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   Sex Life Of Figs: Coevolution Of A Tree & Minute Wasp (Part 2)     Part 1       Part 2       Cystoliths  
© W.P. Armstrong Updated 6 June 2024

Table Of Contents For Part 2

    1.   Fig Species In Edwin Frances Hunter Arboretum & Campus
    2.   The Unusual Ficus dammaropsis Of New Guinea In Arboretum
    3.   Additional Figs In Edwin Frances Hunter Arboretum & Campus
    3B.  "Glabrous" Form Of Rustyleaf Fig In Palomar College Arboretum
    4.   'Vista Caprifig' At Wayne's Word In Twin Oaks Valley, San Diego
    5.   Black Fig Fly Causes Premature Syconia Drop & Severe Crop Loss
    6.   Ficus microcarpa Mature Syconia, Fig Wasps & Bud Scale Stipules
    6B.  A Large Ficus microcarpa On The Campus Of Palomar College
    7.   Ficus rubiginosa Rustyleaf Fig Syconium and Bud Scale Stipules

1. Fig Species In The Edwin Frances Hunter Arboretum

The Palomar College Arboretum has over 20 species of figs (Ficus), including the Palmer fig (F. palmeri) native to Baja California, rock fig (F. petiolaris) native to mainland Mexico, the sacred Bo tree (F. religiosa) native to India, the sycamore fig (F. sycomorus) cited in the Bible, and the large-leaved Roxburgh fig (F. auriculata) native to the Himalayas. We have several large specimen trees, including the Moreton Bay fig (F. macrophylla) native to Australia and the Mysore fig (F. mysorensis) native to southern India. Some of the figs in our collection are 'stranglers' in their native habitat. They completely wrap around a host tree like a giant botanical boa constrictor, eventually shading out and replacing the original tree. Other trees are banyans in their native habitats, with numerous prop roots hanging down from the spreading limbs.

  Strangler Figs and Banyans: Truly Remarkable Trees   
See The On-Line Plant List For The Mulberry Family 

The fig story is very complex and literally thousands of peer-reviewed articles have been published. For more information on the fig and fig wasp, please refer to the Wayne's Word Fig Index page at https://www2.palomar.edu/users/warmstrong/figlinks.htm.

The sacred bo tree (Ficus religiosa) native to India and southeast Asia. Right: The skeletonized leaf of a bo tree with a lovely painted scene. The bo tree is sacred in the Buddhist and Hindu religions. The leaf was sent to this author from a former student traveling in India.

Massive trunk and surface roots of a Moreton Bay fig (Ficus macrophylla) in the Palomar College Arboretum. In its native Australia it is a strangler fig.

This is how large a Moreton Bay fig (Ficus macrophylla) can get in just over one century in southern California! It was planted in Glendora, California in the late 1800s. The enormous surface roots cover 1200 square feet (40 square meters). In its native habitat of eastern Australia, this species becomes a gigantic strangler.

Mysore fig (Ficus mysorensis), a large fig tree native to the state of Mysore in southern India. Leaves of the Mysore fig have an abruptly acuminate (pointed) apex that is sometimes called a "drip tip."

The orange syconia of Ficus mysorensis in the Palomar College Arboretum. This is a strangler fig native to the state of Mysore in southern India. The colorful syconia are lined on the inside with minute male and female flowers. In its native habitat, the female flowers are pollinated by tiny symbiotic wasps.

Leaves from four large fig trees in the Palomar College Arboretum. They have the typical venation and shape of Ficus mysorensis, including an abruptly acuminate apex. They do not match the venation, shape and blunt apex of Indian banyan leaves (F. benghalensis). Right: Ficus bengalensis. Illustration modified from Ficus: The Exotic Species by I.J. Condit, Univ. of California Press, 1969.

  See Leaf Terminology Part II  

The large orange syconia and abruptly acuminate leaf apex (red arrow) of this fig at the top of the hill in the Palomar College Arboretum is typical of Ficus mysorensis. Leaves of the Indian banyan (F. benghalensis) typically have a blunt apex and a different vein pattern. See next image.

The leaf shape and venation of Indian banyan (F. benghalensis) is quite distinct.

Striking leaves of the variegated cultivar of the Indian banyan (F. benghalensis 'variegata'). A small specimen of this tree grows at the top of the hill overlooking the Arboretum.

Strangler Figs and Banyans
  Bark Cloth From Paper Mulberry  

Left: Narrowleaf fig (F. binnendijkii 'alii'), an unusual species native to Java and the Philippines. Right: The large-leaved Roxburgh fig (F. auriculata) native to the Himalayas.

Two closely-related species of Ficus native to Mexico: Ficus petiolaris from the mainland (left) and F. palmeri endemic to the Baja California peninsula (right). Baja California began to separate from mainland Mexico about 10 million years ago. This resulted in isolation and speciation on the Baja Peninsula, and undoubtedly explains some of the differences between present-day F. palmeri and the similar mainland F. petiolaris. Another lesser known Baja California endemic is F. brandegeei that grows on vertical rock walls of the Sierra de la Giganta west of Loreto. It is very similar to F. palmeri, except it leaves, branchlets and syconia are glabrous. Richard Felger and Charles Lowe (1970) have changed the taxonomic status of these figs to subspecies of F. petolaris. According to E.M. Piedra-Malagón, V. Sosa, and G. Ibarra-Manríquez (Systematic Botany 36(1): 80-87, 2011), F. petiolaris, the first name in this complex, is the only species that should be recognized, with a wide distribution from Sonora to Oaxaxa and in Baja California.

