PASPALUM PUBIFLORUM AND P. QUADRIFARIUM (POACEAE) NEW TO CALIFORNIA, WITH A KEY AND NOTES ON INVASIVE SPECIES

2010·6.1 MB·English

by  Richard E Riefner

1
PASPALUM AND
PUBIFLORUM
QUADRIFARIUM
(POACEAE)
P.
NEW
TO
CALIFORNIA, WITH A KEY AND NOTES ON
INVASIVE
SPECIES
Richard Denham
Riefner,
E.
Jr. Silvia
S.
Research Associate
istituto de Botdnica Darwinian
Rancho Santa Ana Botanic Garden
1500 North Avenue
College
Claremont, California 9171 1-3157, U.SA.
[email protected]
Columbus
Travis
J.
1500 North Avenue
College
California 91 71 1-31
57,
'[email protected]
ABSTRACT
RESUMEN
INTRODUCTION
Paspalum
L. (Poaceae, Panicoideae) comprised of approximately 350 which
is species, are distributed pri-
&
marily and
in the subtropical, tropical, warm-temperate regions of the Americas (Zuloaga Morrone 2005;
Denham
However, owing many
et al. 2010). to their utility as turf, forage or ornamental grasses, taxa are
now
widely distributed and have become some of the world’s most troublesome weeds (Holm
et 1979;
al.
GCW
Weber
PIER
2003; 2010; 2010).
The
genus Paspalum, in general, is easily recognized by its unilateral racemes distributed along the
main
axis of the inflorescence, plano-convex spikelets with the upper lemma oriented towards the rachis,
and
the lower glume typically being absent. Confident, species-level determinations, however, often prove
difficult. Comparative ecological studies, such as growth responses to salinity and soil saturation, and veg-
etative morphology, phenology, and habitat associations can improve separation and help explain species
weeds and many
since are generally under-collected thus poorly represented in herbaria, the distribution of
&
known
nonnative taxa in North America poorly (Allen Hall 2003). Paspalum vaginatum Sw. (seashore
is
New
paspalum), native to the subtropical and tropical regions of the World, has been introduced widely and
&
now
is naturalized in warm, coastal regions around the world (Allen Hall 2003; Weber 2003; Zuloaga et
al. 2003). Naturalized populations were reported for the first time for California by Riefner and Columbus
(2008).
762
In this paper, we provide the first documented records of P. pubijlorum Rupr. ex E. Foum. a
qmdrifarium Lam. for California; pubijlorum was collected from Orange and western Riverside cou
P.
New
and quadrifarium from Los Angeles County in southern California. records are also docum^
P.
We
for P. vaginatum, which is invading estuarine and other saline wetlands in southern California. n
mode summary
and
the naturalized status, habitats occupied, of introduction, provide a of the regie
California where recently introduced species of Paspalum have been observed or might become invas:
known
key is also provided to identify the species of Paspalum in the State.
NEW
RECORDS CALIFORNIA
Paspalum pubijlorum (hairyseed paspalum) and quadrifarium (tussock paspalum) have not been reported
P.
previously for California in treatments of the nonnative Poaceae growing outside of cultivation (Hitchcock
& &
1951; Webster 1993; Bossard et al. 2000, 2006; Hrusa et al. 2002; Allen Hall 2003; DiTomaso Healy
&
&
Rebman
2003, 2007; Roberts et 2004; Simpson 2006; Bossard Randall 2007; Clarke 2007;
al. et al.
&
Grewell et al. 2007; Riefner Boyd 2007; Dean et al. 2008; Roberts 2008; Jepson Flora Project 2010; USDA
2010a,
b).
Paspalum pubijlorum is a perennial grass native to the eastern and southwestern United States (Pennsylvania
&
to Texas and Colorado), Mexico, and Cuba (Allen Hall 2003; Denham USDA
et al. 2010; 2010a). In the
United States, it grows on moist open ground and disturbed areas, in wet meadows, on banks and edges of
and
forests, streams, ponds, lakes, irrigation ditches, especially in alkaline or calcareous (Hitchcock
soils
& &
1951; Correll Correll 1975; Allen Hall 2003).
Paspalum pubijlorum has branched decumbent culms
that frequently root the nodes has
at (Fig.
la). It
(2-)3-12 racemes per inflorescence with pubescent, rarely glabrescent or glabrous paired which
spikelets,
mm
and (Denham
are elliptic to obovate-elliptic (2.4-)2.6-3.2 long The number racemes
et al. 2010). of
per inflorescence is not a fixed character and varies considerably; Hitchcock (1951) reports 3-5 racemes,
and and 2-7
Allen Hall (2003) report racemes per
inflorescence. In southern California, populations
typi-
cally have 3-6 racemes per inflorescence, but it is not uncommon to find plants having 2-3 racemes per
inflorescence Paspalum hartwegianum Foum.
(Fig. lb). E. (Hartweg’s paspalum) similar
is to pubijlorum.
P. It
3-23
has simple culms with racemes
erect (also highly variable) per inflorescence, and paired pubescent
mm
spikelets, which are elliptic to obovate and (2.3-)2.6-3.1 long (Denham
et 2010). Accordingly, careful
al.
collecting and documentation in the field is needed to accurately separate pubijlorum from hartwegianum
P.
P.
and
other closely related species; currently, hartwegianum not known
P. is to occur in California.
In southern California, pubijlorum could be confused with
P. robust forms
of P. distichum L. (knotgrass),
which rhizomatous
is a native or stoloniferous perennial with spikelets pubescent only on the back of the
upper
glumes. Its inflorescence is digitate (with two branches), but a third lower branch may occasionally
be Paspalum
present. distichum is a highly variable species; it can be slender and creeping or robust and
Although
cespitose. distichum usually has
P. solitary spikelets, racemes with only paired racemes
spikelets or
with and
paired solitary spikelets can be present on same
the plant. Robust forms of distichum with mostly
P.
3 racemes per inflorescence and paired
spikelets collected in southern California have been Paspalum
called

