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What controls invasive animals?Poster presented May 1999, at the South Florida Restoration Science Forum
Nonindigenous Species Introduced into South FloridaPam L. Fuller and Amy J. Benson, U.S. Geological Survey, Biological Resources Division
IntroductionSouth Florida is host to a wide variety of nonindigenous species, more than any other drainage in the state. Many of these introduced species have become established in this disturbed habitat. A sample of some of these organisms are represented here.
(Letters correspond to map above.)
The Asian clam is a small freshwater mussel. It came to North America from China in the 1920s. The very first records are from the Columbia River basin in the Pacific Northwest. It may have been brought in as food for Chinese immigrants. Or, it may have come in with the importation of the Giant Pacific oyster also from the Asia. This clam is established in southeast Florida. The mechanism for dispersal within North America is unknown. Its maximum length is about 35 mm and lives about 3 years. It is known mostly as a biofouler of many electrical and nuclear power plants across the country. As water is drawn from rivers, streams and reservoirs for cooling purposes so are Corbicula larvae. Once inside the plant, this mussel can clog condenser tubes, raw service water pipes, and fire fighting equipment. Economic problems can result from the decreased efficiency of energy generation. Warm water effluents at these power plants make a hospitable environment for stabilizing populations.
This snail is a tropical freshwater species native to South America. It has been introduced into Florida and is now established in Broward, Dade, Monroe, Palm Beach, and Pinellas counties. It is usually greenish in color with dark and light bands. P. bridgesi is a popular aquarium snail and was probably introduced by aquarium hobbyists or fish farms. One important impact of this snail is that it may be replacing the native applesnail in the Everglades. The rare Everglades Kite feeds on the native applesnail but is not able to readily feed on the introduced species because of the shape of the shell does match that of the kite's beak (Hale 1964).
The native range of this daphnia is freshwater lakes of east Africa, southwest Asia, and east Australia (Havel 1993). It was first reported in Stockton Lake in southwest Missouri in 1991 and can be found in 13 states from Illinois and Ohio down to Texas across to North Carolina and south to Florida. D. lumholtzi has spread much faster than Bythotrephes for reasons unknown. The method of introduction is uncertain. But, coincidentally, one of its first appearances was a lake in Texas where the Nile perch was first introduced to North America (Havel 1993). It is well established in the U.S. Any effects or impacts are yet unknown.
Giant Rams-horn Snail (Marisa cornuarietis)
The giant rams-horn snail is native to northern South
America and several of the southern islands of the Caribbean. It is an
easily recognizable species, brick red in color with a flat coiled shell.
Color may be darker or more vivid. Shell diameter is usually 35-50 mm (2
in.) or larger. Still or slow-moving fresh water, depending on vegetation.
Easily adaptable to captivity, it may invade and damage aquarium vegetation.
It is practically omnivorous and feeds on animal and vegetal detritus.
Acts as a useful aquarium scavenger when not extensively numerous. It has
gills as well as a lung, to ensure an efficient underwater respiration.
A hermaphrodite, it lays eggs in characteristic disk-shape clutches adhering
to various substrates. It is established in Broward, Dade, Monroe, and
Palm Beach counties probably as a result of releases by aquarium hobbyists.
Studies revealed that this species retards the growth of water hyacinths
by feeding on the roots of the plants. It has been suggested that the
snail be used as weed-control agent in the canals of south Florida. The
snail has been released in some areas to control hydrilla. It has also
been released to control snail populations that carry schistosomiasis.
Spectacled caiman (Caiman crocodilius)
Spectacled caimans are native to Central and Southern
America. Although they look similar to native alligators, caimans can be
distinguished by a bony ridge in front of their eyes. Coloration between
the two species is also different - young alligators are black with yellow
bands while caimans are greenish- to brownish-gray with dark brown bands.
Adults attain a length of 6-8 feet. Caimans are established in Dade County,
Florida, and have been reported in other areas of the country. They have
also been observed in Everglades National Park. Discarded pets are the
most likely source of introductions.
Greenhouse frog (Eleutherodactylus planirostris)
Greenhouse frogs were likely brought in on tropical plants
from their native range in the Caribbean (Cuba, Bahamas, and Cayman Islands)
and are now established in many areas of Florida. They are small frogs,
only reaching 1.5" in length, and are active feeding, calling, and mating
at night. Unlike other members of this genus, they are ground-dwellers
(rather than arboreal) and are seldom found more than a few centimeters
off the ground. They are most often found in leaf litter or under logs.
The most unique trait of this frog (and other species of this genus) is
that the eggs are laid in moist leaf litter, not water. The eggs then
develop directly into tiny froglets, without going through a tadpole stage,
a process known as direct development.
Cuban treefrog (Osteopilus septentrionalis)
Cuban treefrogs are believed to have been introduced into
Florida in 1931 in cargo imported from Cuba. Since then they have spread
to 27 counties. They are known to prey on many native frog species including
the southern toad (Bufo terrestris), the narrow mouthed toad (Gastrophryne
carolinensis), the southern leopard frog (Rana sphenocephala),
the green treefrog (Hyla cinerea), and the squirrel treefrog (Hyla
squirella), as well as other Cuban treefrogs. In some areas, these
frogs have caused power outages. They are attracted to the buzzing noise
of electrical transformers and can short out the transformer causing a
localized blackout.
Disclaimer for non-USGS materials
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U.S. Department of the Interior, U.S. Geological Survey, Center for Coastal Geology This page is: http://sofia.usgs.gov/sfrsf/rooms/species/invasive/intro/index.html Comments and suggestions? Contact: Heather Henkel - Webmaster Last updated: 11 June, 2007 @ 11:34 AM (TJE) |
