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Skull shape of a widely-distributed, endangered marsupial reveals little evidence of local adaptation between fragmented populations
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  • Pietro Viacava,
  • Simone Blomberg,
  • Gabriele Sansalone,
  • Matthew Phillips,
  • Thomas Guillerme,
  • Skye Cameron,
  • R. S. Wilson,
  • Vera Weisbecker
Pietro Viacava
The University of Queensland
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Simone Blomberg
The University of Queensland
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Gabriele Sansalone
University of New England
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Matthew Phillips
Queensland University of Technology
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Thomas Guillerme
The University of Queensland
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Skye Cameron
The University of Queensland
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R. S. Wilson
The University of Queensland
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Vera Weisbecker
Flinders University
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Abstract

The biogeographical distribution of diversity among populations of threatened mammalian species is generally investigated through population genetics. However, intraspecific phenotypic diversity is rarely assessed beyond taxonomy-focused linear measurements or qualitative descriptions. Here, we use a technique widely used in the evolutionary sciences – geometric morphometrics – to characterize shape diversity in the skull of an endangered marsupial, the northern quoll, across its 5,000 km distribution range along the northern Australian coast. Skull shape is a proxy of feeding, behaviour, and phenotypic differentiation, allowing us to ask if populations can be distinguished and if patterns of variation indicate adaptability to changing environmental conditions. We analysed skull shape in 101 individuals across the four mainland populations and several islands. We assessed the contribution of population, size, sex, rainfall, temperature, and latitude/longitude to skull shape variation through Principal Components, Procrustes ANOVA, and variation partitioning analyses. Regardless of land area inhabited, northern quoll populations harbour similar amounts of broadly overlapping skull shape variation. Size predicted skull shape best, coinciding with braincase size variation and differences in the cheekbone shape. Size-adjusted population differences explained less variation with far smaller effect sizes, relating to changes in insertion areas of masticatory muscles, as well as the upper muzzle and incisor region. Climatic and geographic variables contributed little or nothing. Strikingly, the vast majority of shape variation - 76% - remained unexplained. Our results suggest a uniform within-species scope for shape variation, possibly due to phenotypic plasticity or allometric constraints. The lack of local adaptation indicates that cross-breeding between populations will not reduce local morphological skull (and probably general musculoskeletal) adaptation because none exists. However, the potential for heritable morphological variation (e.g. specialization to local diets) seems exceedingly limited. We conclude that 3D geometric morphometrics can provide a comprehensive, statistically rigorous phenomic contribution to genetics-based conservation studies.

Peer review status:ACCEPTED

06 Mar 2020Submitted to Ecology and Evolution
06 Mar 2020Assigned to Editor
06 Mar 2020Submission Checks Completed
09 Mar 2020Reviewer(s) Assigned
03 Apr 2020Review(s) Completed, Editorial Evaluation Pending
16 Apr 2020Editorial Decision: Revise Minor
02 Jun 20201st Revision Received
03 Jun 2020Review(s) Completed, Editorial Evaluation Pending
03 Jun 2020Assigned to Editor
03 Jun 2020Submission Checks Completed
10 Jun 2020Editorial Decision: Revise Minor
15 Jun 20202nd Revision Received
16 Jun 2020Submission Checks Completed
16 Jun 2020Assigned to Editor
16 Jun 2020Review(s) Completed, Editorial Evaluation Pending
17 Jun 2020Editorial Decision: Accept