;
synonym
paucispicatum Vasey (Hitchcock 1951). Paspalum paucispicatum (a of
P.
&
2003) has often been confused with pubiflorum (Verloove Reynders 2007a).
P.
(GCW
Paspalum pubiflorum can be weedy when introduced to new regions 2009). In southern California,
can form dense mats that compete for space with low-growing native hydrophytes in riverine and urban
it
creek habitats. Although pubiflorum occupies alkaline habitats, and unlike distichum and vaginatum,
P. P. P.
&
known
which are halophytes (Menzel Lieth 2003), not expected to successfully colonize highly saline
is
it
in California is probably the result of
rge cespitose perennial native to Argentina, Brazil, Paraguay, and Uruguay (Al-
&
len Hall 2003; Zuloaga et al. 2003). In Argentina, P. quadrifarium forms dense tussocks in the Flooding
&
Pampa on banks and weed
grasslands, river or lake shores, is often regarded as a (Ortega Laterra 2003;
Herrera
2005).
et
al.
&
USDA
eastern states (Garbari 1972; Allen Hall 2003; 2010b). has been identified as a noxious weed or a
It is
New
potential invasive pest in South Wales and Queensland, Australia, coastal and the southern United
Italy,
& &
States (Allen Hall 2003; Verloove Reynders 2007b; Bargeron 2008; Sydney Weeds Committees
et al.
2010
).
known
In southern California, quadrifarium most likely escaped from cultivated sources, and currently
P. is
only from a small population growing in disturbed riparian scrub. Accordingly, this species here consid-
is
and and
ered tenuously established dispersal naturalization remains
its
UTM
(NAD
University IIS
Dr., 83)
Rie/ner 09-10 (RSA). Riverside Co.:
D83)11S0550217E
5Jul 2008. Rie/ner 08-215 (RSA). San Diego
t,
(NAD
IIS 0464168E 3674334N,
83) elev. ca.
08-288
(RSA).
known warm
Paspalum vaginatum from and
is temperate, tropical, subtropical regions around the world, and
an
is widely regarded as invasive species; see Erickson and Puttock ISSG and and
(2006), (2008), Riefner
Columbus
(2008) for reviews. Worldwide, and outside of cultivation, vaginatum occupies and
P. coastal salt
brackish water marshes, shallow-water lagoons and
tidal channels, mangroves, coastal shrublands, dunes
and summer-moist
beaches, saltpans, wet pastures, and freshwater riparian and floodplain habitats (Allen
& &
Shaw Weber
Hall 2003; Allen 2003; 2003; Siemens 2006). In southern expanding
California, rapidly
and
populations the formation of dense monocultures
of vaginatum pose
P. a serious threat to the structure,
&
and
function, native species composition of estuarine wetlands Columbus
(Riefner 2008).
Riefner et al.. Two Paspalum species new for California
Paspalum vaginatum, a stoloniferous and rhizomai
bilitation of salt-affected lands, forage, dune stabilizatic n control, and for turf, including specific
&
&
ow
ecotypes and cultivars with improved tolerance to sali Duncan 1998; Duncan Carrow
Duncan
1999; 2003). Paspalum vaginatum cultivars and ecotypes can maintain growth and vigor under
ir-
rigation with seawater, seawater approximately EC^ conductivity of water) 54 dS/m"‘
i.e., is (electrical (deci-
&
Siemens per meter) or -34 ppt (parts per thousand) salt (Duncan Carrow 1999; Lee et al. 2005; Berndt
2007; Pessarakli 2007). For comparison, freshwater habitats contain <0,5 ppt or <1 dS/m-‘ (Cowardin
salt
minimum
et al. 1979); the criterion required for a species to be classified as a halophyte is a salinity level
having an measurement 7-8
electrical conductivity of at least dS/m'^ during significant portions or of
all
the plant’s cycle (Aronson 1989).
