Hyparrhenia variabilis and Hyparrhenia cymbaria (Poaceae): New for the Americas,
Successful in Mexico
Author(s): Heike Vibrans, Edmundo García-Moya, Derek Clayton, and Jorge G. Sánchez-Ken
Source: Invasive Plant Science and Management, 7(2):222-228. 2014.
Published By: Weed Science Society of America
DOI: http://dx.doi.org/10.1614/IPSM-D-13-00107.1
URL: http://www.bioone.org/doi/full/10.1614/IPSM-D-13-00107.1
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Invasive Plant Science and Management 2014 7:222–228
Hyparrhenia variabilis and Hyparrhenia
cymbaria (Poaceae): New for the Americas,
Successful in Mexico
Heike Vibrans, Edmundo Garcı́a-Moya, Derek Clayton, and Jorge G. Sánchez-Ken*
Hyparrhenia cymbaria (boat thatching grass, ipopo grass) and Hyparrhenia variabilis (no common name), robust
African savanna grasses with complex taxonomies, have not yet been reported for the Americas. Large populations
were found in central Jalisco, northeastern Michoacán, and Morelos, Mexico. The species grow in maize and
sorghum fields as well as on roadsides and in old fields, but always in association with present or past sorghum
cultivation; this suggests introduction through contaminated seed material from Africa. Because of the size and
density of the populations, and their native ecology, they are both agricultural pests as well as a potentially dangerous
invaders for the American (sub)tropical grasslands and native scrublands, including the southern United States. The
invasion underlines the importance of effective phytosanitary controls of the seed supply.
Nomenclature: Boat thatching grass, Hyparrhenia cymbaria (L.) Stapf; Hyparrhenia variabilis Stapf.
Key words: Invasive grasses, invasive plants, Jalisco, Michoacán, Morelos, phytosanitary controls, new record.
Two African grasses, boat thatching grass, Hyparrhenia
cymbaria (L.) Stapf and Hyparrhenia variabilis Stapf,
with high invasive potential for the American subtropics
and tropics have been introduced into Mexico. Mexico
has a relatively low proportion and absolute number of
established exotic plant species (Villaseñor and EspinosaGarcı́a 2004). However, there are two groups of plants
that have a high percentage of exotic species, many of them
invasive and transformers of ecosystems. One of these
groups is taxonomic (grasses), and the other functional
(aquatic plants) (Comité Asesor Nacional sobre Especies
Invasoras 2010). Grasses are particularly damaging, as
they change the fire dynamics in the more arid vegetation
types.
Most of the exotic grasses have been introduced
intentionally as pasture and forage; many originated in
Africa (Parsons 1970, 1972; Rzedowski and Rzedowski
1990; Williams and Baruch 2000). Some have apparently
arrived by accident, perhaps as seed contaminants.
DOI: 10.1614/IPSM-D-13-00107.1
* First and second authors: Professor, Postgrado en Botánica,
Campus Montecillo, Colegio de Postgraduados, km 36.5 carretera
federal México–Texcoco, 56230 Montecillo, Mpio. Texcoco,
Estado de México, Mexico; third author: Honorary Research
Fellow (retired), The Herbarium, Royal Botanic Gardens, Kew,
Richmond, Surrey, United Kingdom; fourth author: Independent
Researcher, 03100 México, D.F. Corresponding author’s E-mail:
heike@colpos.mx, heike_texcoco@yahoo.com.mx
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Invasive Plant Science and Management 7, April–June 2014
The genus Hyparrhenia (Panicoideae: Andropogoneae) is
mainly an African savanna genus with over 50 species
(Clayton 1969; Clayton et al. 2006). It contains several
species of forage grasses that are known to be invasive in
tropical regions worldwide, and also in Mexico. Hyparrhenia rufa (Nees) Stapf (jaraguagrass or giant thatching
grass), is very common in the tropical lowlands of the
country and the continent. Hyparrhenia hirta (L.) Stapf
(thatching grass) grows in several parts of Mexico, Central
America, the Caribbean, and South America. Hyparrhenia
bracteata (Humb. & Bonpl. ex Willd.) Stapf (no common
name) has a few populations in Mexico and is more
common further south (Beetle et al. 1983–1995; Davidse
et al. 1994; Dávila et al. 2006; Tropicos database [www.
tropicos.org]; herbarium specimens at MEXU). However,
H. cymbaria (boat thatching grass, ipopo grass) and H.
variabilis have not yet been registered for the American
continent.
