Reproductive coevolution in Ficus

Last updated

The genus Ficus is composed of 800 species of vines, shrubs, and trees, defined by their syconiums, the fruit-like vessels that either hold female flowers or pollen on the inside. In addition to being cultivated by humans for thousands of years, Ficus is also known for their reproductive mutualism with the fig wasp. [1]

Contents

A common fig exposing its many tiny matured, seed-bearing gynoecia. These are pollinated by the fig wasp, Blastophaga psenes. In the cultivated fig, there are also asexual mutants. Ficus plant.jpg
A common fig exposing its many tiny matured, seed-bearing gynoecia. These are pollinated by the fig wasp, Blastophaga psenes . In the cultivated fig, there are also asexual mutants.

Fig trees either produce hermaphrodite fruit (caprifigs) or female figs; only the female figs are palatable to humans. In exchange for a safe place for their eggs and larvae, fig wasps help pollinate the ficus by crawling inside the tiny hole in the apex of the fig, called the ostiole, without knowing whether they crawled into a caprifig or a fig. If the female wasp crawls into the caprifig, she can successfully lay her eggs and die. The males hatch first, mate with the females, dig tunnels out of the caprifig, and die. The females, now covered in fig pollen from the caprifig, fly out to begin the cycle again. If the female wasp crawls into a female fig, she will not be able to successfully lay her eggs despite pollinating the fig with pollen from the caprifig she hatched in. The fig will absorb her body and her eggs as the fruit develops. [2]

History

Aristotle noted in Historia animalium that wild figs contain psenes that begin as grubs, but whose skin splits allowing the psen to fly out. The psen flies into a cultivated fig, and stops it from falling. He noted further that Greek farmers planted wild figs next to cultivated figs, and tied wild fig fruits on to the cultivated trees. [3]

Mechanisms and outcomes

Overall, the coevolution of Ficus and wasps features Ficus being very specific as a host, combined with the tendency of the wasp species to frequent plant species different from that of their specific Ficus host.

Ficus domination in mutualism

Ficus typically control the reproductive mutualism with fig wasps by being highly selective in their choice of pollinator. [4] This high host specificity is proven by the low pollinator sharing ratios found in fig pollinators, especially in the wasp genera Ceratosolen and Kradibia . [5] Contributing to the evolution of Ficus, pollinator specificity in Ficus is a pre-zygotic mechanism of reproductive isolation, in other words, the fig can control which pollen it gets by physically controlling which wasps pollinate it. Morphologically, one way the fig can specify the pollinator it wants includes the diameters of ostioles compared to the head widths of the respective wasp species. While the fig species F. wassa have a diameter of 1.0-1.5 mm, its pollinator K. wassae had an average head width of 0.58 mm. [5]

Pollinator sharing

Mutualism between figs and their wasps is not always strictly one on one: in Neotropical monoecious Ficus (among a few examples with the genus Ficus alone), different plant species may share the same species of pollinator wasp, and in a number of Ficus species, a few species of wasps are able to pollinate the figs (to various degrees) of a single fig species. [5]

Clearly, sharing of pollinators could allow interspecific hybrids to occur more easily, which would threaten the integrity of specific species of both plant or wasp, or allow new species to develop from the hybrids. [5] Hybridization does not appear to have played a major role in the evolution of fig and pollinator lineages, based on a maximum likelihood test on 1991 dat. [6] In Panama, pollinator and host sharing have led to hybridization in figs, but not in their wasps. [7]

Sharing of pollinators has implications for the evolutionary history of the fig-wasp mutualism, because this means specific wasps may have switched hosts, perhaps to new fig species rather unrelated to the original host species -this, along with possible hybridisation, can thus mean that the phylogenies of the figs and their wasp pollinators do not strictly correspond one on one. [5] Due to this shifting of hosts, wasp species which share the same fig species as hosts may not be sister species, but quite unrelated. [6] The process whereby pollinating wasps switch fig host species, known as a host switch, has been identified as an important process in leading to coevolutionary patterns in a community of strangler figs and pollinating wasps in Panama. [8]

