Appendix B
Additional Major Nonnative Plant and Animal Species in the Everglades
This appendix provides additional information about the occurrence and threats posed by invasive plants and animals in the Everglades, as well as available management strategies.
PLANTS
Water Hyacinth (Eichhornia crassipes)
South American water hyacinth is one of the world’s worst invasive species (Mitchell, 1976). It can double its biomass in 6 days (Mitchell, 1976) and has average annual biomass production of up to 250 tons of dry weight per hectare (Spencer and Bowes, 1986). In the Everglades, water hyacinth readily invades wetlands, freshwater lakes, and other open-water habitats, where it effectively outcompetes other floating species, and its dense mats shade out submerged aquatic vegetation. This highly aggressive species is treated using a combination of herbicide and biocontrol agents, including the latest release in 2010, the water hyacinth plant hopper (Megamelus scutellaris). Some biocontrol agents have reduced biomass (> 50 percent) and seed production. Other potential agents are undergoing trials and are in development. However, chemical control, primarily with 2,4-D, is currently the main factor in controlling water hyacinth (Schardt, 1997).
Hydrilla (Hydrilla verticillata)
This Asian species, introduced in Florida in the 1950s, is a submerged aquatic that has become a widespread invader. It can displace aquatic species, affecting the composition and functioning of communities. Heavy infestations clog waterways, interfering with recreation and navigation. It is readily dispersed by boat traffic and has greatly expanded its distribution in recent years. Herbicide
application is the main form of management, but recently detected resistance to the most commonly used herbicide, fluridone, leads to concerns that it will cease to be effective (Puri et al., 2007). Mechanical harvesting is sometimes used for particularly dense infestations.
Air Potato (Dioscorea bulbifera)
Air potato is an Asian vine. It was introduced to the United States as an ornamental, but in many areas of the world (e.g., Africa) its starchy bulbils are used as a food (Ewe et al., 2006). In its introduced range, it spreads vegetatively through dispersal of its bulbils (Rodgers et al., 2013), and it can quickly blanket an area, shading out native vegetation. Chemical control has been used in the past. Recently, a foliage-consuming beetle from China (Lilioceris cheni), released as a biocontrol agent, has been successfully established in the field and is imposing substantial defoliation. A second beetle from China (L. egeria) is under testing and shows promise for its bulbil consumption (Center et al., 2013).
Shoebutton Ardisia (Ardisia elliptica)
This ornamental shrub was introduced from Southeast Asia to Florida in the early 1900s (Gordon and Thomas, 1997). It is bird-dispersed, which facilitated its escape into surrounding natural areas (Ewe et al., 2006), including tree islands, hammocks, and short-hydroperiod wetlands that it readily invades in the Everglades. Highly shade-tolerant, this shrub creates thickets that cast dense shade, excluding regeneration of other species. It is difficult to detect and control. Cutting, followed by herbicide application to the stumps, has been used effectively in some invasions. However, where the population is exceptionally dense, a two-step process of shredding and herbicide application has been the most effective (Rodgers et al., 2013).
Torpedograss (Panicum repens)
This invasive exotic grass is native to Africa and Eurasia and has invaded a broad range of wetland and successional habitats in Florida. Despite its widespread distribution in South Florida, it is not known to reproduce via seeds but spreads rapidly and aggressively via vegetative means. It readily displaces native species and (along with Melaleuca) has expanded rapidly into the marshes around Lake Okeechobee (Ogden et al., 2005). If not controlled, torpedograss is likely to impact CERP performance measures in Lake Okeechobee, such as increased native fish recruitment or the recovery of native vegetation (RECOVER, 2014a). Control efforts are largely through aerial and ground-level herbicide
application. Because it is a grass and the Everglades system has many native grass species, this species is not likely to be a target for biocontrol development (Rodgers et al., 2014a).
