Invasive species, not environmental changes, restrict the population and geographical range of the quokka (Setonix brachyurus)

Abstract

European arrival into Australia had large-scale impacts on the local flora and fauna. Most notably, Europeans brought with them numerous non-native species, including the European red fox (Vulpes vulpes), European rabbit (Oryctolagus cuniculus), and the goat (Capra hircus) among many others. The introduction of these species had significant consequences on native Australian mammals, causing some small-to medium-sized herbivores to become geographically restricted to primarily islands. Here, we examined the dietary ecology of the quokka (Setonix brachyurus), a native marsupial herbivore with a restricted geographic range in Western Australia before and after European arrival. Fossils from south-western Australia and modern specimens were examined via dental microwear texture analysis and stable isotope analysis to assess whether the diet of the quokka had changed dramatically over time. Collectively, we help clarify whether there were any ecological reasons as to why this marsupial became geographically restricted, aside from the presence of invasive predators on mainland Australia. The quokka maintains a browsing diet from the Pleistocene to the present on the mainland, but modern island populations eat drier and tougher foods when living on islands lacking invasive mammals. There is also an apparent shift in the feeding environment of the quokkas on mainland Australia, from more open forests/shrublands in the Pleistocene to denser and wetter forests. Multi-proxy data collectively indicate that the restricted range of the quokka today is most likely a result of predation from non-native taxa and/or other human influences -not because of a lack of suitable habitat.

Dental microwear texture analysis along reptile tooth rows: complex variation with non-dietary variables

“…Furthermore, DMTA has been shown to be effective at discriminating diets between species or populations, even with low sample sizes [12][13][14]. DMTA therefore provides a valuable tool for providing robust insight into the levels of niche partitioning and resource competition for a huge range of modern taxa [6,9,[14][15][16][17][18], and for reconstructing extinct food webs from the diets of fossil taxa [19][20][21][22][23][24][25][26][27][28].…”

Classifying relationships that define interactions between native and invasive species in Australian ecosystems

“…Since their introduction, the radiation of foxes in Australia has been well documented (Dickman 1996). Their dispersal westward was synchronised with extinctions and declines in species such as the toolache wallaby (Macropus greyi), the crescent nail-tail wallaby (Onychogalea lunata), and the numbat (Myrmecobius fasciatus) (Friend 1990;Flannery 2002;Scholtz and DeSantis 2020). The timing of fox dispersal also implicates them in extinctions of various other smallmedium sized marsupials including the broad-faced potoroo (Potorous platyops), the eastern hare-wallaby (Lagorchestes leporides), and the desert bandicoot (Perameles eremiana) (Fig.…”