Tue, Aug 16, 2022: 9:15 AM-9:30 AM
515A
Background/Question/MethodsDuring 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/ConclusionsThe 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.
Results/ConclusionsThe 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.