Ficus subg. Urostigma

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Ficus subg. Urostigma

Description

Monoecious trees, with aerial adventitious roots, mostly hemi-epiphytic and the secondary system of aerial roots anastomosing and forming root-baskets (around trunks of host-trees), secondarily terrestrial (or primarily so) and then often forming pillar roots, sometimes hemi-epilithic, or rarely climbers. — All species develop aerial adventitious roots from the base of the trunk and/or from the branches. Therefore the majority of the species and individuals are hemi-epiphytic (described in detail above, p. 23). The species may also establish on rocky surfaces (or walls) as hemi-epilithic individuals. Light conditions promote establishment in open vegetations (including secondary vegetations and tree plantations). As trees establish close to the soil, they can soon become independent of the host-tree. The species tend to have short trunks and spreading, often flat-topped, crowns.

In exposed places, as sea-shore rocks or hill-tops, species which may grow into large trees, become dwarfed into low carpeting shrubs. Ficus benjamina, F. delosyce, F. kerkhovenii, and F. microcarpa, are among the most powerful hemi-epiphytes, often able to overpower host-trees. Some species, F. acamptophylla, F. depressa, F. globosa, F. microsyce, and F. paracamptophylla, are mostly lianescent with slender stems, using slender aerial roots to all manners of support, sprawling through forest-canopy or festooning forest-edges.

Growth is mostly intermittent, most clearly so in subsect. Urostigma, in which sections with short internodes and different colours of branches mark intermittent seasonal growth, mostly accompanied by deciduousness. The period of bare crown may vary from one day (F. caulocarpa) to some weeks (F. religiosa). The stipules of deciduous species are often much longer than normal, even 10-30 cm long. In some species (of subsect. Urostigma), stipules may form terminal buds. Relatively long stipules are characteristic of sect. Stilpnophyllum. The majority of the species, in particular those of subsect. Conosycea are evergreen and the branches do not show clear features of intermittent growth, at most subpersistent stipules on current growth.
Leaves spirally arranged; — The leaves have short and relatively long petioles in most species of sect. Conosycea and relatively long and slender ones in subsect. Urostigma. Moreover, there often is an articulation at the junction of petiole and lamina in the latter group. The lamina is often broadest below the middle, varying to cordiform, if the petiole is long. The same correlation is found in neotropical and African sections of the subgenus and is associated with occurrence in (relatively) dry habitats. The basal lateral veins mostly differ in length and angle of departure from the other lateral veins. The tertiary venation varies from clearly scalariform to reticulate to largely parallel to the lateral veins. The latter state is pronouncedly present in, e.g. F. benjamina and F. elastica. The variation in venation is similar in the neotropical and African sections of the subgenus. The leaf margin is nearly always entire. The presence of a single waxy gland at the base of the midrib of the lamina beneath is characteristic for the subgenus.
stipules fully amplexicaul. — The perianth usually consists of 3 or 4, sometimes 5, or rarely more, free tepals. There is only one stamen and usually only one stigma. The stigmas are distinctly papillate and strongly coherent (creating a substigmatic layer). The number of staminate flowers is relatively small, rarely more than 10% of the total number, often few, in small figs often only one, or occasionally even absent. There is always one stamen of which the anther usually has two thecae, but generally only one in subsect. Malvanthera. There is usually only one stigma, which sometimes tends to becoming bifid. The stigmas are distinctly papillate; they strongly cohere with those of adjacent flowers, forming a syn-stigmatic layer.
stamens 1; Ovaries whitish or reddish; — The fruits are smooth, reddish, partly reddish, or whitish. In subsect. Malvanthera, they are often partly (to entirely) embedded in the wall of the fig. Deviating characters of fruits are found in sect. Galoglychia (see Berg & Wiebes 1992); they show similarities to the dehiscent drupe. Fruits ellipsoid, smooth, sometimes ± drupaceous or embedded in the wall of the receptacle.

