Ficus

Fig trees
Sycamore Fig, Ficus sycomorus
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Rosales
Family:	Moraceae
Tribe:	Ficeae[1] Gaudich.
Genus:	Ficus L.
Species
About 800, see text

Ficus (pronounced /ˈfaɪkəs/)^[2] is a genus of about 850 species of woody trees, shrubs, vines, epiphytes, and hemiepiphyte in the family Moraceae. Collectively known as fig trees or figs, they are native throughout the tropics with a few species extending into the semi-warm temperate zone. The so-called Common Fig (F. carica) is a temperate species from the Middle East and eastern Europe (mostly Ukraine), which has been widely cultivated from ancient times for its fruit, also referred to as figs. The fruit of most other species are also edible though they are usually of only local economic importance or eaten as bushfood. However, they are extremely important food resources for wildlife. Figs are also of paramount cultural importance throughout the tropics, both as objects of worship and for their many practical uses.

Description

A Ficus carica

Ficus is a pan-tropical genus of trees, shrubs and vines occupying a wide variety of ecological niches; most are evergreen, but some deciduous species are endemic to areas outside of the tropics and to higher elevations.^[3] Fig species are characterized by their unique inflorescence and distinctive pollination syndrome, which utilizes wasp species belonging to the Agaonidae family for pollination.

The specific identification of many of the species can be difficult, but figs as a group are relatively easy to recognize.^[4] Many have aerial roots and a distinctive shape or habit, and their fruits distinguish them from other plants. The fig fruit is an enclosed inflorescence, sometimes referred to as a syconium, an urn-like structure lined on the inside with the fig's tiny flowers. The unique fig pollination system, involving tiny, highly specific wasps, know as fig wasps that enter these closed inflorescences to both pollinate and lay their own eggs, has been a constant source of inspiration and wonder to biologists.^[5] Finally, there are three vegetative traits that together are unique to figs. All figs possess a white to yellowish sap (latex), some in copious quantities; the twig has paired stipules or a circular stipule scar if the stipules have fallen off; and the lateral veins at the base of the leaf are steep, forming a tighter angle with the midrib than the other lateral veins, a feature referred to as a "tri-veined".

Unfortunately, there are no unambiguous older fossils of Ficus. However, current molecular clock estimates indicate that Ficus is a relatively ancient genus being at least 60 million years old,^[5] and possibly as old as 80 million years. The main radiation of extant species, however, may have taken place more recently, between 20 and 40 million years ago.

Some better known species that represent the diversity of the genus include the Common Fig which is a small temperate deciduous tree whose fingered fig leaf is well-known in art and iconography; the Weeping Fig (F. benjamina) a hemi-epiphyte with thin tough leaves on pendulous stalks adapted to its rain forest habitat; the rough-leaved sandpaper figs from Australia; the Creeping Fig (F. pumila), a vine whose small, hard leaves form a dense carpet of foliage over rocks or garden walls. Moreover, figs with different plant habits have undergone adaptive radiation in different biogeographic regions, leading to very high levels of alpha diversity. In the tropics, it is quite common to find that Ficus is the most species-rich plant genus in a particular forest. In Asia as many as 70 or more species can co-exist.^[6]

Ecology and uses

Coppersmith Barbet feeding on White Fig (Ficus virens) fruit

Figs are keystone species in many rainforest ecosystems. Their fruit are a key resource for some frugivores including fruit bats, capuchin monkeys, langurs and mangabeys. They are even more important for some birds. Asian barbets, pigeons, hornbills, fig-parrots and bulbuls are examples of taxa that may almost entirely subsist on figs when these are in plenty. Many Lepidoptera caterpillars feed on fig leaves, for example several Euploea species (Crow butterflies), the Plain Tiger (Danaus chrysippus), the Giant Swallowtail (Papilio cresphontes), the Brown Awl (Badamia exclamationis), and Chrysodeixis eriosoma, Choreutidae and Copromorphidae moths. The Citrus long-horned beetle (Anoplophora chinensis), for example, has larvae that feed on wood, including that of fig trees; it can become a pest in fig plantations. Similarly, the Sweet Potato Whitefly (Bemisia tabaci) is frequently found as a pest on figs grown as potted plants and is spread through the export of these plants to other localities. For a list of other diseases common to fig trees, see List of foliage plant diseases (Moraceae).

