The deserts and semi-deserts in southernmost Africa are inhospitable places with an arid climate, low rainfall, and extreme temperatures. They are the home of the Lithops plant, possibly the weirdest plant in the world.
They are also where Finnish biologist Dr. Tommi Nyman, University of Eastern Finland and NIBIO Svanhovd, Norway, and his South African colleague plant ecologist Prof. Allan Ellis from the University of Stellenbosch have been studying the plants from the evolution point of view. To help them with their study, they chose Specim IQ. The small size of the camera and its long battery life made it optimal for the field conditions, and its high speed could handle the harsh and alternating light.
Hiding in plain sight
All the plants in such a hostile environment need some kind of protection from the animals. The Lithops plants rely on camouflage: each plant is for the most part buried inside the soil, with only the flat tops of their succulent leaves protruding to the soil surface. This makes the Lithops plants virtually invisible.
The problem is, however, that the properties of the soil vary markedly across South Africa, Namibia, and Botswana: the gravel can be brown, grey, yellow, red, or almost white, and the grain size likewise ranges from fine sand to large pebbles. Sooner or later some of the Lithops descendants will find themselves in a hostile environment where they stand out from their surroundings.
Here we come to the core of the evolutionary theory developed by Charles Darwin and Alfred Russel Wallace over 150 years ago: if upper-surface color varies among Lithops individuals, if the coloration is genetically determined and heritable, and if poorly camouflaged individuals get eaten more often than do cryptic ones, then the color and patterning of the plants will over time tend to converge towards the visual properties of the local soil.
One of the most central questions in modern evolutionary research concerns the role of ecological traits in the origin of new species. This travel might reveal some new aspects to this puzzle. The hypothesis: that phenotypic (color) divergence within the genus Lithops is driven by selection for locally optimized camouflage.
Looking for an accurate color measurement tool
When comparing the color of Lithops plants and the terrain, it is essential to get as exact, accurate and objective color measurements as possible. This is where hyperspectral imaging comes in.
The hyperspectral camera is well suited for color measurements since it is more accurate than RGB cameras and, unlike visual inspection, completely objective. It is possible to define the target’s absolute color for instance in Lab color space with the accuracy of ∆E<1, or its relative color in relation to another target as accurately as ∆E=0.2. This is better than human color perception (∆E=1) and clearly superior to RGB cameras that can only reach ∆E=8-10 accuracy.
Why Specim IQ
Next, it was the matter of finding a hyperspectral camera that would work in the extreme conditions in Southern African deserts. A place where distances are long and roads bumpy, the temperatures can vary from freezing nights to sweltering heat during the day, there is dust everywhere, and the light is harsh and changes quickly, you need equipment that meets certain requirements.
What you need is a compact and durable, yet high quality and fast camera. When Tommi Nyman learned about Specim IQ, he knew that this was the camera they wanted for the expedition.
“The terrain is rocky, so you do not want to carry very big and heavy equipment around,” says Dr. Tommi Nyman. “Specim IQ was small and mobile, easy to transport and use in the field, and it was very handy for doing the measurements we wanted.”
IQ’s long battery life was also considered a big plus, as the team spent 3-4 nights camping in the wild, only to return to the town for one night to stock up, refresh – and recharge the batteries. “In the field, you want a camera that works the whole day with one battery,” says Dr. Nyman.
The Specim IQ camera is also fast, which is essential in the harsh and quickly changing light conditions. The light in Africa is harsh and comes directly from above during the day. The shadows are sharp and deep. When a cloud covers the sun, the light conditions can change drastically over a short period of time. So when you set the integration time to certain light conditions, you want to take the image quickly, before the next cloud comes along and completely changes the light conditions.
Not everything goes as planned
At first, everything went according to the plan, and Specim IQ worked just as the team had hoped for. Then, the camera started acting up and finally stopped working altogether. “We contacted Specim to find out if we could solve the problem” recounts Dr. Nyman. Even though Specim personnel was swift to reply and the team got information and instructions from Finland to Africa, nothing could be done.
While they were unable to continue the measurements, luckily there was enough data that at this point for the project to continue. As for the camera, it got shipped back to Specim premises in Finland, where it was opened up to see what had happened.
The first thing noticed during the service was, that the camera showed no marks of the dusty conditions it had been exposed to – the inside of the camera was absolutely clean. However, the IQ camera unit used by the Lithops project was one of the early prototypes and in closer inspection one of the key parts had broken after less than 10 000 images. This known issue has already been redesigned for the production models and the current cameras can take hundreds of thousands of images.
All the required data is now collected, and the Lithops project continues with data analysis. The results will be available later.
As for hyperspectral imaging, there is still plenty of work in ecological research. It is a vast field of study, with questions similar to the ones studied in the Lithops project. Once there is equipment that is easy to transport and use in the field, there surely is a lot of use for it in the ecological research.