title: A low-altitude mountain range as an important refugium for two narrow endemics in the Southwest Australian Floristic Region biodiversity hotspot.
abstract: Low-altitude mountains constitute important centres of diversity in landscapes with little topographic variation, such as the Southwest Australian Floristic Region (SWAFR). They also provide unique climatic and edaphic conditions that may allow them to function as refugia. We investigate whether the Porongurups (altitude 655 m) in the SWAFR will provide a refugium for the endemic Ornduffia calthifolia and O. marchantii under forecast climate change.
  
  
  
  We used species distribution modelling based on WorldClim climatic data, 30-m elevation data and a 2-m-resolution LiDAR-derived digital elevation model (DEM) to predict current and future distributions of the Ornduffia species at local and regional scales based on 605 field-based abundance estimates. Future distributions were forecast using RCP2.6 and RCP4.5 projections. To determine whether local edaphic and biotic factors impact these forecasts, we tested whether soil depth and vegetation height were significant predictors of abundance using generalized additive models (GAMs).
  
  
  
  Species distribution modelling revealed the importance of elevation and topographic variables at the local scale for determining distributions of both species, which also preferred shadier locations and higher slopes. However, O. calthifolia occurred at higher (cooler) elevations with rugged, concave topography, while O. marchantii occurred in disturbed sites at lower locations with less rugged, convex topography. Under future climates both species are likely to severely contract under the milder RCP2.6 projection (approx. 2 °C of global warming), but are unlikely to persist if warming is more severe (RCP4.5). GAMs showed that soil depth and vegetation height are important predictors of O. calthifolia and O. marchantii distributions, respectively.
  
  
  
  The Porongurups constitute an important refugium for O. calthifolia and O. marchantii, but limits to this capacity may be reached if global warming exceeds 2 °C. This capacity is moderated at local scales by biotic and edaphic factors.
authors.affiliation: School of Natural and Built Environments, University of South Australia, GPO Box 2471, Adelaide, SA 5001, Australia Gunnar.Keppel@unisa.edu.au.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Keppel
authors.affiliation: Spatial Sciences, Curtin University, Kent St., Bentley, Western Australia.
authors.forename: Todd P
authors.initials: TP
authors.lastname: Robinson
authors.affiliation: Curtin Institute for Biodiversity and Climate and School of Science, Curtin University, Kent St., Bentley, Western Australia.
authors.forename: Grant W
authors.initials: GW
authors.lastname: Wardell-Johnson
authors.affiliation: Science and Conservation Division, Department of Parks and Wildlife, Locked Bag 104, Bentley Delivery Centre, WA, Australia.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Yates
authors.affiliation: School of Earth and Environment, The University of Western Australia, Crawley, WA 6009.
authors.forename: Kimberly P
authors.initials: KP
authors.lastname: Van Niel
authors.affiliation: Science and Conservation Division, Department of Parks and Wildlife, Locked Bag 104, Bentley Delivery Centre, WA, Australia.
authors.forename: Margaret
authors.initials: M
authors.lastname: Byrne
authors.affiliation: Plant Production Systems, Wageningen University, Droevendaalsesteeg 1, 6708PB Wageningen, the Netherlands.
authors.forename: Antonius G T
authors.initials: AG
authors.lastname: Schut
mesh_terms: D000531:Altitude; D001315:Australia; D044822:Biodiversity; D057231:Climate Change; D018521:Plant Physiological Phenomena; D010944:Plants / Q000145:classification; D000068236:Refugium
keywords: Anthropogenic climate change; Ornduffia calthifolia; Ornduffia marchantii; Southwest Australian Floristic Region (SWAFR); extinction; interspecific interactions; localized endemic; low-altitude mountain; microclimate; refugia; species distribution modelling