The genus is taxonomically difficult because of rampant
polyploidy, apomixis, and hybridization. The basis for
the current understanding of the genus is Clayton (1969).
He adopts a relatively strict species concept in order to
represent the major variations of the group. However, he
says:
In Hyparrhenia the concept of species is peculiarly
difficult, for variation is apparently continuous throughout much of the genus. Both the available cytogenetic
knowledge of the genus, and its successful occupation of
an ecosystem constantly liable to disturbance, offer an
explanation as to why this should be so. It should be
appreciated that herbarium collections are likely to overemphasize the degree of continuity; partly because the
stable populations tend to be more distant from human
occupation and therefore more trouble to collect, and
also because their very uniformity renders them less
interesting to the collector. To the taxonomist, who
must catalogue variation in terms of discrete units, it is a
thought which brings some comfort, but nevertheless
he is faced with a formidable dilemma.’’ … ‘‘The
continuum concept, borrowed from ecology, is helpful
when dealing with entities whose discontinuity is not
readily ascertained. The specimens are visualized as
clustered about a number of noda in a multidimensional
network. (Clayton 1969, pp. 36–37).
A subsequent multivariate analysis of differences between Hyparrhenia cymbaria, H. variabilis and some close
relatives found few clear differences between these groups
(Clayton 1975). However, recent floristic works retain
the two species (Clayton and Renvoize 1982, Clayton et al.
2006).
Here, we report these species from the central-western
part of Mexico, in the states of Jalisco, Michoacán, and
Morelos. They are found mainly in disturbed habitats, but
their native distribution and ecology suggest they can
invade the natural vegetation of the American dry tropics
and subtropics.
Discovery and Identification
The species were first noted by the second author in
autumn of 2010. After the first author identified a specimen
to genus (and determined that it was a taxon not yet
recorded for Mexico), a field trip on February 7, 2011,
yielded three numbered collections, as well as photographs
and observations of numerous populations (Figure 1A–F).
William D. Clayton (Kew) identified the two species from
specimens in 2012. A review of grass specimens of Morelos
by the fourth author and a subsequent field trip in the same
year discovered several populations in Morelos (Figure 1I).
The first collection had been made in the year 2006 but it
was not identified until this review. The Jalisco populations
were not only confirmed in the summers of 2012 and
2013 (Figure 1G and H), but found to be expanding. Dr.
Irma López Muraira (Instituto Tecnológico de Tlajomulco,
Jalisco, personal communication) reported large populations
in the La Barca region in Michoacán in 2012, with
photographs, and new populations near Tlajomulco de
Zuñiga, a few km south of Guadalajara in 2013. A search of
the literature, herbarium databases, the National Herbarium
of Mexico (MEXU), and the herbarium of the Institute of
Botany, University of Guadalajara, Jalisco (IBUG), failed to
show previous collections from Mexico or the American
continent.
Taxonomy
The most striking features of Hyparrhenia, a member of
the tribe Andropogoneae, are their compound inflorescences with bracts (spatheoles) and paired racemes.
However, they share this characteristic with a number of
other genera in the tribe. The diagnostic traits of the genus
are the following:
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the sessile spikelet is inserted laterally on the
internode, and the internode’s tip is free and usually
pointed;
the lower glume of the sessile spikelet is rounded,
not keeled or grooved, sometimes with some shallow
striations;
the upper glume of the sessile spikelet is obtuse to
acute or mucronate;
the fertile lemma is minutely bidentate, and its awn
pubescent to hirtellous;
the pedicelled spikelet does not have a pronounced
callus; and
the base of the racemes are no longer than 10 mm,
usually shorter.
Both Hyparrhenia cymbaria and H. variabilis belong
to Clayton’s (1969) section Pogonopodia and are closely
related to each other. The section is circumscribed by
having only one homogamous pair of spikelets per
spatheole; short, flattened lower raceme bases that are not
much longer than the upper raceme bases; both raceme
bases with beards and without appendages; and an acute to
pungent callus of the sessile spikelet. The closely related
section Hyparrhenia has appendages on the raceme-bases
and overall narrower spatheoles and fewer awns. These
differences are difficult to see and require the use of a
strong hand lens or herbarium microscope.
