Unique Parasite Adna in Moa Coprolites from New Zealandsuggestsmassparasiteextinctionsfollowed COMMENTARY Human-Induced Megafauna Extinctions Kevin D
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COMMENTARY Unique parasite aDNA in moa coprolites from New Zealandsuggestsmassparasiteextinctionsfollowed COMMENTARY human-induced megafauna extinctions Kevin D. Laffertya,1 and Skylar R. Hopkinsb Having split early from Gondwana, Zealandia (now sample can become contaminated where it lies or modern New Zealand) escaped discovery until the late during sample handling, transport, and storage. How- 13th century, and therefore remains an important ever, dedicated aDNA facilities and rigorous protocols glimpse into a human-free world. Without humans help reduce contamination (5). Even then, authentic or other land mammals, diverse and peculiar birds aDNA fragments can be hard to decipher, because evolved in isolation, including several flightless moa short diagnostic DNA barcodes are still unavailable species, the giant pouakai eagle (Harpagornis for most plants and animal species (1). Thus, scientists moorei), the kiwi (Apteryx mantelli), and the kakapo who work with aDNA need to be careful, both in their parrot (Strigops habroptila). This unique community techniques and their interpretation. When it works, the has fascinated paleoecologists, who have spent almost effort pays off with insights not imaginable when pa- two centuries devising new ways to glean information leontologists cracked open that first moa coprolite. from ancient bird remains. In PNAS, Boast et al. (1) apply Boast’s research group has been around the aDNA one recent technological advance, ancient DNA (aDNA) block before, having used first-generation sequencing metabarcoding, to confirm previous discoveries and re- techniques on plant, microbe, and parasite aDNA port new details about moa and kakapo diets, parasites, from moa coprolites to yield family- and even genus- and niches. Their efforts confirm Zealandia was a lot dif- level taxonomic resolution for several taxa that the ferent before humans arrived. moa interacted with (6, 7). However, first-generation Zealandia’s most diverse avian oddities were the techniques are too time-consuming and expensive for moa. Moa research goes back to the early 1800s, compiling a comprehensive ancient food web. To when the Maori told legends to colonizing Europeans make the most from their samples, Boast et al. (1) about giant birds and showed them fossilized moa switched to high-throughput sequencing, which con- bones in caves. Those fossils belonged to at least nine firmed previous first-generation results and unearthed moa species ranging from 1 to 4 m tall, some with several hitherto unknown ecological interactions be- notable sexual dimorphism (2). The moa species have tween the moa and plants, fungi, and parasites. In different fossil distributions, morphology, and gizzard addition to describing these new results, Boast et al. contents, suggesting they partitioned Zealandia’s re- (1) synthesize past findings to add resolution to the sources into distinct ecological niches. To better under- Zealandia food web. stand how moas coexisted and interacted with other In this enhanced snapshot from Zealandia (Fig. 1), species, paleontologists have turned to another abun- an upland moa (Megalapteryx didiformis) stops to eat dant deposit that moas left behind: coprolites (fossilized moss under a southern-beech tree (Nothofagaceae) dung). The 2,000 moa coprolites that have been col- and then defecates feces laced with parasite eggs lected thus far contain plants, fungi, microbes, and in- on the forest floor. As with many other upland moa, testinal parasites (3), a priceless resource for creating it acquired parasitic trematodes when feeding at a ecological snapshots from Zealandia. Until the aDNA small alpine pond and heterakoid nematodes when revolution, however, these snapshots were blurry (4). eating contaminated ferns and other vegetation. How- Sequencing aDNA allows paleontologists to iden- ever, the moa’s real concern is the pouakai, the tify dung-encased organisms at finer resolution than world’s largest eagle and the only moa predator. A they see with a microscope. Studying aDNA is nerve- nearby South Island giant moa (Dinornis robustis) has wracking, because it degrades over time and each no interest in the upland moa’s moss. Instead, it lunges aUS Geological Survey, Western Ecological Research Center, c/o Marine Science Institute, University of California, Santa Barbara, CA 93106; and bNational Center for Ecological Analysis and Synthesis, Santa Barbara, CA 93101-5504 Author contributions: K.D.L. designed research; K.D.L. and S.R.H. performed research; S.R.H. analyzed data; and K.D.L. and S.R.H. wrote the paper. The authors declare no conflict of interest. Published under the PNAS license. See companion article on page 1546. 