NYBG Steere Herbarium Definition of Gynodioecious: Sexual condition of a species that bears pistillate flowers on some plants and bisexual flowers or staminate flowers as well as pistillate flowers on other plants. The important word here is "or" rather than "and" [e.g. Fig (Ficus) & Mulberry (Morus)].

Contrary to many authors, sex determination in Ficus carica is NOT the XX/XY method suggested for mosses, cottonwoods and willows (and the method in most people and fruit flies). According to Condit (1969), the sporophyte chromosome number for most species of Ficus is 2n = 26. Storey (1977) also confirms this number for F. carica, and states that the chromosome-bearing sex-determining alleles are indistinguishable (at least by shape and size).

Sex determination in the common fig (Ficus carica) may be controlled by two pairs of alleles located on one pair of homologous chromosomes. Data from breeding experiments support this hypothesis. [From Storey, W.B. 1975. Figs (pp. 568-589). In: Advances in Fruit Breeding, Purdue University Press, West Lafayette, Indiana.]

The following table shows all the possible crosses between homozygous (GA/GA) & heterozygous (GA/ga) male caprifigs with homozygous (ga/ga) female figs. Possible types of gametes from parents are indicated within brackets [ ], and the sex and genotypic ratio of progeny are shown in blue:

Both long-style and short-style ovaries are fertile and occasionally "less-likely" seeds may develop inside the pollinated short-style ovaries of the caprifig (if there are no wasp larvae to consume the seed tissue inside). According to Rixford (1918) and Condit (1947), fertile seeds are commonly found in the mammoni crop, up to 75 seeds per syconium. According to Valdeyron and Lloyd (Evolution 33, 1979), caprifig syconia seldom contain more than 10 seeds. The seeds result from pollination by wasps from the profichi crop, and from ovaries in which the wasps failed to oviposit. A caprifig seed parent is the only way to obtain homozygous caprifig offspring (GA/GA). When crossed with female trees, homozygous caprifig pollen parents yield 100% heterozygous caprifig offspring (GA/ga).

Of all the 11 possible genotypic progeny (see above table), only two (1/4 ga/ga and 1/2 ga/ga) result in female trees. If you eliminate the "less likely" homozygous pollen parents (GA/GA) and the "less likely" caprifig seed parents (GA/GA and GA/ga), there would be a 50/50 ratio of zygotic combinations resulting in heterozygous caprifigs and homozygous female trees (1/2 GA/ga and 1/2 ga/ga). [See genotypes with asterisk in lower right box of above table.] In wild populations of the Mediterranean region, caprifig and female trees occur in similar frequencies (Valdeyron and Lloyd, 1979).

According to Storey (Recent Advances in Fruit Breeding, 1975), all commercial caprifigs probably originated from common edible fig seeds (from female (ga/ga) trees) and, therefore, are heterozygous (GA/ga). According to Condit (1920), cuttings of Smyrna figs and caprifigs were introduced into California in 1882. The fruit from these trees all dropped because of the lack of caprification. In 1890 caprifig cuttings with wasp-bearing syconia were also introduced. It is impossible to be certain if any of these caprifigs were homozygous. Naturalized female trees that have been pollinated develop syconia that are conspicuously pinkish-red inside, with numerous drupelets (endocarps) containing viable seeds.

1. The apparent increase in male caprifigs in wild (naturalized) populations (e.g. creeks and riverbeds in the Vista area of northern San Diego County) may be due (in part) to chance caprifig seed parents giving rise to more caprifig (GA/GA and GA/ga) zygotic combinations. To test this hypothesis, caprifig syconia (mammoni crop) from naturalized populations should be studied in order to determine their percentage of viable seeds. If the original naturalized figs were caprifigs (rather than female trees), and if they were the seed AND pollen parents, this would most certainly favor caprifig progeny (regardless of whether they were homozygous or heterozygous caprifig parents).

2. It might also be that some of the original or present-day caprifigs in the Vista area (northern San Diego County) are homozygous (GA/GA) and would always give rise to caprifig offspring.

3. Many of the closely-spaced caprifigs in Vista populations may have originated asexually from adventitious stems.

4. There may be selective survival factors limiting the female trees. (i.e. caprifigs may survive better in wild, naturalized locations).

