Evidence of Subdivisions on Evolutionary Timescales in a Large, Declining Marsupial Distributed across a Phylogeographic Barrier

Pleistocene-dated biogeographic barriers drove divergence within the Australo-Papuan region in a sex-specific manner: an example in a widespread Australian songbird

Understanding how environmental change has shaped species evolution can inform predictions of how future climate change might continue to do so. Research of widespread biological systems spanning multiple climates that have been subject to environmental change can yield generalizable inferences about the neutral and adaptive processes driving lineage divergence during periods of environmental change. We contribute to the growing body of multi-locus phylogeographic studies investigating the effect of Pleistocene climate change on species evolution by focusing on a widespread Australo-Papuan songbird with several mitochondrial lineages that diverged during the Pleistocene, the grey shrike-thrush (Colluricincla harmonica). We employed multi-locus phylogenetic, population genetic and coalescent analyses to (1) assess whether nuclear genetic diversity suggests a history congruent with that based on phenotypically defined subspecies ranges, mitochondrial clade boundaries and putative biogeographical barriers, (2) estimate genetic diversity within and genetic differentiation and gene flow among regional populations and (3) estimate population divergence times. The five currently recognized subspecies of grey shrike-thrush are genetically differentiated in nuclear and mitochondrial genomes, but connected by low levels of gene flow. Divergences among these populations are concordant with recognized historical biogeographical barriers and date to the Pleistocene. Discordance in the order of population divergence events based on mitochondrial and nuclear genomes suggests a history of sex-biased gene flow and/or mitochondrial introgression at secondary contacts. This study demonstrates that climate change can impact sexes with different dispersal biology in different ways. Incongruence between population and mitochondrial trees calls for a genome-wide investigation into dispersal, mitochondrial introgression and mitonuclear evolution.

Genomic data show little geographical structure across the naturally fragmented range of the purple-gaped honeyeater

Using single nucleotide polymorphisms and mitochondrial DNA sequences we find some evidence of genetic structure within a widespread and naturally fragmented species, the purple-gaped honeyeater (Lichenostomus cratitius), of southern Australian mallee shrublands. The very earliest stages of differentiation either side of the Nullarbor Barrier may already have been arrested by gene flow, some of which may have been anthropogenically induced.

Southern hairy-nosed wombats (Lasiorhinus latifrons) in the Gawler Ranges region of South Australia: population growth from 1988 to 2016

The southern hairy-nosed wombat (Lasiorhinus latifrons) is the faunal emblem of South Australia. It is also considered to be an agricultural pest, as its burrowing activities can cause significant damage to agricultural land and infrastructure. Unfortunately, much of our knowledge of this species’ population dynamics is limited and/or out of date. The aim of this study was to estimate the distribution and abundance of southern hairy-nosed wombats in the Gawler Ranges region of South Australia, and to identify any changes since the last survey in 1988. Using a combination of satellite imagery and a ground survey conducted in May 2016, we mapped the distribution of wombat warrens in the region and counted and measured all warrens within 1000 randomly selected 1-km2 cells. We estimate the current wombat population in the Gawler Ranges to be 240095 (149051–311595), an increase from 14373 in 1988. This population growth is most likely linked to a long-term decline in the European rabbit population following the release of RHVD in the 1990s. In 2016 the IUCN upgraded the conservation status of southern hairy-nosed wombats from ‘Least Concern’ to ‘Near Threatened’. Our findings suggest that this may not have been warranted.