Belongs within: Moraceae.
Ficus section Conosycea is a group of fig species found primarily in Asia and Australasia, with two species in Madagascar. Syconia of Conosycea species generally have three basal bracts, and they are pollinated by wasps of the genera Deilagaon, Eupristina, Platyscapa, Waterstoniella and Parapristina (Berg 1989).
Of banyans and stranglers
Published 10 January 2024
There can be little question that Ficus, the figs, stands out among all the world’s plant genera. Not only are figs among the dominant tree species in many tropical and subtropical habitats, their unique morphology makes them easily one of the plant world’s most instantly recognisable taxa. Ficus species have a unique floral morphology in which the minute flowers are clustered into enclosed, fruit-like inflorescences called syconia. The basic structure of a syconium is comparable to the compond flower-heads of composites (Asteraceae) such as daisies or dandelions, but the fleshy base of the flower-head has been extended up and around the component florets. Entrance to the syconium is restricted to a minute opening, the ostiole, at its upper end. Pollination of figs is the purview of specialised micro-wasps of the family Agaonidae. Female agaonids crawl into the syconium through the ostiole, typically losing their wings and antennae in the process so they become unable to leave. Pollen carried by the wasp fertilises the female florets within the syconium, beginning the development of seeds. The wasp lays her eggs within the syconium and then dies. After the eggs hatch, the developing wasp larvae feed on the syconium tissue until reaching maturity, after which they mate. The wingless males never leave the fig in which they grew but the winged females crawl out through the ostiole, carrying with them a load of pollen that will be deposited when they enter another fig to begin the cycle anew.
About 850 species of Ficus have been recognised around the world, so obviously attempts have been made to divide the genus into more manageable sections. Among these is the section Conosycea, an Indo-Australian assemblage with two species found in Madagascar (Berg 1989). Conosycea has been recognised as a section of the subgenus Urostigma, members of which are united by the production of aerial roots, leaves with only a single waxy gland at the base of the midrib, and a monoecious reproductive system with both male and female flowers contained within a single syconium (Rasplus et al. 2021). Conosycea species have the male flowers dispersed among the female flowers within the syconium, which bears three basal bracts (Berg 1989). The agaonid wasps associated with section Conosycea are active pollinators, taking it upon themselves to collect pollen into specialised patches of setae before leaving in search of a new host.
Many species of the subgenus Urostigma, including the representatives of section Conosycea, grow as hemi-epiphytes, commonly known as ‘stranglers’. The germinating fig typically begins its life in the crook of a tree branch, though for many species some other raised position such as the side of a rock-face or the wall of a building will do just as well. As the fig grows, it extends one or more major roots towards the ground below. Lateral roots extending from the major root encircle the host tree. In some cases, these lateral roots do not develop until the major root(s) have reached the ground; in others, the major root sends out lateral roots as it descends. In some species, the major root grows as a broad flattened slab (Corner 1985). Typically, the lateral roots form a lattice that completely surrounds the host tree, leading to the latter’s demise as it becomes choked out by the rampant fig. By that point, however, the root network has become sturdy enough to support the fig by itself, and the fig continues its life as an independent tree.
Several Conosycea species are familiar to the humans that live alongside them. Ficus benghalensis is the banyan of India, famed for the large size to which it can grow as spreading branches become supported by descending aerial roots. Some renowned examples are among the largest single trees in the world in terms of canopy size, with the largest known individuals covering close to two hectares! Popular ornamental species include the weeping fig F. benjamina and the Chinese banyan F. microcarpa. The Chinese banyan has, however, come to be regarded as a serious invasive in parts of the Americas. Also widely grown as an ornamental is the rubber plant F. elastica. This species stands out from other Conosycea due to its distinctive leaf venation, long stipules and long basal bracts, leading to its historical treatment as its own section (Berg 1989). However, modern molecular studies have supported associating F. elastica with the section Conosycea (Rasplus et al. 2021). As such, this is a strangler that many of you may have lurking in the corner of your own home.
Systematics of Conosycea
<==Ficus sect. ConosyceaB88 |--F. benjamina Linnaeus 1767B88, R-SN07 |--F. chrysolepisB88 |--F. (subsect. Conosycea) crassirameaB88 | |--F. c. var. crassirameaB88 | `--F. c. var. patelliferaB88 |--F. drupaceaB88 |--F. glaberrimaB88 | |--F. g. var. glaberrimaB88 | `--F. g. var. bracteata [incl. F. adamii]B88 |--F. microcarpaB88 | |--F. m. var. microcarpaH90 | `--F. m. var. hilliiH90 |--F. novoguineensisB88 |--F. (subsect. Dictyoneuron) retusa Linnaeus 1767B88, R-SN07 |--F. sumatranaB88 `--F. sundaicaB88
*Type species of generic name indicated
References
Berg, C. C. 1989. Classification and distribution of Ficus. Experientia 45: 605–611.
[B88] Bouček, Z. 1988. Australasian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International: Wallingford (UK).
Corner, E. J. H. 1985. Ficus (Moraceae) and Hymenoptera (Chalcidoidea): figs and their pollinators. Biological Journal of the Linnean Society 25: 187–195.
[H90] Harden, G. J. (ed.) 1990. Flora of New South Wales vol. 1. New South Wales University Press.
Rasplus, J.-Y., L. J. Rodriguez, L. Sauné, Y.-Q. Peng, A. Bain, F. Kjellberg, R. D. Harrison, R. A. S. Pereira, R. Ubaidillah, C. Tollon-Cordet, M. Gautier, J.-P. Rossi & A. Cruaud. 2021. Exploring systematic biases, rooting methods and morphological evidence to unravel the evolutionary history of the genus Ficus (Moraceae). Cladistics 37: 402–422
[R-SN07] Retana-Salazar, A. P., & K. Nishida. 2007. First gall-inducing thrips on Elaphoglossum ferns: a new genus and species of thrips, Jersonithrips galligenus from Costa Rica (Insecta, Thysanoptera, Phlaeothripidae). Senckenbergiana Biologica 87 (2): 143–148.