5. Another plausible explanation has been suggested by Boris Igic of the UCSD Department of Biology. A study by Professor J.R. Kohn of UCSD has shown that inbreeding depression affects sex ratios (Nature 335: 431-433, 1988). Self-pollinated populations of hermaphroditic caprifigs may not suffer negative effects from inbreeding depression. They may actually survive and multiply faster than unisexual female trees. This hypothesis certainly deserves further research, particularly with respect to caprifig populations.

1. Syconium: Complex inflorescence (flower cluster) consisting of hollow, fleshy structure (peduncular tissue) lined on the inside with numerous tiny unisexual flowers. The ripe syconium is NOT a true fruit in the strict botanical sense, it is actually a fleshy, flask-shaped, modified stem lined on the inside with many tiny one-seeded fruits (drupelets). [It Is Also Called A Multiple Fruit]

2. Ficus carica has 2 sexual forms, the "male" caprifig and female tree (edible fig). The caprifig is monoecious [i.e. with separate male (staminate) flowers and separate female (pistillate) flowers. It is functionally male because it produces pollen. Edible figs contain only long-style female flowers. Since functional male trees are hermaphroditic, Ficus carica is usually considered gynodioecious rather than dioecious.

3. Short-style female flowers and male flowers are determined by a pair of dominant genes on the same chromosome [GA]; recessive alleles result in long-style female flowers and suppression of male flowers [ga]. The caprifig may be homozygous [GA/GA] or heterozygous [GA/ga], while the female tree must be homozygous recessive [ga/ga].

4. Caprifigs are native to Caria, an ancient region of Asia Minor between the Black Sea and Mediterranean Sea. This is essentially the present-day region of Turkey. The prefix capri refers to goat, and apparently caprifigs were fed to livestock. Old World gynodioecious figs belong to the Subgenus Ficus. Other fig species of tropical and subtropical regions belong to different subgenera, including many ornamental figs such as the rustyleaf fig (F. rubiginosa), Moreton Bay fig (F. macrophylla), Indian laurel fig (F. microcarpa), benjamin fig (F. benjamina), sycomore fig (F. sycomorus), Indian rubber tree (F. elastica), the Bo tree (F. religiosa) and many other species. The latter species are monoecious, with male flowers, short-style female flowers and long-style female flowers all in the same syconium. At least 1,000 different species of Ficus are known, all with their own "in house" pollinator wasp. Some fig species have more than one species of wasp. Some tropical fig trees, including F. rubiginosa, F. benjamina and F. bengalensis become "banyans" and "stranglers" in their native habitats.

5. Fig flowers have no petals and are characteristic of the Mulberry Family (Moraceae) and the closely-related Nettle Family (Urticaceae) and Marijuana Family (Cannabaceae).

1. Winged female wasp (Blastophaga psenes) enters pore (ostiole) and lays an egg (oviposits) inside each ovary of short-style female flower. She inserts her ovipositor through stylar canal into ovary of flower.

2. Wasp eggs hatch into larvae inside the ovaries, one larva per ovary. The larva feeds on the embryo sac tissue (developing endosperm) and the nucellar tissue surrounding the embryo sac, hence no seed is produced.

3. Larvae develop into adult wasps through metamorphosis in about 10-12 weeks. The males chew their way out of their ovary container and then locate female wasps still contained within ovaries of short-style female flowers.

4. Hymenopteran Orgy Inside Syconium: The male wasp chews a hole in the ovary containing a female wasp, inserts his long abdomen and inseminates the female inside. He goes from ovary to ovary, mating with females who he never sees and who never see him.

5. The female wasps emerge from their ovary containers and escape through the pore (ostiole) at the end of the syconium. The impenetrable scales that line the ostiole become passable at this crucial time of wasp exodus. Wingless males stay behind and die. Female wasps are dusted with pollen from male flowers as they leave the caprifig syconium. The anthers must mature and release pollen at precisely the right time, 3 months after the female flowers were mature and receptive. This is a classic case of protogyny in which self-pollination within the syconium does not occur.

6. Female wasps search for another receptive syconium containing receptive female flowers (with ovaries) to deposit eggs. The ostiole of the young syconium must be passable at this critical time. Soon after it becomes impervious to insect entry. Time is of the essence since the tiny female wasps only live a short time (several days-weeks?).

7. Caprifigs produce 3 crops of syconia per year: the profichi which ripen in early summer; the mammoni which ripen in fall; and the mamme which overwinter on the tree and ripen in spring. Only the ripe profichi crop shed pollen, and these are used to pollinate the smyrna-type (Calimyrna) female figs of commerce. Wasp larvae overwinter in the mamme crop. Some seeds may develop in the mammoni crop in ovaries without larvae.

