Ecological opportunity and the evolution of habitat preferences in an arid-zone bird: implications for speciation in a climate-modified landscape.

Janette A Norman,Les Christidis

doi:10.1038/srep19613

Janette A Norman, Les Christidis

Open Access

https://doi.org/10.1038/srep19613

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Abstract

Bioclimatic models are widely used to investigate the impacts of climate change on species distributions. Range shifts are expected to occur as species track their current climate niche yet the potential for exploitation of new ecological opportunities that may arise as ecosystems and communities remodel is rarely considered. Here we show that grasswrens of the Amytornis textilis-modestus complex responded to new ecological opportunities in Australia’s arid biome through shifts in habitat preference following the development of chenopod shrublands during the late Plio-Pleistocene. We find evidence of spatially explicit responses to climatically driven landscape changes including changes in niche width and patterns of population growth. Conservation of structural and functional aspects of the ancestral niche appear to have facilitated recent habitat shifts, while demographic responses to late Pleistocene climate change provide evidence for the greater resilience of populations inhabiting the recently evolved chenopod shrubland communities. Similar responses could occur under future climate change in species exposed to novel ecological conditions, or those already occupying spatially heterogeneous landscapes. Mechanistic models that consider structural and functional aspects of the niche along with regional hydro-dynamics may be better predictors of future climate responses in Australia’s arid biome than bioclimatic models alone.

Highlights

Australia’s arid biome provides a unique opportunity to study how species have responded to new ecological opportunities arising from past climate change
We evaluated the best-fit evolutionary model using time-calibrated molecular phylogenies of selected Australian Chenopodiaceae, in conjunction with paleobotanical and climate data, to determine if; (i) chenopod shrubland (CS) habitat preferences were ancestral or recently evolved, (ii) the extent to which ecological and evolutionary responses correlated with past climate fluctuations, and (iii) whether new ecological opportunities were associated with niche expansion or contraction
The Thick-billed Grasswren (A. modestus) favours dense CS dominated by black bluebush and old man saltbush (Atriplex nummularia) with subspecies located in the Lake Eyre and Lake Frome drainages (A. m. inexpectatus), and the Finke River drainage (A. m. modestus) (Fig. 1)

Summary

Introduction

Australia’s arid biome provides a unique opportunity to study how species have responded to new ecological opportunities arising from past climate change. This is a relatively young biome formed as the result of increasing aridity over the past six million years[12,13] with major climate and landscape changes leading to the rapid evolution of distinctive arid-adapted vegetation communities[13]. We evaluated the best-fit evolutionary model using time-calibrated molecular phylogenies of selected Australian Chenopodiaceae (saltbushes and bluebushes), in conjunction with paleobotanical and climate data, to determine if; (i) chenopod shrubland (CS) habitat preferences were ancestral or recently evolved, (ii) the extent to which ecological and evolutionary responses correlated with past climate fluctuations, and (iii) whether new ecological opportunities were associated with niche expansion (increased habitat diversity) or contraction (habitat specialisation). We employed a population genetics approach to test for an association between habitat preference and demographic response to late Pleistocene climate change

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