Martina Harianja, PhD student, writes:

Imagine that you were eight times as big as a grain of sugar, and you live in a fast-flowing stream. To get food, you need to swim against the current. What properties would need to accomplish this? 

Semi-aquatic bugs in the genus of Rhagovelia offer a brilliant approach. Their body length ranges from two to four millimetres as an adult, and so they are rather small. To fight that current they have fan-like rowing structures on their middle legs.

The structures, only found in this genus or ‘group’ of insects, are used to skate against the stream current. Unlike other semi-aquatic bugs which cannot exploit a swift-flowing environment, the fan structures make it possible for them. Very impressive, isn’t it?

This group is one example of specimens I’ve been observing, among others within a group called the Gerromorphan bugs.

Bugs in lockdown:

So that I could continue my research, I brought the Gerromorphan bug samples home with me, along with a microscope and a light source, before the University closed to help reduce the spread of COVID-19.

The name ‘bug’ is used to refer to an insect that has a piercing, sucking
mouth-part, like a straw (a rostrum).
Therefore, not all insects are bugs, but all bugs are insects.

The samples were collected from Malaysian Borneo between 2011 and 2014 by Dr Sarah Luke during her PhD. Gerromorpha comprises water striders and pond skaters whose habitats range from freshwater to ocean surfaces. All semi-aquatic bugs are predators in nature.

The fan-like structures on the legs of the Rhagovelia genus reflect the different habitat preferences of different species. For example, some other bugs, such as Ventidius, are found in slow-flowing streams, and as you can guess, they don’t have any special attribute for fast-flowing streams as in Rhagovelia bugs. These adaptations and habitat preferences mean that we can predict the type of environment by looking at the species that exist there, and vice versa.

Oil palm plantations and biodiversity:

In tropical regions, where biodiversity is the highest, large areas of forest have been converted to oil palm plantations. Palm oil is used in a wide array of products and it is predicted that further expansion of oil palm will be needed to meet global demand. There has also been growing concerns about its negative impact on biodiversity and so, if we are to produce more palm oil, its sustainability needs to be improved.

Some studies have found that certain management approaches within oil palm plantations can have positive impacts on biodiversity. The more ecologically friendly managed areas support more wildlife. These findings are important for both policy and industry because they highlight that management can have substantial effects on biodiversity conservation, as well as providing recommendations for how to improve this in practice.

Palm oil and semi-aquatic bugs:

Aiming to study the impact of forest fragmentation on biodiversity and ecosystem functions, the Stability of Altered Forest Ecosystems (SAFE) Project has been looking at a variety of landscapes in Malaysian Borneo. The Gerromorphan bugs I have been working on were collected from old growth forests, logged forests, oil palms with forested river margins, and oil palm without forested river margins.

The twice-logged forest is due to be converted to oil palm plantations in the near future. The conversion will include the preservation of river margins of varying widths, to assess whether width influences local wildlife and ecosystem functions. If this replanting occurs in the next couple of years, I will be able to collect more data to compare with the data I already have. My findings will reveal how habitat change and different management strategies (i.e. in terms of different widths of preserved river margin) affect biodiversity, particularly semi-aquatic bugs.

Where do we go from here?

In other parts of my PhD, I am interested in studying the impact of management of agricultural systems on biodiversity and the movement of insects around an environment. I will work in smallholder oil palm plantations in Peninsular Malaysia where local farmers have been cultivating oil palm alongside other crops, such as banana, durian, pineapple, and rambutan. 

Insect movement has so far been studied very little despite the significance it has for biodiversity conservation. It can affect foraging activity, reproduction and predator avoidance. For my own study, I will observe butterflies and dragonflies in the polyculture (several crops) landscape of smallholding farmers and compare it with a monoculture (single crop) oil palm landscape to help enrich our understanding of how species use the different landscapes.

This can be used to inform conservation-policy and sustainability guidelines, such as The Roundtable on Sustainable Palm Oil (RSPO). Besides this, my findings will have direct implications for oil palm agricultural practice, particularly for smallholders who grow several different plants.

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Read more about Restoring River Borders for Biodiversity by Dr Sarah Luke

Discover how Our Solutions are in Nature in our Biodiversity Week resource by the Insect Ecology Group

Dr Sarah Luke tells us more about dragonflies and damselflies in plantation rivers in A diversity of dragonflies in oil palm plantations

See more from the Insect Ecology group by following them on Twitter: @InsectGroup