Invasive Plant Science and Management 2011 4:265–273 Invasion Alert Corallita (Antigonon leptopus): Intentional Introduction of a Plant with Documented Invasive Capability Janelle M. Burke and Antonio DiTommaso* Corallita (Antigonon leptopus) is a perennial vine, lauded as an ornamental for its vigorous growth, and plentiful (usually) pink flowers, and even its ability to smother unsightly landscapes. In the United States it thrives in horticultural zones 8 to 10, and also is successfully grown worldwide in tropical climates. When corallita is neglected, it can grow quickly over other vegetation, spreading beyond its area of introduction. Once established, it is difficult to eradicate because it produces many tuberous roots that can propagate vegetatively. Its fruits are buoyant, allowing for successful seed dispersal in water. The islands of Guam (South Pacific Ocean) and St. Eustatius (Caribbean Sea) represent two regions where corallita has become so pervasive that it threatens local diversity. In Florida, already it is classified as a Category II invasive. Our report reviews the literature and past studies of corallita, in addition to adding new taxonomic and distribution information from herbarium specimens to clarify the identity and geographic range. It is recommended that introductions of this plant by the horticultural industry in both tropical and temperate regions be closely monitored to prevent spread. On tropical island nations, we advise against any new introductions. Nomenclature: Corallita; coral creeper; Mexican creeper; corallina, bellisima; Antigonon leptopus Hook. & Arn. Key words: Ornamental, Polygonaceae, tropics, vine. Like many other members of the Polygonaceae [e.g., roadside weed in its native Mexico (Howard 2001; Reynoutria japonica Houtt., Emex spinosa (L.) Campd., Pichardo and Vibrans 2009), but it is on tropical islands Persicaria perfoliata (L.) H. Gross], Antigonon leptopus where corallita has become most pervasive and problematic Hook. & Arn. (corallita) is documented as an invasive (Figure 2). On Christmas Island (Indian Ocean), corallita species of natural areas (Ernst and Ketner 2007; Pichardo is reported as ‘‘…rampant on sea and inland cliffs and in and Vibrans 2009; Raju et al. 2001). It climbs using previously mined areas …where it may be hampering the tendrils, and persists vegetatively by producing numerous annual migration of crabs and interfering with natural tubers (Pichardo and Vibrans 2009). The flowers are regeneration’’ (Swarbrick and Hart 2000). On St. visited by a myriad of pollinators (bees, flies, humming- Eustatius, the vine is particularly pervasive, smothering birds, butterflies), facilitating sexual reproduction outside whole areas of vegetation and killing the undergrowth of its natural range (Raju et al. 2001). (STENAPA 2007). It has been estimated to cover 20% of Corallita is native to Mexico and is cultivated as an the island of St. Eustatius (Caribbean Sea) (STENAPA ornamental for its showy flowers (Figure 1), and has been 2007), and on Fiji (Pacific Ocean) and Christmas Island introduced across the tropics. It is a reported pest from the (Indian Ocean), it is a documented threat to the local flora South Pacific to Africa and India (Raju et al. 2001). It is a (PIER 2009; Swarbrick and Hart 2000). In the United States, it is hardy in horticultural zones 8 to 10 (Scheper 2004) and is commonly cultivated in Arizona, Florida, DOI: 10.1614/IPSM-D-10-00088.1 Hawaii, Louisiana, New Mexico, South Carolina, and * Ph.D. Candidate, Department of Plant Biology, and Associate Texas (Freeman and Reveal 2005). Professor, Department of Crop and Soil Sciences, Cornell This invasion alert aims to summarize the current University, Ithaca, NY 14853. Corresponding author’s E-mail: knowledge of the natural history and invasive biology of [email protected] corallita and call attention to its invasive potential. Burke and DiTommaso: Invasion Alert: Antigonon leptopus N 265 Downloaded from https://www.cambridge.org/core. IP address: 170.106.202.58, on 26 Sep 2021 at 08:34:29, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1614/IPSM-D-10-00088.1 Figure 1. Images clockwise from top left: (A) Habit of Antigonon leptopus on roadside in St. Eustatius. (B) Detail of flower. (C) Seedling with cotyledons and first leaf. (D) Tuberous root produced from seedling. (E) Detail of inflorescence and leaf morphology. All photos by J. Burke. Natural History, Taxonomy, and Distribution vegetation. Leaves are alternate and usually 10 to 16 cm (3.9 to 6.3 in) long. Leaf shape is variable, but usually is Plant Traits. Corallita is a perennial vine, climbing by deltoid or cordate, the apex acute or acuminate (Figure 1E; tendrils at the end of the inflorescence axes. The base of the Duke 1960). An individual plant can propagate under- plant can become slightly woody with age. Stems are ground via roots, or spread above ground by the