Ficus rubiginosa, the rusty fig or Port Jackson fig (damun in the Dharug language), is a species of flowering plant in the genus Ficus native to eastern Australia. Beginning as a seedling that grows on other plants (hemiepiphyte) or rocks (lithophyte), F. rubiginosa matures into a tree high and nearly as wide with a yellow-brown buttressed trunk. The leaves are oval and glossy green and measure from long and wide.

The fruits are small, round, and yellow, and can ripen and turn red at any time of year, peaking in spring and summer. Like all figs, the fruit is in the form of a syconium, an inverted inflorescence with the flowers lining an internal cavity. F. rubiginosa is exclusively pollinated by the fig wasp species Pleistodontes imperialis, which may comprise four cryptospecies. The syconia are also home to another fourteen species of wasp, some of which induce galls while others parasitise the pollinator wasps and at least two species of nematode. Many species of bird, including pigeons, parrots, and various passerines, eat the fruit. Ranging along the Australian east coast from Queensland to Bega in southern New South Wales (including the Port Jackson area, leading to its alternative name), F. rubiginosa grows in rainforest margins and rocky outcrops. It is used as a shade tree in parks and public spaces, and when potted is well-suited for use as an indoor plant or in bonsai.

Taxonomy

left|thumb|Ficus rubiginosa figs (syconia) and the rusty undersides of the leaves

Ficus rubiginosa was described by French botanist René Louiche Desfontaines in 1804, from a type specimen whose locality is documented simply as "New Holland". In searching for the type specimen, Australian botanist Dale Dixon found one from the herbarium of Desfontaines at Florence Herbarium and one from the herbarium of Étienne Pierre Ventenat at Geneva. As Ventenat had used Desfontaines' name, Dixon selected the Florence specimen to be the type in 2001. Indeed, rusty fig is an alternate common name; others include Illawarra fig and Port Jackson fig.

In 1806, German botanist Carl Ludwig Willdenow gave it the botanical name Ficus australis in Species Plantarum, but this is a nomen illegitimum as the species already had a validly published name. Italian botanist Guglielmo Gasparrini broke up the genus Ficus in 1844, placing the species in the genus Urostigma as U. rubiginosum. In 1862, Dutch botanist Friedrich Anton Wilhelm Miquel described Urostigma leichhardtii from material collected from Cape Cleveland, Queensland, noting it had affinities to F. rubiginosa. In 1867, he placed Urostigma as a subgenus in the reunited Ficus, which resulted in the taxon becoming Ficus leichhardtii. Miquel also described Ficus leichhardtii variety angustata from Whitsunday Island, later classified as F. shirleyana by Czech botanist Karel Domin. Queensland state botanist Frederick Manson Bailey described Ficus macrophylla variety pubescens in 1911 from Queensland, Domin later renaming it Ficus baileyana. All these taxa were found to be indistinguishable from (and hence reclassified as) F. rubiginosa by Dixon in 2001.

Joseph Maiden described variety lucida in 1902, and Bailey described variety glabrescens in 1913. Both had diagnosed their varieties on the basis of their hairlessness. Maiden described a taxon totally devoid of hair, while Bailey described his as nearly glabrous (hairless). As Bailey's description more closely matched Dixon's findings (that these variants were only partly and not completely hairless), Dixon retained Bailey's name and reclassified it as Ficus rubiginosa forma glabrescens in 2001 as it differed only in the lack of hairs on new growth from the nominate form.

The trunk is buttressed and can reach in diameter. The bark is yellow-brown.

Alternately arranged on the stems, the ovate (egg-shaped), obovate (reverse egg-shaped) or oval-shaped leaves are anywhere from long and wide, on -long petioles (stalks that join the leaves to stems). They are smooth or bear tiny rusty hairs. There are 16 to 62 pairs of lateral veins that run off the midvein at an angle of 41.5–84.0°, while distinct basal veins run off the midvein at an angle of 18.5–78.9°. Often growing in pairs, the figs are yellow initially and measure across.

