Ficus


Ficus is a genus of about 850 species of woody trees, shrubs, vines, epiphytes and hemiepiphytes 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 common fig is a temperate species native to southwest Asia and the Mediterranean region, 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 considerable cultural importance throughout the tropics, both as objects of worship and for their many practical uses.

Description

Ficus is a pantropical 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. Fig species are characterized by their unique inflorescence and distinctive pollination syndrome, which uses wasp species belonging to the family Agaonidae for pollination.
The specific identification of many of the species can be difficult, but figs as a group are relatively easy to recognize. 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, known as fig wasps that enter via ostiole these subclosed inflorescences to both pollinate and lay their own eggs, has been a constant source of inspiration and wonder to biologists. Finally, three vegetative traits together are unique to figs. All figs possess a white to yellowish 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 "triveined".
No unambiguous older fossils of Ficus are known. However, current molecular clock estimates indicate that Ficus is a relatively ancient genus being at least 60 million years old, 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, a small, temperate deciduous tree whose fingered fig leaf is well known in art and iconography; the weeping fig, a hemiepiphyte with thin, tough leaves on pendulous stalks adapted to its rain forest habitat; the rough-leaved sandpaper figs from Australia; and the creeping fig, 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, Ficus commonly is the most species-rich plant genus in a particular forest. In Asia, as many as 70 or more species can co-exist. Ficus species richness declines with an increase in latitude in both hemispheres.

Ecology and uses

Figs are keystone species in many tropical forest ecosystems. Their fruit are a key resource for some frugivores including fruit bats, and primates including: capuchin monkeys, langurs, gibbons and mangabeys. They are even more important for birds such as Asian barbets, pigeons, hornbills, fig-parrots and bulbuls, which may almost entirely subsist on figs when these are in plenty. Many Lepidoptera caterpillars feed on fig leaves, for example several Euploea species, the plain tiger, the giant swallowtail, the brown awl, and Chrysodeixis eriosoma, Choreutidae and Copromorphidae moths. The citrus long-horned beetle, 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 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.
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 are traditionally used in Mesoamerica to produce papel amate. Mutuba is used to produce barkcloth in Uganda. Pou leaves' shape inspired one of the standard kbach rachana, decorative elements in Cambodian architecture. Indian banyan and the Indian rubber plant, as well as other species, have use in herbalism.
Figs have figured prominently in some human cultures. There is evidence that figs, specifically the common fig and sycamore fig, 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 BCE were found in the early Neolithic village Gilgal I. These were a parthenogenetic type and thus apparently an early cultivar. This find predates the first known cultivation of grain in the Middle East by many hundreds of years.
The 1889 book 'The Useful Native Plants of Australia’ records that Ficus aspera had the common names "Rough-leaved Fig", "Purple Fig" and "White Fig" and that Indigenous Australians of the Rockhampton region referred to them as "Noomaie" and in Cleveland Bay "Balemo". It also states that the fruit which is black can be eaten.

Fig fruit and reproduction system

Many fig species are grown for their fruits, though only Ficus carica is cultivated to any extent for this purpose. A fig "fruit" is a type of multiple fruit known as a syconium, derived from an arrangement of many small flowers on an inverted, nearly closed receptacle. The many small flowers are unseen unless the fig is cut open.
The fruit typically has a bulbous shape with a small opening 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 could not 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 only one of the many tiny matured, seed-bearing gynoecia found inside one fig – if you cut open a fresh fig, individual fruit will appear as fleshy "threads", each bearing a single seed inside. The genus Dorstenia, also in the fig family, exhibits similar tiny flowers arranged on a receptacle but in this case the receptacle is a more or less flat, open surface.
Fig plants can be monoecious or gynodioecious. Nearly half of fig species are gynodioecious, and therefore have some plants with inflorescences with long styled pistillate flowers, and other plants with staminate flowers mixed with short styled pistillate flowers. 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.
All the native fig trees of the American continent are hermaphrodites, as well as species like Indian banyan, weeping fig, Indian rubber plant, fiddle-leaved fig, Moreton Bay fig, Chinese banyan, sacred fig and sycamore fig. The common fig is a gynodioecious plant, as well as lofty fig or clown fig, Roxburgh fig, mistletoe fig, F. pseudopalma, creeping fig and related species. The hermaphrodite common figs are called "inedible figs" or "caprifigs"; in traditional culture in the Mediterranean region they were considered food for goats. 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. Caprifigs have three crops per year; common figs have two. The first crop is larger and more juicy, and is usually eaten fresh. In cold climates the breba crop is often destroyed by spring frosts. Some parthenocarpic cultivars of common figs do not require pollination at all, and will produce a crop of figs in the absence of caprifigs or fig wasps.
Depending on the species, each fruit can contain hundreds or even thousand of seeds. Figs can be propagated by seeds, cuttings, air-layering or grafting. However, as with any plant, figs grown from seed are not necessarily genetically identical to the parent and are only propagated this way for breeding purposes.

