Table Of ContentSPOROBOLUS
POTOSIENSIS (POACEAE:
NEW
A RHIZOMATOUS
ERAGROSTEAE):
FROM
SAN
SPECIES LUIS POTOSI, MEXICO,
NEW
AND
A COMBINATION
IN AIROIDES
S.
JOSEPH WIPFF STANLEY
JONES
K. and D.
S.M. Tracy Herbarium
Department Rangeland and Management
Ecology
of
A&M
Texas
University
TX
77845-2126,
College Station, U.S.A.
ABSTRACT
new
Sporobolus potosiensis a rhizomatous species from San Luis Potosi, Mexico that
is dil
rom
its closest putative relative, S. airoides, by having conspicuous and slender rhizor
1
.)
A
lacking trichomes behind the ligule, and generally smaller in stature.
:.) 3.)
A
ombination proposed
is at the subspecific rank: S. airoides subsp. regis. key to
hizomatous species of Mexican Sporobolus, as well as S. nealleyi and 5". airoides, is provic
Sporolobus potosiensis es una nueva especie rizomatosa de San Luis Potosi, Mexico, que
difiere de su pariente putative mas proximo S. airoides por tener rizomas conspicuos y mas
1
.)
delgados, 2 ausencia de tricomas detras de la ligula, y 3 tamano mas pequeno generalmente.
.) .)
Se propone una nueva combinacion de rango
subespecifico: airoides subsp. Se ofrece
S. regis.
Sporobolus a genus of approximately 60 species, distributed throughout
is 1
the tropics, subtropics and temperate areas (Clayton and Renoize 986). The
1
species of Sporobolus intergrade to such an extent that their limits are seldom
sharply defined (Clayton and Renvoize 1986). There are approximately 60
New
known
World
species of Sporobolus to occur in the (Judziewicz and
Peterson 1989) and 28 species are reported from Mexico (Beetle 1987), only
two which
species of have been reported rhizomatous:
as virginicus (L.)
-S".
Kunth
and
S. regis I.M. Johnston. Sporobolus virginicus, a strongly rhizoma-
tous perennial, found on sandy beaches and at the bases of sand dunes from
is
Virginia to Texas, south to Brazil and Peru, the West Indies, and the tropics
Old World
of the (Reeder 1975; Pohl 1980).
known
Sporobolus regis only from Coahuila, Mexico (Beetle 1987).
is
new
Johnston (1943) stated that his species, was probably most
S. regis,
Munro
and Lamson-
closely related to 5'. airoides (Torr.) Torr. 5". wrightii ex
and from
Scribner differed these species in having pubescent leaf sheaths,
tufts of trichomes in the axils of the panicle branches, and very coarse
163-
SiDA 1994
16(1): 169.
Sid A 1994
164 16(1)
mentioned culms and
rhizomes. Johnston (1943) also that "the bases of the
younger nodes of the rhizomes bear shredded remnants of old leaves."
the
The presence of shredded remnants of old leaves on the rhizomes needed
further investigation, since grass rhizomes usually produce modified leaves
termed (Gould and Shaw Examination of the holotype
"scale leaves" 1983).
Holmgren
2655 (GH, acronyms according revealed
{Stewart to et 1990)},
al.
that not rhizomatous and that the "rhizomes" are the portion of the
S. regis is
culms covered by with their sheaths decomposed and their nodes
soil,
developing adventitious roots, thus resembling rhizomes. All of the tillers,
specimen and
or shoots, of the type are erect lack lateral (horizontal) shoots.
Because of the obvious remnants of the culm sheaths, and the lack of "scale
leaves" on the culms, there little doubt that the "rhizomes" of 5". regis are
is
culms responding being buried.
in fact to
distinguished from by densely pubescent
Sporobolus regis is S. airoides its
sheaths and tuft of trichomes in the axils of the panicle branches. In our
opinion, these characters are not significant to warrant the recognition of
cS^.
at the specific rank, but are significant to warrant infraspecific recog-
regis
The However,
nition. lack of rhizomes places this taxon in S. airoides. these
(SW
unique and coupled with distribution
distinct characters restricted
its
Coahuila) justify the recognition of this taxon at the subspecific rank, thus
new
necessitating the following combination.
&
Wipff
Sporobolus airoides (Torr.) Torr. subsp. regis (I.M. Johnst.) S.D.
comb,
Jones, et stat. nov. basionym: Sporobolus I.M Johnst., Arnold Arbor.
regis
J.
km
MEXICO.
24: 393-394 (1943). Type: Coahuila: salt flat 4 SE of Laguna del Rey,
potosiensts^ipii S.D.Jones the second rhizomatous species
Sporobolus
Sc is
known new
to occur in Mexico. This species was originally identified at
TABS
from specimens that were either unidentified or misidentified as S.
MEXU, MO, TEX
MICH,
Specimens were requested from
Vasey.
nealleyi
US
and determine whether additional collections could be found.
to
non-rhizomatous, gypsophilous of
Sporobolus nealleyi a cespitose, species
is
southwestern United and northern Mexico. Chase (1951) and
the States
Correll and Johnston (1970) reported nealleyi as rhizomatous or subrhi-
S.
None
zomatous. of the specimens examined, including the holotype {Nealley,
US), had rhizomes. However, the densely tufted and persistent bases can be
covered by and then appear to be shortly rhizomatous or subrhizoma-
soil
Mexico, reported
tous, as already discussed above. Sporobolus nealleyi, in
is
Nuevo
from Coahuila, Leon, and San Luis Potosi (Reeder 1975; Beetle
1987). appears that reports from San Luis Potosi are based on misidenti-
It
of Based upon specimens examined, the
collections
fied S. potosiensis.