The species of the section are mainly perennial, robust
plants with brightly colored, relatively short spatheoles
(Figure 1A and B). These usually enclose the raceme-pairs
that have short peduncles. The racemes are reflexed within
the spatheoles. There are three to eight awns per pair, and
these awns have a hairy column.
The two new species share stilted roots, three to five
awns (sometimes up to six) per raceme pair, and glabrous
pedicelled spikelets. Both have the chromosome number
2n 5 20. However, in Hyparrhenia cymbaria the partial
inflorescences are smaller, and the callus tends to be obtuse,
square, or broader than long. Hyparrhenia variabilis has
partial inflorescences that tend to be longer, but there is
considerable overlap. The best distinguishing characteristics
are the length of the awns (1.8 to 3.2 cm [0.71 to 1.26 in]
Vibrans et al.: New Hyparrhenia in Mexico
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Figure 1. (A) Comparison of partial inflorescences of the two Hyparrhenia species; H. cymbaria is from the specimen H. Vibrans
8413 from Jalisco, and H. variabilis from the H. Vibrans et al. specimen from Morelos. (B) Inflorescence of Hyparrhenia cymbaria. (C)
Stilted roots. (D) Habit and size of a plant in 2011, near the site of collection number H. Vibrans 8414 in Michoacán; the vegetation in
the background on the other side of the road is a Hyparrhenia population. (E) Population in an old field, near (D), in 2011. (F) An
individual in a cropped maize field near (D), in 2011. (G) A roadside population near the site of (D), but in 2013. (H) Hyparrhenia
invading grass/bushland, 2013. (I) A field margin population of Hyparrhenia variabilis in Morelos, with a sorghum field in
the background.
in H. variabilis vs. 0.5–1.6, sometimes up to 2.0 cm, in H.
cymbaria) and the oblong or cuneate, obtuse or acute callus
(if the callus is square, then the spatheole is longer).
The two species cannot be separated absolutely; Clayton
(1969) presents a scatter diagram to show the differences.
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Invasive Plant Science and Management 7, April–June 2014
The author comments extensively on the difficulties of
separating species in the complex genus Hyparrhenia; he
asserts that the choice is either to recognize imperfectly
separated species, or to recognize only one, an extremely
variable one. He states:
H. variabilis and H. cymbaria are obviously very closely
related, for not only do the dimensions of their floral
parts intergrade almost completely, but they share
the same habit, distribution and chromosome number.
The decision to maintain both species is guided chiefly
by the fairly sharp difference in the shape of the callus,
but also, let it be admitted, by an intuitive feeling that the
distinctive little ovate spatheoles of typical H. cymbaria
merit separation. (Clayton (1969)
As mentioned in the introduction, a subsequent analysis
involving several traits did not resolve the problem
(Clayton 1975). Table 1 shows Clayton’s descriptions of
the species in comparative form, and Figure 1A shows
partial inflorescences of the two taxa.
The other Mexican species of Hyparrhenia can be
distinguished easily. Neither H. rufa nor H. hirta have the
conspicuous spatheoles of our two species, which are
bicolored to reddish when dry. Hyparrhenia bracteata has
hairy spatheoles—in H. variabilis and H. cymbaria these
structures are glabrous.
Distribution and Ecology
In Africa, Hyparrhenia cymbaria is found mainly within
a broad corridor along the eastern half of the continent,
from southern Sudan, Kenya, and Tanzania to KwaZulu–
Natal and the western coastal region of South Africa. There
are also some populations in West Africa (Cameroon),
Madagascar, and the Comoro Islands. Hyparrhenia variabilis occupies the same East African corridor, without the
West African and island sites (Clayton 1969). It is also
known in Java, where it is presumably exotic. The Atlas
of Living Australia (cited 2012) records some specimens
in cultivation and at agricultural research stations, but
also one from a wild population (Queensland, 1982, on
bauxite mining tailings). The southernmost sites in South
Africa are at approximately 33uS for H. cymbaria and 29uS
for H. variabilis (Clayton 1969; SANBI–SIBIS database
2013).
Ecological information is relatively scarce for such an
important and dominant species. Clayton (1969) indicates
that H. cymbaria is ‘‘a common species in tall grass savanna,
with a preference for the upland regions,’’ and H. variabilis
is ‘‘ … commonly a dominant constituent of tall grass
savanna, occurring on a wide range of soil types.’’
