Evolutionary and contemporary responses to habitat fragmentation detected in a mesic zone marsupial, the long‐nosed potoroo (Potorous tridactylus) in south‐eastern Australia

Abstract

Aim Outside of Australia's Wet Tropics, studies of the biogeographical patterns of unglaciated Southern Hemisphere mesic environments are limited, and have primarily focused on herpetofauna. In this study mitochondrial DNA (mtDNA) and microsatellite (nuDNA) analyses were used to investigate the impact of biogeographical barriers on the evolutionary history of the widespread Australian marsupial Potorous tridactylus, as well as the effect of recent human‐mediated habitat fragmentation. Location Australia; Queensland, New South Wales, Victoria, and Tasmania. Methods Three hundred and fifty‐four individuals from 39 sites (representing 16 regional populations) across the species range were assessed for mtDNA Control Region and microsatellite (10 loci) variation. Genetic diversity, phylogeographical relationships and population structure were examined, as well as evidence for isolation by distance and past population expansion. Results Three highly divergent and reciprocally monophyletic mtDNA lineages were resolved (two mainland, one Tasmanian). A deep phylogeographical break, not associated with any obvious biogeographical barrier, was present on the mainland. Within the northern mainland and Tasmanian lineages, sub‐structuring was coincident with the presence of physical barriers to gene flow. Fine‐scale structuring was also present, with regional populations highly differentiated. Main conclusions This study expands on previous studies of Australia's mesic biome. Major phylogeographical breaks were identified, that dated to the Miocene (within the mainland) and Pliocene (isolation of Tasmanian), and differed from those described for the region's herpetofauna in age or location. The major mainland break appears species specific within this topographically complex region of Australia. Tasmanian populations were isolated from the mainland well before the most recent flooding of Bass Strait. Minor phylogenetic breaks within Tasmanian and northern NSW were associated with known biogeographical barriers. An absence of sub‐structuring within the southern mainland lineage suggests extensive historical connectivity. The presence of regional population structure suggests that post‐European settlement, local populations have become isolated and differentiated.

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

“…The Tasmanian and southern mainland populations of devils show a clear pre‐LGM phylogenetic split, suggesting a lack of gene flow across the Bass Strait land bridge during the LGM. This pattern is consistent with several other mammals, frogs and reptiles, which show pre‐LGM divergence and no evidence for subsequent dispersal (Dubey & Shine, ; Frankham, Handasyde, & Eldridge, ; Gongora et al., ; Symula, Keogh, & Cannatella, ). In contrast, the thylacine (White, Mitchell, et al, ) and several other reptiles and frogs (Chapple, Keogh, & Hutchinson, ; Schäuble & Moritz, ) show evidence of dispersal and gene flow across the Bass Strait land bridge in the late Pleistocene.…”

“…Typically these patterns are consistent with two wellcharacterized biogeographic barriers-the Nullarbor and Lake Eyre regions-at Plio-Pleistocene timescales. In contrast, devils along with several species of birds and mammals (Clegg, Hale, & Moritz, 1998;Cooper, Adams, & Labrinidis, 2000;Dolman & Joseph, 2015;Pestell, Cooper, Saint, & Petit, 2007) show pre-LGM divergence and no evidence for subsequent dispersal (Dubey & Shine, 2010;Frankham, Handasyde, & Eldridge, 2016;Gongora et al, 2012;Symula, Keogh, & Cannatella, 2008). In contrast, the thylacine (White, Mitchell, et al, 2018) and several other reptiles and frogs (Chapple, Keogh, & Hutchinson, 2005…”

Ancient mitochondrial genomes reveal the demographic history and phylogeography of the extinct, enigmatic thylacine (Thylacinus cynocephalus)

“…Koalas ( Phascolarctos cinereus ) never crossed the land bridge to reach Tasmania, whilst several mammals (e.g. Frankham, Handasyde & Eldridge, ; Gongora et al., ), frogs (e.g. Symula, Keogh & Cannatella, ) and reptiles (e.g.…”

Lines in the land: a review of evidence for eastern Australia's major biogeographical barriers to closed forest taxa

“…8C), and it is reasonable to expect that closed forests would have been extirpated from these regions during historical dry periods. Several studies suggest that one or other of these regions may have acted as a barrier to some species of closed forest reptiles (Sumner et al, 2010;Dubey et al, 2012;Pepper et al, 2014), assassin spiders (Rix & Harvey, 2012), and mammals (Frankham, Handasyde & Eldridge, 2015), although sampling designs were often unable to distinguish between the two. Along with probable impacts of Mio-Pleistocene vicariance of closed forests, the sandstone Escarpment is also considered an ecological barrier for some snakes because it is unsuitable to support thermoregulation (Sumner et al, 2010).…”