Mexico probably northern
distribution of nealleyi in restricted to
S. is
Nuevo
Coahuila and Leon.
The Specimens
closest putative relative oi S potosiensis S. airoides. of 5".
is
.
resemble depauperate individuals of but
superficially airoides,
potostensis
.S.
from by having conspicuous and slender rhizomes,
differ S. airoides 1.) 2.)
lacking trichomes behind the ligule, and being smaller in stature.
3.)
does not have rhizomes and usually has conspicuous
Sporobolus airoides
trichomes behind the though some very depauperate specimens were
ligule,
examined that did not have trichomes. Sporobolus airoides usually a robust
is
cm may
plant to 150 but depauperate specimens resemble S potosiensis
tall,
.
conspicuous rhizomes.
general appearance, except the
in for
cm
Inflorescences 15-25 wide, foLuid on dry soils in open ground,
2. (5-)
cm
2. Inflorescences 1-3 5 wide, restncied to gypsifeious soils S nealltyi Vasey
&
Wipff
S.D. Jones
(I.M. Johnst.)
Back of sheaths glabrous; base of inflorescence primary branches glabrous
3
.
cm cm
Inflorescences 4.0-9 wide, 12-18 long, open; branches
4.
&
Wipff
Jones
spreading; plants inland, not coastal potosiensis
S.
cm 2-8 cm
4. Inflorescences 0.6-1.0 wide, long, contracted; branches
Kunth
appressed; plants coastal S. virginicus (L.)
&
Sporobolus potosiensis Wipff S.D. Jones, sp. nov. (Figs. 1-4)
mm
1.2-1.4
antheris longis, luteolis.
3,
cm
18-5 with
Vlants (Fig. perennial, erect, tall slender rhizomes (Fig.
1) 1
mm
cm
2) to 14.5 long, 1.3-3.5 wide. Leaves 4-5, cauline, subcoriaceous;
sheaths glabrous, margins ciliate; collar (Fig. 4) abaxially glabrous, yellowish,
mm
margins conspicuously long ciliate with trichomes to 5-5 long; blades
mm
cm
6.2-24.0 long, 0.6-2.5 wide, folded or involute; abaxial surface
flat,
minutely scaberulous along
glabrous; adaxial surface papillose, antrorsely
mm
raised veins; margins antrorsely scaberulous; ligules 0.1-0.3 long,
membrane, truncate, lacking long trichomes behind the ligule.
ciliolate
cm cm
12-18
an open panicle, long, 4.0-9-0 wide, glabrous;
Inflorescences
cm
lower branches 3.0-8.0 long, nonfloriferous in the proximal 1/3-1/2;
mm
pedicels 0.2-2.2 long, glabrous; spikelets appressed to tertiary branches.
mm mm
1.6-2.5 long, 0.5-1.1 wide, glabrous, mottled
Spikelets (Fig. 3)
mm
/im
purplish, with one glumes unequal; glumes 1.0-1.5 long.
floret;
FIG. Photograph >r.,
of
1.
mm
veinless, lanceolate; 1.3-2.1 long; conspicuously 1-veined,
jefo;z^^///;;2^j
vein green; lanceolate with white-hyaline margins in the distal half, slightly
mm
shorter than lemma; lemmas 1.5-2.3 long; conspicuously 1-veined, vein
green, ovate-lanceolate, mottled purplish with white-hyaline margins in
mm
1.6-2.2 long, 2-veined, grooved or furrowed between
distal half;/;^/e^j
mm
lemma
veins, similar to texture and color; anthers 1.2-1.4 long,
3,
mm
yellowish. 0.9-1. long, 0.4-0. mmyNxde. Chromosome number
C^ryo/jj^j 5
The specific epithet refers to the State of San Luis Potosi, Mexico; the only
Known
Distribution: only from the Rio Verde River Valley, San Luis
Mexico.
Potosf,
km
MEXICO.
Typus: San Luis Potosi: 9 al E de Rio Verde, sobre la carretera a Rayon,
1000 m, terrenos aluviales pianos con vegetacion de zacatal halofilo con Prosopis,
alt.
24790 MICH!;
graminea dominance, 16 Sept 1967,/. Rzedoivskt (holotype: isotypes: LL!,
MICH!, TAES!, WIS).
MEXICO.
San
Additional specimens examined (paratypes): Luis Potosi: in the valley of
(TAES); in the valley of the Rio Verde and in the Sier
14-15 l95A,Sohm
San Francisco-Patios-Cardenas-Rayon, Sept
N
(RR
mi
del Maiz, 0.7 of Las Tablas crossing in town), alkal
1010 m, 22°17'N, 99°52'W,
Samolus, Vig/mra, Flaveria,
alt.
SW
km
Wells (ARIZ, TEX); ± 5 al de Tablas, alt. 1000 m, 2
(MEXU); Region de Llanos de Angostura municipio de Rio Verde, 900 m, 29 1980,
Jul
alt.
N
km
(MEXU);
Bravo 14 0.65 (0.4 mi) of the Escuela Primera in Las Tablas, on gravel road
m
Hwys
running between 70 and 80, 1097 (3600 27 Jul 1979, Lane 25386
alt. ft), &J. E.
(TEX).
Fryxelt
ACKNOWLEDGMENTS
We
thank Tony A. Re2nicek (MICH) for his assistance with the Latin
We
description and review of the manuscript. thank Charlotte G. and John
R. Reader (ARIZ), and an anonymous reviewer review and
for their
We
suggestions. also would like to thank the Curators at the following
GH, MEXU, MICH, MO,
TEX/LL,
herbaria loaning specimens: and US.
for
REFERENCES
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