Before New Zealand’s giant flightless birds, moa, went extinct about 600 years ago, they played a critical role in the archipelago’s ecosystem. Their loss may have flow on effects for other species.

The ecological role that moa played is still not fully understood.

New research, published in Biology Letters, sheds light on the relationship between moa; a type of native truffle-like fungus; and a tree.

The study relied on moa coprolites – fossilised dung –which included those previously believed to belong to kākāpō. DNA analysis in fact showed that some belonged to one of the smallest species of moa, the upland moa, Megalapteryx didinus.

Upland moa – sometimes referred to as “mountain goat moa” – were less than 50kg, although among the other 9 species, the largest grew to more than 3m and 250kg. There used to be a large number of large, flightless birds foraging on New Zealand’s forest floors in the absence of large mammals.

Studying poop pays off

“We’re very interested, as palaeoecologists – ecologists studying past ecosystems – in the dynamics between species,” lead author Alexander Boast tells Cosmos.

“It’s very difficult to do this,” Boast adds.

“If you look at the bone fossil record, you can infer things about diet or behaviour. But to actually have direct evidence of an interaction is very hard. Coprolites are great that way because you’ve got the last day or two behaviour of an animal from hundreds of thousands or millions of years ago.”

Boast’s team at the Manaaki Whenua – Landcare Research government institute in NZ, has found itself becoming kind of experts on Late Quaternary coprolites in New Zealand, which makes him laugh. The Quaternary period includes the last 2 epochs in Earth’s history: the Pleistocene (2.58 million to 11,700 years ago) and the Holocene (11,700 years ago to today).

“We’ve been studying coprolites that are quite recent in age,” Boast says. “That’s convenient in New Zealand because if you’re wanting to study extinctions, New Zealand happened quite late on the global sphere.”

Humans settled New Zealand about 700 years ago, Boast says – much later than most other parts of the world. This means it had a relatively “pristine” natural ecosystem until very recently.

“The oldest coprolites they’ve found in New Zealand date to about 8,000 years ago, but one of the ones we studied was about 600–700 years old,” Boast says. Another coprolite was 2,000 years old.

Boast says that his team used advanced metabarcoding to analyse the DNA preserved in the coprolites, enabling the researchers to identify not only the species that produced the ancient dung, but also its food.

By accident, the team identified a native fungus eaten by the ancient moa.

Moa truffles please

The brightly-coloured fungus, Gallacea scleroderma, belongs to a group of “truffle-like” fungi including true truffles themselves. This group doesn’t open up to release its spores like mushrooms that we’re all familiar with.

Instead, Boast explains: “They can’t disperse these spores naturally. They’re actually adapted for dispersal by animals.”

“A good example is, of course, the truffle itself. It doesn’t even emerge above the ground and develops fully in the ground. And it was dispersed originally by things like wild boar which would by attracted to the very strong scent.”

But birds don’t have very strong senses of smells like mammals do. Boast’s team suggests that the truffle-like fungi in New Zealand adapted a way around this.

“Birds have very strong colour vision and they will forage predominately by sight,” Boast explains. “So it looks like there’s been some kind of mimicry. Effectively, these fungi look like berries on the forest floor which is remarkable.”

Boast adds that there is strong evidence that modern birds like the kākāpō – itself critically endangered – also fed on the fungus.

Love triangle ecosystem

The fungi in question are also mycorrhizal which live in the soil and have a close symbiotic relationship with native trees – often big, forest-forming trees.

“Eucalyptus, for example, are totally dependent on mycorrhizal fungi,” Boast says. “And in New Zealand, we’ve got the southern beech which comprise something like a third to two-thirds of all the forests in New Zealand.”

He says that, in the case of the moa-fungus-tree relationship, there is a “tripartite mutualism”.

Now that one of the links in that chain – the moa – has been removed, there might be flow on effects for the fungus and trees, and beyond. Boast says the extent of the effects are still being understood.

The fungus, now less able to proliferate, may be important for soil health as well as the spread of southern beech trees.

Boast says invasive species such as wallaby, deer and wild pigs now fill the ecological niche left by the moa and may be exacerbating the problem.

“Exotic fungi often are mycorrhizal too, and they’re not symbiotic with native trees but with exotic trees. There was a paper discussing a potential ecological meltdown, where you’ve got a new mutualism pushing in to create a new ecosystem.”

Such changes could take thousands of years to fully take form, Boast says. For now, it’s clear that the moa’s absence is having an impact on its fungi and tree friends.

“We think the moa might have been particularly good dispersers compared to some of the other native birds,” he says. “They’ve got a big body, they could have consumed a lot of things and they might have moved between different habitat types.”

“Of course, it’s very cool to look at a past ecosystem, but we’re trying to understand just how complex ecosystems were in the past, and what kind of long-term legacy impacts of extinction might be,” Boast emphasises.

“It’s why we see this work as being very important and I would like to keep progressing more.”