1To whom correspondence should be addressed. Email: [email protected]. www.pnas.org/cgi/doi/10.1073/pnas.1722598115 PNAS | February 13, 2018 | vol. 115 | no. 7 | 1411–1413 Downloaded by guest on September 24, 2021 Fig. 1. The ancient Zealandia food web was much different from that in present-day New Zealand, and it included several ecological interactions that Boast et al. (1) revealed by sequencing aDNA from moa coprolites. For instance, the upland moa (M. didiformis) ate moss, ferns, mycorrhizal fungi that require animal-assisted dispersal, and aquatic vegetation. The upland moa also accidentally ate (and was infected by) aquatic trematode larvae (Notocotylidae) and apicomplexan parasites (Eimeriidae), which still exist in extant kiwi. Other parasites that once infected moas, like several heterakoid nematode species, have not been seen since the moa extinctions. Dashed arrows indicate interactions lost since the moa extinctions. forward and snaps up a tasty-looking mushroom near a southern- named it Aotearoa. The Maori hunted the moa, which had only feared beech trunk. It is lucky to have found this gem, because kakapos the pouakai, and drove the nine moa species extinct within ∼200 y (10). and upland moas also seek out Cortinarius mushrooms. The fungal Boast et al. (1) show that some species that interacted with the spores will pass through the giant moa’s digestive system, in which moa survived their loss. For instance, the upland moa’s Eimeriid live apicomplexan parasite oocysts (Eimeriidae) and an ascarid coccidians still parasitize extant kiwi. Likewise, animal-dispersed nematode or two. Later, defecated fungal spores will have the mycorrhizal fungi still exist in New Zealand’s modern forests even chance to establish a mycorrhizal relationship with a new host tree, without extant animal dispersers (11). These fungi might be eco- and a kiwi might accidentally eat the defecated oocysts. Ancient logical anachronisms, like the giant fruits in the Americas that rot paradise, it turns out, had abundant dung and parasites. under their trees without extinct mammalian megafauna to eat Such interactions continued within this robust Zealandia them and disperse their seeds (12). Just as the long-lived trees ecosystem, despite environmental and climate fluctuations (8, in the Americas have slowly declined without their ancient seed 9), until the first Maori landed their canoes on Zealandia and dispersers, so too might the moa-dispersed fungi and their 1412 | www.pnas.org/cgi/doi/10.1073/pnas.1722598115 Lafferty and Hopkins Downloaded by guest on September 24, 2021 southern-beech tree hosts decline unless they adapt to use new a chewing louse (Huiacola extinctus) went extinct (17), along with spore dispersers or moa deextinction ideas become reality (13). its host, the huia (a wattlebird hunted for its feathers). More re- Other species were not robust. Without moa, the pouakai starved. cently, the louse Rallicola (Aptericola) pilgrimi was lost after its Pouakai is the most obvious secondary extinction to follow the moa, host, the smallest kiwi (Apteryx owenii), was translocated to but Boast et al. (1) suggest that other species fell like a teetering predator-free islands (18). Therefore, most New Zealand extinc- Jenga tower after a critical piece is pulled. In particular, several heter- tions have probably been parasite extinctions. akoid nematode species had coevolved to specialize on moa, and Society will decide whether we preserve, ignore, or extirpate have not been seen since the moa disappeared. Other moa and species we find insignificant, threatening, or disgusting. Some pouakai parasites (most likely several never-seen, host-specific lice) point out that parasites deserve protection because they can were probably lost. These secondary extinctions result because play important roles as consumer species (19). Others consider coevolved complex systems cannot evolve robustness to swift, un- that ignoring these associated species is taxonomic chauvinism predictable events like the Maori ’s arrival and rapid domination (14). (20); it is like counting sunken ships in a naval battle, without How many secondary extirpations or extinctions occurred is not yet mourning the sailors that go down with those ships. The extent clear, and will remain unknown until there are larger sequence librar- to which we value host vessels or their parasite passengers is ies from extant species that can be used to confirm their absences. To most often answered by veterinarians. When veterinarians treated understand the past with aDNA, one must also sequence the present. the last remaining California condors in 1987, they found the Between the ancient moa extinctions and the present, Euro- condor louse, Colpocephalum californici, a symbiont whose an- peans and their introductions further altered New Zealand’s bio-