According to the Flora Zambesiaca (Cope 2002), Hyparrhenia cymbaria grows in ‘‘wooded grassland, on open
hillsides, on the edges of evergreen forest and along stream
banks, 480 to 1,680 m’’ (1,575 to 5,512 ft), and
Hyparrhenia variabilis in ‘‘tall grassland and open woodland on a variety of soils, also common on roadsides and
in areas of abandoned cultivation, 700 to 1,560 m.’’ The
Flora of Tropical East Africa (Clayton and Renvoize 1982)
widens the altitudinal range of Hyparrhenia cymbaria to
1,000 to 2,800 m and of H. variabilis to 600 to 2,200 m.
Comparing the maps and some of the specimen citations
in Clayton (1969) with the Koeppen–Geiger climate types
(Kottek et al. 2006), the species occur in a wide range of
climates. The majority of the sites have an Aw climate
(equatorial, winter dry), but also Am (equatorial, monsoonal), BSh (hot-arid, summer dry), as well as Cwa/Cwb
(warm-temperate with hot or warm summers), and Cfa/
Cfb (warm-temperate, humid, with hot or warm summers). The species grow in hot or warm places, usually with
a dry season. No appreciable difference appears to exist
between the two taxa.
Both species are described as weedy and common in
secondary, fire-dependent riverside grasslands in Central
Africa, as well as in vegetation derived from degraded
forests and cultivated soils, and H. variabilis also colonizes
termite hills (Vesey-Fitzgerald 1963). Stromgaard (1986)
found Hyparrhenia variabilis in somewhat older (. 10 yr)
successional stadia of swidden agriculture. He references
older literature reporting very dense root layers for
grasslands dominated by the species, which make cropping
impossible. Also, an earlier work (Boughey et al. 1964)
indicates that Hyparrhenia variabilis excretes allelopathic
substances that impede the growth of nitrogen-fixing
bacteria. Stromgaard (1986) suggests that the dense root
system together with the toxins might impede succession
by woody plants. However, more recent literature is
ambivalent in attributing low-nitrogen grasslands to either
competition or inhibition (see introduction and results of
Lata et al. 2004).
The species are used for thatching roofs in their native
area, as the names indicate. They are palatable for livestock
when young.
In Mexico, the western populations occur more or
less between La Piedad de Cabadas in Michoacán, to a
point approximately 60 km (37 mi) east of Guadalajara,
at altitudes between 1,500 and 1,700 m, a belt about
100 km long. The area of the Morelos populations is still
small and is located east of the capital Cuernavaca,
between 1,300 and 1,400 m. All of the populations
found were near present or past sorghum cropland, and
grow in disturbed habitats: in maize and sorghum
fields as agrestal weeds, as well as on roadsides, in
plantations, and around human settlements as ruderals.
The two species appear to be naturalized. The region has
BSh and Cwa climates, which coincide with the data
from Africa.
The following voucher specimens were collected:
Hyparrhenia cymbaria
MEXICO. MICHOACÁN. Mpio. Yurecuaro: Federal
Highway # 110 from La Piedad towards Vista Hermosa. 20u20925.30N, 102u10927.70W, 1,667 m. Along the
Vibrans et al.: New Hyparrhenia in Mexico
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Table 1. Comparison of the morphological characteristics of Hyparrhenia cymbaria and H. variabilis; the data were taken from Clayton
(1969). The most important differentiating characteristics are in boldfaced letters.