Distribution

Africa: present Asia-Tropical: Australasia: Pantropical: present adjacent parts of Malesia and to the Pacific region: present eastern Brazil: present neotropics: present northern Borneo: present northern Central America and Mexico: present the Guiana region: present western Malesia: present
The subgenus is pantropical and comprises c. 280 species, of which c. 100 in the Neotropics and c. 80 in Africa. It is represented by 68 indigenous species in Malesia. The main centre for the neotropical section Americana is the northern Andean region, secondary centres are found in northern Central America and Mexico, the Guiana region, and eastern Brazil. In Africa, where the Ficus flora is dominated by the endemic section Galoglychia, it occurs in a wide range of habitats. In Australia, the subgenus is for the greater part represented by subsect. Malvanthera, which extends to adjacent parts of Malesia and to the Pacific region. In Malesia the majority of the species belong to subsect. Conosycea, which is centred in western Malesia (with a high concentration of species in northern Borneo) and is associated with humid forest. The other Asian subdivision, subsect. Urostigma, is largely an element of the mainland flora, partly Indian, partly Sino-Himalayan. The subsection extends to Malesia, often in drier types of vegetation, and westwards to Africa, mainly to regions with savannah woodland.

Pollination

Whereas most other subgenera of Ficus have one genus of pollinating fig wasps, and subg. Sycidium two, subg. Urostigma has 13 genera, of which 7 in sect. Galoglychia and one in sect. Americana. Pleistodontes is the genus associated with sect. Stilpnophyllum and Deilagaon, Eupristina (Eupristina and Parapristina), Platyscapa, and Watersoniella with sect. Urostigma (see Wiebes 1994).
A. Berg, C.C. & J.T. Wiebes, African fig trees and fig wasps in Verh. Kon. Ned. Akad. Wet., afd. Natk. 89. 1992, B. Wiebes, J.T., The Indo-Australian Agaoninae (pollinators of figs) in Verh. Kon. Ned. Akad. Wet., afd. Natk. 92. 1994

Taxonomy

This most speciose subgenus is uniform in features of the leaves, as the position of the waxy glands, as well as in features of the figs, as the constant number and position of the basal bracts and the absence of lateral bracts. The flowers are also rather uniform in the construction of the perianth, the number of stamens, and in the stigma. Deviations occur in the fruits of some subdivisions of the African sect. Galoglychia (see Berg & Wiebes 1992) and in the ‘monothecal’ anthers, ‘immersed’ fruits, and often bifid and not or hardly papillate stigmata of subsect. Malvanthera. The subgenus can be subdivided into 4 sections:
  • Section Urostigma (c. 90 spp.) ranges from West Africa to the Pacific.
  • Section Americana (c. 100 spp.) is confined to the Neotropics. It is in its overall variation not essentially different from the Palaeotropical section Urostigma. The main differentiating character is the presence of two instead of three basal bracts.


The differences between these two sections and the other two are more pronounced. The structure of the ostiole may indicate that the latter two sections are derived from the same ancestral stock.
  • Section Galoglychia (72 spp.) is confined to the African region. It is quite distinct in the structure of the ostiole, which is slit-shaped because of the two descending upper ostiolar bracts, and it has always two basal bracts. The morphological and ecological differentiation is wider than in the other sections, and includes, e.g., cauliflory.
  • Section Stilpnophyllum (c. 20 spp.) in Australia and adjacent parts of the Pacific and Malesia, but with a single species (F. elastica) in the Sino-Himalayas.

  • Subg. Urostigma
    • Sect. Urostigma
      • Subsect. Urostigma
      • Subsect. Conosycea
    • Sect. Americana
    • Sect. Galoglychia
    • Sect. Stilpnophyllum
      • Subsect. Stilpnophyllum
      • Subsect. Malvanthera

Citation

Gasp. - in Verh. Nederl. Inst. Amsterdam. 1849: 133
Sata - in J. Jap. Bot. 1934: 347
Gasp. - in Fl. Ind. Bat. 1859: 332
Mildbr. & Burret - in Bot. Jahrb. Syst. 1912: 174
Gasp. - in Ann. Sci. Nat. Bot. 1845: 343
Corner - in Gard. Bull. Singapore. 1960: 370
Gasp. - in Rendiconti Reale Accad. Sci. Fis. 1845: 81
L. - in Contr. Hort. Inst. Taihoku Imp. Univ. 1944: (as ‘Urostigmae’)
Miq. - in London J. Bot. 1847: 525