Dipterocarp seed production and survival in Singapore

What is it about?

The rain forests of large parts of Southeast Asia show a unique phenomenon. They are dominated by a family of giant trees called dipterocarps, and at irregular intervals, the plants flower together and produce huge amounts of fruit. The mass fruiting, or masting, is supposed to overwhelm seed-eating animals with food. Singapore's nature reserves are mostly forest regrown after logging and clearance but still contain some dipterocarp trees. During the last masting in 2014, we found that long-tailed macaques eat the seeds mostly while they are still on the trees. A good proportion are not eaten and fall to the ground. Even then, many do not germinate even though they are not damaged. It could be that the scattered dipterocarp trees are not cross-pollinated effectively and many seeds are genetically in-bred and therefore non-viable. We need more comparisons with more intact forests elsewhere to confirm this.

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Why is it important?

Southeast Asia's rain forests have been logged and cleared at unsustainable rates in the past few decades. For the remnants that remain, can the unique phenomenon of masting that satiates seed predators, therefore allowing enough seeds to escape and establish, function properly? Insufficient predator satiation coupled with lower viability can threaten the long term prospects of the selectively logged or fragmented forest remnants even if they can escape further deforestation.

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