Pole-to-pole climate research: Adaptation lessons from tiny springtails

They are about one millimetre long. Your foot lands on hundreds of them with each step you take in the woods. Their scientific name is Collembola, but their appearance has earned them the common name of springtails. Creeping through the topsoil, springtails thrive anywhere on Earth with enough moisture -- from the Arctic to the tropics to the Antarctic.

A collaborative project between Norwegian and South African researchers is focusing on springtails as model systems in order to study adaptive responses to changes in the physical environment.

Threat of invasion

Changes in habitat -- whether due to climate change, human activity such as large-scale development projects, or other factors -- elicit different responses in different species.

The response patterns of species can have major impacts on an ecosystem. Some species may be decimated or completely disappear, while others may distribute more extensively. Problems may arise when, for instance, an invasive species enters a new area through human activity and displaces indigenous species. Conspicuous examples of this in Norway include the dreaded invasion of gardens by Spanish slugs and the introduced Pacific oyster out-competing its native cousins.

What defines a species as "invasive"? Are there indications that invasive species are better at surviving changes in living conditions than indigenous species? And what then are the implications for the distribution of various species as a result of coming changes in climate?

Excellent model species

One approach to answering these questions involves focusing on the lowly Collembola.

"Collembola are one of the oldest groups of terrestrial animals; their ancestors were here roughly 400 million years ago," says Professor Hans Petter Leinaas of the Integrative Biology Group at the University of Oslo's Department of Biology.

"Collembola are very suitable as experimental model organisms because there are so many different species of them, and it is easy to study aspects of their adaptation in the laboratory," explains Professor Leinaas. "Each species responds to environmental changes in a way that reflects the environment to which it is adapted."

Nature's recyclers

Springtails have a distinctive appearance that most resembles a primitive insect group, but scientists believe they probably branched off the evolutionary line of crustaceans.

"Collembola have maintained and thrived on a primitive way of life. They subsist on decaying vegetable matter on the ground, serving a valuable function by decomposing and converting nature's finite matter, much like earthworms do. One square metre of coniferous forest in Norway typically contains 100,000 to 200,000 Collembola specimens," says Professor Leinaas.

Invaders endure climate change better

On sub-Antarctic Marion Island, far off the coast of South Africa, indigenous species of Collembola exist alongside invasive alien species of Collembola introduced by seal hunters from Europe, for example, or through earlier domestication of animals on the island.

Professor Leinaas collaborated with his South African colleague, Professor Steven Chown of Stellenbosch University, to study how these springtail species respond to rises in temperature and drought, two important elements of climate change. For the project the professors investigated three to five indigenous species and three to five alien species.

"It turns out the invasive springtails function better in warmer environments than the indigenous do. In addition, the invaders do better compared to the indigenous when exposed to drought after a warmer period. This latter point is of particular interest," adds the Norwegian professor, "since Marion Island and other sub-Antarctic islands have become substantially dryer in recent decades."

Increasing threat

The researchers also looked at the impact on characteristics such as growth and reproductivity as the temperature rises -- by means such as counting their eggs and measuring how quickly the springtails evolve.

"Our studies show that the alien springtail species we have studied cope better and better as temperatures climb from 5°C to 20°C. There is good reason to believe that this is a general trend that also applies to other species," explains Professor Leinaas.

When it comes to dealing with cool conditions, invasive springtails do just as well as their indigenous counterparts. This means the invaders could also colonise cooler islands of the Southern Ocean, underlining the importance of maintaining current quarantines between the islands.

"The findings from our Marion Island project highlight the point that invasive species can expand their distribution, becoming more of a threat when the climate changes," Professor Leinaas stresses.

Long-standing collaboration

Like many good researcher alliances, Professors Leinaas and Chown were brought together more by coincidence than design. When the South African gave a talk in Oslo back in 1996, the Norwegian was on hand. As the two chatted afterwards, they realised they had many common research interests -- including adaptability to climate change in cooler zones.

As Professor Leinaas recalls, "Professor Chown had already worked a great deal on Marion Island, while I had in-depth experience from Svalbard. We also had complementary expertise, so we quickly agreed to work together."

Their first joint project on Marion Island received funding under the Research Council's South African-Norwegian cooperation programme. Now, as a follow-up to that project, the two men have acquired partners in France and Sweden, the latter of whom has received funding under the South African-Swedish Research Partnership Programme.

Mapping unknown species

In their current project, the scope has been widened beyond Marion Island to encompass studies on Svalbard and the Nordic mainland and in the South African province of Western Cape.

"The Western Cape has a vegetation type that supports the world's highest species diversity per land area," according to Professor Leinaas, "but little is known about diversity among invertebrates there. The situation is completely different from Marion Island, where we have a comprehensive overview of Collembola species and can easily tell them apart."

This means that to begin with, the Western Cape springtail species must be characterised. The French researchers are lending a hand in this, using genetic techniques such as DNA analysis.

"We have already found lots of springtail diversity," confirms the professor, "species which by and large were unknown. But we have also found an old, not-so-nice acquaintance from Europe, an extremely invasive species accounting for about three-quarters of all the animals we have collected. This was an unpleasant surprise that we need to study more closely."

The researchers hope the project will enhance understanding of how climate change affects populations and ecosystems, and are planning to make comparisons between the northern and southern hemispheres.