Current and historical factors influencing patterns of species richness and turnover of birds in the Gulf of Guinea highlands

Authors

  • Catherine H. Graham,

    Corresponding author
    1. Museum of Vertebrate Zoology, University of California, Berkeley, CA, USA
    2. Department of Ecology and Evolution, State University of New York, Stony Brook, NY, USA
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  • Thomas B. Smith,

    1. Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA
    2. Center for Tropical Research, Institute of the Environment, University of California, Los Angeles, CA, USA
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  • Marc Languy

    1. World Wildlife Fund for Nature, East Africa Regional Programme Office, Nairobi, Kenya
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*Catherine Graham, Department of Ecology and Evolution, State University of New York, Stony Brook, NY 11794, USA.
E-mail: cgraham@life.bio.sunysb.edu

Abstract

Aim  The aims of this paper are to: examine how current and historical ecological factors affect patterns of species richness, endemism and turnover in the Gulf of Guinea highlands, test theoretical biogeographical predictions and provide information for making informed conservation decisions.

Location  The Gulf of Guinea highlands in West Africa.

Methods  We used multivariate and matrix regression models, and cluster analyses to assess the influence of current climate and current and historical isolation on patterns of richness and turnover for montane birds across the highlands. We examined three groups of birds: montane species (including widespread species), montane endemics and endemic subspecies. We applied a complementarity-based reserve selection algorithm using species richness with irreplaceability measures to identify areas of high conservation concern.

Results  Environmental factors influenced richness for all groups of birds (species, endemic species and subspecies). Areas with high and consistent annual rainfall showed the highest species and endemic richness. Species clusters for all groups of birds generally differentiated three major montane regions, which are topographically isolated. Multiple mantel tests identified these same regions for endemic species and subspecies. The influence of historical isolation varied by species group; distributions of endemic montane species and subspecies were more associated with historical breaks than were all montane species, which included widespread non-endemic species.

Main conclusions  Our analyses indicated important geographical structure amongst the bird assemblages in the highlands and, therefore, conservation prioritization should include mountains from within the geographical subregions identified in these analyses because these regions may harbour evolutionarily distinct populations of birds.

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