Hyparrhenia cymbaria
Life form
Rhizome
Height
Culms
Hyparrhenia variabilis
Robust perennial, grows in tufts
Slender and creeping, with small cataphylls
Short, clad in hard cataphylls
2–4 m
1.5–3 m
Initially slender and rambling, later erect and
Often initially decumbent, supported by stilt
stout, up to 8 mm (0.31 in) in diameter, with
roots
stilt roots at the base
Leaf sheaths
Usually glabrous, but can be ciliate on the
Glabrous, sometimes pubescent at the base
margins and/or pubescent at the base
Ligule
Up to 1 mm long
Up to 2 mm long
Leaf blade
Up to 45 cm long and 6–20 mm wide, rigid to
Up to 45 cm long and 15 mm wide, firm,
subflaccid, dull green, glabrous or hirsute at the
glabrous or rarely hirsute at the base
base
Spathate panicle
Large, typically 20–40 cm long, dense, much-branched
Spatheoles
Boat-shaped, narrowly ovate in profile, 0.8–1.8
Boat-shaped, lanceolate in profile, 1.4–2.4 cm
long and 3–4 mm wide, glabrous
(–2.1) cm long and 3–4 mm wide, glabrous,
enclosing shortly awned racemes
Color of spatheoles
Beautiful colored, turning a bright russet red at
At maturity russet red, tinged with yellow and
maturity
green
Peduncle of spatheoles
Short, 3–8 mm long, 1/3 to 1/2 as long as the
Short, 3–9 mm long, up to about 1/3 as long as
spatheole, bearded above with white or
spatheole, bearded above with white hairs
yellowish hairs
Racemes
0.7–1.3 cm long, 3–5(–6)-awned per pair,
0.8–1.3 cm long, 3–5-awned per pair,
projecting laterally from the spatheole.
projecting laterally from the spatheole
Raceme bases
Subequal, very short, up to 0.5 mm long, the tip
Subequal, short, the upper about 1 mm long,
with or without a scarious frill up to 0.2 mm
with a scarious rim up to about 0.2 mm long
long
at the tip.
Homogamous spikelets
4–6(–7) mm long, glabrous to puberulous,
7–9 mm long, glabrous to puberulous, ciliate
ciliate on the margins
on the margins
Sessile spikelets
3.8–4.5 mm long, glabrescent to sparsely and
4–5 mm long, glabrescent to sparsely and
shortly pubescent, often becoming purplish
shortly pubescent
Callus
Square or broader than long, 0.2–0.3 mm long,
Cuneate, 0.5–1 mm long, narrowly obtuse to
broadly rounded at the base
subacute at the base
Apex of sessile spikelet
With an awn 0.5–1.6(–2.0) cm long, rarely
With an awn 1.8–3.2 cm long
almost suppressed (note: in the description
by Clayton it says 0.5–1.6[–2.0] mm, but
this is an error)
Caryopsis of sessile spikelet Cylindrical, 3 mm long
No information
Pedicelled spikelets
4–5 mm long, glabrous to puberulous, ciliate
5–8 mm long, glabrous to puberulous, ciliate on
on margins
margins
Apex of pedicelled spikelets Acuminate or sometimes with an awn point up
With an awn point 1–4 mm long
to 1.5 mm long
Habitat
A common species in tall grass savanna, with a
Commonly a dominant constituent of tall grass
preference for the upland regions
savanna, occurring on a wide range of soil types
Chromosome numbers
2n 5 20, 30
2n 5 20
Eastern Africa from Ethiopia to Transvaal
Distribution
The eastern half of Africa from Eritrea to KwaZulu–
(northeastern South Africa); also in Java
Natal in South Africa, reaching the west coast in
the Cameroon area and in northern Angola, also
Madagascar and the Comoro Islands
Altitude (from the Flora
480–1,680 m
700–1,560 m
Zambesiaca, Kew)
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Invasive Plant Science and Management 7, April–June 2014
highway, several 100 m, several specimens, sparse, 7 Feb
2011, H. Vibrans 8413 (MEXU, CHAPA).
Hyparrhenia variabilis
MEXICO. MICHOACÁN. Mpio. Yurecuaro: Federal
Highway #110 from La Piedad towards Vista Hermosa,
Municipality of Yurecuaro, near the small village of
Cerro Blanco, 20u20923.30N, 102u12920.30W, 1,690 m,
abundant in a nearby field with winter vegetation; the
specimens were taken from green plants near the highway
that had recently been cut, 7 Feb 2011, H. Vibrans 8414
(MEXU, CHAPA). JALISCO: Federal Toll Highway
#15 from La Barca to Guadalajara, 20u23921.40N,
102u42950.50W, 1,535 m, abundant in an abandoned
Agave plantation, 7 Feb 2011, H. Vibrans 8415B (MEXU,
CHAPA). MORELOS. Mpio. Zacualpan de Amilpas:
Tlacotepec, roadside, 11 Oct 2006, R. Cerros T., A. Flores
et al. 2693 (HUMO, MEXU). Cuautla: Highway near the
entrance from Cuautla towards Amacuzac, 18u519000N,
98u569090W, 1,390 m, on both sides of the road, several
populations, 12 Oct 2012, J. G. Sánchez-Ken, H. Vibrans,
and E. Garcı́a w/o number (MEXU). Cuautla: Federal
Highway 115D Jantetelco–Cuautla, east of Cuautla,
approximately 2 km south of the interchange with highway
115/160, 18u50900.50N, 98u55922.10W, 1,358 m, abundant on roadsides and edges of fields in the area, 20 Oct
2012, H. Vibrans, J. G. Sánchez-Ken, and E. Garcı́a w/o
number (MEXU, CHAPA).
