Distribution of C3 and C4 Plants in the Late Pleistocene of South Australia Recorded by Isotope Biogeochemistry of Collagen in Megafauna

Abstract

Stable carbon-isotope analyses (expressed as a ¹³C:¹²C ratio relative to that of a standard: δ¹³C) on fossilised collagenic material in megafaunal bones can provide information regarding the palaeodiet (e.g. C₃ and/or C₄ plants) of these animals. Isotope analyses were performed on collagenic material extracted from bones of Sthenurus spp., Diprotodon spp. and Macropus spp. from Cooper Creek, Henschke Cave, Baldina Creek, Dempsey’s Lake and Rocky River in South Australia. The percentage of trees and shrubs estimated from palaeofloral records in south-eastern Australia and the dietary preferences of megafauna were found to be positively correlated. The dietary preferences of megafauna analysed from South Australian localities indicate that megafauna were opportunistic and changed their diet in response to environmental change. This suggests that megafauna diet can not be founded on dental morphology alone. Fossilised collagenic material in vertebrate remains can provide an insight into the broadscale nature of the vegetation. This approach is a good compliment for other palaeoecological data (e.g. sedimentology, spore–pollen, diatoms) by providing evidence for past climates in relation to the proportion of C₃ and C₄ plants.