In the heart of Singapore Botanic Gardens on a humid Saturday afternoon, a group of students from NUS’ Applied Biogeography module trek along a beaten cement path as the sounds of various birds and insects fill the air. Their professor eagerly calls them over to look at a palm tree, its pleated leaves larger than their faces. “So here you see an example of adaptation, where the understory foliage has larger leaves for more sunlight,” Professor Gretchen explains excitedly as the rest listen with great interest. The plant in question, with a quick iNaturalist identification, turned out to be the Vanuatu Fan Palm (Fig 1), a common species found in the understory layer of tropical forests. Its large leaves allow for the tree to absorb more sunlight due to the low sunlight penetration in the understory, while its pleated texture helps the plant save energy. Such is an example of the unique adaptation strategies that different species adopt to help them survive in the forest.

Figure 1: Vanuatu Fan Palm (Licuala grandis) found in the understory layer of the tropical rainforest.
Credit: Charmayne Seah, February 5, 2022

 

Beyond Singapore Botanic Gardens, tropical forests are crucial to our Earth’s ecosystems, making up a staggering 8% of the total land surface on Earth (Butler, 2021). These forests also have a unique structure with their various layers and are home to a wide variety of wildlife. As such, it is vital for us to study and understand different adaptation mechanisms which help the ecosystem flourish. For instance, the Rose Cactus (Leuenbergeria bleo) tree (Fig 2), a species of cacti native to Panama and Columbia (NParks, 2021), has adapted to protect itself from predators by growing sharp thorns on its trunk to deter animals from eating it. Adaptations like these are particularly common in the tropics at the understory and canopy levels of the rainforest where there are more natural predators. Other species which also adopt the same strategy include the Silk Floss Tree (Chorisia speciosa) (Fig 3) and Guinea Bactris (Aiphanes minima) (Keller, 2021).

Figure 2: Close up of the Rose Cactus (Leuenbergeria bleo) tree’s spikey trunk at SBG. Credit: Charmayne Seah, February 5, 2022

 

Figure 3: Close up of the Silk Floss Tree (Chorisia speciosa) tree’s spikey trunk. Credit: Phillip’s Natural World

 

An interesting comparison to make is the different types of root adaptations between tropical rainforests and freshwater wetlands. For instance, to cope with the lack of nutrients in the soils, trees in tropical rainforests might overcome this by having buttress roots which also help stabilise the tree in shallow, saturated soils (Britannica, n.d.) (Fig 4). On the other hand, the Mempisang-belt of the freshwater wetlands sees more stilt roots (Fig 5) and pneumatophores. This helps to stabilize the trees’ large biomass in soggy and nutrient-poor soils, as well as allowing the trees to breathe even at high tides. This is just one of many wonderful examples of how different species have different adaptation strategies even within the same climate.

 

Figure 4: Buttress roots of a tree in Henrietta Creek, Australia. Credit: Flickr, August 2, 2007

 

Figure 5: Picture of the mangrove stilt roots in San Salvadore Island, Bahamas. Credit: Daniel Mosquin, July 21, 2015

 

I truly believe that there is definitely a lot of value in continuing to study and better understand tropical rainforests, as well as freshwater wetlands. Singapore Botanic Gardens has come a long way in restoring and conserving these precious ecosystems. I believe that greater public education on its importance could help Singaporeans better value our natural habitats and hopefully create a better relationship between humans, animals and the environment.

 

Written by: Charmayne Seah Soon Ee

NUS Applied Biogeography (GE4224), AY21/22 Sem 2