life
we
Although cannot identify specific vaginatum ecotypes/cultivars that have been introduced to
P.
southern California or those growing outside of cultivation in wildlands, high-salinity tolerant plants are
now
established in tidal wetland habitats, including sea beaches within the high tide zone (Fig. 2a). These
sibly establish as far north as central California.
In the coastal lowland wetlands of the Hawaiian Islands, vaginatum is highly invasive in brackish
P.
wetlands (i.e., the mixohaline salinity classification [0.5-30 ppt salt] of Cowardin et al. 1979) (Bantilan-
Smith et 2009). Although vaginatum occupies a variety of wetland and saline environments in southern
al. P.
vaginatum highly invasive predominately in brackish wetland habitats.
is
As a result of continuing field documentation, unvegetated sand flats and mudflats located along tidal
creeks and lagoons at the head of coastal bays and estuaries appear most vulnerable to colonization by P.
and
vaginatum (Fig. 2b). Tidal mudflats are highly productive areas for invertebrates provide rich foraging
habitat for shorebirds at low tide and other birds and fish at high tide (EPA 2010). Worldwide, invasions of P.
vaginatum are converting unvegetated or sparsely vegetated tidal flats and shallow lagoon habitats to vegetated
habitat and food resources^of shorebirds (Siemens 2006; ISSG 2008; Bird Life Imernational 2009).
Human
activities such as dredging and filling have contributed to the loss of tidal mudflats in southern
&
now
Desmond
California (Williams 2001). Invasions by nonnative species, however, also pose a threat
and
to estuarine wetland ecosystems (Grewell 2007). Accordingly, development of urban watershed
et al.
estuary conservation management plans should include identification and eradication programs to deter the
spread of nonnative plants, especially potentially invasive halophytes that could further degrade sensitive
estuarine wetlands in southern California.
DISCUSSION
and a review of pertinent literature and electronic database:
1
,
summary
Consortium Herbaria of the distributional records
the of California (2010),
s
a
document and where
current naturalized status, occupied habitats, invasive behavior, speculate recentl)
introduced Paspalum species might become invasive. These data are summarized in Table 1. Naturalizatior
categories shown in Table are somewhat subjective, but follow Hrusa et al. (2002) in order to allow con-
1
new
sistency in data compilation of
and
Dean pointed out the confusion regarding identifications the relal
(2008) recently
et al.
Parodi in California,
ized distributions of Paspalum notatut
Considering the ongoing difficulties with separating P. distichum from P. vaginati provide the following
key that will serve to identify the species and varieties of Paspalw occur in California.

Journal of the Botanical Research Institute of Texas 4(2)
ACKNOWLEDGMENTS
We Holiman Rancho Ana
greatly appreciate the efforts of Harvey Brenneise and Irene (Library of Santa
with document and Garn Wallace (Wallace Laboratories, El
Botanic Garden) for assistance retrieval, to
and Fred Hrusa, California
Segundo, California) for helpful discussion of salinity analysis classifications.
anonymous comments
Department of Food and Agriculture (CDA), and an reviewer provided helpful that
from the International Foundation for Applied Research in the Natural Sciences (IFARNS) to study alkaline al-
southern
luvial habitats in coastal California.
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