Wed. Dec 7th, 2022
DNA from the poo of extinct four-meter-tall birds reveals lost ecosystem

A thousand years ago, giant 12-foot-tall ratites roamed New Zealand, peacefully snacking on plants and fungi. Then people came along. Within two hundred years, the giant moa—along with many of their closest cousins—were dead at the hands of our species.

What was the world of the moa like? Even though New Zealand has a lot of well-preserved wilderness, studying that doesn’t give us an answer. When a species disappears, it takes part of its ecosystem with it, so understanding the consequences of the moa’s extinction can help us better understand the environment in which many surviving species — some of which are critically endangered.

Some key answers lie in something the moa left behind: old bird droppings. It tells us that the moa probably played an important role in spreading the fungi that play a crucial role in New Zealand’s forests.

Pre-human preservation

A team of researchers in Australia and New Zealand, led by paleobiologist Alexander Boast, has extracted DNA from 23 ancient dung samples. These samples, called coprolites, ranged between 124 and 1,557 years old, and they came from three different species of moa and the kakapo, New Zealand’s fuzzy, confused-looking and critically endangered walking parrot.

New Zealand’s climate, abundant cave systems and relatively recent human colonization all make it a prime spot for paleobiology, and the moa in particular is a “model organism in [ancient] DNA research,” said Morten Allentoft, an ancient DNA researcher who was not involved in this article. “The moa represent some of the world’s best-studied extinct organisms,” he told Ars. “We know a lot more about moa than about many of the [living] birds in New Zealand.”

Moa droppings are proving to be a source of information. They have been studied for years by researchers examining them for microscopic clues about what the animals they deposited were eating. In fact, researchers have extracted genetic information from it before, but with newer techniques, Boast and his colleagues were able to collect much more than was previously possible.

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One of the findings this yielded was that moa “may have played an irreplaceable role in the proliferation of fungi essential to a dominant forest type in [New Zealand]”, write Boast and his colleagues. The coprolites contain genetic material from mushrooms that are colorful — often an indicator that they evolved to attract the attention of grazing animals — and rely on animals to eat them and spread their spores. No grazing animals, no spreading of fungi.

New Zealand’s beech forests, which currently have unexplained missing spots, depend on close relationships with fungi. The coprolites suggest that the moa may have played a critical role in dispersing both the beech seeds and the spores of the fungi they needed to survive. The small populations of kakapo cannot do the heavy lifting on their own, so the demise of the birds has important consequences for the forests.

There also doesn’t seem to be an easy way to fill the gap. Mammals introduced to New Zealand by humans, such as the red deer, don’t seem to be able to absorb the slack. Even if a mammal fills roughly the same slot in an ecosystem as a giant moa, native New Zealand fungi don’t seem to be able to survive their digestive system. “This is potentially alarming in light of current species reductions and local extinctions,” the authors write.

Trained interpretation

Although the coprolites provided a lot of information about the ecosystems around the moa, questions remain. “We can’t go back and directly observe or test all the hypotheses put forth here,” Allentoft said. “But that has to be accepted in areas of research dealing with the prehistoric past.”

What the paper does make clear, he emphasized, is that extinction always means more than just the loss of an iconic species. “We could also lose a range of associated species and their ecological interactions. It has a big impact.”

PNAS2018. DOI: 10.1073/pnas.1712337115 (About DOIs).

By akfire1

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