Distribution and habitat

thumb|right|Lithophytic Ficus rubiginosa growing on [[Narrabeen Group|Narrabeen sandstone at Barrenjoey, New South Wales]]

Ficus rubiginosas range spans the entire eastern coastline of Australia, from the top of the Cape York Peninsula in north Queensland to the vicinity of Bega on the south coast of New South Wales. Fig seedlings often grow from cracks in stone where seeds have been lodged, in locations such as cliffs and rock faces in natural environments, F. rubiginosa has been planted widely in Malta since the early 1990s but has not been observed to fruit.

Ecology

The fruit is consumed by many bird species including the rose-crowned fruit dove (Ptilinopus regina), wompoo fruit dove (P. magnificus), wonga pigeon (Leucosarcia melanoleuca), topknot pigeon (Lopholaimus antarcticus), Pacific koel (Eudynamys orientalis), Australian king parrot (Alisterus scapularis), Australasian figbird (Sphecotheres vieilloti), green catbird (Ailuroedus crassirostris), regent bowerbird (Sericulus chrysocephalus), satin bowerbird (Ptilonorhynchus violaceus) and pied currawong (Strepera graculina), and spectacled flying fox (Pteropus conspicillatus). It is one of several plant species used as food by the endangered Coxen's fig parrot. Many fruits drop onto the ground around the tree, though others are dispersed by animals that eat them. Psyllids have almost defoliated trees in the Royal Botanic Gardens in Sydney in spring. P. imperialis has been transported to Hawaii, California, and Israel, where it has been observed to pollinate its host.

They can live to 100 years or more and have been known to resprout after bushfire, bearing fruit within three years. Their larvae are thought to feed on the larvae of the pollinator wasp. Several genera of uncommon larger wasp species enter the immature figs before other wasps and induce galls, which may impact on numbers of pollinator wasps in the fig later. An example of this is Pseudidarnes minerva,

Nematodes of the genus Schistonchus are found in the syconia (and the pollinator wasps) of many species of fig, with F. rubiginosa hosting two species. They appear to be less species-specific than wasps. S. altermacrophylla is generally associated with F. rubiginosa though it has been recorded on several other fig species.

Cultivation

thumb|right|As bonsai, [[Auburn Botanic Gardens]]

Ficus rubiginosa was first cultivated in the United Kingdom in 1789, where it is grown in glasshouses. It is useful as a shade tree in public parks and on golf courses. Not as prodigious as other figs, F. rubiginosa is suited to slightly more confined areas, such as lining car parks or suburban streets. However, surface roots can be large and intrusive and the thin bark readily damaged when struck. Tolerant of acid or alkaline soils, it is hardy to US Hardiness Zones 10B and 11, reaching high in 30 years. Planting trees apart will eventually result in a continuous canopy.<!-- cites previous 4 sentences --> The trees are of great value in providing fruit for birds and mammals, though drop large quantities of fruit and leaves, leaving a mess underfoot.

In a brief description, William Guilfoyle recorded a variegated fig from New South Wales "12–15&nbsp;ft high" in 1911 as F. rubiginosa variety variegata. A variegated form is in cultivation on Australia's east coast, It is a chimera lacking in chlorophyll in the second layer of the leaf meristem.<!-- cites previous three sentences -->

Despite the relatively large size of the leaves, it is popular for bonsai work as it is highly forgiving to work with and hard to kill; the leaves reduce readily by leaf-pruning in early summer. Described as the best tree for a beginner to work with, it is one of the most frequently used native species in Australia. Its bark remains smooth, and does not attain a rugged, aged appearance. Known as "Little Ruby", a narrow-leaved form with its origins somewhere north of Sydney is also seen in cultivation.

F. rubiginosa is also suited for use as a houseplant in low, medium or brightly lit spaces, although a variegated form requires brighter light. It has gained the Royal Horticultural Society's Award of Garden Merit. It is easily propagated by cuttings or aerial layering.

See also

  • Ficus macrophylla

Notes

References

  • Jared Bernard et&nbsp;al.: New Species Assemblages Disrupt Obligatory Mutualisms Between Figs and Their Pollinators. In: Front. Ecol. Evol., 19 November 2020. doi:10.3389/fevo.2020.564653. See also:

:*Jared Bernard: Figs show that nonnative species can invade ecosystems by forming unexpected partnerships. On: The Conversation. 19 January 2021. Also on Science<sup>alert</sup>