Macro-scale bird species richness patterns of the East Asian mainland and islands: energy, area and isolation

Authors

  • Tzung-Su Ding,

    1. School of Forestry and Resource Conservation, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan
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  • Hsiao-Wei Yuan,

    1. School of Forestry and Resource Conservation, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan
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  • Shu Geng,

    1. Department of Agronomy and Range Science, University of California, One Shield Avenue, Davis, CA 95616, USA
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  • Chao-Nien Koh,

    1. Institute of Ecology and Evolutionary Biology, and Department of Life Science, National Taiwan University, Taipei
    2. Division of Forest Protection, Taiwan Forestry Research Institute, No. 53, Nan-Hai Road, Taipei 100, Taiwan
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  • Pei-Fen Lee

    Corresponding author
    1. Institute of Ecology and Evolutionary Biology, and Department of Life Science, National Taiwan University, Taipei
      *Pei-Fen Lee, Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei 106, Taiwan.
      E-mail: leepf@ntu.edu.tw
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*Pei-Fen Lee, Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei 106, Taiwan.
E-mail: leepf@ntu.edu.tw

Abstract

Aim  To create a map of bird species richness (BSR) in East Asia and to examine the effect of area, isolation, primary productivity, topographic heterogeneity, and human population density on BSR.

Location  East Asia (from 70° E to 180° E longitude), including the eastern half of the Palaearctic Region, the entire Oriental Region, and the entire Wallacea Subregion.

Methods  The breeding ranges of 2406 terrestrial bird species were mapped and overlaid to create a species richness map. The BSR map was transformed into a 100 × 100 km quadrat system, and BSR was analysed in relation to land area, average normalized difference vegetation index (NDVI), elevation range, and average population density.

Results  In general, BSR declined from the Tropics to the Arctic. In mainland East Asia, however, BSR was highest around the Tropic of Cancer, and fluctuated between 30° and 50° N. Islands had lower BSR than adjacent mainland areas. The NDVI was strongly positively correlated with BSR in mainland areas and on islands. For mainland areas, NDVI explained 65% of the BSR variation, and topographic heterogeneity explained an additional 6% in ordinary least-squares regression. On islands, NDVI explained 66% of BSR variation, island area explained 13%, and distance to mainland accounted for 1%.

Main conclusions  In East Asia, we suggest that primary productivity is the key factor underpinning patterns of BSR. Primary productivity sets the upper limits of the capacity of habitats to support bird species. In isolated areas such as islands and peninsulas, however, BSR might not reach the richness limits set by primary productivity because the degree of isolation and area size also can affect species richness. Other factors, such as spatial heterogeneity, biotic interactions, and perturbations, may also affect species richness. However, their effects are secondary and are not as strong as primary productivity, isolation, and area size.

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