Singapore is no doubt a diverse country. But beyond the cultural diversity it is best known for, its diversity of flora and fauna found in its tropical lowland rainforest is immense. This ecosystem occupies much of Singapore’s remaining natural areas. Tropical lowland rainforests are located where both temperatures and precipitation are high, resulting in a high species diversity. Because of this, there are many different interactions between species, including the incredible relationship between wasps and plants that I discovered during my field trip with our NUS Applied Biogeography module this February.

Don’t Bee Scared! – An introduction to wasps and galls

While wasps are typically feared for their stings, they are actually harmless unless provoked. Like all insects, wasps reproduce via egg-laying. In the rainforest, they lay their eggs inside leaves, forming structures known as galls. Galls are swollen sacs that appear as bumps on the surfaces of leaves. Even though galls can also be formed by other species, such as aphids, mites and even bacteria, wasps are the key contributor to the formation of galls. What I found most interesting was that different species of wasps lay their eggs on different plant species! Hence, each plant species only supports one type of wasp egg. On my trip to the Singapore Botanic Gardens, I spotted two different plant species with two visually different galls.

Galls forming on the Kelat Oil plant (Syzygium myrtifolium), a native plant species. The galls appear to start as small green bumps (A) before growing larger in size and turning yellowish-red (B). Further research suggests that the galls on Syzygium myrtifolium are formed by a wasp in the Anselmella genus, which also forms galls on other species in the Syzygium genus. (Source: Mak Wei Jie Alvern)

In this photo you can see galls forming on the Medang plant (Litsea accedens). The galls appear to start as light green bumps (C) before turning dark red (D), whilst the galls remain roughly the same size. (Source: Mak Wei Jie Alvern)

The buzz about wasps – Why are wasps important pollinators?

Much like how plant leaves provide the necessary support for wasps to reproduce and grow, wasps are responsible for the pollination of plants. Despite its cousin, bees, taking much of the spotlight, wasps are also very important pollinators. Wasps derive nutrition from the nectar of plants. Whilst sucking on the nectar, their body comes into contact with pollen produced by the anthers (male reproductive organs of flowers). After consuming the nectar, they fly to other plants, where the pollen stuck on their bodies is released onto the stigma (female reproductive organ of flowers). This is how wasps help to pollinate other plants much like bees do.

The ability of wasps as pollinators have long been derided, due to their lack of hairs which reduces the attachment of pollen to their bodies. In actual fact, many wasps have developed hairs. Wasps have also evolved to feed only on nectar, increasing their frequency of travel to plants, and thus the efficiency of pollination. Hence, wasps should not be seen as secondary to bees as pollinators.

 

A Scoliid wasp, possibly Campsomeriella collaris, on a flower along the Singapore Botanic Garden’s SPH Walk of Giants. (Source: Mak Wei Jie Alvern)

Another view of a Scoliid wasp, possibly Campsomeriella collaris, on a flower along the Singapore Botanic Garden’s SPH Walk of Giants. (Source: Mak Wei Jie Alvern)

Conclusion

What I learned on this field trip is that wasps are incredibly important to our natural environment. Protecting these wasps not only helps to protect them, but also other plant species that thrives from their pollination. While Singapore does not yet specifically protect these tiny creatures, we can do our part. Stand back and enjoy wasp activity – do not provoke wasps as they are harmless unless disturbed. Also, we can plant flowering species that provide habitat and nutrition for these wasps. We should all reduce the use of pesticides in our gardens and natural areas and plant trees to ensure the survival of wasps and their plant hosts.

Written by: Mak Wei Jie Alvern