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Extinctions stemming from environmental change often trigger trophic cascades and coextinctions. Bottom–up cascades occur when changes in the primary producers in a network elicit flow-on effects to higher trophic levels. However, it remains unclear what determines a species' vulnerability to bottom–up cascades and whether such cascades were a large contributor to the megafauna extinctions that swept across several continents in the Late Pleistocene. The pathways to megafauna extinctions are particularly unclear for Sahul (landmass comprising Australia and New Guinea), where extinctions happened earlier than on other continents. We investigated the potential role of bottom–up trophic cascades in the megafauna extinctions in Late Pleistocene Sahul by first developing synthetic networks that varied in topology to identify how network position (trophic level, diet breadth, basal connections) influences vulnerability to bottom–up cascades. We then constructed pre-extinction (~80 ka) network models of the ecological community of Naracoorte, south-eastern Sahul, to assess whether the observed megafauna extinctions could be explained by bottom–up cascades. Synthetic networks showed that node vulnerability to bottom–up cascades decreased with increasing trophic level, diet breadth and basal connections. Extinct species in the Naracoorte community were more vulnerable overall to these cascades than were species that survived. The position of extinct species in the network – tending to be of low trophic level and therefore having relatively narrow diet breadths and fewer connections to plants – made them vulnerable. However, these species also tended to have few or no predators, a network-position attribute that suggests they might have been particularly vulnerable to new predators. Together, these results suggest that trophic cascades and naivety to predators could have contributed to the megafauna extinction event in Sahul.

It is indisputable that much of Australia's modern biodiversity decline was triggered by European settlement. However, the driver(s) of pre-European extinctions and extirpations are more challenging to identify, particularly on islands where animals are faced with the additional pressures imposed by isolation. Kangaroo Island, South Australia, has been identified as a potential haven for the reintroduction of endangered animals, but the genetic relationship between reintroduction candidates on the mainland and their extinct relatives on Kangaroo Island is poorly understood. Here, we present a late Pleistocene to mid-Holocene genetic record from Kangaroo Island based on bulk bone metabarcoding of two thousand bone fragments excavated from Kelly Hill Cave. We detect 33 species of bird, reptile, fish and mammal and report additional intra-specific genetic diversity in Kangaroo Island's now extinct population of spotted-tailed quoll. Furthermore, we provide genetic evidence that the Eastern grey kangaroo formerly inhabited Kangaroo Island. Taken together, these data establish a more complete baseline of local biodiversity against which reintroduction programmes and bushfire recovery measures can be evaluated, which is more important than ever in light of the recent fires that devastated much of Kangaroo Island's flora and fauna.

Predators are critical components of ecosystems, but large marsupial carnivores have suffered major declines and extinctions in Australia. To inform predator restoration efforts on Kangaroo Island (South Australia) we examined the survival histories and potential extirpation factors of large marsupial carnivores that previously occurred on Kangaroo Island, King Island and Flinders Island, located off the southern coastline of the Australian mainland. Through a review of historical accounts and fossil evidence, we determined that the pattern of species persistence and extirpation on Kangaroo Island parallels that observed on King and Flinders Islands. Fossil data supports the terminal Pleistocene–early Holocene extinction of the thylacine (Thylacinus cynocephalus) from Kangaroo Island and the Tasmanian devil (Sarcophilus harrisii) from both Kangaroo and Flinders Islands. Though eastern quoll (Dasyurus viverrinus) fossils have been found on both Kangaroo and Flinders Islands, and western quoll (D. geoffroii) on Kangaroo Island, contemporary evidence for their post-European persistence is unclear. In contrast, fossil, museum and anecdotal data supports the presence of the spotted-tailed quoll (D. maculatus) on all three islands and, contrary to established knowledge, its post-European persistence on Kangaroo Island. The loss of T. cynocephalus, S. harrisii, D. geoffroii and D. viverrinus from these islands appears to be commensurate with late to terminal Pleistocene–early Holocene climate change and associated changes in vegetation communities. In contrast, anthropogenic persecution of D. maculatus appears to be the principal cause of its post-European extirpation. We recommend D. maculatus as a suitable candidate marsupial carnivore for reintroduction to Kangaroo Island.

Predators are critical components of ecosystems, but large marsupial carnivores have suffered major declines and extinctions in Australia. To inform predator restoration efforts on Kangaroo Island (South Australia) we examined the survival histories and potential extirpation factors of large marsupial carnivores that previously occurred on Kangaroo Island, King Island and Flinders Island, located off the southern coastline of the Australian mainland. Through a review of historical accounts and fossil evidence, we determined that the pattern of species persistence and extirpation on Kangaroo Island parallels that observed on King and Flinders Islands. Fossil data supports the terminal Pleistocene–early Holocene extinction of the thylacine (Thylacinus cynocephalus) from Kangaroo Island and the Tasmanian devil (Sarcophilus harrisii) from both Kangaroo and Flinders Islands. Though eastern quoll (Dasyurus viverrinus) fossils have been found on both Kangaroo and Flinders Islands, and western quoll (D. geoffroii) on Kangaroo Island, contemporary evidence for their post-European persistence is unclear. In contrast, fossil, museum and anecdotal data supports the presence of the spotted-tailed quoll (D. maculatus) on all three islands and, contrary to established knowledge, its post-European persistence on Kangaroo Island. The loss of T. cynocephalus, S. harrisii, D. geoffroii and D. viverrinus from these islands appears to be commensurate with late to terminal Pleistocene–early Holocene climate change and associated changes in vegetation communities. In contrast, anthropogenic persecution of D. maculatus appears to be the principal cause of its post-European extirpation. We recommend D. maculatus as a suitable candidate marsupial carnivore for reintroduction to Kangaroo Island.