Another possibility is the evolution of cheating. Where a single fig species is able to use multiple wasp species to pollinate itself, and some wasp species may be better at this than others, a certain wasp species may not need to end up evolving to become a better pollinator, as opposed to simply using the fig as a brood chamber. Wasp species which share the same fig species compete for resources. Where wasp species may visit numerous hosts, if one fig species evolves to be a better host, the wasp may shift hosts, rendering its other shared fig hosts incidentally visited, and thus improperly pollinated, and the wasp a 'cheat' when it visits them. [6]

Cospeciation

Cospeciation, where the evolution of one of a pair (or more) of species is influenced by the evolution of the other of the pair, appears to have occurred in the history of the Ficus-wasp mutualism, despite some significant differences in the fig and pollinator phylogenies. [6] [9]

Cryptic wasp species

Complicating the identification of fig-wasp relationships is the existence of cryptic species: some groups of wasps are morphologically similar, but genetic markers show that they have been functioning as independent species that have not interbred for millions of years. [10]

Related Research Articles

<i>Ficus</i> Genus of flowering plants in the mulberry family Moraceae

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 (F. carica) 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.

<span class="mw-page-title-main">Fig wasp</span> Group of mostly pollinating insects whose larvae live in figs

Fig wasps are wasps of the superfamily Chalcidoidea which spend their larval stage inside figs. Some are pollinators but others simply feed off the plant. The non-pollinators belong to several groups within the superfamily Chalcidoidea, while the pollinators are in the family Agaonidae. While pollinating fig wasps are gall-makers, the remaining types either make their own galls or usurp the galls of other fig wasps; reports of their being parasitoids are considered dubious.

<span class="mw-page-title-main">Coevolution</span> Two or more species influencing each others evolution

In biology, coevolution occurs when two or more species reciprocally affect each other's evolution through the process of natural selection. The term sometimes is used for two traits in the same species affecting each other's evolution, as well as gene-culture coevolution.

<span class="mw-page-title-main">Agaonidae</span> Family of wasps

The family Agaonidae is a group of pollinating fig wasps. They spend their larval stage inside the fruits of figs. The pollinating wasps are the mutualistic partners of the fig trees. Extinct forms from the Eocene and Miocene are nearly identical to modern forms, suggesting that the niche has been stable over geologic time.

<span class="mw-page-title-main">Syconium</span> Type of fruit produced by plants of the genus Ficus

Syconium is the type of fruit borne by figs, formed by an enlarged, fleshy, hollow receptacle with multiple ovaries on the inside surface. In essence, it is really a fleshy stem with a number of flowers, so it is considered both a multiple and accessory fruit.

<i>Ficus pumila <span style="font-style:normal;">var.</span> awkeotsang</i> Variety of climbing fig

Ficus pumila var. awkeotsang, also known as the jelly fig, aiyu, or ai-yu, is a variety of Ficus pumila, and a member of the fig family Moraceae, native to Taiwan. The plant is known for its use in making aiyu jelly.

<i>Ficus aurea</i> Species of strangler fig

Ficus aurea, commonly known as the Florida strangler fig, golden fig, or higuerón, is a tree in the family Moraceae that is native to the U.S. state of Florida, the northern and western Caribbean, southern Mexico and Central America south to Panama. The specific epithet aurea was applied by English botanist Thomas Nuttall who described the species in 1846.

Pegoscapus is a genus of fig wasp native to the Americas. They range from Florida and Mexico in the north to Argentina in the south. Fig wasps have an obligate mutualism with the fig species they pollinate. Pegoscapus pollinates species in section Americana of the subgenus Urostigma.

Ficus maxima is a fig tree which is native to Mexico, Central America, the Caribbean and South America south to Paraguay. Figs belong to the family Moraceae. The specific epithet maxima was coined by Scottish botanist Philip Miller in 1768; Miller's name was applied to this species in the Flora of Jamaica, but it was later determined that Miller's description was actually of the species now known as Ficus aurea. To avoid confusion, Cornelis Berg proposed that the name should be conserved for this species. Berg's proposal was accepted in 2005.

