A. elliptica is one of the world’s 100 worst invasive alien species (Lowe et al., 2004). This ornamental shrub has been widely introduced around the tropics and sub-tropics from it native South-East Asia, and has since escaped from cultivation, becoming a particular problem weed in southern Florida and the Everglades, also Hawaii, and has naturalized in Australia, Puerto Rico and likely in other countries. Birds and some mammals are the main local dispersal agents via consumption of the edible berries. It is shade tolerant and can form monotypic stands in moist areas displacing native vegetation. Planting of A. elliptica has been banned in some areas, though its continued availability via ornamental plant dealers means further introduction may be likely.
Ardisia elliptica is in the family Primulaceae. This family includes about 58 genera and 2590 species of trees, shrubs and herbs widely distributed throughout tropical and subtropical regions of the world (Stevens, 2012). It includes the subfamilies Myrsinoidea and Theophrastoidacea, both previously treated as separate families. Member of the family Primulaceae can be recognized by their usually spirally arranged leaves sometimes with dark dots or lines. Their flowers are sympetalous with stamens borne opposite to the petals and an ovary with several to many ovules and free-central placentation; the stigma is not lobed (Stevens, 2012). The subfamily Myrsinoidea includes 41 genera and 1435 species. Ardisia is the largest genus within this subfamily including about 450 species. The most common vernacular name in English is the shoebutton ardisia.
The following description is taken from the Flora of China (Chen and Pipoly, 1996). Shrubs 1-2 m tall, with angular branchlets, 3-4.5 mm in diameter, glabrous, conspicuously black, punctate-lineate, longitudinally ridged. The petiole is marginate, 5-10 mm long; and the leaf blade is 6-12(-16) cm long and 3-5(-7) cm broad, oblanceolate or obovate in shape, subleathery, dull and densely punctate abaxially, especially along the margin, base cuneate, margin revolute, entire, apex obtuse or acute; with lateral 12-34 veins on each side of the midrib, marginal vein present. Inflorescences are axillary or subterminal on basally thickened lateral branches, subumbellate or umbellate. Flowers are leathery, pink or white, 6(-8) mm. Pedicel ca. 1-2 cm, minutely and densely white verruculose, densely punctate. Sepals broadly ovate, ca. 1 mm, densely black punctate, base rugose and subauriculate, margin subentire, scarious, minutely ciliate, apex rounded. Petals almost free, broadly ovate, densely punctate, glabrous, margin hyaline, scarious, entire, apex long attenuate. Stamens subequalling petals; anthers linear-lanceolate, punctate dorsally, longitudinally dehiscent, transversely septate-lobed, apex apiculate. Pistil as long as petals; ovary glabrous, pellucid punctate; ovules numerous, multiseriate. Fruit subglobose, red or purplish black, ca. 8 mm in diameter, minutely punctate, fleshy.
The following are differences observed between the description from China, above, and that of Wagner et al. (1999), where A. elliptica is introduced and invasive in Hawaii. In Hawaii, the shrubs are noted to be taller, up to 4 m tall, with smaller range of leaf sizes (6-9 cm long, 1.5-4 cm wide) and petiole lengths (4-8 mm long). Leaves are alternate, a character not expressed above, and flower and fruit sizes also vary. Inflorescences axillary, umbellate to racemose, peduncles 1.5-3 cm long, pedicels ca. 1 cm long; sepals suborbicular, ca. 2 mm long, the surface black punctate, margins hyaline and ciliolate; corolla lobes pale lavender, lanceolate, conspicuously punctate. Drupes red when immature, black at maturity, globose, ca. 5 mm in diameter, densely punctuate.
In Florida, USA, FLEPPC (2009) record A. elliptica as taller still, with heights up to 5 m, and much larger leaves up to 20 cm long, and in the same state there are also records of plants up to 6 m tall and with basal diameters of 15 cm.
The exact native range is debated, though it is generally accepted as South and South-East Asia. USDA-ARS (2009) report its native range to be from Taiwan and the Ryukyu Islands of Japan in the northeast, to Papua New Guinea in the southwest, to India in the west, including Indonesia, Malaysia, the Philippines, Thailand, Sri Lanka and Vietnam. It is uncertain, however, whether it is native to southern, coastal China, Myanmar and Cambodia.
It has also been widely introduced pan-tropically, and the distribution table is highly likely to have underestimated the number of countries where it is actually present.
