Rarity-weighted richness

Description Rarity weighted richness is a measure that combines endemism and species richness of amphibians, birds, mammals, reptiles and a representative set of plant taxa in each 10 km cell. This index lowers the contribution of wide ranging species to overall species richness and highlights the areas that have a relatively high proportion of narrow‐range species. Species ranges were rasterised at 1 km resolution from polygon maps from the IUCN Red List (IUCN Red List of Threatened Species (2019) Version 2019.2. http://www.iucnredlist.org), the Global Assessment of Reptile Distributions (GARD) (Roll et al. (2017), Version 1.5, https://datadryad.org/stash/dataset/doi:10.5061/dryad.83s7k) and the Botanical Information and Ecology Network (BIEN) database (Enquist et al. 2019 and Maitner et al. 2017, version 4.1. http://bien.nceas.ucsb.edu/bien/biendata/). Additional vascular plant species ranges were created from point data from the IUCN Red List (IUCN Red List of Threatened Species (2019) Version 2019.2. http://www.iucnredlist.org), Botanic Gardens Conservation International (BGCI) (https://www.bgci.org/) and the Global Biodiversity Information Facility (GBIF) (https://www.gbif.org/). Species range maps were refined, when possible, by removing unsuitable areas using information on species’ habitat preferences and species' known altitudinal limits. Habitats distributions were obtained from the global map of terrestrial habitat types (Jung et al. in prep), while altitudinal data was obtained from the Global Multi-resolution Terrain Elevation Data (GMTED2010) (USGS). This refinement process produced Areas of Habitat (AOH) maps for each species (Brooks et al. 2019).

Each grid cell of the species’ AOH was then scored for range-size rarity (the proportion of the species’ AOH the cell represents; i.e. size of grid cell/AOH). The total score for each cell was calculated by summing scores across all the species whose AOH intersected with it. Higher values occur in cells with more species that have smaller ranges (i.e. both the number of species and the degree to which their ranges are restricted contribute to the range rarity score).

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</Brooks, T. M. et al. (2019). Measuring Terrestrial Area of Habitat (AOH) and Its Utility for the IUCN Red List. Trends in Ecology & Evolution 34:977–986. doi.org/10.1016/j.tree.2019.06.009.

BGCI (2019). ThreatSearch online database. www.bgci.org/threat_search.php.

Enquist, B.J. et al. (in prep.). Botanical big data shows that plant diversity in the New World is driven by climatic-linked differences in evolutionary rates and biotic exclusion.

Jung, M. et al. (in prep). A global map of species terrestrial habitat types.

Maitner, B.S. et al. (2017). The BIEN R package: A tool to access the Botanical Information and Ecology Network (BIEN) database. Methods in Ecology and Evolution; 9:373–379. doi/10.1111/2041-210X.12861.

Roll, U. et al. (2017), The global distribution of tetrapods reveals a need for targeted reptile conservation, Nature Ecology & Evolution, 1: 1677–1682, doi.org/10.1038/s41559-017-0332-2.

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IUCN species richness data, threatened species, Key biodiversity areas, ecoregions
Global , Pacific , Bougainville , Papua New Guinea
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