Downy Rose Myrtle (Rhodomyrtus tomentosa)
This Asian shrub was introduced as an ornamental and has now spread into pine flatwoods and some cypress stands, where it can displace native species. It occurs in many counties of central and South Florida, particularly along the coast. The extent of its infestation is unclear, however, and on-the-ground surveys/observations are required to detect it unambiguously. Herbicide application and shredding have been the most effective methods for controlling it. A potential biocontrol agent is currently under testing and development (Rodgers et al., 2014a).
Cogongrass (Imperata cylindrica)
Cogongrass is native to southeastern Asia and is a highly aggressive, widespread exotic grass in the southeastern United States (Evans et al., 2007). It has a deep, dense rhizomatous mat (Byrd and Bryson, 1999), allowing it to resprout readily, even after fire. The chemical residue it exudes into the soil can hinder establishment of some species (Koger and Bryson, 2004), and it can alter fire regimes (Lippincott, 2000). This species negatively affects native biodiversity and is one of the few that has been definitively shown to result in native species extirpations, particularly of low-stature forbs in pine savannas of the southeastern United States (Brewer, 2008). Its coverage is estimated at ~1 million acres in Florida (Miller, 2007), including pine flatwood and freshwater marsh communities. Control efforts include mechanical removal (often repeated), herbicide application, and repeated prescribed fire. No biocontrol agents have been identified (Rodgers et al., 2014a), and it is an unlikely candidate for that program because of its close phylogenetic relationships with many native species in the Everglades (P. Tipping, USDA, personal communication, 2013).
Water Lettuce (Pistia stratiotes)
Water lettuce is a native of temperate to tropical regions of South America. Its status in Florida is uncertain; it may be another “native invader” (Evans, 2013). In any event, it is a highly invasive floating macrophyte that has invaded many open-water and wetland habitats in the Everglades (Rodgers et al., 2014a). This species can take advantage of elevated nutrients and quickly expand its distribution (along with Eichhornia) (Ogden et al., 2005), clogging waterways
and shading out submerged aquatic species. Herbicide application is the most effective control method, and it has been used quite successfully in many canals in South Florida. Biocontrol agents released to control this species have had minimal impact on its abundance.
Tropical American Water Grass (Luziola subintegra)
This nonnative aquatic grass species was first reported in 2007 from Lake Okeechobee. Plants with aquatic and terrestrial morphologies were documented. Preliminary observations suggest that this species could become a highly aggressive invader capable of displacing native species and altering structure and function of these aquatic habitats. Herbicide application has been used to control this species.
Black Mangrove (Lumnitzera racemosa)
This nonnative mangrove was planted in Fairchild Tropical Botanic Garden in 1966-1971 (14 plants) and an infestation was discovered in nearby Miami-Dade County in 2008 (Possley, no date). It is listed as a priority species and focused eradication efforts are under way and expected to be successful (Possley, no date).
Mile-a-Minute (Mikania micrantha)
This invasive vine is also known as climbing hempweed, Chinese creeper, and bittervine. It has recently been detected in the Redlands area of Miami-Dade County. It is fast-growing and potentially invasive; it is listed as a priority species. Because of its currently limited distribution efforts are focused on containment and eradication.1
Skunk Vine (Paederia foetida)
This Asian vine was introduced to the United States in the late 1800s as a potential fiber plant. It has a woody root stock and can produce trailing aboveground vines that extend ~10 m in length. It is widely distributed in Florida. It can reproduce vegetatively and via seed that is dispersed by frugivorous birds. It can invade a wide range of habitats where it can displace native species and
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1 See http://www.freshfromflorida.com/Divisions-Offices/Plant-Industry/Pests-Diseases/MikaniaMicrantha-Mile-a-minute.
blanket stands of trees (University of Florida, Institute of Food and Agricultural Sciences Extension).
Climbing Cassia (Senna pendula)
This evergreen South American shrub is an ornamental widely cultivated in Florida. It has escaped into the wild and is naturalized in South Florida. Some of its characteristics suggest that it may become highly invasive, as it is known to invade hammocks and cypress strands (Richard and Ramey, 2007). Further, it is a legume, and therefore its capacity for nitrogen fixation should be considered when evaluating its potential invasiveness.
