|
NAS - Nonindigenous Aquatic Species |
Hygrophila
polysperma (Roxb.) T. Anders.
Common Name: East Indian hygrophila, Indian swampweed, Miramar
weed
Taxonomy: Division-Magnoliophyta (Angiosperms); Class-Magnoliopsida
(Dicots); Subclass-Asteridae; Order-Scrophulariales; Family-Acanthaceae (Acanthus
Family); Genus-Hygrophila
Description: Perennial rooted and rhizomatous aquatic herb;
submersed to emergent, may become terrestrial in habit; having round to square
stems bearing opposite, elliptic,
and sessile leaves; producing flowers
at the leaf axil (Les and Wunderlin 1981; Angerstein and Lemke 1994).
Native Range: India and Malaysia (Angerstein and Lemke 1994) a geographic
region refered to as the East Indies.
Map indicates recorded presence in at least one site within the drainage (USGS
Hydrologic Unit 8), but does not necessarily
imply occurrence throughout.
Distribution - United States: Well established in Florida
and Texas since the 1960s.
Florida
1960's: First recorded for Florida in
1965 along a roadside, north of Tampa (Les and Wunderlin 1981).
1970's: Next documented in1979 from canals
in two new drainages 1) Able Canal (Les and Wunderlin 1981), draining the Caloosahatchee
River in western Florida and 2) Miramar and City of Margate Canals (V. Vandiver,
Univ of Florida, pers. comm.), part of the Everglades drainage in eastern Florida.
1980's: During
the 1980's occurrence in Florida increased nearly 10-fold as populations were
found at 29 new sites. Included were well known infestations at the Loxahatchee
River, in 1986, and the Withlacoochee River in 1989. By 1989 the range of
Hygrophila polysperma extended northward through central Florida to the
Santa Fe River, Columbia County (FLDEP 1988-94). Also known was a disjunct westward
location, along a roadside in Tallahassee, in the Florida Panhandle [Katherine
M. Gilbert s.n. (FLAS), 1988].
1990's: By
1999 Hygrophila polysperma was known from at least 22
rivers/streams, 13 lakes, 2 ditches and 7 canal systems in Florida. This
accounts for 20 counties and a total of 17 drainages in the state. More tolerant
to the herbicides and grass carp used to control hydrilla, hygrophila is replacing
hydrilla as the number one non-native aquatic weed in some southeast Florida
canals (Duke et al. 2000).
Texas occurrence does not follow a pattern of rapidly expanding distristibution,
probably due to fewer and more widely dispersed water bodies in that region.
Nonetheless, the magnitude of Texas infestations is severe, affecting several
sensitive spring fed rivers and other disjunct sites.
1960's: Plants in the San Marcos River,
Hays County, Texas were first collected in 1969 (Angerstein and Lemke 1994).
1970's: Additional localities within the
San Marcos drainage were recorded in the 1970s, including Sessoms Creek, Hays
County (Angerstein and Lemke 1994).
1990's: In
1994 plants were discovered in spring fed portions of the Comal River system,
Comal County, and in 1998, at San Felipe Springs, located in a far western drainage
of Val Verde County, Texas (D. Lemke, Southwest Texas State University, pers.
comm.)
Reams (1953) mentioned that Hygrophila polysperma when "placed in
lakes in the Richmond area quickly establishes itself" and in a personal
communication to Schmitz (1985) elaborated that it was established in the Richmond,
Virginia area lakes for 15-20 years, until extremely cold winter temperatures
occurred in the 1970's. However, documentation as to whether the species has
naturalized in Virginia is not available (Sutton 1995).
References:
Angerstein, M.B. and D.E. Lemke. 1994. First records of the aquatic weed
Hygrophila polysperma (Acanthaceae) from Texas. Sida 16(2):365-371.
Duke, D., P. O'Quinn and D.L. Sutton. 2000. Control of hygrophila and other
aquatic weeds in the Old Plantation Water Control District. Aquatics 22(3):4-8.
(FLDEP) Florida Department of Environmental Protection, Bureau of Aquatic
Plant Management. 1988-1994. Florida Aquatic Plant Surveys, electronic data.
Bureau of Aquatic Plant Management, Florida Department of Environmental Protection,
Tallahassee, FL.
Les, D.H. and R.P. Wunderlin. 1981. Hygrophila polysperma (Acanthaceae)
in Florida. Florida Scientist 44(3): 189-192.
Reams, W.M. Jr. 1953. The occurrence and ontogeny of hydathodes in Hygrophila
polyspera T. Anders. New Phyto. 52: 8-13.
Schmitz, D.C. 1985. Hygrophila polysperma - a review of the scientific
literature. Florida Department of Environmental Protection, Tallahassee,
Florida.
Sutton, D.L. 1995. Hygrophila is replacing hydrilla in South Florida. Aquatics
17(3): 4,6,8,10.
Many thanks to University of Florida, Center
for Aquatic and Invasive Plants, for the superb photographs.
Author: C. C. Jacono
Revision Date: 8 Septermber 2003