How do you describe your main lines of research?

My aim is to study the evolution of cooperation and punishment in nature, mostly between plants and microbes, but also between plants and animals, like ants. We are interested in why symbioses form, and what drives them to fall apart. I’m particularly interested in cheating in nature, and how organisms evolve strategies to benefit from being associated with cooperators, without cooperating themselves. Cheating is a driver of innovation, it is more common than people imagine. 

When did you first decide to focus on mycorrhizal fungi, and why?

When I was 19, I left university thinking I wanted to become a biologist by doing, not reading. It was naïve, but the intention landed me in a tropical rainforest in Panama where I studied tropical roots and fungi. While the dirt of rainforests may seem un-glamorous, it felt like a frontier, like the wild west. It was so unknown. Everyone was concentrating on all the diversity above ground, but the action for me has always been below ground.

Is working in the Netherlands different from working in the US in any way?

The work-life balance is radically different. People leave the office by 17.30, it is rare that people come into the lab on weekends. And I learned to take a proper summer holiday. 

What work does the market analogy do? Is it primarily a reminder to think of the fungi as selfish and of their strategies as rational, as opposed to thinking of them as altruistic?

When people use the word analogy, I like to clarify that, yes, it can be an analogy. However, it is also an analytical tool. Economics gives us a mathematical framework to analyse trade strategies in a predictive, quantitative manner. This is different from storytelling.

Are there hazards in drawing analogies between human agents and microbial linages?

There are always hazards in drawing parallels between human agents and microbes, especially when language is interpreted in different ways by different people. Words like “decision” can give the impression that a noncognitive organism shows “intent”, even though we are talking about strategies built into the DNA of the organism. More interestingly, language – especially economic language – may limit us. If I am studying how a fungal network moves and trades resources, I am relying on my own knowledge of economic trade strategies. But maybe the organism is using a strategy unknown in human markets? I may miss really innovative strategies because of my notions of what makes a “successful” trader.

Do you think that mycorrhizal markets have anything to teach us about how to run economic markets?

In some ways yes. These markets have been shaped by natural selection for hundreds of millions of years – all in the absence of cognition. There are clear lessons here about the efficient movement and trade of resources. But our economic system has become so radically different to the trade practiced underground. If it was stripped away of all its politics, and only the trade algorithms were left….I think we could draw some lessons.

Some very popular accounts have described trees and fungi as helping each other. For example, Suzanne Simard describes trees from different species as using fungal networks to feed and support one another.  Do you view your own work as empirically disconfirming such claims? Or are you simply using more careful language?

Simard and I agree on one very important point: these underground networks are incredibly complex and incredibly important. But I disagree with her view that forests should be considered as one “organism” that are “supercooperators”, and I am not convinced that plants use the fungal network to help dying and sick individuals. I see microbes - not as passive accessories to plants - but dynamic, powerful actors in their own right. Our work has shown that fungi can discriminate among good and bad plant partners, that they can hoard resources, that they can move resources across the network to get a better price. They are anything but passive.

In your gripping Ted talk you describe fungi as ‘little stockbrokers’ using clever ‘trade strategies’. Is such language just poetic frill, or does it involve a more substantive commitment? Do you think it is possible to avoid agential characterisations of these phenomena?

Yes, it is poetic frill. I like that phrase. But I try to use poetic frill backed by precise and quantitative science. 

Philosophers of biology make much of the possibility of flipping between different gestalts or perspectives, when it comes to evolution. For example, we can flip between viewing symbionts as parts of a single, evolving holobiont, or as separately evolving lineages in their own right. What do you make of these sorts of debates?

These debates are key, and philosophy plays a huge role in looking at how our individual vantage points play into what language we use. But as an evolutionary biologist, I feel strongly that we should speak of organisms in their own right. The phrase holobiont muddies the water, and makes that “own right” less clear. 

Do you think that cooperation has been generally neglected in evolutionary research, compared to competition? Why?

We used to say that, but I think it has changed in the last 20 years. The importance of cooperation is well recognized. Now we just need people to realise that there is this beautiful inherent tension in cooperation. It’s this tension that drives innovation. 

One of your successes has been in developing a new methodology for making resource exchanges visible.  If you could magic up a piece of kit with a novel way of interrogating your model systems (eg speed up evolution to watch it in real time; keep unculturable strains alive in the lab, etc) what would it be?

I would want to make resource exchange even MORE visible – we are still literally in the dark. I want to watch nutrient exchange in real-time, simultaneously across a whole network. Can you imagine all the trade deals taking place right now, under our feet? I want to see those interactions, live, in the soil.

The video ‘Underground market’, that you made in collaboration with Nils Hoebers, features cute little sound effects of bleeps and clicks as fungal hyphae make contact with tree roots. What do you make of the finding by a team in Grenoble that trees make ultrasonic screaming sounds when they are drought-stressed? Do you have any time for descriptions of trees and fungi as communicating with one another?

It comes back to language: ultrasonic noise was linked to stress. Does this mean we need to call it “screaming”? I agree it can help garner attention, but “screaming” implies the tree wants to be heard by something. It’s the same issue with the tree communication literature. It is clear that chemicals can travel across networks under stress conditions, but is this a directed signal or a passive cue? More research is needed in this area before we can feel confident that a signal is being sent to convey specific information, and that the receiver uses this information in a way that has direct benefits. 

You’ve spoken in the past about finding it difficult to persuade farmers that evolutionary biology matters for them. What do you find persuades them best?

I would take that statement back. I think we are in a new era where farmers can see the benefits of an evolutionary vantage point. Agriculture is really on the verge of major change. For example, the recognition and desire to harness the microbial world in agriculture is a positive sign. Farmers recognise the rapid adaptability of microbes, and are open to using this adaptability to help drive crop resilience and growth. I hope I can see those results in my lifetime.

What has been the proudest moment of your career, so far?

There is an award in the Netherlands to promote “unfettered research”. It was such an honour to be recognized for doing bold science. Plus it was like the opposite of digging dirt, because there was lots of applause and photos and even a banner that came furling down with a drawing of me. It was absurd and amazing at the same time. 

Are there any ways in which you think biological education needs to be done differently?

There is still structural racism in academia. This means diverse voices and ideas are not heard. This also comes at a cost to creativity. In my mind, creativity and natural history are paramount in research, but both are being swept aside.

You are fantastic at public engagement. What’s the secret?

Fantastic is a big word. I think the bar is so low at the moment that most attempts at engagement are appreciated. This is changing now too. The Netherlands, for example, is really supportive of forging links between science and art. We have government funds to host an artist in residence every year. 

It is fairly common for eminent or emeritus biologists to turn their attention to big-picture ideas, and occasionally even to write in philosophy journals. Do you have any such projects that you’re saving for after retirement?

We are working on launching a non-profit organization called SPUN, Society for the Protection of Underground Networks. The aim is to conserve unique underground ecosystems in the face of rapid environmental change. There is a world under our feet that we can’t even begin to comprehend. A teaspoon of soil can contain millions of individual fungi and several thousand species of microbes. We’ve identified just 1% of the micro-organisms that live there. We want the youth to care about the underground. It needs to be the disappearing rainforest or melting arctic of their generation. But there is no platform fighting for the underground – yet.