Feathered Mosquitofern (Azolla pinnata)
Feathered mosquitofern is an aquatic floating fern that is establishing in canals and some open-water habitat in South Florida (Pemberton and Bodle, 2009). This species is native to parts of Africa, Asia, and Australia, but recent molecular evidence suggests that the subspecies invading the Everglades is of Australian origin, suggesting that biocontrol efforts that focus on Australian insects may be fruitful (Madeira et al., 2013). Earlier research indicates that the native herbivorous weevil Stenopelmus rufinasus, which uses native Azolla spp., has been found in association with A. pinnata and is a potential “native” biocontrol agent (Pemberton and Bodle, 2009) that has not, to our knowledge, been investigated further. Currently, herbicide application is used for control.
ANIMALS
Gambian Pouched Rat (Cricetomys gambianus)
Gambian pouched rats are established on Grassy Key in the Florida Keys, despite a long-term eradication effort. Although they are currently restricted to Grassy Key, the concern is that they could be inadvertently or deliberately carried to mainland South Florida. They are difficult to trap (Witmer et al., 2010b), as witness the persistence of the Grassy Key population. As they are the largest muroid rodent in the world, their impact in the Everglades could be enormous, although there is no substantial research on the magnitude of this threat should they become established. They also carry monkeypox. The Florida Fish and Wildlife Conservation Commission (FWC) and U.S. Department of Agriculture plan to continue trapping on Grassy Key to the extent that funding permits (Rodgers et al., 2014a), though they are hindered by the fact that they cannot gain access to six private properties (Witmer et al., 2010a).
Northern African Python (Python sebae)
The northern African python is apparently still established in Dade County—two individuals were captured and a third was photographed in March 2013 (C. Romagosa, Auburn University, perconal communication, 2013). Were they to become widespread, their impacts might be similar to those of the Burmese python. Other than monitoring, there is no long-term management plan at this time.
Oustalet’s Chameleon (Furcifer oustaleti)
A population of this large chameleon was discovered in rural Dade County in 2011; FWC removed a large number of them, and an interagency team is periodically monitoring the population (Rodgers et al., 2013). It is unclear what observation would trigger management activity or further research.
Veiled Chameleon (Chamaeleo calyptratus)
This large chameleon is native to the Middle East. A breeding population was discovered in Lee County in 2002, and recently, another population was discovered in an agricultural area in south Miami-Dade County less than 4 miles from the boundary of Everglades National Park (Rodgers et al., 2014a). Their presence is suspected to have resulted from “intentional releases by reptile enthusiasts” (Rodgers et al., 2014a).
Spectacled Caiman (Caiman crocodilus)
This crocodilian is native to southern Mexico and southward to Argentina. It can attain 8 feet in its native habitat but usually is less than 6 feet long in Florida, where its distribution results from escapes or releases from the pet trade (Florida Fish and Wildlife Conservation Commission, 2014). Breeding populations have been reported from Miami-Dade and Broward counties; its northern expansion is limited by occasional freezes (Florida Fish and Wildlife Conservation Commission, 2014). Control methods include egg collection and hunting.
Nile Monitor (Varanus niloticus)
This large predatory lizard, native to Africa, is said to be adaptable and intelligent (Bennett, 1998). It is a generalist feeder, and impacts on South Florida’s fauna are unknown, although it has a high potential for predation and competition (Rodgers et al., 2014a). It is established in several South Florida locations, and control methods—currently applied in piecemeal fashion—include snares,
traps, and hunting (Rodgers et al., 2014a). It is monitored in Palm Beach County (Rodgers et al., 2014a).
Cuban Tree Frog (Osteopilus septentrionalis)
This tree frog is ubiquitous and common throughout the Everglades, and there is substantial evidence that it depresses native tree frog populations (Rodgers et al., 2014a; Smith, 2005; Wyatt and Forys, 2004). In the Picayune Strand Restoration Project, the Cuban tree frog colonized and dominates the restored areas, rather than native tree frogs that are found in the reference sites (RECOVER, 2014b). Predicted climate change is likely to be favorable for the Cuban tree frog (Rödder and Weinsheimer, 2009). The Everglades Invasive Reptile and Amphibian Monitoring Program records Cuban tree frogs on its routes (Rodgers et al., 2014a), but there is no coordination or management effort for this tree frog, and basic research on its impacts and possible control methods is needed (Rodgers et al., 2014a).