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
It is generally accepted that A. elliptica has been widely introduced during the 1900s, and is cultivated throughout the tropics and has naturalized in many countries. It was introduced to the Seychelles around 1900 (Seychelles Environment, 2009), and it was imported to Florida for use as an ornamental plant also by 1900, and had already been reported as having escaped from cultivation in south Florida by 1933 (Small, 1933). It was also likely to have been introduced to countries close to its native range limits early on, such as Australia and some Pacific islands.
Scoring 11 and failing a risk assessment for the Pacific (PIER, 2009), A. elliptica is not recommended for further planting, and in both Hawaii and Florida, it is a declared invasive species and control programmes are in operation in both (USDA-ARS, 2009). It is also on noxious weed lists in French Polynesia and Australia. However, it is still available as a ‘rare’ tropical ornamental, even from companies based in areas where it is well established as an invasive species, such as Florida (e.g. http://toptropicals.com/catalog/uid/Ardisia_elliptica.htm).
Wet and humid habitats tend to be preferred by A. elliptica, such as moist and wet forests and open areas. In southern China, it is noted to be found on roadsides, in scrubland, near villages, on field edges and in coastal areas (Chen and Pipoly, 1996). In Hawaii, it has become naturalised in disturbed forest, mesic forest and lower portions of wet forest, commonly in wet, lowland areas at altitudes below 550 m (Wagner et al., 1999), and it is noted in moist valleys up to 500 m in French Polynesia (PIER, 2009). It forms secondary thickets in moderately wet places in Jamaica (Adams, 1972), whereas in southern Florida it is now abundant in hammocks, old fields, disturbed wetlands, and tree islands in marshes, forming monotypic stands in the forest understory, such as where it is invading cypress and mangrove areas (Langland and Burks, 1998; FLEPPC, 2009), and it is a serious invasive species in hardwood forests and abandoned agricultural land (Randall et al., 1996). It also exists as isolated, naturalised specimens in riparian vegetation within areas of dry rainforest associated with the monsoon belt of northern Australia (Csurhes and Edwards, 1998).
In a disturbed area of the Everglades National Park, A. elliptica does not occur in all habitat types, nor is it evenly distributed among those where it does occur (Koop, 2004). Seed mortality and mean germination speed was lower in closed canopied forests that in open exposed habitats, and the work of Koop (2004) suggested that differential water availability between habitats may influence the patchy distribution, and the lack of adequate moisture for seeds in exposed habitats such as pine forests and wetland prairies during the dry season has contributed to this. However, as some of the habitats where it currently occurs were pine forests and wetland prairies prior to disturbance, substrate disturbance and canopy formation may have altered the soil microenvironment thus favoring the establishment of A. elliptica (Koop, 2004).
The chromosome number of A. elliptica is recorded as 2n = 48 (Chen and Pipoly, 1996), though the ploidy of other species within the genus is not known.
A. elliptica can begin to reproduce at 1-2 years of age under optimal conditions, or 2-4 years otherwise. Species of Ardisia do not produce nectar or other specialized floral resources such as oils or resins, and, based on floral morphology are thought to be pollinated by small bees (Pascarella, 1997), relying on pollinating insects and frugiverous birds and mammals to complete its life cycle.
Five species (A. escallonioides, A. hirtella, A. elliptica, A. sieboldii and A. wallichii) from three subgenera in the genus Ardisia were all found to be self-compatible but not agamospermous, which is likely to be a general characteristic of the genus Ardisia (Pascarella, 1997). Four of the five species exhibited autogamy, which was strongly associated with stamen position, anther dehiscence type, protogyny, and inflorescence type (Pascarella, 1997).
Physiology and Phenology
In China, A. elliptica was observed to flower from February to April, and fruit from September to November (Chen and Pipoly, 1996). However, where introduced and invasive in Florida, it is seen to flower and fruit all year round (FLEPPC, 2009). Seeds, however, are thought to be relatively short-lived, and may not survive for more than six months.
It is a shade-tolerant, evergreen shrub that grows rapidly, forming dense monotypic stands that prevent establishment of all other species. Juveniles can probably survive for many years in low light conditions in a forest understory, but then grow rapidly if a break in the canopy occurs. It is however, probably not resistant to fire. It is thought to be able to live for 25-40 years, at least, though no firm data for longevity are available.