<i>Ficus insipida</i> Species of fig tree from the Neotropics

Ficus insipida is a common tropical tree in the fig genus of the family Moraceae growing in forest habitats along rivers. It ranges from Mexico to northern South America.

<i>Ficus americana</i> Species of fig tree native to the Neotropics

Ficus americana, commonly known as the West Indian laurel fig or Jamaican cherry fig, is a tree in the family Moraceae which is native to the Caribbean, Mexico in the north, through Central and South America south to southern Brazil. It is an introduced species in Florida, USA. The species is variable; the five recognised subspecies were previously placed in a large number of other species.

<i>Ficus pleurocarpa</i> Species of epiphyte

Ficus pleurocarpa, commonly known as the banana fig, karpe fig or gabi fig, is a fig that is endemic to the wet tropical rainforests of northeastern Queensland, Australia. It has characteristic ribbed orange and red cylindrical syconia. It begins life as a hemiepiphyte, later becoming a tree up to 25 m (82 ft) tall. F. pleurocarpa is one of the few figs known to be pollinated by more than one species of fig wasp.

<i>Ficus watkinsiana</i> Species of epiphyte

Ficus watkinsiana, commonly known as strangler fig, Watkins' fig, nipple fig or the green-leaved Moreton Bay fig is a hemiepiphytic fig that is endemic to Australia. The species exists in three populations—one in northeast Queensland and the others in southeast Queensland and northeast New South Wales. It also has been introduced to Kauai island (Hawaiʻi).

<i>Ficus obliqua</i> A tree, the small-leaved fig

Ficus obliqua, commonly known as the small-leaved fig, is a tree in the family Moraceae, native to eastern Australia, New Guinea, eastern Indonesia to Sulawesi and islands in the southwestern Pacific Ocean. Previously known for many years as Ficus eugenioides, it is a banyan of the genus Ficus, which contains around 750 species worldwide in warm climates, including the edible fig. Beginning life as a seedling, which grows on other plants (epiphyte) or on rocks (lithophyte), F. obliqua can grow to 60 m (200 ft) high and nearly as wide with a pale grey buttressed trunk, and glossy green leaves.

<span class="mw-page-title-main">Wasp</span> Group of insects

A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. The wasps do not constitute a clade, a complete natural group with a single ancestor, as bees and ants are deeply nested within the wasps, having evolved from wasp ancestors. Wasps that are members of the clade Aculeata can sting their prey.

<i>Ficus hispida</i> Species of tropical fig tree

Ficus hispida, also known as the opposite leaf Fig, is a small tree in the family Moraceae, with a distribution ranging from India and southern China southwards to northern Australia. It is morphologically gynodioecious, but functionally dioecious. Male trees are hermaphrodites with both staminate flowers that produce pollen and pistillate flowers that produce almost no seeds but can form galls containing pollinator wasp larvae. Female trees have pistillate flowers that do produce seeds but are inhospitable to pollinator wasp larvae.

<i>Blastophaga psenes</i> Species of wasp

Blastophaga psenes is a wasp species in the genus Blastophaga. It pollinates the common fig Ficus carica and the closely related Ficus palmata. Without a colony or nest, these wasps breed in figs, and the adults live for only a few days or weeks. They locate the fig they wish to pollinate through olfactory senses.

<i>Ceratosolen</i> Genus of wasps

Ceratosolen is an Old World wasp genus in the family Agaonidae. They are pollinators of the monoecious fig subsections Sycomorus and Sycocarpus, and the section Neomorphe, all belonging to the subgenus Sycomorus. The genus is native to the Palearctic, Afrotropical, Indomalayan and Australasian realms.

Wiebesia pumilae is a fig wasp species in Genus Wiebesia, Family Agaonidae. W. pumilae is the pollinator of Ficus pumila var. awkeotsang and Ficus pumila var. pumila. The scientific name was first published as Blastophaga pumilae in 1967 by Hill.

