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Climate Change on Fast-forward

Biologists from Freie Universität Berlin use fungi to study the effects of global warming.

Dec 15, 2016

Greenhouse experiments allow scientists to study the effects of soil fungi and other environmental factors on plant communities.

Greenhouse experiments allow scientists to study the effects of soil fungi and other environmental factors on plant communities.
Image Credit: Matthias Rillig

Climate change is in full swing, but how do flora and fauna respond to it? Are there only losers, or do some species actually benefit? And how do certain species manage to adapt? Biologists all over the world are engaged in lab experiments to find out. But how realistic are they?

“The parameters used in the lab are changed to simulate future environmental conditions, but the change is generally dramatic and very fast. Global warming, though, and the increase in carbon dioxide concentrations in the atmosphere, elevated nitrogen input and ocean acidification – all of that takes place very, very slowly,” says Matthias Rillig, a professor of plant ecology at Freie Universität Berlin.

He is interested in what happens when environmental factors change gradually and on a fluid basis. What Rillig wants to know is whether nature is able to adapt to slow processes of change, and if so, how. Through microevolution or other mechanisms? The European Research Council (ERC) just recently approved a grant of 2.4 million euros for Rillig to find answers to these questions.

Environmentally induced evolutionary processes are difficult to trace in plants that have comparatively long generation times. “It might take 50 years to observe what happens in a one-year species when atmospheric CO2 rises at a relatively realistic slow rate. Not to mention trees!” Rillig explains.

By contrast, the next generation of spore-forming soil fungi – Rillig’s specialty – arises within a shorter period, anywhere from a few hours to a few days. These species can be used to study the effects of environmental changes across many generations in a kind of fast-forward setting. “We’re talking about the kind of fungus that you might find growing in the fridge if you leave something sitting there for too long,” Rillig says with a smile. His team collected 30 isolates of various groups of these kinds of “housekeeping fungi,” all of which break down organic material, from soils around Berlin.

Rillig’s “lab rats” are microscopic in scale and cannot really be seen in a Petri dish except in full colonies. They include a “furry” kind of mold called Mucor, delicate sac fungi from the genus Fusarium, and other ascomycetes. The fungi are enclosed with culture media in sterile containers with separate temperature controls. This takes place individually, in peaceable “communities,” or as competing neighbors. Some enter the experiment together with their native soil so researchers can observe the changes in the typical microcosm for each species all at once.

After that, the plan is to change the living conditions for the fungi very gradually, over a period of several months. Each experiment will have a control group in which everything remains unchanged. “Our main focus is on warming, but we will also be studying the influence of toxins and changes in vital resources,” Rillig explains. The development of the experimental setups is part of the project and represents its first phase. This is necessary because such involved, long-lasting experiments have not been performed on fungi in the past.

Although the “test subjects” look practically identical to the naked eye, the structure of the colonies is shown to vary widely when viewed under a microscope. “And no wonder, either. After all, there are many millions of years of evolutionary history between them. They are now only about as similar as a sheep and grasshopper,” he says, drawing a comparison.

What results does he expect the experiments to yield? “Environmental changes will not have the same effects on all fungi. For one thing, they are very diverse in terms of what they require of their biotic and abiotic – meaning mineral – environments. For another, they have different maximum temperatures where the only thing they can do is grow,” Rillig says. He expects to see changes in growth rate and appearance among some species, while some will probably fall by the wayside entirely.

One key experiment aims to show how and to what extent changes in the physiology of the fungi and the composition of their symbiotic communities take place through microevolution. With this in mind, researchers will take a series of sterile samples to study the fungi from a biochemical and genetic standpoint.

“We know that abrupt environmental changes do not leave enough time for evolutionary adaptation or for completely new variations in the genome,” Rillig explains. “But if something changes gradually, multiple generations are involved. In that situation, individual lines can be selected, or genes can change through mutation,” he explains. At the end of the experiments, the researchers aim to find this out by sequencing the complete genomes of the fungi.

Rillig’s project also has a political element, as one of the reviewers of the grant application pointed out. Even if the fungi may be able to adapt well, that does not mean that there is no need for concern about climate change. There are in fact indications that some species suffer surprisingly little adverse effect due to the changing conditions and not only survive, but even thrive. Some diatoms, for example, manage to draw more material for formation of shells from acidifying ocean water than ever before.

But that is little help to other species whose habitats are disappearing entirely, like polar bears, whose ice floes are literally melting out from under them. If the top of the food chain is vacant, the whole ecosystem changes. One thing is certain: Many species of animals and plants will no longer exist in the future. However – and this is the only good news – new species are constantly evolving as well, no matter what crises may affect the Earth.

This text originally appeared in German on September 24, 2016 in the Tagesspiegel newspaper supplement published by Freie Universität.