Research ArticleCONSERVATION BIOLOGY

Globally threatened vertebrates on islands with invasive species

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Science Advances  25 Oct 2017:
Vol. 3, no. 10, e1603080
DOI: 10.1126/sciadv.1603080
  • Fig. 1 Percentage of highly threatened vertebrates breeding on islands by vertebrate class.

    Numbers above the bar give the total number of highly threatened species that breed on islands. Color shading indicates the number of taxonomic orders within each island vertebrate class.

  • Fig. 2 Attributes of islands globally with and without highly threatened vertebrates.

    Comparisons of (A) island size (km2), (B) absolute latitude, and (C) GDP between islands with and without highly threatened terrestrial vertebrate species. Islands with highly threatened vertebrates were larger, more equatorial, and in countries with lower GDP per capita.

  • Fig. 3 The ecoregions of islands globally with and without highly threatened vertebrates.

    Comparisons across (A) marine realms, (B) biogeographic realms, and (C) terrestrial habitats for islands with and without highly threatened terrestrial vertebrate species present. Islands with highly threatened vertebrates were located primarily in the central Indo-Pacific, Oceania, and the Neotropics and supported primarily tropical and subtropical moist broadleaf forest habitats.

  • Fig. 4 The global distribution of highly threatened vertebrates.

    Location of islands supporting populations of highly threatened (A) amphibians, (B) reptiles, (C) birds, (D) mammals, and the number of islands with breeding populations per highly threatened species (E).

  • Fig. 5 The 1030 islands with highly threatened native vertebrates and information on the presence or absence of invasive vertebrates.

    Of these, 779 (76%) had at least one invasive vertebrate species present. Mammals were the most common invader on these islands (753 islands; 97% of islands with highly threatened vertebrates).

  • Table 1 Taxonomic comparisons of the 2919 highly threatened terrestrial vertebrates and the 1189 highly threatened terrestrial vertebrates on islands.

    CR, critically endangered; EN, endangered.

    Taxonomic classAll terrestrial vertebrates (11)All terrestrial vertebrates from islands
    Total taxa (% of
    described taxa)
    # of CR and EN
    (% of total)
    Red List category
    (% of total)
    Total CR and EN
    (% of total CR and EN)
    Red List category
    (% of total CR and EN)
    CRENCREN
    Amphibia6106 (24%)1255 (21%)498 (8%)757 (12%)319 (25%)109 (34%)210 (34%)
    Reptilia4160 (17%)486 (12%)162 (4%)324 (8%)282 (58%)105 (58%)177 (37%)
    Aves9538 (38%)566 (6%)187 (2%)379 (4%)296 (52%)119 (52%)177 (40%)
    Mammalia5337 (21%)612 (11%)187 (4%)425 (8%)292 (48%)96 (48%)196 (33%)
    Total25,1412919 (12%)1034 (4%)1885 (7%)1189 (41%)429 (36%)760 (64%)
  • Table 2 Biogeographic island patterns (total and % of total) for the 2890 breeding populations of highly threatened amphibians, reptiles, birds, and mammal species.
    Island characteristicAmphibianReptileBirdMammal
    Latitude
      Polar0 (0%)0 (0%)58 (5.68%)1 (0.17%)
      Temperate56 (13.8%)137 (15.7%)465 (45.5%)97 (16.4%)
      Tropical351 (86.2%)734 (84.3%)499 (48.8%)492 (83.4%)
    Biome*
      Boreal forests/taiga0 (0%)0 (0%)14 (1.4%)0 (0%)
      Deserts and xeric shrublands10 (2.5%)62 (7.1%)93 (9.1%)14 (2.4%)
      Flooded grasslands and savannas2 (0.5%)7 (0.8%)2 (0.2%)4 (0.7%)
      Mangroves48 (11.8%)61 (7%)24 (2.3%)26 (4.4%)
      Mediterranean forests, woodlands, and scrub7 (1.7%)84 (9.6%)97 (9.5%)18 (3.1%)
      Montane Grasslands and Shrublands38 (9.3%)72 (8.3%)38 (3.7%)36 (6.1%)
      Temperate broadleaf and mixed forests14 (3.4%)11 (1.3%)188 (18.4%)22 (3.7%)
      Temperate conifer forests3 (0.7%)2 (0.2%)12 (1.2%)5 (0.8%)
      Temperate grasslands, savannas, and shrublands0 (0%)0 (0%)30 (2.9%)0 (0%)
      Tropical and subtropical coniferous forests0 (0%)24 (2.8%)12 (1.2%)3 (0.5%)
      Tropical and subtropical dry broadleaf forests74 (18.2%)92 (10.6%)113 (11.1%)67 (11.4%)
      Tropical and subtropical grasslands, savannas and shrublands0 (0%)0 (0%)7 (0.7%)15 (2.5%)
      Tropical and subtropical moist broadleaf forests211 (51.8%)443 (50.9%)297 (29.1%)379 (64.2%)
      Tundra0 (0%)0 (0%)68 (6.7%)1 (0.2%)
    Biogeographical realm*
      Afrotropic61 (15%)125 (14.4%)209 (20.5%)55 (9.3%)
      Antarctic0 (0%)0 (0%)33 (3.2%)0 (0%)
      Australasia17 (4.2%)54 (6.2%)263 (25.7%)150 (25.4%)
      Indo-Malay157 (38.6%)153 (17.6%)97 (9.5%)232 (39.3%)
      Nearctic1 (0.2%)14 (1.6%)37 (3.6%)7 (1.2%)
      Neotropic150 (36.9%)206 (23.7%)109 (10.7%)54 (9.2%)
      None0 (0%)13 (1.5%)27 (2.6%)0 (0%)
      Oceania9 (2.2%)209 (22.3%)160 (15.7%)61 (10%)
      Palearctic12 (2.9%)97 (11.1%)87 (8.5%)31 (5.3%)
    Marine realm
      Arctic0 (0%)0 (0%)0 (0%)1 (0.2%)
      Central Indo-Pacific81 (19.9%)362 (41.6%)223 (21.8%)317 (53.7%)
      Eastern Indo-Pacific0 (0%)25 (2.9%)106 (10.4%)2 (0.3%)
      Southern Ocean0 (0%)0 (0%)58 (5.7%)0 (0%)
      Temperate Australasia12 (2.9%)1 (0.1%)160 (15.7%)16 (2.7%)
      Temperate Northern Atlantic6 (1.5%)84 (9.6%)39 (3.8%)25 (4.2%)
      Temperate Northern Pacific33 (8.1%)50 (5.7%)106 (10.4%)51 (8.6%)
      Temperate South America5 (1.2%)2 (0.2%)51 (5%)5 (0.8%)
      Temperate Southern Africa0 (0%)0 (0%)109 (10.7%)0 (0%)
      Tropical Atlantic145 (35.6%)225 (25.8%)69 (6.8%)34 (5.8%)
      Tropical Eastern Pacific3 (0.7%)3 (0.3%)35 (3.4%)3 (0.5%)
      Western Indo-Pacific122 (30%)119 (13.7%)66 (6.5%)136 (23.1%)
    Island area (km2)
      Mean (SD)115,509.54 (199,904.4)66,076.1 (179,042.9)21,439.87 (88,367.3)112,081.68 (233,663.7)
      Median65,721.0119.8223.475567852.55
    Income (GDP)
      High income111 (28.2%)396 (46.2%)558 (55.6%)129 (23.5%)
      Upper middle income135 (34.3%)166 (19.3%)224 (22.3%)81 (14.8%)
      Lower middle income100 (25.4%)214 (24.9%)184 (18.3%)294 (53.6%)
      Low income48 (12.2%)82 (9.6%)37 (3.7%)44 (8%)
    Human inhabitants
      Absent9 (2.2%)260 (30.2%)428 (41.9%)87 (14.7%)
      Present398 (97.8%)606 (69.6%)594 (58.1%)502 (85.1%)
      Unknown0 (0%)2 (0.2%)0 (0%)1 (0.2%)
    Invasive vertebrates
      Present387 (95.1%)640 (73.5%)666 (65.2%)524 (88.8%)
      Absent5 (1.2%)65 (7.5%)279 (27.3%)23 (3.9%)
      Unknown15 (3.7%)166 (19.1%)77 (7.5%)43 (7.3%)
    Endemism (# of breeding islands)
      Mean (SD)1.3 (1.1)3.1 (6.6)3.5 (5.6)1.9 (2.4)
      Minimum1111
      25%1111
      50%1111
      75%1232
      Maximum13774026

    *Data from Spatz et al. (77).

