Borneo hosts as estimated 40 species of Section Conosycea figs often known as “stranglers” or botanically as hemi-epiphytes = half epiphytes. In this article we will refer to Section Conosycea figs as stranglers but note that stranglers may also grow as standalone trees or as epiphytes with only one or two aerial roots.
Orange arrow: Calyptrate bud cover covering the a young fig fruit of Ficus forstenii
Blue arrow: Hairy stipule covering the growing tip of the twig. Most stranglers have smooth or slightly fuzzy stipules e.g. Ficus subgelderi. However there are several stranglers with very hairy stipules (as well as F. forstenii as illustrated above) including F. cucurbitina, F. consociata and F. drupacea.
Persistent stipules: Once the bud expands into leaves the stipule withers and falls off = cauducus. However a few stranglers retain their dried stipules for long periods after they have withered including F. paracamptophylla and some F. annulata.
All photos by Shuai LIAO of a Ficus forstenii growing at Sg Mokodou, Kg Nalumad, Sabah taken on 7 September 2019. Collection # 20190359
Stranglers begin their growth as epiphytes with a seed lodged in a hole or epiphytic plant clump in a host tree. Once established the fig sapling drops down thin aerial roots to the ground below. Once the aerial roots have accessed ground water and nutrients in the soil the fig grows rapidly, expanding the number and size of the aerial roots as well as branching in the canopy.
The aerial roots of figs contain “reaction wood” cells which expand under external pressure. As the host tree expands its girth each year the fluid transport cells under the surface bark of the host (the xylem and the phloem) come under pressure from the reaction wood cells of the fig roots which expand against the host. Fig roots also readily anastomose or join together in a sort of web so when this happens the host tree is trapped on all sides . The joint pressure from the tightening of the web and the outward growth of the host tress effectively strangles the host within 18 months.
Note that because palms have a very solid trunk with a fixed girth and with the liquid transport tubes spread across the interior of whole trunk they cannot be strangled by figs.
Blue Arrow: Shows the ostiole closed by 3 bracts. The ostiole is a one way gate blocking the entrance way into the interior of the hollow fig where the tiny fig flowers are located. The ostiole only opens once when the fig flowers are ready to be pollinated to allow access for female fig wasps carrying ripe pollen from other figs of the same species.
Green Arrow: Shows some white frass or ejecta from a hole drilled into the fig by a non pollinating parasitic fig wasp.
Orange Arrow: Shows white latex leaking from the stipule damaged during the collection. See below
The Blue Arrow shows an ant eating the wax. The wax is also “stolen” by wax eating small parrots and by a wax eating squirrel.