FIRST RECORDS OF THE AQUATIC WEED HYGROPHILA POLYSPERMA (ACANTHACEAE) FROM TEXAS

7 Pages·1994·3.9 MB·English

by  Michelle B Angerstein

WEED
RECORDS OF THE AQUATIC
FIRST
HYGROPHILA POLYSPERMA (ACANTHACEAE)
FROM
TEXAS
MICHELLE ANGERSTEIN
B.
Bee County
College
3800 Road
Charco
BeevilkTX
78102, U.S.A.
DAVID LEMKE
E.
Department Biology
of
Southwest Texas State University
TX
San Marcos, 78666, U.S.A.
weed, are reported from the Comal and San
nd
illustrations of the species are provided.
dc convertirse en una mala hierba acuatica, de los rios Comal y San Marcos de Tejas central, y se
Key
words: Hygrophila, Acanthaceae, aquatic weeds, Texas.
we
In the spring of 1994 began to question the identification of several aquatic
Hays
macrophyte collections from the upper San Marcos River in County, Texas,
SWT. The
on deposit at specimens in question had been variously identified as
&
Cham.) Nees Ludwigta
either Hygrophila (Schlecht. (Acanthaceae) or
lacustris
(Onagraceae) and represented vouchers from two separate studies of
repens Forst.
macrophyte (Lemke Contributing
the river's flora 1989, Staton 1992). to the
of making an accurate determination was the that most of the
difficulty fact
common
specimens comprised only material, a deficiency of aquatic plant
sterile
we
collections. Ultimately, however, were able to secure both flowering and
them
fruiting material of these plants and to identify as Hygrophila polysperma
(Roxb.) T. Anderson, a previously unreported vascular hydrophyte from Texas
that has the potential to become a troublesome aquatic weed.
80
Hygrophila R.Br, comprises approximately species distributed primarily
in the Old World tropics, particularly Indochina and Malaysia, with only a few
The
African and American species (Long 1970). only representative of the ge-
nus native to the U.S. H. which distributed from Florida to eastern
is lacustris, is
,
366 SiDA 1994
16(2)
& &
Wooten
Texas (Correll Correll 1975, Godfrey 1981). Hygrophilapolyspernm
a native of India and Malaysia that was introduced into the United States in the
is
940s and quickly became a popular aquarium plant (Innes 947). In the U.S.
1 1
the species has been reported as naturalized in lakes and drainage canals in south
&
Our
Wunderlin and
Florida (Les 1981). recent observations collections
field
indicate that the species also naturalized in and along the San Marcos and
is
Comal Hays and Comal Furthermore,
rivers respectively, counties, Texas.
in,
herbarium records indicate that H. polyspemia has been well-established in the
San Marcos River for at least 25 years (see specimen citations below).
We
surmise that H. polyspemia was introduced into Texas river systems either
through by documented by
directly cultivation local aquatic plant nurseries, as
Hannan
(1969) for the hydrophytic pteridophyte Ceratopteris thalictroides (L.)
dumping
Brongn., or indirectly through careless by aquarists. Profuse vegeta-
m
&
Bowes
tive reproduction well developed H. polysperma (Spencer 1985,
is
Van Dijk 1986) and even small fragments produce and grow
et will roots
al.
We
new
into individuals. therefore feel likely that isolated introductions of
it is
may
plants cultivated for sale have resulted in the establishment of the species
Comal
both and San Marcos
in the river systems.
The may
high growth potential of H. polysperma pose a serious threat to the
native flora and biotic integrity of the Comal and San Marcos river ecosystems.
(Lemke and
Several studies 1989, Staton 1992, U.S. Fish Wildlife Service 1994)
have suggested that elements of the native biota of these two river systems are
High
being displaced or otherwise adversely affected by exotic plant species.
growth
potential, profuse vegetative reproduction, lack of seasonal variation in
CO2
biomass, low light compensation and saturation points, a low compensa-
and change
tion point, the capacity to rapidly resource acquisition ability in re-
make
sponse to environmental change are characteristics that H. polysperma a
&
competitive plant and potentially serious weed (Spencer Bowes 1985, Botts
Kovach The
et 1990, et 1992). species included on the federal of
al. al. is list
noxious aquatic weeds (U.S. Department of Agriculture 1983) and listed as a
is
category II species by the Exotic Pest Plant Council of the State of Florida, in-
dicating that population rapidly expanding and has the potential to invade
its is
and
disrupt native vegetation in that state (Lantz 1993); however, the species
is
not currently recognized as a potentially harmful aquatic weed in Texas.
To we
facilitate the identification of future collections of this species, provide
the following key, description and illustration (Fig.
1):
KEY TO TEXAS OF HYGROPHILA
SPECIES
ND
Lemke, Hygrophila polysperma from Texas
A
Fig Hygrophila polysperma, Distal
p
1
B drawn sam
form,
roots Terrestrial to
368 SiDA 1994
16(2)
Hygrophilapolysperma(Roxb.)T.