Several populations were large—many thousands of
individuals—and often dominant, even monospecific
(Figure 1G). They generally formed patches. From
observations, the species appear to be serious weeds in
sorghum and maize, and probably difficult to control.
Discussion
These species are new records for Mexico and the
Americas. They are widespread in their home range,
covering an ample spectrum of warm-temperate and
tropical climate types, which suggests adaptation to
variable ecological conditions. They are known to be
intolerant, either because of their dense root network
or through chemical inhibition. As such, the species
have potential for becoming serious invasive plants and
agricultural weeds in most of the warmer regions of the
Americas, including the southern United States and the
cerrado regions of Brazil.
We do not know the pathway of introduction for
certain. Intentional introduction is unlikely, because these
species are not prime pasture grasses; some reference
would presumably have turned up in the agricultural
literature and a purposeful introduction would probably
only involve a single genotype. However, the fact that a
mixture of genotypes/species was introduced, and that all
of the sites were associated with present or past sorghum
cultivation, points to introduction with contaminated
sorghum seeds from Africa. This underlines the importance of phytosanitary controls of the seed supply; these
exist in Mexico but the legal basis is a negative list of
regulated species in the Mexican Official Norm (Norma
Oficial Mexicana) NOM-043-FITO-1999, which does not
contain the species reported here. We suggest amending
national regulations to include the species as soon as
possible, both in Mexico and in other countries of the
Americas. However, the example of this invasion also
showcases the limits of these negative lists, which cannot
possibly include all potential invaders.
These plants are quite conspicuous, and several large
populations are easily visible from a major highway, the
Mexico City–Guadalajara toll road (Autopista de Occidente). The species must have existed in the region for
some time, and it is surprising that it has not been collected
and described previously. We suggest that this might be
due to a precipitous drop in general botanical collections in
Mexico in the last 15 yr after the completion of some large
floristic projects, and the dearth of competent general
florists interested in weedy species.
Considering the experience with the eradication of
invasive plants in other regions (e.g., Pluess et al. 2012;
Rejmanek and Pitcairn 2002), we do not think these
species can be eradicated easily from their present area.
However, they can be prevented from reaching other
regions. No information on management or eradication
measures was found in the literature. Because of their
(apparent) similarity in ecology, we suggest that the two
species can be treated as a single taxon for management
purposes, pending the availability of better data.
A more detailed mapping of their distribution in Mexico
and investigation on the biology/ecology of the two species
is urgently needed in order to evaluate the possibilities
of containment. Do the two species reported here form
separate populations? Do they interbreed? Are there
differences in their ecology and invasiveness? What
measures can be taken to avoid their expansion into
natural areas? Do they require additional measures of
control in agriculture, or can they be controlled with the
conventional weed management of the region? Outreach to
farmers of the region would be a useful and rapid method
of slowing further expansion.
Literature Cited
Atlas of Living Australia (no date) http://bie.ala.org.au/species/
Hyparrhenia+variabilis. Accessed July 30, 2012
Beetle AA, Miranda-Sánchez JA, Jaramillo-Luque V, Rodrı́guezRodrı́guez AM, Aragon-Melchor L, Vergara-Batalla MA, ChimalHernández A, Dominguez-Sepulveda O (1995) Las Gramı́neas de
Mexico IV. México, D.F.: Secretarı́a de Agricultura, Ganaderı́a y
Desarrollo Rural. 372 p
Vibrans et al.: New Hyparrhenia in Mexico
N
227
Boughey AS, Munro PE, Meiklejohn J, Strang RM, Swift MJ (1964)
Antibiotic reactions between African savanna species. Nature 203:
1302–1303
Clayton WD (1969) A revision of the genus Hyparrhenia. Kew Bull
Additional Series II. Kew, UK: Kew Botanical Garden. 196 p
Clayton WD (1975) Some discriminant functions for Hyparrhenia:
studies in the Gramineae: XLI. Kew Bull 30:511–520
Clayton WD, Renvoize SA (1982) Flora of Tropical East Africa.
