Ancient DNA tracks the mainland extinction and island survival of the Tasmanian devil

Abstract

Aim The Tasmanian devil (Sarcophilus harrisii), currently restricted to the island of Tasmania, was found over most of the Australian mainland prior to its extinction ~3,000 years ago. Recent debate has focused on the roles of humans, climate change and dingoes as drivers of the mainland extinction. Determining past genetic diversity and population dynamics of both populations is a fundamental component to understand why the species went extinct on mainland Australia, but survived in Tasmania. Here, we investigate the phylogeography and demographic history of the Tasmanian devil across southern Australia over the last ~30k years. Location Australia. Taxon Tasmanian devil (Sarcophilus harrisii). Methods We used complete and partial mitochondrial DNA (mtDNA) genomes from 202 devils representing the extinct mainland (n = 17) and the extant Tasmanian (n = 185) populations to investigate the population dynamics of southern mainland and Tasmanian devils. The samples were sub‐fossil bones, historical museum specimens and modern tissue samples, dating from the present to 17k years before present. Using summary statistics, frequentist inference and Bayesian phylogenetic analysis we explored whether levels of genetic diversity were similar, and if the southern mainland experienced a gradual rather than an abrupt decline prior to its extinction. Results MtDNA genomes from mainland devils suggest that this population was larger and had more genetic diversity than the Tasmanian population. Directly dated samples indicates that the southern mainland population expanded after the last glacial maximum and remained stable until its extinction. The Tasmanian population has much lower diversity and descends from a single mtDNA lineage ~3,000 years ago. The recent origin for all Tasmanian mtDNA diversity is concordant with a previously documented late‐Holocene population bottleneck and is broadly contemporaneous with the extinction of the southern mainland population. Main conclusions This pattern shows striking similarity to the demographic history of thylacines, suggesting that a shared factor initiated population declines in both species on the southern mainland and in Tasmania. El Niño Southern Oscillation (ENSO)‐related climate change is the only factor common to both mainland Australia and Tasmania. Additional, direct or indirect, pressures from humans and/or dingoes on the mainland may have ultimately resulted in their extinction.

Island area, body size and demographic history shape genomic diversity in Darwin's finches and related tanagers

“…Habitat area is a key determinant for population sustenance (Gibbs, ; Lino, Fonseca, Rojas, Fischer, & Ramos Pereira, ) and maintaining viable (i.e., genetically diverse, noninbred) populations (Frankham, , ). Multiple studies have shown that island species have less genetic diversity and increased inbreeding compared to their mainland counterparts (Brüniche‐Olsen, Jones, et al, ; Eldridge et al, ; Frankham, ; Palkopoulou et al, ). We add to this body of evidence by exploring how genomic diversity is influenced by the size of the island itself.…”

Hope and caution: rewilding to mitigate the impacts of biological invasions

“…Several factors have been implicated in the mainland extinction of the devil and the thylacine. These include climate, humans and dingoes, although recent modelling suggests that the influence of dingoes was not strong [89,90]. Dingoes never reached Tasmania and the thylacine was hunted to extinction there in the twentieth century, leaving the devil as the largest predator [91].…”

A native apex predator limits an invasive mesopredator and protects native prey: Tasmanian devils protecting bandicoots from cats

“…by relaxing lethal control of apex predators; Cunningham et al 2019b). In areas of the Australian mainland where restoring dingo populations remains socially unacceptable, it is worth exploring whether devils could fill the void, given they were present on the mainland until approximately 3200 years ago (White et al 2018) and the synergistic causes of their extinction (climate, dingoes and human intensification) are sufficiently understood (Brown 2006;Br€ uniche-Olsen et al 2014;Prowse et al 2014;Br€ uniche-Olsen et al 2018). This could begin with a carefully controlled experimental reintroduction of devils to a bounded landscape to assess whether they can perform key top-down functions in ecosystems on mainland Australia, as modelling suggests (Hunter et al 2015).…”