Anderson, Linn. Soc, Bot. 9:426. 1876.
J.
Justidapolysperma^oxh.,Y\.lnA. 1:120. 1820.
Hemuk/phispo/ysperma {Roxh.)Nees in Wall., Pi. Asiat. Rar. 3:30. 1832.
m
Perennial rhizomatous terrestrial or aquatic herbs to Stems ascen-
1 .5 tall.
more
dant or rarely erect, or less 4-angled, puberulent to giabrate, with abun-
dant elongate or rarely rounded cystoliths in the epidermis. Leaves opposite,
broadly elliptic to oblanceolate, acute at apex, attenuate to a subpetiolar base,
mm mm
7-65 2-10
minutely denticulate to entire, long, wide, mostly gla-
brous but those subtending the flowers hispid, especially on the margins, the
abaxial and adaxial surfaces with abundant elongate cystoliths. Flowers solitary
mm
uppermost 4-5
in the axils of leaves, sessile. Bracts narrowly lanceolate,
mm
4-5
long, herbaceous. Calyx equally 5-lobed, the lobes scarious-margined,
long, united basally, hispid. Corolla bluish-white (yellowish in dried specimens),
mm
5-6
long, the upper lip 2-lobed, the lower lip 3-lobed, puberulent. Fertile
mm
stamens Ovary
included, filaments glabrous, anthers 2-celled, long.
2, ca. 1
mm
stigma
hispid distally, the style ca. 3 long, sparingly hispid, the flattened,
mm mm
6-7
0.3 long. Capsule long, mostly glabrous but with a few distal
ca.
mm
Blooming
hairs. Seeds flattened, round, ca. 0.8 diameter. mostly Sep-Oct.
In the San Marcos and Comal H. polysperma most often found grow-
rivers,
is
we
ing completely submersed, although have frequently encountered both emer-
gent and terrestrial individuals along the upper San Marcos River. Submersed
m
individuals have longer stems (0.3-1.5 with elongate internodes (20-54
tall)
mm mm
(17-65 and
long), relatively large oblanceolate leaf blades long), pro-
duce abundant upper
adventitious roots at the nodes. Terrestrial individuals are
mm
cm
(10-20 with (2-16
of shorter stature shorter internodes long),
tall)
mm
smaller elliptic leaves (7-25 long), and bear roots almost exclusively on the
We
rhizome. have observed flowers and fruits primarily on terrestrial individu-
als and, occasionally, on emergent shoots of partially submersed plants; in both
cases the distal leaves subtending the flowers are marginally hispid. These ob-
who
servations accord well with those of Sculthorpe (1967) cited numerous
examples of normally terrestrial plants (e.g., species oiAlisma L.,Bacopa Aublet,
Campanula Gratiola Nomaphila BL, Ranunculus and Rotala that can
L., L., L., L.)
common
grow submerged
even deep
entirely in water, leading to their use as
ornamental plants in aquaria; submersed individuals of such species were usu-
ally found to be characterized by elongation of the leaf blade, loss of pubescence.
Two
previous studies of the aquatic macrophytes of the San Marcos River
document Lemke
failed to the occurrence there of H. polysperma. (1989) incor-
rectly identified collections of this species as H. lacustris, while Staton (1992)
misidentified her collections as Ludivigia repens. Hygrophila lacustris, a native of
the southeastern U.S., occurs in only a few counties in southeast Texas (Brazoria,
Angerstein and Lemke, Hygrophila polysperma from Texas 369
Chambers, Fort Bend, Hardin, Harris, Jackson, Montgomery, Orange, and
Walker muddy
where grows emergent
counties), as a terrestrial or plant along
it
&
stream and pond margins (Wasshausen The
1966, Correll Correll 1975).
cm cm
plants are typically erect herbs to 80 with leaves mostly 5-12 long
tall
and borne
flowers in distinct axillary clusters along the length of the stem.
Hygrophila polysperma, in contrast, usually found submersed, the leaves of the
is
mm
7-25
aerial shoots are typically long, and the flowers are solitary in the axils
uppermost
of the
leaves.
When
introduced to the aquarium plant market, H. polysperma was though
first
common
to be a species oiLuckvigia L. and was given the name "oriental ludwigia"
(Innes 947). Vegetatively, the terrestrial shoots of H. polysperma are very similar
1
known
to those of L. repens, a native species also from the San Marcos and Comal
and
elliptic leaves short internodes.
,
jctures, however, the two species are
The
readily separable by nodal morphology. petioles of L. repens are subtended
mm
by a pair of minute, glandular stipules than long, while the connate
less
1
number
leaf bases of H. polysperma are exstipulate but bear a of setiform hairs to
mm
long
1.5 (Fig.
