Phylogeographic parallelism: concordance of patterns in closely related species illuminates underlying mechanisms in the historically glaciated Tasmanian landscape

Abstract

<jats:title>Abstract</jats:title><jats:p>Phylogeography provides a means to understand mechanisms that shaped the distribution and abundance of species, including the role of past climate change. While concordant phylogeographic relationships across diverse taxa suggest shared underlying mechanisms (“phylogeographic parallelism”), it is also possible that similar patterns are the product of different mechanisms (“phylogeographic convergence”), reflecting variation among taxa in factors such as environmental tolerances, life histories, and vagility. Hence, phylogeographic concordance among closely related and ecologically similar species can yield a more confident understanding of the past mechanisms which shaped their distribution and abundance. This study documented mitochondrial and nuclear phylogeographic patterns in the ectotherm skink, <jats:italic>Niveoscincus metallicus</jats:italic>, which occupies historically glaciated regions of Tasmania, and contrasted these with the closely related and broadly sympatric <jats:italic>N. ocellatus</jats:italic>. Major phylogeographic breaks were similar in location between the two species, and indicative of isolation caused by retreat from high elevation areas during glaciations, but with long-term persistence at multiple low elevation sites. Hence, Pleistocene glacial refugia were altitudinal rather than latitudinal, a pattern mirrored in other temperate Southern Hemisphere taxa. This study also examined phylogeographic patterns across the intermittently inundated Bassian Isthmus between mainland Australia and the island of Tasmania, and revealed that structuring is similarly maintained when populations were physically isolated during interglacial rather than glacial stages.</jats:p>

Persisting in a glaciated landscape: Pleistocene microrefugia evidenced by the tree wētā Hemideina maori in central South Island, New Zealand

“…Likewise, in the Southern Hemisphere (e.g. Tasmania, South Island of New Zealand), some species similarly appear to retreat from glaciated areas to refugial zones (Dussex, Wegmann, & Robertson, 2014; Kreger, Shaban, Wapstra, & Burridge, 2020; Leschen, Buckley, Harman, & Shulmeister, 2008; McCulloch et al., 2010; McKinnon, Jordan, Vaillancourt, Steane, & Potts, 2004; Neiman & Lively, 2004; Weston & Robertson, 2015).…”

“…Similarly, in North America, coastal and offshore microrefugia including Haida Gwaii (Pruett et al., 2013), Alexander Archipelago (Lucid & Cook, 2004), parts of the Arctic (Waltari & Cook, 2005) and even small pockets within the ice sheets (Marr, Allen, & Hebda, 2008), apparently facilitated species persistence outside major Beringian and Pacific Northwest refugia. In the Southern Hemisphere, microrefugia have been inferred to allow species persistence at sites affected by Pleistocene glaciations in Tasmania (Cliff, Wapstra, & Burridge, 2015; Kreger et al., 2020), Victoria (Bell, Griffin, Hoffmann, & Miller, 2018; Endo et al., 2015; Slatyer et al., 2014) and Patagonia (Breitman, Avila, Sites, & Morando, 2012), evidenced by high regional genetic diversity. In addition to idiosyncratic patterns generated by microrefugia, physiologically distinct lineages can exhibit divergent biogeographic histories under glaciation: temperate–adapted species typically undergo range contraction, whereas cold‐adapted, montane species experience range expansion via down‐slope extension of alpine habitat (DeChaine & Martin, 2004; Trewick, Wallis, & Morgan‐Richards, 2000).…”

The roles of aridification and sea level changes in the diversification and persistence of freshwater fish lineages

“…'flindersi' have suggested that the separation of drainages by tectonic shifts across the region (Dickinson et al, 2002; Gallagher et al, 2003) isolated populations following a dispersal event facilitated by river capture or flooding (Unmack et al, 2013). Regardless of the mechanism, divergence between Tasmanian and mainland lineages prior to the Pleistocene has been reported for birds (Lamb et al, 2019), lizards (Chapple et al, 2011; Dubey & Shine, 2010; Kreger et al, 2019), butterflies (Norgate et al, 2009) and other freshwater fish (Coleman et al, 2010), suggesting that climatic oscillations during the LGM alone did not drive the speciation of N . 'flindersi'.…”

“…Regardless of the mechanism, divergence between Tasmanian and mainland lineages prior to the Pleistocene has been reported for birds (Lamb et al, 2019), lizards (Chapple et al, 2011;Dubey & Shine, 2010;Kreger et al, 2019), butterflies (Norgate et al, 2009 and other freshwater fish (Coleman et al, 2010), suggesting that climatic oscillations during the LGM alone did not drive the speciation of N.…”