| dc.description.abstract | Northern ecosystems are experiencing dramatic changes due to anthropogenically
accelerated climatic warming. Understanding the impacts of this on fauna and flora is key to
predicting the long-term sustainability of northern environments. This requires long-term data sets
of ecosystem response to environmental change from environments and climates contiguous to
contemporary conditions. One event is the climatic warming recorded at the Pleistocene-
Holocene transition that resulted in the extinction of 35 megafaunal genera and loss of the
mammoth steppe biome in East Beringia. Previous studies have relied on spatially and
temporally correlating bone remains, but coprophilous fungi preserved in lake sediments have
recently been used as a complimentary proxy for reconstructing megaherbivore populations.
A high-resolution record spanning this transition has been reconstructed using a sediment
core collected from Gravel Lake, central Yukon Territory. Pollen and coprophilous fungi were
complimented by radiocarbon-dated bone remains from Alaska and Yukon Territory. Results
indicate the local extirpation of megaherbivores at the beginning of the Holocene (ca. 11,000 to
10,400 cal yr BP) by a decline in coprophilous fungi and a lack of bone remains from Yukon
Territory. However, skeletal records indicate the loss of mammoths and horses at ca. 13,000 cal
yr BP, 2000 years prior to the fungi records. At this time, pollen assemblages from Gravel Lake
indicate the last environments contiguous with the mammoth steppe from this region. The data
highlight a faunal turnover at ca. 13,000 cal yr BP with the proliferation of browsing taxa, but it
is still unclear why only mammoth and horse populations are lost and not other grazing taxa such
as bison and muskox.
A secondary study analysed remains preserved in mastodon dung dated to the marine
isotope stage 5a/4 transition of Nova Scotia. Results indicate a wetland rich in charophytes,
sedges, cattails, bulrushes and bryophytes in a spruce-dominated boreal forest. The limited
diversity and abundance of coprophilous fungi in the dung could be attributed to a browser
feeding habit. If so, this could have a considerable impact on understanding the influence of
feeding ecologies on the presence of coprophilous taxa in lake sediments, and thus inferences of
megaherbivore abundance. | en_US |
