title: Global patterns of freshwater species diversity, threat and endemism.
abstract: OBJECTIVE
  Global-scale studies are required to identify broad-scale patterns in the distributions of species, to evaluate the processes that determine diversity and to determine how similar or different these patterns and processes are among different groups of freshwater species. Broad-scale patterns of spatial variation in species distribution are central to many fundamental questions in macroecology and conservation biology. We aimed to evaluate how congruent three commonly used metrics of diversity were among taxa for six groups of freshwater species.
  
  
  METHODS
  Global.
  
  
  METHODS
  We compiled geographical range data on 7083 freshwater species of mammals, amphibians, reptiles, fishes, crabs and crayfish to evaluate how species richness, richness of threatened species and endemism are distributed across freshwater ecosystems. We evaluated how congruent these measures of diversity were among taxa at a global level for a grid cell size of just under 1°.
  
  
  RESULTS
  We showed that although the risk of extinction faced by freshwater decapods is quite similar to that of freshwater vertebrates, there is a distinct lack of spatial congruence in geographical range between different taxonomic groups at this spatial scale, and a lack of congruence among three commonly used metrics of biodiversity. The risk of extinction for freshwater species was consistently higher than for their terrestrial counterparts.
  
  
  CONCLUSIONS
  We demonstrate that broad-scale patterns of species richness, threatened-species richness and endemism lack congruence among the six freshwater taxonomic groups examined. Invertebrate species are seldom taken into account in conservation planning. Our study suggests that both the metric of biodiversity and the identity of the taxa on which conservation decisions are based require careful consideration. As geographical range information becomes available for further sets of species, further testing will be warranted into the extent to which geographical variation in the richness of these six freshwater groups reflects broader patterns of biodiversity in fresh water.
authors.affiliation: Institute of Zoology, Zoological Society of London Regent's Park, London, NW1 4RY, UK.
authors.forename: Ben
authors.initials: B
authors.lastname: Collen
authors.affiliation: Institute of Zoology, Zoological Society of London Regent's Park, London, NW1 4RY, UK ; Synchronicity Earth 32a Thurloe Place, London, SW7 2HQ, UK.
authors.forename: Felix
authors.initials: F
authors.lastname: Whitton
authors.affiliation: Institute of Zoology, Zoological Society of London Regent's Park, London, NW1 4RY, UK ; Department of Genetics, Evolution and Environment, University College London Gower Street, London, WC1E 6BT, UK.
authors.forename: Ellie E
authors.initials: EE
authors.lastname: Dyer
authors.affiliation: Conservation Programmes, Zoological Society of London Regent's Park, London, NW1 4RY, UK.
authors.forename: Jonathan E M
authors.initials: JE
authors.lastname: Baillie
authors.affiliation: Department of Biology, Northern Michigan University Marquette, MI, 49855, USA.
authors.forename: Neil
authors.initials: N
authors.lastname: Cumberlidge
authors.affiliation: Global Species Programme, IUCN 219c Huntingdon Road, Cambridge, CB3 ODL, UK.
authors.forename: William R T
authors.initials: WR
authors.lastname: Darwall
authors.affiliation: Global Species Programme, IUCN 219c Huntingdon Road, Cambridge, CB3 ODL, UK.
authors.forename: Caroline
authors.initials: C
authors.lastname: Pollock
authors.affiliation: Institute of Zoology, Zoological Society of London Regent's Park, London, NW1 4RY, UK.
authors.forename: Nadia I
authors.initials: NI
authors.lastname: Richman
authors.affiliation: Institute of Zoology, Zoological Society of London Regent's Park, London, NW1 4RY, UK.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Soulsby
authors.affiliation: Institute of Zoology, Zoological Society of London Regent's Park, London, NW1 4RY, UK.
authors.forename: Monika
authors.initials: M
authors.lastname: Böhm
keywords: Congruence; conservation planning; decapods; diversity metric; geographical range; species richness