Cane Toad (Rhinella marina, formerly Bufo marinus)
Despite the fact that the cane toad is a legendary invader with major impacts in Australia and elsewhere (Lever, 2001), there does not appear to be concern over its possible impacts in the Everglades. They are uncommon in the heart of the Everglades but very common in suburban areas (C. Romagosa, Auburn University, personal communication, 2013). There has been no substantial study of status or impacts throughout the Everglades, despite the fact that Punzo and Lindstrom (2001) found that ingestion of its eggs causes massive mortality among several native Everglades vertebrates.
Purple Swamp Hen (Porphyrio porphyrio)
This species established in the Everglades ca. 1996 and has spread widely from an initial location in Pembroke Pines despite sustained efforts (which terminated in 2009) to limit the population (Rodgers et al., 2013). This is a highly aggressive, territorial species that is omnivorous, feeding on, among other things, eggs and young of waterfowl. There is no current coordinated monitoring or control effort (Rodgers et al., 2014a).
Asian Swamp Eel (Monopterus albus)
This is a large, generalized predator that has now spread substantially into the Everglades (Rodgers et al., 2014a). It appears to be expanding northward and
is commonly found in some canals (Kline et al., 2013). There is no coordinated monitoring or management (Rodgers et al., 2014a).
Mayan Cichlid (Cichlasoma urophthalmus)
This fish became abundant in the estuarine zone of northern Florida Bay, and density of native fishes varies inversely with density of the Mayan cichlid (Trexler et al., 2000). It has now become intermittently abundant even in the northern reaches of Everglades National Park (Trexler et al., 2000). Observational data show interference competition with and predation on several native fish species (Trexler et al., 2000), although no research has linked the Mayan cichlid to population-level impacts on native species. The Mayan cichlid and other introduced fish potentially affect various CERP performance measures, such as regional population sizes of fishes, crayfish, grass shrimp, and amphibians.
Pike Killifish (Belonesox belizanus)
The pike killifish persisted in small populations in canals east of the Everglades for over 20 years before dramatically spreading across much of the Everglades, where its density fluctuates greatly locally (Trexler et al., 2000). There is no definitive evidence of impact or lack of impact on any native species.
Black Acara (Cichlasoma bimaculatum)
Black acara populations fluctuate locally and the species is common in solution holes (Trexler et al., 2000). There is no evidence of impact on native species.
Giant African Land Snail (Lissachatina fulica)
This snail, slated for eradication, was discovered in Miami in 2011. It eats a wide variety of vegetation, including agricultural, horticultural, and native species (Rodgers et al., 2014a). In addition, it is an intermediate host of rat lung-worm, which can infect humans and cause meningitis (Rodgers et al., 2014a). A prior infestation occurred in 1966; eradication took 10 years and cost $1 million. Eradication in this case again seems likely (Rodgers et al., 2014).
Mexican Bromeliad Weevil (Metamasius callizona)
This species, introduced in the late 1980s, attacks bromeliads, including species of conservation concern. It has spread widely in the Everglades. There is no coordinated regional monitoring because of lack of funding. A parasitic
fly was approved for release as a biological control but has not established a population. Research is ongoing by University of Florida scientists on a biological control agent (Rodgers et al., 2014a).
Rugose Spiraling Whitefly (Aleurodicus rugioperculatus)
First discovered in South Florida in 2009 and rapidly spreading throughout the region, this whitefly attacks and kills many host plants, both native and nonnative, and achieves massive densities (Stocks and Hodges, 2012). There is no research on its ecological impact. A parasitic fly was approved for release as a biological control but has not established a population (Rodgers et al., 2014a). Research on biological or chemical control methods is under way at the University of Florida.
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