This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
A truffle is an unsubtle object. These odoriferous, lumpy subterranean fungi -- technically called sequestrate fungi, since their spores are never released to the air -- typically rely on animals to find and eat them, dispersing their spores when they heed the call of nature. If a truffle is in the same room, or, really, the same zip code, you will know about it.
But that is just because they have evolved to appeal to mammals. In a world without mammals, what does a truffle become?
New Zealand was once such a place. Before humans arrived in the 1200s AD (NZ was the last major habitable land mass to be discovered by humans), the only mammals were a couple of species of bat. The land was dominated by birds who had evolved into the niches mammals occupy elsewhere. To take but one example, there were nine species of now-extinct ostrich-like moa, the largest of which reached nearly 12 feet tall and over 500 pounds.
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Most birds, no matter their size, have notoriously poor senses of smell (the kiwi, an iconic New Zealand bird, is one big exception). On the other hand, they have wonderful vision. So in New Zealand, truffles became Easter eggs.
At least, that has been the hypothesis. A new study of fossil bird poo has provided more … er… solid proof. Scientists in Australia, New Zealand, and California subjected 23 fossilized feces called coprolites – found by the thousands in New Zealand caves -- to high-throughput DNA sequencing designed to detect the presence of as many different organisms as possible to determine what five different species of ancient New Zealand birds were eating. It revealed that at least three species were indulging in ‘shrooms, one from a known truffle-making group. The results were published this February in PNAS.
The team detected DNA from the mushroom-forming genera Cortinarius, Inocybe, and Armillaria in coprolites from two species of moa – including the giant one – and the critically endangered kakapo parrot. Because these fungi are symbiotic or parasitic with plants and not decomposers, it’s likely their presence in feces was the result of their consumption by the bird. They also found DNA evidence that the birds were eating the decomposing fungi Lepiota(mushrooms), Geastrum(earthstars), and Lycoperdon (puffballs).
Cortinarius is one of the mushroom groups that has at least partially truffle-ized in New Zealand. While the rest of the world’s truffles are brown and boring to look at (though positively exhilarating to smell), Kiwi truffles, like the Cortinarius that’s halfway to becoming a truffle (secotioid) at the top of this page, tend to be lurid, an adaptation that strongly hints they were marketing themselves to birds. And now there is proof that the birds were buying what the fungi were selling.
Reference
Boast, Alexander P., Laura S. Weyrich, Jamie R. Wood, Jessica L. Metcalf, Rob Knight, and Alan Cooper. "Coprolites reveal ecological interactions lost with the extinction of New Zealand birds." Proceedings of the National Academy of Sciences (2018): 201712337.
