo western Chihuahua. All of these North American plants fall well within the A. sor-
the Rio region in
on PCA, and from the true Brazilian A. marginalis in the features given in the key.
zogonensis cluster the differ
and
and herbarium work needed explain the distribution variation oiAristida
Further are to fully
field
and
seems not
and coincidental, a
between
apparent intermediacy A. gibbosa A. sorzogonensis
marginalis.
Its
many boundaries
As with species oiAristida, species are likely to
hybridization or introgression.
result of
name
and should not be discarded as inconsequential.
be decipherable, the
delicate, yet
Strahan and Re-evaluation of the gibbosa complex
Allred, Aristida
4. Aristida sorzogonensis Presl, in C. Presl, Reliq. haenk. l(2-4):224. 1830. Type: in Luzonia ad Sorzogon,
J r.
—
Mostly Mexico and Central America, with a few specimens from northern South America
Distribution.
(Fig. 18).
by and with on
Aristida sorzogonensis characterized blades that are curling, pilose hairs the
flat
is
adaxial surface and with thickened margins. The culms do not branch above the base and the nodes are
may
0-4
which
not gibbous, with nodes elevated above the base. Panicles be pulvinate or non-pulvinate,
a minor feature, but the visual differences are immediately noticeable (Figs. 14-17). As has been done
is
—
H
Journal of the Botanical Research Institute of Texas 2(1)
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0.4-
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0.3i
V
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component Gro
of the principle analysis of
: