DOI: 10.5061/dryad.vx0k6djtn
title: Data for: Contemporizing island biogeography theory with anthropogenic drivers of species richness

description: Aim: Island biogeography theory states that species richness increases
 with habitat diversity and decreases with isolation from source pools.
 However, ecological theory must incorporate effects of human activity to
 explain contemporary patterns of biodiversity. We contemporized island
 biogeography theory by conceptualizing island trajectories of how species
 richness changes over time with accelerating land development and economic
 trade, which increase extinction and immigration rates, respectively. With
 this contemporized theory, we then articulate and empirically assess
 expected relationships of native, introduced, and total species richness
 with natural and anthropogenic metrics of habitat diversity and isolation
 from source pools. Location: Greater Caribbean region. Time period:
 Database finalized in 2020. Methods: We built a database of 1075 native
 and introduced reptiles and amphibians (herps) for 840 Caribbean islands.
 For each island, we calculated natural and anthropogenic metrics of island
 habitat diversity and isolation from source pools and used linear model
 averaging to assess the expected relationships under the contemporized
 theory for 15 major herp clades. Results: Natural habitat diversity
 metrics exhibited positive relationships with native and introduced
 species richness, strengthening total species richness–area relationships
 across herp clades. Geographic isolation exhibited negative relationships
 with native and positive relationships with introduced species richness,
 weakening total species richness–isolation relationships. Economic area,
 based on developed land, and economic isolation, based on maritime trade,
 exhibited negative relationships with native species richness, but
 positive and negative relationships, respectively, with introduced species
 richness. Total species richness relationships with these two
 anthropogenic metrics were strongest in clades with many introduced
 species. Main conclusion: A contemporized island biogeographic theory that
 includes the effects of land development and economic trade on species
 extinction and immigration explained current Caribbean herp species
 richness patterns. As human activity continues to accelerate, the
 contemporized theory we articulate here will increasingly predict island
 biogeography of the Anthropocene.
description: We built a database of 840 islands based
 on the Global Administrative Areas shapefile (version 3.6, GADM, 2012)
 grouped into 72 banks. Banks were based on historical land connections and
 underwater topography (GEBCO Compilation Group, 2020) and included
 Bermuda. <em>Species
 Richness Data</em> We
 performed an extensive literature search of island-level herp records
 (searches completed June 2020; see Methods Supp. Info. Section 1 of the
 manuscript). Native status was given to extant species indicated in the
 literature as being native to an island. Introduced status was given to
 non-native species established on an island indicated from the literature
 or if a non-native species had multiple records in Global Biodiversity
 Information Facility, which included data from multiple sources (see
 Methods Supp. Info. Section 1 of the manuscript), that spanned multiple
 geographic locations and years on an island. We used several sources to
 standardize species names and taxonomy including caribherp.org (Hedges,
 2020), Reptile Database (Uetz et al., 2020), Amphibian Species of the
 World 6.1 (Frost, 2020), the Integrated Taxonomic Information System
 (ITIS, accessed June 2020), and GBIF. Our search yielded 1075 extant
 species of herps on 72 banks. Species were grouped into clades defined by
 taxonomic class, order, suborder, family, and genus. We identified 154
 reptilian and 42 amphibian clades. Native, introduced, and total species
 richness values per bank per clade were calculated. Not all clades
 contained enough species on enough banks to fit robust regressions. Based
 on a power analysis of the fit of the all-herps model, only 15 clades were
 retained for analysis.  <em>Island Bank Data</em>
 We calculated four common natural habitat
 diversity metrics: geographic area, island spread, topographical
 complexity, and natural area; and one anthropogenic metric: economic area.
 Geographic area was the sum of contemporary land area of each island in
 each bank from the Global Administrative Areas shapefile (version 3.6,
 GADM, 2012). Island spread was one minus the total bank land area divided
 by bank extent estimated as the area of the minimum convex polygon around
 the islands. Topographic complexity was the standard deviation of
 terrestrial elevation of each bank from STRM Digital Elevation Data (90m
 resolution; version 4, Jarvis <em>et al</em>., 2008). Natural
 area and economic area were the total proportion of bank area covered by
 natural or economic land cover types in the Annual International
 Geosphere-Biosphere Programme classification layer of the MODIS Land Cover
 Type Yearly Global 500m data (Friedl & Sulla-Menashe, 2015).
 Natural area included all forest, grassland, wetland, savanna, and
 shrubland land cover types. Economic area included all cropland and urban
 land cover types. The “cropland/natural vegetation mosaics” type was split
 evenly between the two metrics. Bare ground and permanent water cover
 types were excluded. We
 calculated a natural and an anthropogenic metric of source pool isolation:
 geographic isolation and economic isolation. Mainland South and Central
 America plus the continental islands Cuba and Hispaniola have acted as
 natural source pools for all Caribbean herps. We used the minimum distance
 from the geographic centroid of a bank to the shoreline of the nearest
 mainland or continental island source as geographic isolation (see Methods
 Supp. Info. Section 3 of the manuscript for comparison to other isolation
 metrics). We estimated economic isolation from individual ship dockings at
 ports in the greater Caribbean region in March, June, September, and
 December of 1979, 1991, 2003, and 2015 for cargo, cruise, and passenger
 ships (Loyd’s, 2020). We took the inverse of one plus the summed total
 number of ship visits from outside a bank to docks within each bank across
 all months, years, and ship types as our economic isolation metric.Bank
 population density was estimated as the number of people living on a bank
 averaged over every five years from 2000 to 2015 (Population Count version
 4, CIESIN, 2018) divided by bank area. References: CIESIN. (2018). Gridded Population of the World,
 Version 4 (GPWv4): Population Count, Revision 11 [Data set]. Palisades,
 NY: NASA Socioeconomic Data and Applications Center (SEDAC).
 https://doi.org/10.7927/H4JW8BX5 Friedl, M., & Sulla-Menashe, D. (2015).
 MCD12Q1 MODIS/Terra+Aqua Land Cover Type Yearly L3 Global 500m SIN Grid
 V006 [Data set]. NASA EOSDIS Land Processes DAAC.
 https://doi.org/10.5067/MODIS/MCD12Q1.006 Frost, D. R. (2020). Amphibian Species of the
 World. Amphibian Species of the World: An Online Reference. Version 6.1.
 https://amphibiansoftheworld.amnh.org/ GADM. (2012). Global Administrative Areas (3.6)
 [Digital Geospatial Data]. University of California, Berkley.
 www.gadm.org GBIF. (2020).
 Global Biodiversity Information Facility. GEBCO Compilation Group. (2020). GEBCO 2020 Grid
 [Map]. doi:10.5285/a29c5465-b138-234d-e053-6c86abc040b9 Hedges, S. B. (2020). Caribherp. Caribherp:
 Amphibians and Reptiles of Caribbean Islands.
 http://www.caribherp.org/ Jarvis, A., Reuter, H. I., Nelson, A., &
 Guervara, E. (2008). Hole-filled seamless SRTM data V4 [Map].
 International Centre for Tropical Agriculture (CIAT).
 http://srtm.csi.cgiar.org Loyd’s. (2020). Lloyd’s of London.
 https://www.lloyds.com/ Uetz,
 P., Freed, P., & Hošek, J. (2020). The Reptile Database.
 http://reptile-database.org/
description: All data are provided in csv format and can be opened with
 Microsoft Excel or any text editor.