Leaves of the Sacred Fig (F. religiosa)

The wood of fig trees is often soft and the latex precludes its use for many purposes. It was used to make mummy caskets in Ancient Egypt. Certain fig species (mainly F. cotinifolia, F. insipida and F. padifolia) are traditionally used in Mesoamerica to produce papel amate (Nahuatl: āmatl). Mutuba (F. natalensis) is used to produce barkcloth in Uganda. Pou (F. religiosa) leaves' shape inspired one of the standard kbach rachana, decorative elements in Cambodian architecture. Weeping Fig (F. benjamina) and Indian Rubber Plant (F. elastica) are identified as powerful air-cleaning plants in the NASA Clean Air Study. Indian Banyan (F. bengalensis) and the Indian Rubber Plant, as well as other species, have use in herbalism. The latter is known to be a hyperaccumulator of benzene and methane, and urban or potted plants should be considered toxic for that reason.

A page from the Mexican Huexotzinco Codex, painted on āmatl

Figs have figured prominently in some human cultures. There is evidence that figs, specifically the Common Fig (F. carica) and Sycamore Fig (F. sycomorus), were among the first — if not the very first — plant species that were deliberately bred for agriculture in the Middle East, starting more than 11,000 years ago. Nine subfossil F. carica figs dated to about 9400–9200 BC were found in the early Neolithic village Gilgal I (in the Jordan Valley, 13 km north of Jericho). These were a parthenocarpic type and thus apparently an early cultivar. This find predates the cultivation of grain in the Middle East by many hundreds of years.^[7]

Cultural and spiritual significance

Fig trees have profoundly influenced culture through several religious traditions. Among the more famous species are the Sacred Fig tree (Peepul, Bodhi, Bo, or Po, Ficus religiosa) and the Banyan Fig (Ficus benghalensis). The oldest living plant of known planting date is a Ficus religiosa tree known as the Sri Maha Bodhi planted in the temple at Anuradhapura, Sri Lanka by King Tissa in 288 BC. It is one of the two sacred trees of Islam, and there is a sura in Quran named "The Fig" or At-Tin (سوره تین), and in East Asia, figs are pivotal in Buddhism, Hinduism and Jainism. Siddhārtha Gautama, the Supreme Buddha, is traditionally held to have found bodhi (enlightenment) while meditating under a Sacred Fig (F. religiosa). The same species was Ashvastha, the "world tree" of Hinduism. The Plaksa Pra-sravana was said to be a fig tree between the roots of which the Sarasvati River sprang forth; it is usually held to be a Sacred Fig but more probably seems to be a Wavy-leaved Fig (F. infectoria). The Common Fig tree is cited in the Bible, where in Genesis 3:7, Adam and Eve cover their nakedness with fig leaves. The fig fruit is also included in the list of food found in the Promised Land, according to the Torah (Deut. 8). Other important plants reported included: wheat, barley, grapes, pomegranates, olives, and dates (representing the honey). Jesus cursed a fig tree for bearing no fruit (Mark 11:12-14). The fig tree was sacred in ancient Cyprus where it was a symbol of fertility.

Fig pollination and fig fruit

A Common Fig syconium (fruit)

Many are grown for their fruits, though only Ficus carica is cultivated to any extent for this purpose. Furthermore, the fig fruits, important as both food and traditional medicine, contain laxative substances, flavonoids, sugars, vitamins A and C, acids and enzymes. However, figs are skin allergens, and the sap is a serious eye irritant. The fig is commonly thought of as fruit, but it is properly the flower of the fig tree. It is in fact a false fruit or multiple fruit, in which the flowers and seeds grow together to form a single mass. The genus Dorstenia, also in the figs family (Moraceae), exhibits similar tiny flowers arranged on a receptacle but in this case the receptacle is a more or less flat, open surface.

Depending on the species, each fruit can contain up to several hundred to several thousand seeds.^[8]

Inside of a ripe brown Turkish fig

A fig "fruit" is derived from a specially adapted type of inflorescence (an arrangement of multiple flowers). In this case, it is an involuted, nearly closed receptacle with many small flowers arranged on the inner surface. Thus the actual flowers of the fig are unseen unless the fig is cut open. In Chinese the fig is called wú huā guǒ (simplified Chinese: 无花果; traditional Chinese: 無花果), "fruit without flower"^[9]. In Bengali, where the Common Fig is called dumur, it is referenced in a proverb: tumi jeno dumurer phool hoe gele ("You have become [invisible like] the dumur flower").

The syconium often has a bulbous shape with a small opening (the ostiole) at the outward end that allows access to pollinators. The flowers are pollinated by very small wasps that crawl through the opening in search of a suitable place to lay eggs. Without this pollinator service fig trees cannot reproduce by seed. In turn, the flowers provide a safe haven and nourishment for the next generation of wasps. This accounts for the frequent presence of wasp larvae in the fruit, and has led to a coevolutionary relationship. Technically, a fig fruit proper would be one of the many tiny mature, seed-bearing flowers found inside one fig — if you cut open a fresh fig, the flowers will appear as fleshy "threads", each bearing a single seed inside.

