Introduction to Section Urostigma stranglers: 6 Borneo species

PHOTO ABOVE: This Ficus virens growing on the floodplain of the Tempassuk river at Kota Belud in Sabah is believed to have the widest canopy  (70 m) of any tree in Borneo.

INTRODUCTION TO THE 6 SECTION UROSTIGMA  STRANGLERS FOUND IN BORNEO

World 27 spp. Borneo: 6 spp.

Borneo hosts 6 species of Section Urostigma stranglers including 2 of Borneo’s biggest fig trees F. caulocarpa and F. virens and the introduced Bo Tree (F. religiosa) sacred to Buddhists, Hindus and Jains. None are  endemic. All species are monoecious (bisexual).  For recent taxonomy see;

Chanturasuwan (2013) A revision of Section Urostigma

The 2 most common Section Urostigma stranglers in Borneo Ficus virens and Ficus caulocarpa are easily distinguished from each other. Ficus caulocarpa always has reddish brown  petioles (leaf stalks) whilst with Ficus virens the petioles are always light green.  

How to distinguish  Section Urostigma stranglers from Section Conosycea stranglers.  

• Fig fruits normally with short stalks ( F. religiosa  which has no stalk (peduncle) is an exception)
• 4 species of Section Conosycea fig fruits also have stalks but these are all bat figs which ripen green.
• Urostigma fig fruits ripen white first later developing pink or purple spots.  Again F. religiosa is an exception as the figs ripen reddish green) Conosycea figs tend to ripen yellow/orange/red/black without spotting. ( F. microcarpa  ripens white pink purple black but is not spotted)
• Fig fruits are normally ramiflorus, densely packed on old growth branches. Conosycea figs normally grow in the leaf axils
• Articulated leaves with long stalks (petioles) with hinges or elbows (pulvinus) at both ends enabling the leaf to flex in the wind.
• Inside Section Urostigma figs the male stamens are clustered around the ostiole  in all Borneo species whilst with Section Conosycea stranglers the male stamens are spread throughout the interior of the fig fruit.
• All are deciduous, shedding their leaves in one event which are then immediately replaced.
• The twigs show evidence of seasonal intermittent growth by changes in the length and color of the internodes.
• The intermittent seasonal growth is reflected in differences in the stipules of Sections Conosycea and Section Urostigma. Dormant Urostigma stipules are short blunt,conical  and brown.

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