Dietary responses of Sahul (Pleistocene Australia–New Guinea) megafauna to climate and environmental change

Abstract

Abstract.-Throughout the late Quaternary, the Sahul (Pleistocene Australia-New Guinea) vertebrate fauna was dominated by a diversity of large mammals, birds, and reptiles, commonly referred to as megafauna. Since ca. 450-400 Ka, approximately 88 species disappeared in Sahul, including kangaroos exceeding 200 kg in size, wombat-like animals the size of hippopotamuses, flightless birds, and giant monitor lizards that were likely venomous. Ongoing debates over the primary cause of these extinctions have typically favored climate change or human activities. Improving our understanding of the population biology of extinct megafauna as more refined paleoenvironmental data sets become available will assist in identifying their potential vulnerabilities. Here, we apply a multiproxy approach to analyze fossil teeth from deposits dated to the middle and late Pleistocene at Cuddie Springs in southeastern Australia, assessing relative aridity via oxygen isotopes as well as vegetation and megafaunal diets using both carbon isotopes and dental microwear texture analyses. We report that the Cuddie Springs middle Pleistocene fauna was largely dominated by browsers, including consumers of C 4 shrubs, but that by late Pleistocene times the C 4 dietary component was markedly reduced. Our results suggest dietary restriction in more arid conditions. These dietary shifts are consistent with other independently derived isotopic data from eggshells and wombat teeth that also suggest a reduction in C 4 vegetation after~45 Ka in southeastern Australia, coincident with increasing aridification through the middle to late Pleistocene. Understanding the ecology of extinct species is important in clarifying the primary drivers of faunal extinction in Sahul. The results presented here highlight the potential impacts of aridification on marsupial megafauna. The trend to increasingly arid conditions through the middle to late Pleistocene (as identified in other paleoenvironmental records and now also observed, in part, in the Cuddie Springs sequence) may have stressed the most vulnerable animals, perhaps accelerating the decline of late Pleistocene megafauna in Australia.

The phylogenetic signal in tooth wear: What does it mean?

“…between certain distantly related taxa), but to document differences in diet when they might not necessarily be expected based on tooth morphology alone. Differences between closely related taxa have been captured, for instance, in bovids (Scott, 2012; Ungar, Merceron, & Scott, 2007), cervids (Berlioz, Kostopoulos, Blondel, & Merceron, 2017), ungulates (Schulz, Calandra, & Kaiser, 2010), feliforms (DeSantis & Haupt, 2014; DeSantis, Tseng, et al, 2017), canids (DeSantis et al, 2015), primates (Scott et al, 2005; Ungar, Grine, & Teaford, 2008), and macropodids (DeSantis, Field, Wroe, & Dodson, 2017; Prideaux et al, 2009). Indeed, many bioarchaeological studies have demonstrated distinctive and predictable diet‐related differences in both gross dental wear and microwear within a single species, Homo sapiens (Rose & Ungar, 1998).…”

What does the occurrence of Sporormiella (Preussia) spores mean in Australian fossil sequences?

“…The microfossil record and the sediment facies of fine clay with little silt (Field and Dodson, ) indicates a lacustrine and non‐fluvial setting, an interpretation confirmed by electromagnetic survey (see Field et al ., ). Discrepancies in dating studies, interpreted by some researchers as indicating site disturbance, have no support in the systematically compiled site data investigating the geomorphology, archaeology and fossil faunal sequences (see discussion in Field and Wroe, ; DeSantis et al ., ). Notably, contrary to the unsupported assertions of Grün et al .…”

“…The lower (SU9) and upper (SU6A, SU6B) layers have several megafauna taxa in common although the species diversity appears to have contracted significantly by the time SU6A/B formed (Fillios et al ., ; see also DeSantis et al ., ).…”

“…The aim here is to describe the environmental setting from a new pollen and spore record and to examine the abundance of Sporormiella spores in sediments enclosing the bones of extinct megafauna. The Cuddie Springs sequence provides an opportunity to compare environments and Sporormiella abundance in the presence of humans, and in times long pre‐dating a human presence in Sahul from sediments deposited around 400 ka (Grün et al ., ; Field et al ., ; DeSantis et al ., ).…”

“…Previous work established a sequence of megafauna, archaeology and palaeoenvironmental data (Dodson et al ., ; Field and Dodson, ; Field et al ., , , , 2013; Field, ; Fillios et al ., ; DeSantis et al ., ). The top ∼2.2 m in the centre of the basin contains two horizons where bones are concentrated.…”