Abstract
Bandicoots (Peramelemorphia) are a unique order of Australasian marsupials whose sparse fossil record has been used as prima facie evidence for climate change coincident faunal turnover. In particular, the hypothesized replacement of ancient rainforest-dwelling extinct lineages by antecedents of xeric-tolerant extant taxa during the late Miocene (~10 Ma) has been advocated as a broader pattern evident amongst other marsupial clades. Problematically, however, this is in persistent conflict with DNA phylogenies. We therefore determine the pattern and timing of bandicoot evolution using the first combined morphological + DNA sequence dataset of Peramelemorphia. In addition, we document a remarkably archaic new fossil peramelemorphian taxon that inhabited a latest Quaternary mosaic savannah-riparian forest ecosystem on the Aru Islands of Eastern Indonesia. Our phylogenetic analyses reveal that unsuspected dental homoplasy and the detrimental effects of missing data collectively obscure stem bandicoot relationships. Nevertheless, recalibrated molecular clocks and multiple ancestral area optimizations unanimously infer an early diversification of modern xeric-adapted forms. These probably originated during the late Palaeogene (30–40 Ma) alongside progenitors of other desert marsupials, and thus occupied seasonally dry heterogenous habitats long before the onset of late Neogene aridity.
Highlights
Bandicoots (Peramelemorphia) are a speciose order of Australasian marsupials that appeared early in the evolutionary history of Australidelphia[1]
Yaralids are united by a single unique symplesiomorphy – retention of a ‘complete’ centrocrista formed by the postparacrista and premetacrista on the upper molars[21]. This has since been identified in a range of Oligocene−Miocene bandicoots[16,17,18], and is ancestral amongst marsupials[25], but otherwise lost in crown perameloids prompting assertions of a Miocene ‘bottleneck’ within Peramelemorphia, as well as other Australasian marsupials[26], whereby the radiation of crown taxa occurred only after the decline of rainforest-restricted stem forms, perhaps in response to climate change, ecological competition and/or vicariance events[3,9,10,15,19,20,21,22,23,24,26,27]
We test the long-standing hypotheses of Miocene faunal turnover and the recent origin of modern Australasian marsupials, by using the first total evidence morphological +multi-gene sequence dataset of Peramelemorphia incorporating examplars of all extinct and living genera named in the published literature
Summary
Bandicoots (Peramelemorphia) are a speciose order of Australasian marsupials that appeared early in the evolutionary history of Australidelphia[1]. DNA-based cladogenic scenarios for these groups envisage a latest Oligocene–early Miocene split (~20–30 Ma) between the xeric-adapted chaeropodids and thylacomyids versus predominantly mesic peramelids[1,4] This contrasts with published morphological data, which posits both a late Miocene–Pliocene diversification of Australian Peramelinae concurrent with increasing aridity[9,10], and late Miocene vicariant origins for Peroryctinae and Echymiperinae (historically united as Peroryctidae)[11] accompanying New Guinean tectonic uplift. Our improved molecular clock constraints and coupled ancestral area analyses enable more precise timing for the nascent dispersal of crown bandicoots into open mosaic habitats, and refines burgeoning DNA-based evidence for Australia’s modern arid-zone marsupials as members of enduring, adaptable clades[32]
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