Obligate mutualism is a special case of mutualism where an ecological interaction between species mutually benefits each other, and one or all species are unable to survive without the other. In some obligate relationships, only one species is dependent on the relationship. For example, a parasite may require a host in order to reproduce and survive, while the host does not depend at all on the parasite. Fig and fig wasps are an example of a co-obligate relationship, where both species are totally dependent on the relationship. The fig plant is entirely dependent on the fig wasp for pollination, and the fig wasp requires the fig plant for reproductive purposes. Many insect-fungi relationships are also co-obligate: the insect disperses, and in some cases protects, the fungi while the fungi provide nutrients for the insects. This interaction allows insects and fungi to, as a group, inhabit previously inhospitable or unreachable environments. Though obligate relationships need not be limited to two species, they are often discussed as such, with the relationship being made up of a host and a symbiont, though the terms are often attributed arbitrarily.

References

  1. ↑ Suleman, Nazia; Sait, Steve; Compton, Stephen G. (2015). "Female figs as traps: Their impact on the dynamics of an experimental fig tree-pollinator-parasitoid community" (PDF). Acta Oecologica. 62: 1–9. Bibcode:2015AcO....62....1S. doi:10.1016/j.actao.2014.11.001.
  2. ↑ "Fig." Columbia Electronic Encyclopedia, 6th ed.
  3. ↑ Aristotle. Historia animalium. p. 557b25.
  4. ↑ Ma, Wen J.; Peng, Yan Q.; Yang, Da-R.; Guan, Jun M. (2009). "Coevolution of reproductive characteristics in three dioecious fig species and their pollinator wasps". Symbiosis. 49 (2): 87–94. Bibcode:2009Symbi..49...87M. doi:10.1007/s13199-009-0018-x. S2CID   36627180.
  5. 1 2 3 4 5 Moe, Annika M. (2011). From pattern to process: Ecology and evolution of host specificity in the fig-pollinator mutualism (PhD Thesis). hdl:11299/117438. OCLC   759912423.[ page needed ]
  6. 1 2 3 4 Wieblin, George Daniel (1991). Phylogeny and ecology of dioecious fig pollination (PhD Thesis). Ann Arbor: Harvard University. ISBN   978-0-599-51772-1.[ page needed ]
  7. ↑ Satler, JD; Herre, EA; Heath, TA; Machado, CA; Gómez Zúñiga, A; Jandér, KC; Eaton, DAR; Nason, JD (January 2023). "Pollinator and host sharing lead to hybridization and introgression in Panamanian free-standing figs, but not in their pollinator wasps". Ecology and Evolution. 13 (1): e9673. Bibcode:2023EcoEv..13E9673S. doi:10.1002/ece3.9673. PMC   9848820 . PMID   36699574.
  8. ↑ Satler JD, Herre EA, Jandér KC, Eaton DA, Machado CA, Heath TA, Nason JD (2019). "Inferring processes of Coevolutionary Diversification in a Community of Panamanian Strangler Figs and Associated Pollinating Wasps". Evolution. 73 (11): 2295–2311. doi:10.1111/evo.13809. PMID   31339553. S2CID   198191457.
  9. ↑ Rønsted, Nina; Weiblen, George D.; Cook, James M.; Salamin, Nicholas; Machado, Carlos A.; Savoainen, Vincent (2005). "60 million years of co-divergence in the fig-wasp symbiosis". Proceedings of the Royal Society B: Biological Sciences . 272 (1581): 2593–2599. doi:10.1098/rspb.2005.3249. PMC   1559977 . PMID   16321781.
  10. ↑ Molbo, D; Machado, CA; Sevenster, JG; Keller, L; Herre, EA (13 May 2003). "Cryptic species of fig-pollinating wasps: implications for the evolution of the fig-wasp mutualism, sex allocation, and precision of adaptation". Proceedings of the National Academy of Sciences of the United States of America. 100 (10): 5867–72. Bibcode:2003PNAS..100.5867M. doi: 10.1073/pnas.0930903100 . PMC   156293 . PMID   12714682.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.