1. Female trees (incl. the Smyrna-type figs such as the Calimyrna) produce 2 crops of syconia annually: a breba crop (which ripens in early summer) and a 2nd or main crop which ripens in fall. Smyrna-type figs are homozygous recessive for the caducous (early deciduous) trait [pp] and require pollination in order for the fruit to set. Note: numerous varieties of edible figs are heterozygous for the dominant persistent gene [Pp] and do not require wasp pollination. Since [P] is lethal to the egg receiving it, homozygous dominant offspring [PP] are not possible; caprifigs may be caducous [pp] or persistent [Pp].

2. Calimyrna (California-grown Smyrna-type fig) has no male flowers; therefore it must be pollinated by fig wasp with pollen from the profichi crop of caprifig. The pollen is carried to the immature 2nd or main crop during the receptive stage (early summer).

3. Bags of wasp-filled caprifigs (profichi crop) are stapled in Calimyrna trees (June in California).

4. The emerging gravid female wasps instinctively try to lay their eggs in the most convenient syconium, which in this case are the young receptive 2nd crop of the Calimyrna.

5. The styles of Calimyrna female flowers are much longer than the short-style caprifig, in fact, they are longer than the wasp's ovipositor. The female wasp is unable to lay her eggs (oviposit) in ovaries of long-style Calimyrna flowers; however, she does pollinate the flowers in her desperate attempt to oviposit. Without wasp larvae a seed develops inside each ovary, and each ovary becomes a minute one-seeded fruit (drupelet). The mature one-seeded drupelets impart a superior nutty flavor to Calimyrna figs and your fig newtons.

6. Without the fig wasp, the syconia of Calimyrna trees would not ripen and would fall off the trees. They must be pollinated in order to set fruit. The annual crop in California is worth over 2 million dollars. One disadvantage of wasp pollination is the transmission of a fruit rotting fungus ("endosepsis"). This involves the treatment of the mamme crop with a fungicide and the distribution of mamme figs among the profichi crop at the proper time in early spring. This elaborate fungus treatment plus the distribution of profichi crop to Calimyrna fig trees in June is labor intensive (and expensive).

7. There are literally hundreds of named cultivars of edible female figs with persistent syconia. Their syconia develop and set without pollination. The seedless (hollow) drupelets inside still have a hard endocarp layer and are crunchy. The term parthenocarpic is often used for these figs since they don't require pollination. Actually the term parthenocarpic only applies to the drupelets inside, which are technically the fruits developing without pollination or fertilization. Some examples of parthenocarpic fig cultivars are brown turkey, black mission, kadota, conadria, adriatic and many more.

8. In cultivated figs, parthenocarpy generally refers to the development of the ovaries of female flowers within the syconium into drupelets without fertilization. According to W.B. Storey (Advances in Fruit Breeding, 1975), there are 2 genetically determined forms of parthenocarpy: stimulative and vegetative. Stimulative parthenocarpy includes the insertion of the ovipositor down the stylar canal into the ovary of short style flowers. It can also be induced by blowing air into the syconium, or by spraying the syconium with a plant growth regulator. The mature drupelets may contain a wasp (if an egg was laid in the ovary) or it may be empty. Vegetative parthenocarpy involves the formation of drupelets without any external stimulation, and is responsible for the hollow drupelets inside common figs such as "black mission," "kadota," and "brown turkey." [Some author use the term parthenocarpy to describe the ripening of seedless fig syconia on the tree without any pollination or fertilization.]

9. I have seen reports that female cultivars may produce apomictic seeds--i.e. without pollination and subsequent fertilization. The following Russian reference indicates that apomixis occurs in Ficus; however, there are also references that question its occurrence in Ficus carica.