A number of insects are observed feeding on A. elliptica in both its native and introduced ranges, though none of these appear to limit growth or reproduction, and are generalists in their feeding behaviour.
Little is recorded on the exact environmental requirements of A. elliptica. It is a species of the humid tropics and not tolerant of frost. It prefers permanently moist soils and is not tolerant of drought.
From searches of the native range in Malaysia in 2004 and 2005, the dominant herbivore on A. elliptica was found to be the pagoda bagworm (Pagodiella hekmeyeri, Family: Psychidae), a generalist pest of oil palm, and two species of chrysomelid beetles and a juvenile Hemiptera species were also observed on A. elliptica (Ewe et al., 2005).
Propagules remain viable after passage through the guts of frugivorous birds, which are reported as the principal dispersal agents, attracted to the numerous red to blackish fruits (PIER, 2009), though small mammals also play a role. In Florida, the grey catbird (Dumetella carolinensis) was noted to be a significant dispersal agent (Langeland and Burks, 1998), though long-distance dispersal by raccoons (Procyon lotor), although less frequent than bird dispersal, may be important in determining invasion rates (Koop and Horvitz, 2005).
Long distance introduction of A. elliptica has been largely, if not entirely, due to its use as an ornamental species, and as it remains available from nurseries and seed catalogues, further introduction may still be likely.
A. elliptica forms dense monotypic thickets below the forest canopy which crowds out native understory plants, and shade-tolerance and tolerance of wet soil conditions contribute to its success as an invasive species (Langland and Burks 1998). A. elliptica, along with A. crenata, also has the capacity in Florida to displace native species such as Ardisia escallanoides (marlberry) and the endangered Argythamnia blodgettii (Blodgett’s silverbush) (Ewe et al., 2005).
Potential for pharmaceutical applications from extracts of plants from the genus Ardisia were noted by Kobayashi and de Mejía (2005), and other species are widely used in China for such purposes. More specifically, antibacterial activity against four serovars of salmonella was observed with plant extracts from A. elliptica (Phadungkit and Luanratana, 2006), and there were positive effects on the reduction of breast cancer cells (Moongkarndi et al., 2004). It is also occasionally used as firewood for home use.
In parts of its native range in South-East Asia, the berries are known to be eaten, and plant parts are used for the preparation of traditional medicines.
As an ornamental shrub, A. elliptica offers benefits as a low windbreak and physical barrier when planted as a hedge.
A. elliptica shares a similar but more restrictive native and exotic range as compared to A. crenata (the coral ardisia), another invasive weed. The latter is also native to much of China and mainland Japan as well as Myanmar, and is also invasive in South Africa and well as in areas overlapping the invasive range of A. elliptica. A. crenata differs, however, by having bright red rather than black fruits, and leaf margins that are subrevolute, crenate, or undulate rather than revolute and entire.
In Florida, USA, A. elliptica is similar to the native marlberry Ardisia escallonioides, and the native myrsine Rapanea punctata (Myrsine floridana), though it differs by having a larger growth habit and conspicuous axillary clusters of mauve flowers (FLEPPC, 2009).
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Hand-pulling of seedlings is effective when plants are small, if rather time-consuming. Medium-sized plants can be mown, but then regrowth must be managed, such as with herbicide applications (PIER, 2009).
Ewe et al. (2005) made two surveys of central and northern peninsula Malaysia in 2004 and 2005 to look for potential biocontrol agents, but found only generalist herbivores as natural enemies.
In areas with a dense groundcover of seedlings, a broadcast spray of glyphosate is effective, although desirable plants will also be killed if not carefully avoided. Mature shrubs can be treated with a basal application of triclopyr mixed with oil (Randall et al., 1996). PIER (2009) noted from work in Hawaii that A. elliptica is susceptible to 2,4-D, especially after mowing, while triclopyr, dicamba and metsulfuron are less effective. Glyphosate is also reported as effective as a foliar spray and as a basal bark treatment, with tebuthiuron, triclopyr and triclopyr ester also proving effective (PIER, 2009). Siso and Burzycki (2004) found cut stump treatments with triclopyr to be 95% effective, though results were significantly different between sites, indicating that further study is needed.
More study is required at the genus level, with the identification of other Ardisia spp. that are also used in the ornamental trade, and on which other species have also shown signs of invasiveness. Analysis of ploidy levels within the genus may also be revealing.
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