Fig plants can be monoecious (hermaphrodite) or gynodioecious (hermaphrodite and female).^[10] Nearly half of fig species are gynodioecious, and have plants with inflorescences (syconium) with long styled pistillate flowers, or have plants with staminate flowers mixed with short styled pistillate flowers.^[11] The long flowers styles tend to prevent wasps from laying their eggs within the ovules, while the short styled flowers are accessible for egg laying.^[12]

All the native fig trees of the American continent are hermaphrodites, as well as species like Indian Banyan (F. benghalensis), Weeping Fig (F. benjamina), Indian Rubber Plant (F. elastica), Fiddle-leaved Fig (F. lyrata), Moreton Bay Fig (F. macrophylla), Chinese Banyan (F. microcarpa), Sacred Fig (F. religiosa) and Sycamore Fig (F. sycomorus).^[13]

On the other hand the Common Fig (Ficus carica) is a gynodioecious plant, as well as F. aspera, Roxburgh Fig (F. auriculata), Mistletoe Fig (F. deltoidea), F. pseudopalma, Creeping Fig (F. pumila) and related species.

The hermaphrodite Common Figs are called "inedible figs" or caprifigs; in traditional culture in the Mediterranean region (including the San Francisco Bay Area), they were considered food for goats (Capra aegagrus). In the female fig trees, the male flower parts fail to develop; they produce the "edible figs". Fig wasps grow in Common Fig caprifigs but not in the female syconiums because the female flower is too long for the wasp to successfully lay her eggs in them. Nonetheless, the wasp pollinates the flower with pollen from the caprifig it grew up in. When the wasp dies, it is broken down by enzymes inside the fig. Fig wasps are not known to transmit any diseases harmful to humans.

When a caprifig ripens, another caprifig must be ready to be pollinated. In temperate climes, wasps hibernate in figs, and there are distinct crops. Common Fig caprifigs have three crops per year; edible figs have two. The first (breba)^[14] produces small fruits called olynth. Some parthenocarpic cultivars of Common Figs do not require pollination at all, and will produce a crop of figs (albeit sterile) in the absence of caprifigs or fig wasps.

There is typically only one species of wasp capable of fertilizing the flowers of each species of fig, and therefore plantings of fig species outside of their native range results in effectively sterile individuals. For example, in Hawaii, some 60 species of figs have been introduced, but only four of the wasps that fertilize them have been introduced, so only four species of figs produce viable seeds there. This is an example of mutualism, in which each organism (fig plant and fig wasp) benefit each other, in this case reproductively.

The intimate association between fig species and their wasp pollinators, along with the high incidence of a one-to-one plant-pollinator ratio have long led scientists to believe that figs and wasps are a clear example of coevolution. Morphological and reproductive behavior evidence, such as the correspondence between fig and wasp larvae maturation rates, have been cited as support for this hypothesis for many years^[15]. Additionally, recent genetic and molecular dating analyses have shown a very close correspondence in the character evolution and speciation phylogenies of these two clades.^[5]

Selected species

Gallery

Ficus abutilifolia.   Ficus altissima.   Figs of a variegated Ficus aspera.   Mistletoe Fig, Ficus deltoidea.   Ficus erecta.   Ficus ilicina.   Ficus lutea.   Ficus mollis.   Ficus mauritiana.   Ficus pseudopalma.   Ficus variegata in Mong Kok, Hong Kong.   Giant Ficus obliqua, Border Ranges National Park, Australia.   Ficus auriculata.   Fruits on the trunk of a Ficus in India.   Fruits of Clown Fig tree at Flamingo Gardens, Davie, Florida.   Trunk of Sacred Fig at Flamingo Gardens.   Fruits of Sacred Fig at Flamingo Gardens.

List of famous fig trees

• Ashvastha — the world tree of Hinduism, held to be a supernatural F. religiosa
• Bodhi tree — a F. religiosa
• Charybdis Fig Tree of the Odyssey, presumably a F. carica
• Curtain Fig Tree — a F. virens
• Ficus Ruminalis — a F. carica
• Plaksa — another supernatural fig in Hinduism; usually identified as F. religiosa but probably F. infectoria
• Santa Barbara's Moreton Bay Fig Tree — a F. macrophylla
• Sri Maha Bodhi — another F. religiosa. Planted in 288 BC, the oldest human-planted tree on record
• The Great Banyan — a F. benghalensis, a clonal colony and once the largest organism known
• Vidurashwatha — "Vidura's Sacred Fig tree", a village in India named after a famous F. religiosa that until recently stood there

See also