The Sex Life Of Figs: Palomar College Lecture by WPA A Petrified Fig Syconium From The Cretaceous Period Bogus Nonpollinator Fig Wasps With Long Ovipositors Calimyrna Fig & Its Amazing Pollinator Wasp Caprifig Fig Overwintering Mamme Crop Cauliflory In Tropical Species Of Figs (Ficus) Coevolution Of Fig & Fig Wasp: Vicarious Selection Evolution Of Dioecious Fig Species Ficus dammaropsis: A Remarkable Fig From New Guinea Fig Pith Sculpture: Microscopic Carvings From The Azores Figs Of The Holy Land (Their Role In World Religions) Gall Controversy: Do Fig Wasps Really Induce Gall Formation?      Hybrid Between Common Edible Fig & Creeping Fig Multiple Fruits Of The Mulberry Family (Moraceae) Pollination Patterns In Dioecious Figs Sex Determination & Life Cycle Of Common Fig (Ficus carica) Sexuality In Figs--Plant Sexuality & Political Correctness Strangler Figs & Banyans: Truly Remarkable Trees Summary Of Common Fig (Ficus carica) Life Cycle The Amazing Fig/Fig Wasp Relationship The Creeping Fig (Ficus pumila)--Source Of Grass Jelly Vicarious Selection In Figs (Richard Dawkin's Model) Wild Figs (Higueras) In Baja California & Gulf Islands Reference Articles Cited In The Above On-Line Pages

Fig References Armstrong, W.P. 1995. "To Be Or Not To Be A Gall." Pacific Horticulture 56: 39-45. Armstrong, W.P. 1988. "The Calimyrna Fig and Its Wasp." California Garden 79: 135-138. Armstrong, W.P. 1986. "Fig Encounters of the Hymenopteran Kind." Zoonooz 59 (7): 17-19. Armstrong, W.P. and S. Disparti. 1988. "Wild Figs and Wasps of the Californias." Environment Southwest No. 521: 7-11. Condit, I.J. 1969. Ficus: The Exotic Species. University of California Division of Agricultural Sciences. Condit, I.J. 1955. "Fig Varieties: A Monograph." Hilgardia: 11: 323-538. Condit, I.J. 1947. The Fig. Chronica Botanica Co., Waltham, Mass. Condit, I.J. 1920. "Caprifigs and Caprification." California Agriculture Experimental Station Bulletin 319: 341-377. Galil, J. 1977. "Fig Biology." Endeavour 1: 52-56. Galil, J. 1968. "An Ancient Technique for Ripening Sycomore Fruit in East-Mediterranean Countries." Economic Botany 22: 178-190. Galil, J. 1967. "Sycomore Wasps From Ancient Egyptian Tombs." Israel Journal of Entomology II: 1-10. Galil, J. and G.Neeman. 1977. "Pollen Transfer and Pollination of the Common Fig (Ficus carica L.)." New Phytol. 79: 163-171. Galil, J. and D. Eisikovitch. 1974. "Further Studies On Pollination Ecology in Ficus sycomorus. II. Pocket Filling and Emptying by Ceratosolen arabicus." Magr. New Phytol.. 73: 515-528. Janzen, D.H. 1979. "How To Be A Fig." Ann. Rev. Ecol. Syst. 10: 13-51. Janzen, D.H. 1979. "How Many Babies Do Figs Pay For Babies." Biotropica 11 (1): 48-50. Moran, R.V. 1982. "Figs and Wasps (Part I)." Environment Southwest No. 496: 10-15. Moran, R.V. 1982. "Figs and Wasps (Part II)." Environment Southwest No. 497: 13-17. Ramirez, W. 1977. "A New Classification of Ficus." Ann. Miss. Bot. Gard. 64: 296-310. Ramirez, W. 1974. "Coevolution of Ficus and Agaonidae." Annals of the Missouri Botanical Garden 61: 770-780. Ramirez, W. 1969. "Fig Wasps: Mechanism of Pollen Transfer." Science 163: 580-581. Rixford, G.P. 1918. "Smyrna Fig Culture." U.S. Department of Agriculture Bulletin No. 732: 1-48. Sisson, R.F. 1970. "The Wasp That Plays Cupid To A Fig." National Geographic Magazine 138 (5): 690-697. Storey, W.B. 1975. "Figs." In: Advances in Fruit Breeding, Purdue Univ. Press, 1975, pp. 568-589. Storey, W.B., Enderud, J.E., Saleeb, W.F., and E.M. Nauer. 1977. The Fig. Jurupa Mountains Cultural Center, Riverside, California. Valdeyron, G. and D.G. Lloyd. 1979. "Sex Differences and Flowering Phenology in the Common Fig, Ficus carica L." Evolution 33 (2): 673-685. Wiebes, J.T. 1979. "Co-evolution of Figs and Their Insect Pollinators." Ann. Rev. Ecol. Syst. 10: 1-12.

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