    †Data from Spalding et al. (70).

    ‡Data from the International Monetary and World Bank Open Data (72, 73).

    • Table 3 Highlighted islands from the threatened island biodiversity database that support highly threatened vertebrate species, including those which are found nowhere else in the world.

      These islands are uninhabited or minimally inhabited and contain at least one of the most damaging invasive species known (17). Consideration of these islands for invasive species management would deliver major impacts for the conservation of island species.

      IslandCountry/territoryNumber of highly threatened vertebrates presentDamaging invasives present
      GoughSaint Helena, Ascension and Tristan da Cunha6Mus musculus
      MonaPuerto Rico5Felis catus, M. musculus, Rattus rattus, and Sus scrofa
      AmsterdamFrench southern territories4F. catus, M. musculus, and Rattus norvegicus
      SocorroMexico3F. catus and M. musculus
      San JoseMexico2Canis familiaris and F. catus
      Moho TaniFrench Polynesia2F. catus and Rattus exulans

    Supplementary Materials

    • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/10/e1603080/DC1

      Supplementary Materials and Methods

      fig. S1. Systematic review process flowchart for identifying islands with breeding populations of highly threatened terrestrial vertebrate species.

      fig. S2. Systematic review process flowchart for identifying islands with non-native terrestrial invasive vertebrate species (invasive vertebrates) on islands with highly threatened vertebrate species.

      table S1. Current and historic breeding status assigned to each highly threatened terrestrial vertebrate species on an island.

      table S2. Island status category definitions describing the presence or absence of invasive non-native vertebrates on each island and the status applied to each invasive vertebrate on each island.

      table S3. The 40 highly threatened vertebrate species that experienced population extinctions (extirpations) across ≥50% of their islands.

      table S4. The 320 species of invasive vertebrates found on islands with highly threatened vertebrates.

      table S5. The number and percentage of each invasive vertebrate group on islands with highly threatened vertebrate species.

      table S6. The highly threatened vertebrate species on islands with invasive vertebrates and minimal human populations (<100 people).

      data file S1. The 1189 highly threatened vertebrate taxa from the IUCN Red List (version 2013.2).

      data file S2. The 1288 islands with highly threatened terrestrial vertebrates.

      References (7886)

    • Supplementary Materials

      This PDF file includes:

      • Supplementary Materials and Methods
      • fig. S1. Systematic review process flowchart for identifying islands with breeding populations of highly threatened terrestrial vertebrate species.
      • fig. S2. Systematic review process flowchart for identifying islands with non-native terrestrial invasive vertebrate species (invasive vertebrates) on islands with highly threatened vertebrate species.
      • table S1. Current and historic breeding status assigned to each highly threatened terrestrial vertebrate species on an island.
      • table S2. Island status category definitions describing the presence or absence of invasive non-native vertebrates on each island and the status applied to each invasive vertebrate on each island.
      • table S3. The 40 highly threatened vertebrate species that experienced population extinctions (extirpations) across ≥50% of their islands.
      • table S4. The 320 species of invasive vertebrates found on islands with highly threatened vertebrates.
      • table S5. The number and percentage of each invasive vertebrate group on islands with highly threatened vertebrate species.
      • table S6. The highly threatened vertebrate species on islands with invasive vertebrates and minimal human populations (<100 people).
      • References (78–86)

      Download PDF

      Other Supplementary Material for this manuscript includes the following:

      • data file S1 (Microsoft Excel format). The 1189 highly threatened vertebrate taxa from the IUCN Red List (version 2013.2).
      • data file S2 (Microsoft Excel format). The 1288 islands with highly threatened terrestrial vertebrates.

      Download Data Files S1 and S2

      Files in this Data Supplement:

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