Phytochemicals

Fig fruits, especially the exocarp and seeds, contain monosaccharide sugars and mixed phytochemicals, such as flavonoids, gallic acid, chlorogenic acid, rutin, and epicatechins, the contents of which are higher in dark figs compared to those in light-colored varieties. Ripe fruits contain higher amounts of polyphenols and sugar than unripe fruits, and drying generally increases the contents of these constituents per unit of weight.

Mutualism with the pollinating fig wasps

Each species of fig is pollinated by one or a few specialised wasp species, 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 and can become invasive species. This is an example of mutualism, in which each organism 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. Additionally, recent genetic and molecular dating analyses have shown a very close correspondence in the character evolution and speciation phylogenies of these two clades.
According to meta-analysis of molecular data for 119 fig species 35% have multiple pollinator wasp species. The real proportion is higher because not all wasp species were detected. On the other hand, species of wasps pollinate multiple host fig species. Molecular techniques, like microsatellite markers and mitochondrial sequence analysis, allowed a discovery of multiple genetically distinct, cryptic wasp species. Not all these cryptic species are sister taxa and thus must have experienced a host fig shift at some point. These cryptic species lacked evidence of genetic introgression or backcrosses indicating limited fitness for hybrids and effective reproductive isolation and speciation.
The existence of cryptic species suggests that neither the number of symbionts nor their evolutionary relationships are necessarily fixed ecologically. While the morphological characteristics that facilitate the fig-wasp mutualisms are likely to be shared more fully in closer relatives, the absence of unique pairings would make it impossible to do a one-to-one tree comparison and difficult to determine cospeciation.

Systematics

With 800 species, Ficus is by far the largest genus in the Moraceae, and is one of the largest genera of flowering plants currently described. The species currently classified within Ficus were originally split into several genera in the mid-1800s, providing the basis for a subgeneric classification when reunited into one genus in 1867. This classification put functionally dioecious species into four subgenera based on floral characters. In 1965, E. J. H. Corner reorganized the genus on the basis of breeding system, uniting these four dioecious subgenera into a single dioecious subgenus Ficus. Monoecious figs were classified within the subgenera Urostigma, Pharmacosycea and Sycomorus.
This traditional classification has been called into question by recent phylogenetic studies employing genetic methods to investigate the relationships between representative members of the various sections of each subgenus. Of Corner's original subgeneric divisions of the genus, only Sycomorus is supported as monophyletic in the majority of phylogenetic studies. Notably, there is no clear split between dioecious and monoecious lineages. One of the two sections of Pharmacosycea, a monoecious group, form a monophyletic clade basal to the rest of the genus, which includes the other section of Pharmacosycea, the rest of the monoecious species, and all of the dioecious species. These remaining species are divided into two main monophyletic lineages. One consists of all sections of Urostigma except for section Urostigma s. s.. The other includes section Urostigma s. s., subgenus Sycomorus, and the species of subgenus Ficus, though the relationships of the sections of these groups to one another are not well resolved.

Selected species

Subgenus ''Ficus''

The following species are typically spreading or climbing lianas:
Numerous species of fig are found in cultivation in domestic and office environments, including:
Fig trees have profoundly influenced culture through several religious traditions. Among the more famous species are the sacred fig tree and other banyan figs such as 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 BCE. The common fig is one of two significant trees in Islam, and there is a sura in Quran named "The Fig" or At-Tin. In Asia, figs are important in Buddhism and Hinduism. In Jainism, the consumption of any fruit belonging to this genus is prohibited. The Buddha is traditionally held to have found bodhi while meditating for 49 days under a sacred fig. The same species was Ashvattha, 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 is Ficus virens. According to the Kikuyu people, sacrifices to Ngai were performed under a sycomore tree and if one was not available, a fig tree would be used. 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 one of the traditional crops of Israel, and is included in the list of food found in the Promised Land, according to the Torah. Jesus cursed a fig tree for bearing no fruit. The fig tree was sacred in ancient Cyprus, where it was a symbol of fertility.

List of famous fig trees

General references