Abstract
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.
Highlights
IntroductionThe relationship between environmental change and species evolution is convoluted due to the plethora of ways in which species are impacted by and can respond to change
Supplementary information The online version of this article contains supplementary material, which is available to authorized users.The relationship between environmental change and species evolution is convoluted due to the plethora of ways in which species are impacted by and can respond to change
For length-variable marker data, four genetic clusters were identified (Appendix S4). Three of these clusters align with the geographic ranges of strigata, harmonica and rufiventris and boundaries of their respective mitochondrial clades: Tasmania, east Australian and south-west/central
Summary
The relationship between environmental change and species evolution is convoluted due to the plethora of ways in which species are impacted by and can respond to change. Understanding the population processes affected by environmental change is important for informing predictive models of species’ responses to future climate change. Climatic oscillations throughout the Pleistocene (~2.5–0.01 million years ago; Ma) impacted the evolution of biota across the globe through fragmentation, displacement and extinction (Hewitt 2004). Populations surviving glacial maxima in disconnected refugia often diverged under effects of different climatic and ecological pressures and genetic drift (Avise 1998, 2000). Australo-Papua, remained largely free from Pleistocene glaciation and instead experienced cycles of aridity and sea-level fluctuations (Barrows et al 2002; Byrne et al 2008)
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