ľ�ϸ���Ӱ��

Parasites not only play a crucial role in maintaining biodiversity within ecosystems, they are part of this biodiversity themselves. In fact, it is not unlikely that the majority of species on earth are parasites. Despite this, parasites are often overlooked in biodiversity research and conservation efforts. That needs to change, says zombie ant researcher Charissa de Bekker.

Who likes parasites? They cause disease and death and they are hardly cute or beautiful. Yet, they play a crucial role in ecosystems by helping to maintain biodiversity. How exactly do they do that?

“Parasites help keep populations in check so that no single species becomes dominant,” De Bekker explains. “They also play a crucial role in food webs. For instance, some parasites alter their host’s behavior, making it more likely that the host will be eaten by another animal.”

People do not very often encounter parasites in a way that sparks wonder.

Part of biodiversity

But parasites do not just influence biodiversity—they are biodiversity themselves, a fact that is often overlooked. In fact, some biologists suspect that parasites might actually account for the majority of species on Earth.

De Bekker: “A broad definition of a parasite is any organism that takes nutrients away from another organism, causing harm to that other organism. Viewed that way, parasites include animals, plants, fungi, bacteria, and viruses that live at the expense of other organisms. This means parasites could very well be the largest group of species on Earth—after all, virtually every organism, even parasites themselves, has parasites. But we cannot say for sure, because our mapping of biodiversity is still far from complete, especially for parasites.”

We should treat some parasites the same as other species that play key roles in ecosystems, such as predators.

Overlooked

The latter is an important point because, as De Bekker explains, parasites are often left out when an ecosystem’s biodiversity is mapped. De Bekker: “They are usually only considered when someone specifically studies parasites within an ecosystem, not when broader biodiversity is being assessed.”

Why is that? “We tend to think very negatively about parasites,” De Bekker explains. “They make organisms sick and do not give anything in return. So we assume they have no real value. When parasites affect us directly, like in the case of diseases that harm crops we rely on, we often know a bit more about them.”

Even biologists, from whom you might expect a broader perspective, often overlook parasites. De Bekker: “I think there is a practical reason for this: it is hard to secure funding for parasite research. On top of that, it likely has to do with how we are raised. People do not very often encounter parasites in a way that sparks wonder.”

Parasite conservation

There is also no such thing as parasite conservation in conservation biology. But De Bekker believes there should be. “We should treat some parasites the same as other species that play key roles in ecosystems, such as predators.”

But how do you protect parasites? After all, by definition, they rely on one or more other species to survive. According to De Bekker, there is no clear answer—at least not yet. “We simply do not know enough about most parasites,” she says. “For example, we still have a lot to learn about how they interact with their hosts and what impact that has on populations.”

Going Back Outside

That is why biologists need to spend more time in the field again, De Bekker argues. “These days, most biological research happens in the lab. Old-school biology—where people go into nature, make observations, and collect very detailed data—has become rare. But we now have tools like artificial intelligence that can help us process large amounts of data. So maybe it is time to get back out there and find out what is happening in nature.”

In 2022, a student of De Bekker described ecological factors that influence the occurrence of the zombie ant parasite that De Bekker studies. “The journal found it remarkable that we had gathered so much data from the field and asked us to put extra emphasis on that in our introduction. But to me, this felt just like old-fashioned biology from the 1960s.”

Making them attractive

How can we get people to care more about parasites? According to De Bekker, it helps to showcase charismatic examples. “When I talk about my research on fungi that turn ants into zombies, people often ask me if they can see this happening in the Netherlands as well. The truth is, these fungi exist worldwide, but they have likely disappeared from Europe—even though the ants are still here. That is probably because human activity has altered the environment. The conditions in which these fungi can survive, no longer exist here. I often notice people's disappointment when they realize this. By using such striking examples, people realise they feel regret that they can no longer witness these phenomena in nature themselves.”