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Ficus treubii: Are male figs toxic to animals ?

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ABOVE: Ficus treubii. A cross section of an almost “ripe” male fig with the fig wasps about to emerge from the gall flowers. Note the magenta stain which rapidly develops on the recently cut surfaces indicating a form of oxidation known as the Schiff process. This likely indicates the presence of an anti-fungal or toxic compound similar to potassium permanganate. This compound is obviously present in male figs but not female figs.

An over-ripe male fig from which the fig wasps have already left. Note the white male flowers (stamens with anthers)  on the right hand side  surrounding the rotting bracts of the ostiole. Note the purple stain in the flesh.
Ficus treubii. An almost ripe female seed fig from the same location (but different plant) in the Crocker Range, Sabah. Note the presence of latex and the absence of a purple stain.
Leaves of the male  Ficus treubii tree. There is no evidence as yet in any fig that the leaves of male plants differ from the leaves of female plants

Ficus treubii is dioecious i.e. separate female and male trees. Male fig trees produce male figs which act as brood chambers for fig wasps whilst  only female fig trees produce seed figs. Ripe female Ficus treubii female figs are slightly smaller than male figs.  The difference in leaf size between the two sexes in the photo above is not thought to be significant.  Typically young earth fig trees of most species produce larger leaves than larger older trees.

Male Ficus treubii fig tree growing next to a drain stream behind Mushroom Shed 84 on the Kota Kinabalu to Tambunan road in Sabah. The arrow points to a single ripe male fig. See close up photo below. There is a small colony of both male and female F. treubii fig trees growing along the stream.

A single ripe male Ficus treubii fig. Note the wide open ostiole indicating that the fig wasps have already departed the fig. There are several possible reasons why Ficus treubii may have developed toxic male figs (1) To deter animals from eating the figs and predating the fig wasps growing inside (2) To prevent fungi attacking the fig and killing the fig wasps.  In general animals do not eat male figs but to date this has been thought to be  due to the fact that male figs are tasteless. The photographs above are the first proof that male fig trees may produce toxic compounds to deter  animals from eating the male figs.
Mushroom Shed 84 is about  one hours drive  from Kota Kinabalu on the very wet western slopes  of the Crocker Range at an altitude of approx 1,000 m ASL.

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