2).
member
Hygrophila polysperma the second adventive aquatic of the Acan-
is
thaceae to be reported from Texas in recent years. Ramamoorthy and Turner
documented
992) the occurrence oiNomaphila (Vahl) Nees, another
stricta
( 1
Malaysian species, from San Felipe Springs in Val Verde County and surmised
that this species was also introduced by aquarists.
^^y
A,!
A
B
-
p^'
'
Comparison morphology nHygrophib^ndLmlu
Fic. of nodal A.
2. ifu,. H,grol,h,l„l«l,.,pm,,.,.
i
Amy
B. Uuhcgia Drawn by Mai
repens. L.
. .
370 SiDA 1994
16(2)
New
Specimens examined. TEXAS. Comal Co.: Comal River, Landa Park, City of Braunfels,
m
100 upstream of Pecan Island, mid-channel, in 1-2 of water, 21 Feb 1994, Angerstein
ca. ft
New
94-1 (BRIT, SWT, TEX); Comal River, Landa Park, City of Braunfels, in spring run
underneath Landa Dr., 23 Feb 1994, Angerstein 94-2 (SWT). Fiays Co.: San Marcos River
Nov
below Southwest Texas State University campus, 30 1969, Tablers.n. (SWT); shoreline
Nov
sandbar formed mouth of Sessoms Creek, 22 (SWT); San Marcos
at \91'b, Litchfield s.n.
Riverdownstream from Clear Springs Aprs, spillway, Jul \9lG, (SWT); South-
5 Litchfield s.n.
Aug
west Texas State University raceway in gravel substrate, 28 976, Litchfield s.n. (SWT); San
1
Marcos River Thompson's Island below county road bridge, 6 Mar 99 Staton (SWT);
at n.
1 s.
1 ,
San Marcos River upstream from Purgatory Island, 26 Apr 1991 Staton (SWT); San Marcos
s.n.
,
26jun
River University Blvd., \99\,Bierner91-7 (TEX); Rio Vista Park, Purgatory
at Is-
1
land, City of San Marcos, 30 Mar 1994, Angeistein 94-5 (SWT, TAES); San Marcos River, Lions'
Park San Marcos, 30 Mar 1994, Angerstein 94-6 (SWT); San Marcos River, Sewall Park,
area,
San Marcos, along edge of concrete channel, 30 Mar 1994, Angerstein 94-7 (SWT, TEX); South-
Mar
west Texas State University campus pond beside Freeman Bldg., 30 1994, Angerstein 94-8
(SWT, TAES); Southwest Texas State University campus pond directly in front ofJ.C. Kellam
Mar SWT).
Bldg., 30 1994, Angerstein 94-9 (BRIT,
ACKNOWLEDGMENTS
We
would like to thank the Parks and Recreation Department of the City of
New
Braunfels, Texas, for permission to collect in Landa Lake, the Center for
36:207-214.
Bot.
CoRRELL, D.S. and H.B. Correi
Univ
States, 2 vols. Stanford
Woot
Godfrey, R.K. and
J.W.
WT
Innes, 1947. Hygrophila. a new aquarium plant. Aquarium (Brooklyn) 16:30-31
KovACH, C.W, J.P KuRDZiBi,, R. Bowman, Wagner and J.M. Lawrence. 1992. The effect;
J.
of and disturbance on proximate composition, allocation of production, photosynthe-
stress
respiration, and chlorophyll levels in Hygrophila polysperma (Roxb.) Anders. (Acanthaceae)
sis,
Environm. Exp. Bot. 32:479-486.
Lantz, PS. 1993. Florida's most invasive species. Palmetto 3:6-7.
1
Lemke, D.E. 1989. Aquatic macrophytes of the upper San Marcos River, Flays Co., Texas
32:289-291
Southw. Naturalist
D.H. and R.P Wunderlin. 19^1 Hygrophila polysperma
Les,
.
44:189-192.
Sci.
Long, R.W. 1970. The genera of Acanthaceae in the south
Arbor 51:257-309.
s
AND T
Lemke, Hygrophila polysperma from
HY, T.P. and B.L. Turner. 992. Nomaphila
1
W.
Spencer, and G. Bowes. 1985. Li
San Marcos River. M.S. thesis, Southwest Texas State University, San Marcos.
United States Department OF Agriculture. 19<S3. Noxious weeds. Fed. Reg. 48:20037-20047.
United State.s Fish and Wildlife Service. 1994. Draft San Marcos and Comal Springs and
NM.
associated aquatic ecosystems (revised) recovery plan. Albuquerque,
W.T
Van Dijk, G.M., D.D. Thayer and Haller. 1986. Growth oiHygrophi/a and Hydrilla in
Managem.
flowing water. Aquatic 24:85-87.
PI.
J.
Wasshausen, D.C. 1966. Acanthaceae. In: C.L. Lundell, ed. Flora of Texas 1:223-282.