Gramineae (Part 3). Kew, UK: Kew Botanical Garden. http://plants.
jstor.org/flora/ftea008991. Accessed July 30, 2012
Clayton WD, Vorontsova MS, Harman KT, Wiliamson H (2006)
GrassBase—The Online World Grass Flora. http://www.kew.org/
data/grasses-db.html. Accessed July 27, 2012
Comité Asesor Nacional sobre Especies Invasoras (2010) Estrategia Nacional sobre Especies Invasoras en México, Prevención, Control
y Erradicación. México, D.F.: Comisión Nacional para el Conocimiento y Uso de la Biodiversidad, Comisión Nacional de Áreas
Protegidas, Secretarı́a del Medio Ambiente y Recursos Naturales. 91 p
Cope TA (2002) Gramineae (Hyparrhenia variabilis and Hyparrhenia
cymbaria). In Pope GV, Martins ES, eds. Flora Zambesiaca, Volume 10,
part 4, online version. http://apps.kew.org/efloras/namedetail.do?flora5
fz&taxon58887&nameid523353 and http://apps.kew.org/efloras/
namedetail.do?qry5namelist&flora5fz&taxon58886&nameid523337.
Accessed July 30, 2012
Davidse G, Sousa-Sánchez M, Chater AO (1994) Alismataceae
a Cyperaceae. Flora Mesoamericana 6. México, D.F.: Instituto de
Biologı́a, Universidad Nacional Autonoma de México. 543 p
Dávila P, Mejı́a-Saules MT, Gómez-Sanchez M, Valdes-Reyna J, Ortiz JJ,
Morin C, Castrejon J, Ocampo A (2006) Catálogo de Gramı́neas de
México. México, D.F.: Universidad Nacional Autónoma de México. 671 p
Kottek M, Grieser J, Beck C, Rudolf B, Rubel F (2006) World Map of
the Köppen-Geiger Climate Classification Updated. Meteorol Z 15:
259–263 http://koeppen-geiger.vu-wien.ac.at/present.htm. Accessed
February 17, 2014
228
N
Invasive Plant Science and Management 7, April–June 2014
Lata JC, Degrange V, Raynaud X, Maron PA, Lensi R, Abbadie L
(2004) Grass populations control nitrification in savanna soils. Funct
Ecol 18:605–611
Parsons JJ (1970) The ‘‘Africanization’’ of the New World tropical
grasslands. Tübinger Geogr Stud 34:141–153
Parsons JJ (1972) Spread of African pasture grasses to the American
tropics. J Range Manag 25:12–17
Pluess T, Cannon R, Jarošı́k V, Pergl J, Pyšek P, Bacher S (2012) When
are eradication campaigns successful? A test of common assumptions.
Biol Invasions 14:1365–1378
Rejmanek M, Pitcairn MJ (2002) When is eradication of exotic pest
plants a realistic goal? Pages 249–253 in Veitch CR, Clout MN, eds.
Turning the Tide: The Eradication of Invasive Species. Proceedings of the International Conference on Eradication of Island
Invasives. Gland, Switzerland and Cambridge, UK: IUCN, Invasive
Species Specialist Group
Rzedowski J, de Rzedowski GC (1990) Nota sobre el elemento africano
en la flora adventicia de México. Acta Bot Mex 12:21–24
SANBI (South African National Biodiversity Institute (2013) Integrated
Biodiversity Information System (SIBIS). http://sibis.sanbi.org/faces/
SearchSpecies/Search.jsp?151. Accessed December 5, 2013
Stromgaard P (1986) Early secondary succession on abandoned shifting
cultivator’s plots in the miombo of South Central Africa. Biotropica
18:97–106
Vesey-Fitzgerald DF (1963) Central African grasslands. J Ecol 51:
243–274
Villaseñor JL, Espinosa-Garcia FJ (2004) The alien flowering plants of
Mexico. Divers Distrib 10:113–123
Williams DG, Baruch Z (2000) African grass invasion in the Americas:
ecosystem consequences and the role of ecophysiology. Biol Invasions
2:123–140
Received December 21, 2013, and approved February 25, 2014.