title: A climate change context for the decline of a foundation tree species in south-western Australia: insights from phylogeography and species distribution modelling.
abstract: OBJECTIVE
  A worldwide increase in tree decline and mortality has been linked to climate change and, where these represent foundation species, this can have important implications for ecosystem functions. This study tests a combined approach of phylogeographic analysis and species distribution modelling to provide a climate change context for an observed decline in crown health and an increase in mortality in Eucalyptus wandoo, an endemic tree of south-western Australia.
  
  
  METHODS
  Phylogeographic analyses were undertaken using restriction fragment length polymorphism analysis of chloroplast DNA in 26 populations across the species distribution. Parsimony analysis of haplotype relationships was conducted, a haplotype network was prepared, and haplotype and nucleotide diversity were calculated. Species distribution modelling was undertaken using Maxent models based on extant species occurrences and projected to climate models of the last glacial maximum (LGM).
  
  
  RESULTS
  A structured pattern of diversity was identified, with the presence of two groups that followed a climatic gradient from mesic to semi-arid regions. Most populations were represented by a single haplotype, but many haplotypes were shared among populations, with some having widespread distributions. A putative refugial area with high haplotype diversity was identified at the centre of the species distribution. Species distribution modelling showed high climatic suitability at the LGM and high climatic stability in the central region where higher genetic diversity was found, and low suitability elsewhere, consistent with a pattern of range contraction.
  
  
  CONCLUSIONS
  Combination of phylogeography and paleo-distribution modelling can provide an evolutionary context for climate-driven tree decline, as both can be used to cross-validate evidence for refugia and contraction under harsh climatic conditions. This approach identified a central refugial area in the test species E. wandoo, with more recent expansion into peripheral areas from where it had contracted at the LGM. This signature of contraction from lower rainfall areas is consistent with current observations of decline on the semi-arid margin of the range, and indicates low capacity to tolerate forecast climatic change. Identification of a paleo-historical context for current tree decline enables conservation interventions to focus on maintaining genetic diversity, which provides the evolutionary potential for adaptation to climate change.
authors: School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia and.
authors: Eleftheria
authors: E
authors: Dalmaris
authors: Science and Conservation Division, Western Australian Department of Parks and Wildlife, Locked Bag 104, Bentley Delivery Centre, Bentley, 6983 WA, Australia cristina.ramalho@dpaw.wa.gov.au.
authors: Cristina E
authors: CE
authors: Ramalho
authors: School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia and Science and Conservation Division, Western Australian Department of Parks and Wildlife, Locked Bag 104, Bentley Delivery Centre, Bentley, 6983 WA, Australia.
authors: Pieter
authors: P
authors: Poot
authors: School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia and.
authors: Erik J
authors: EJ
authors: Veneklaas
authors: School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia and Science and Conservation Division, Western Australian Department of Parks and Wildlife, Locked Bag 104, Bentley Delivery Centre, Bentley, 6983 WA, Australia.
authors: Margaret
authors: M
authors: Byrne
mesh_terms: D005075:Biological Evolution; D057231:Climate Change; D018742:DNA, Chloroplast / Q000235:genetics; D017753:Ecosystem; D005052:Eucalyptus / Q000235:genetics / Q000502:physiology*; D014644:Genetic Variation; D005828:Genetics, Population; D006239:Haplotypes; D008962:Models, Theoretical; D058974:Phylogeography; D013021:South Australia; D014197:Trees; D014904:Western Australia
chemical_list: D018742:DNA, Chloroplast
keywords: Climate change; Eucalyptus wandoo; LGM; Myrtaceae; evolution; forest decline; haplotypes; last glacial maximum; phylogeography; refugia; species distribution modelling; tree decline.