Shoebutton ardesia, Ardisia elliptica, is a tropical shrub or small tree
not native to Florida but now occurring as an invasive species in the southern
half of the state. The typical growth form in undamaged plants is a single,
smooth stem that gives rise to short, perpendicular branches. Plants may send
up additional stems from the rootstock, particularly after damage. Individuals
produce strong taproots that produce highly branched lateral roots.
The leaves are alternate, oblong to oval, pointed at the tips, smooth and
leathery/rubbery, 8-20 cm long, pink to reddish in young plants and turning dark green
with age. Star-shaped flowers, to 13 mm wide with pale violet-colored petals
occur in axillary clusters. Fruits are round, berry-like drupes, 6 mm wide
that are white when young and turning red and then dark purple to black when
ripe, and capable of staining fingers. The flesh of the ripe fruit is juicy when broken and
white in color, and each fruit contains a single seed (Langland and Burks 1998,
Francis undated, ISSG).
Potentially Misidentified Species
Two native Florida plants, marlberry (Ardisia
escallonioides) and myrsine (Rapanea punctata) are related to Ardisia elliptica
and similar in appearance. Langland and Burks (1998) note that A.
elliptica can be distinguished from these native plants by its larger
growth habit and conspicuous clusters of violet axillary flowers.
A. elliptica may also be confused in Florida with a non-native congener,
the coral ardisia A.
crenata, whose distribution in the state is broader but still partly
overlaps that of A. elliptica. The scalloped leaf margins and
persistent bright red fruits of A. crenata aid in distinguishing it from
HABITAT AND DISTRIBUTION
The native distribution of Ardisia elliptica is not entirely certain, and the
original range of the species has variously included India, Sri Lanka, China
Taiwan, Malaya, Southeast Asia, Indonesia, and the Philippines (Tomlinson 1986,
Langland and Burks 1998, Yuen-Po 1999).
The plant is an introduced exotic that now occurs in the East Indies and Okinawa,
Japan, and has become naturalized in south Florida, Hawaii, and the Caribbean
(Langland and Burks 1998, Francis undated).
Florida Exotic Pest Plant Council collection records indicate that Ardisia elliptica is
present in the southern half of the IRL watershed in St. Lucie, Martin, and
Palm Beach counties. Wunderlin et al. (1995) also indicate the plant is present
in Brevard County, based on vouchered specimens. Brevard is the northernmost
county from which the plant has been collected.
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
Adult trees can reach a height of 6 m and attain a basal trunk diameter of 15
cm. Adult mortality due to old age is rare in Florida and Francis (undated)
suggests a likely lifespan of 10-25 years or more.
Shoebutton ardisia is an understory species that forms dense monotypic thickets
in moderately wet soil conditions. This invasive plant is now established in
south Florida and is abundant in natural areas such as hammocks, marsh islands,
cypress and mangrove habitats, and also in disturbed systems such as altered
wetlands and fallow fields (Langland and Burks 1998).
Reproduction in Ardisia elliptica is sexual and the species flowers and
fruits sporadically throughout the year in south Florida (Long and Lakela 1971,
Langeland and Burks 1998). Individuals attain sexual maturity in 2-4 years.
Flowers are insect-pollinated Individual plants possess both male and female
flowers and there is a high degree of autogamy or self-fertilization
Fruit production is moderate, up to 400 fruits on large adults in bright
forested sites (ISSG), but year-round production likely increases the overall
reproductive capacity of individuals.
Propagules remain viable after gut passage and seed dispersal has been reported
as primarily through frugiverous birds (Langeland and Burks 1998, Francis
undated), particularly the gray catbird (Dumetella carolinensis) in
Florida. However, recent studies examining the spread of Ardisia elliptica in
Everglades national Park suggest that long-distance dispersal by raccoons
(Procyon lotor), although less frequent than bird dispersal, may be of
primary importance in determining invasion rates (Horvitz and Koop 2005, Koop
and Horvitz 2006).
Seeds reportedly do not remain viable for more than 6 months (ISSG).
Experimental evidence suggests germination rates are high; 75% of seeds planted
in commercial potting mix with no pretreatment germinated 42-81 days after
sowing. Seedlings may grow up to 1 m in the first year, but 0.25 to 0.5 m/year
is a more typical rate for both seedlings and established shrubs (Francis
This tropical species is restricted largely to the southernmost Florida
counties, most likely due to cold intolerance. Published thermal tolerance
information is lacking, but prediction models by Braun (2006) suggest
Ardisia elliptica will remain restricted to the southern half of
peninsular Florida. In contrast, the models suggest the congener A.
crenata (also non-native) has potential to spread through Florida and
across the Gulf coast into Texas.
Ardisia elliptica grows well in moderately wet soil conditions including
mesic forest and lower portion of wet forest as well as mangroveanand cypress
stands and marsh habitats (Adams 1972, Wagner et al. 1990, Langland and Burks
1998). Tolerance for wet soils is a key feature of shoebutton ardisia's
Ardisia elliptica is a shade-tolerant forest understory plant whose seedlings
and young plants can survive in forested low-light conditions for several
years. Juveniles take rapid advantage of breaks in the canopy layer and
quickly mature to reproductive adulthood (ISSG).
Ardisia elliptica tends to form monotypic thickets where conditions permit.
It relies on pollinating insects and frugiverous birds and mammals to complete
its life cycle.
A measurable amount of insect herbivory is directed at Florida A.
elliptica populations, but there has been no discernable effect on curtailing the spread of
the species (Dominguez and others 2002).
Ardisia elliptica had already been imported to Florida for use as an
ornamental plant by 1900 and by 1933 the species had been reported as having
escaped from cultivation in south Florida (Small 1933, Morton 1976, Austin
1978, Gordon and Thomas 1997).
Unintentional release to natural areas through animal-facilitated seed
dispersal is likely the principal route of entry for this species in Florida.
Although A. elliptica is no longer commercially sold as an ornamental, a
large number of ornamental plantings remain in south Florida.
Potential to Compete With Natives
Ardisia elliptica forms dense single-species thickets below the forest canopy
to crowd out native understory plants (Langland and Burks 1998).
Shade-tolerance and tolerance for wet soil conditions contribute to the success
of this species as an aggressive invader.
Possible Economic Consequences of Invasion
Prior to recognizing its invasive potential, Ardisia elliptica was a
much-utilized ornamental species in south Florida. The fruits are edible but
bland, and have little commercial potential. The plant is utilized
for fuel wood in some parts of the world (Morton 1974, Francis undated).
None of these marginal economic benefits offset the fact that A.
elliptica is extremely invasive and ecologically damaging. It is listed by
ISSG as among "100 of the Worst" global invasive organisms. It is also
listed as a Category I invasive exotic plant in Florida, indicating that
the species is currently altering native plant communities by displacing native
species and changing community structures or ecological functions. A PIER
species risk assessment considering potential impacts on Hawaii and
other Pacific islands scored A. elliptica as a "high risk" species
likely to cause significant ecological or economic harm.
Resource managers in Miami-Dade and Broward counties and staff at Everglades
National Park have initiated costly eradication programs targeting A.
elliptica (Langland and Burks 1998).
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