pentagonal in cross section, commonly 1 to 3 m long (3.3 production of stolons. Plants easily persist in the soil by to 9.8 ft) (although they can reach 9 to 12 m in length; producing tuberous roots (Figure 1D), formed from an Scheper 2004), and quickly sprawl over surrounding extensive root crown. Tuberous roots can range in size from 266 N Invasive Plant Science and Management 4, July–September 2011 Downloaded from https://www.cambridge.org/core. IP address: 170.106.202.58, on 26 Sep 2021 at 08:34:29, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1614/IPSM-D-10-00088.1 Figure 2. Global geographic distribution map of Antigonon leptopus, excluding Mexico and Central America (its native range). Filled circles represent a collection of a plant growing spontaneously; gray gradients circles indicate cultivated specimens. Distribution data were drawn from herbarium specimens from BH, F, MO, NY, P, TEX, and US (standardized herbarium acronyms from Index Herbariorum, 1990). , 0.5 g to 300 g (0.02 to 10.6 oz) (Ernst and Ketner and Wood 1965), although four species has been the 2007), but can reach 1.0 to 1.5 kg (2.2 to 3.3 lb) in older common consensus (Duke 1960; Ewing 1982; Standley plants (Englberger 2009). and Steyermark 1946). Corallita (Antigonon leptopus) is the The flowers of corallita are arranged in long, branching most morphologically variable and geographically wide- inflorescences, which are quite striking when hanging over spread. In contrast, A. amabile W. Bull, A. cordatum M. a trellis or fence. The flowers are 0.4 to 2 cm in diameter Martens & Galeotti and A. platypus Hook. & Arn. are (Ewing 1982), with five tepals, these light pink to deep relatively well-defined, based on morphological characters pink, magenta, or almost red (Figure 1B). There also is a and geographic distribution. The native ranges of the four white-flowered cultivar, although commonly it is not species overlap to some extent; specifically corallita overlaps invasive. Eight stamens are fused into a column; at the base with A. platypus and A. cordatum in Mexico. Corallita can of this column copious nectar is produced. The tepals be distinguished from the latter species by the leaf petiole: enlarge after fertilization, become papery in texture, and corallita has a slender petiole, whereas the petiole of A. surround the fruit. The fruits are achenes, 0.6 to 1.0 cm platypus and A. cordatum is winged, with the leaf lamina long, trigonous, acute and winged at apex, brown, dull, and decurrent along the petiole. Leaf blade size and shape are buoyant. The seed is large, and comprises 70% of the fruit phenotypically plastic (shape in particular is correlated with weight (Jones and Earle 1966), and includes ruminate sun exposure) and thus are not reliable taxonomic endosperm. Chromosome counts for A. leptopus vary from characters. 2n 5 14, 40 to 48 (Freeman and Reveal 2005). The base Putative hybrid populations between corallita and A. number for the Polygonaceae likely is x 5 7 (Brandbyge platypus have been discovered in Oaxaca and Jalisco, 1993), suggesting that corallita (and possibly the whole Mexico (Burke, unpublished data). Results from compar- genus) is of polyploid origin. ative morphological studies suggest that invasive popula- tions of A. leptopus are not of hybrid origin because they Taxonomy. All species within the genus Antigonon are lack diagnostic characters of A. platypus, namely the winged perennial vines, which can become semiwoody at the base. petiole and small flowers. Ongoing taxonomic study by J. The native range of this genus extends from western Baja Burke (unpublished) has focused on species delimitation as California south to Costa Rica (Duke 1960). Other species part of a taxonomic revision of Antigonon. A complete of Antigonon often are cultivated, both within and outside taxonomic treatment, including species descriptions, dis- their native range, for their showy flowers and prolific tribution, and key to species is forthcoming. nectar production (Duke 1960; Ortı´z 1994; Pichardo and Vibrans 2009), although corallita is the only species which Distribution. The native range of corallita has been thus far has been documented as an invasive. unclear because it is cultivated as an ornamental and also is Species delimitations in Antigonon have been taxonom- a roadside weed within Mexico (Pichardo and Vibrans ically difficult with one to eight species recognized by 2009), Central America, and the Caribbean. Herbarium different taxonomists (Brandbyge 1988, 1993; Graham collections have helped to clarify the history of introduc- Burke and DiTommaso: Invasion Alert: Antigonon leptopus N 267 Downloaded from https://www.cambridge.org/core. IP address: 170.106.202.58, on 26 Sep 2021 at 08:34:29, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1614/IPSM-D-10-00088.1 tion of corallita through cultivation, and thus to infer its other species in the genus as well.