  See Ficus palmeri in Baja California  

Syconia of Ficus sycomorus. These structures are NOT galls. They are fleshy structures lined on the inside with hundreds of tiny male and female flowers. They are essentially an inside-out flower cluster (inflorescence). The syconium in center has been sectioned to show the numerous flowers on the inside. Although this species of fig has its own pollinator wasp (Ceratosolen arabicus), there is also a nonpollinator wasp Sycophaga sycomori that lays eggs inside the short-style flowers. Oviposition and the presence of nonpollinator wasp larvae not only initiate the development of endosperm tissue, but also the enlargement and ripening of the syconium containing wasp-bearing drupelets without pollination. Since the normal course of events is to abort unpollinated syconia, the entire syconium could be viewed as a gall occupied by nonpollinator wasps.

2. Another Unusual Fig Native To New Guinea

Ficus dammaropsis, an unusual fig from the rain forests of New Guinea, has large leaves up to two feet (0.6 m) wide and three feet (0.9 m) long. The leaves are used by indigenous people of New Guinea for wrapping pork and for lining their cooking ovens. The bark is used in making string and head coverings. A baseball-sized syconium (multiple fruit) is also shown in the right photo. According to A.B. Graf (Tropica, 1978), the syconia are harvested by native Melanesians of Kikiepa, New Guinea. Because this species is so unusual among figs, it was once classified as a separate genus and species Dammaropsis kingiana.

Ficus dammaropsis from the rain forests of New Guinea. It was once placed in the genus Dammaropsis, but its multiple fruit is clearly a large syconium typical of the genus Ficus.

  Ficus dammaropsis: A Remarkable Fig From New Guinea   

3. Other Fig Species In The Edwin Frances Hunter Arboretum

  See Ficus palmeri in Baja California  

A. Ficus virens from New South Wales, Australia. B. Originally identified as F. superba, this could be another F. virens. Both of these specimens are small trees at the top of the hill overlooking the Arboretum. They develop as stranglers in their native habitats.

Ficus virens from the campus of UC Riverside.

Ficus amadiensis native to tropical east Africa. It was previously identified as F. natalensis. Note the aerial prop root developing from the main trunk.

A. This tree was originally identified as a rustyleaf fig (Ficus rubiginosa); however, the leaves do not have the characteristic brownish-red underside of typical F. rubiginosa in San Diego County. B. Ficus ingens native to South Africa.

3B. "Glabrous" Rustyleaf Fig (Ficus rubiginosa) in Palomar College Arboretum
Note: Technically Not Glabrous: Minute hairs may be visible on underside of leaves (abaxial surface), especially on veins, with 10x magnification (hand lens or dissecting microscope).

Although underside (abaxial surface) of leaf appears glabrous to naked eye, the veins are covered with minute hairs (trichomes). The general term for plant part covered with trichomes is pubescent. The microscopic white dots are calcareous deposits caled cystolths within enlarged epidermal cells called lithocysts.

Following Image: Pubescent Rustyleaf Fig in Twin Oaks Valley

The brown hairs (trichomes) on underside of rustyleaf fig leaf (Ficus rubiginosa) in Twin Oaks Valley produce unique rust color of leaf surface; however, the color is variable depending on density of hairs. There are also numerous microscopic lithocysts partially concealed by the brown hairs..

  Cystoliths On Fig Leaves  

Sandpaper fig (cf. Ficus coronata) native to Queensland, Australia. Short, stiff hairs give the upper sides of leaves a rough, sandpaper texture. The botanical name that describes this type of pubescence is "scabrous."

  See Wayne's Word Leaf Shapes, Margins & Surfaces  
Strangler Figs & Banyans: Truly Remarkable Trees

4. 'Vista Caprifig' at Wayne's Word Headquarters in Twin Oaks Valley

5. Black Fig Fly Lays Eggs In Ostioles Causing Premature Syconia Drop

The black fig fly (Silba adipata): Insect Order Diptera, Family Lonchaeidae. Female fly deposits eggs through ostioles of syconia on caprifigs & female trees. Maggots (larvae) damage syconia interior resulting in premature syconia drop. This Mediterranean-Middle East fly can cause serious crop losses. It has reached California, including San Diego County.

Female black fig fly ovipositing in ostiole of 'Calimyrna' syconium.

6. Ficus microcarpa Syconia, Wasps & Bud Scale Stipules

Indian laurel fig (Ficus microcarpa) and its symbiotic wasp (Eupristina verticillata) from syconia on Palomar College campus. One wasp is squeezing through an exit tunnel cut by male wasps (white arrow).
Note: With the exception of Ficus elastica, most species of figs have a pair of protective bud scales. These are technically referred to as "bud scale stipules." The bud scales are shed soon after the new branch emerges and elongates. Stipules also include the bract-like or woody outgrowths at the base of leaves. In fact, in swollen thorn acacias of Central America, the pairs of "thorns" are actually stipules occupied by symbiotic ants. See following image of mature bud scale stipules in F. microcarpa.

  Swollen Thorn Acacia On Evolution Page  

Indian laurel fig (Ficus microcarpa) is a popular indoor container plant also used for bonsai. It can also develop into a large outdoor tree with massive trunk, such as following tree on campus of Palomar College. Some of these remarkable growth variations may be attributed to cultivars, such as 'Golden Gate' grown primarily for bonsai.

7. Ficus rubiginosa Bud Scale Stipules

This tree in my Twin Oaks Valley neighborhood, San Diego County, definitely has the symbiotic fig wasp Pleistodontes imperialis.
F. rubiginosa On This Page Without Rust-Colored Leaves
  F. rubiginosa Symbiotic Fig Wasp (Pleistodontes imperialis)