COS 50-6 - Dining at the mammoth buffet: megaherbivore diets illuminate mechanisms of species coexistence in Pleistocene Siberia

Tuesday, August 16, 2022

9:15 AM – 9:30 AM EDT

Location: 515A

Presenting Author(s)

JG

Jacquelyn Gill

Associate Professor of Paleoecology and Plant Ecology
University of Maine, Maine, United States

Coauthor(s)

AM

Alessandro Mereghetti

PhD Candidate
University of Maine, Maine, United States
BS

Beth Shapiro

UC Santa Cruz, California, United States
VP

Valery Plotnikov

Academy of Sciences of the Sakha Republic
Yakutsk, Russia
AP

Albert Protopopov

Academy of Sciences of the Sakha Republic
Yakutsk, Russia
KJ

Karen James

University of Maine
Orono, Maine, United States
VH

Victoria Herridge

Natural History Museum, London, United Kingdom
LD

Love Dalen

Swedish Museum of Natural History, Sweden
EM

Ethan Mackenzie

University of Maine
Orono, Maine, United States
MM

Mikayla Mason

University of Maine, United States
NB

Noa Buzby

University of Maine, United States
TB

Thomas Bertsch

University of Maine, Maine, United States
DF

Dan Fisher

University of Michigan, United States

Background/Question/Methods

During the late Pleistocene, the circumboreal “mammoth steppe” was the largest biome in the world, supporting a diverse guild of cold-adapted megaherbivores including woolly mammoths (Mammuthus primigenius), woolly rhinoceros (Coelodonta antiquitatis), steppe bison (Bison priscus), and horses (Equus sp.). This no-analog community is thought to have been highly diverse and productive, and while it’s uncertain whether the mammoth steppe was maintained by keystone herbivores or glacial climates, the mechanisms supporting the coexistence of its diverse guild of megafauna remains poorly understood. Niche theory predicts that megaherbivore coexistence may be enabled by dietary specialization, and there is some evidence for this in contemporary megafaunal communities. However, this theory remains untested for the extinct megafaunal communities of the Pleistocene, in part because of gaps in our understanding of Pleistocene megafauanal diets. To better understand whether and how extinct megaherbivores partitioned their diets, we analyzed a unique set of 59 coprolites (sub-fossil feces) collected from the Belaya Gora region of the Sakha Republic, Russia. Plant communities derived from pollen, plant macrofossils, and ancient DNA (aDNA) were analyzed with non-metric multidimensional scaling to achieve an unprecedented taxonomic resolution for dietary and environmental reconstruction. The coprolite producers were identified with aDNA and dung morphology.

Results/Conclusions

The coprolites ranged from 20,000 to >50,000 BP in age, representing environments and diets for woolly mammoths, bison, woolly rhinos, and horses prior to the Last Glacial Maximum. Despite variable climates in western Beringia across that interval, NMDS of pollen-derived vegetation (i.e., the regional environment) indicate cohesion of the mammoth steppe through time. Woolly mammoths represented the broadest NMDS ordination space, consistent with their hypothesized role as keystone species. In contrast, woolly rhinos and steppe bison did not overlap in ordination space, suggesting either a temporal niche segregation or the utilization of microhabitats within the mammoth steppe. Plant macrofossil and aDNA data complement, but don’t completely overlap with, pollen data, and are interpreted as representing megaherbivore diets. Results from plant macrofossils and aDNA indicate that 1) mammoth steppe “grazers” consumed woody browse in addition to grasses and forbs, and 2) show evidence of dietary niche partitioning (i.e., NMDS space was segregated by taxon). Our results not only illuminate the mechanisms facilitating the coexistence of Pleistocene megaherbivores, but also support a top-down control of the vanished mammoth steppe. Further, our results suggest that Arctic megaherbivores may act as a buffer, promoting the resilience of Arctic vegetation to climate change.