A thousand years ago, gigantic 12-foot-tall flightless birds roamed New Zealand, snacking peacefully on plants and fungi. Then humans came along. Within two hundred years, the giant moa—along with a host of their close cousins—were dead at our species’ hands.

What did the world of the moa look like? Even though New Zealand has lots of well-preserved wilderness, studying that won’t give us an answer. When a species disappears, it takes a chunk of its ecosystem with it, so understanding the ramifications of the moa extinction can help us better understand the environment that many surviving species—some of them critically endangered—evolved in.

Some important answers lie in something the moa left behind: ancient bird poop. It tells us that the moa were probably instrumental in spreading the fungi that play a critical role in New Zealand’s forests.

Pre-human preservation

A team of researchers in Australia and New Zealand, led by paleobiologist Alexander Boast, 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, befuddled-looking, and critically endangered flightless parrot.

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

Moa droppings, it turns out, are a wellspring of information. They’ve been studied for years by researchers examining them for microscopic clues about what the animals that deposited them were eating. Researchers have even extracted genetic information from them before, but newer techniques allowed Boast and his colleagues to gather far more than previously possible.

Sowing seeds

One of the findings that this turned up was that moa “may have provided a potentially irreplaceable dispersal role for fungi essential for a dominant forest type in [New Zealand],” write Boast and his colleagues. The coprolites contained genetic material from mushrooms that are colorful—often an indicator of having evolved to attract the attention of grazing animals—and that rely on animals to eat them and disperse their spores. No grazing animals, no fungus dispersal.

New Zealand’s beech forests, which have some currently unexplained missing patches, rely on close relationships with fungi. The coprolites suggest that the moa may have played a pivotal role in dispersing both the beech seeds and the spores of the fungi they needed to survive. The tiny populations of kakapo can’t do all the heavy lifting on their own, and so the demise of the birds has important implications for the forests.

There doesn’t seem to be an easy way to fill the gap, either. Mammal species that have been introduced to New Zealand by humans, like the red deer, don’t seem to be able to pick up 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 systems. “This is potentially alarming in light of current species reductions and local extinctions,” the authors write.

Educated interpretation

Although the coprolites yielded lots of information on the ecosystems surrounding the moa, questions remain. “We cannot go back and directly observe or test all the hypotheses brought forward here,” said Allentoft. “But this has to be accepted in research fields that deal with the prehistoric past.”

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

PNAS, 2018. DOI: 10.1073/pnas.1712337115  (About DOIs).

https://arstechnica.com/?p=1260893