SUPPORTING INFORMATION
Species pool, human population, and global vs. regional invasion patternsBy Q. Guo, B.V. Iannone III, G.C. Nunez-Mir, K.M. Potter, C.M. Oswalt, S. Fei
Appendix S1: List of data sources used to compile exotic species data for both mainland areas (N = 100) and islands (N = 89).
Chown, S., Gremmen, N. & Gaston, K. (1998) Ecological biogeography of southern ocean islands: species-area relationships, human impacts, and conservation. The American Naturalist, 152, 562-575.
Chown, S.L., Hull, B. & Gaston, K.J. (2005) Human impacts, energy availability and invasion across Southern Ocean Islands. Global Ecology and Biogeography, 14, 521-528.
Daehler, C.C. (2006) Invasibility of tropical islands by introduced plants: partitioning the influence of isolation and propagule pressure. Preslia, 78, 389-404.
Dawson, W., Keser, L.H., Winter, M., Pyšek, P., Kartesz, J., Nishino, M., Fuentes, N., Chytrý, M., Celesti-Grapow, L. & van Kleunen, M. (2013) Correlations between global and regional measures of invasiveness vary with region size. NeoBiota, 16, 59-80.
Essl, F., Moser, D., Dirnböck, T., Dullinger, S., Milasowszky, N., Winter, M. & Rabitsch, W. (2013) Native, alien, endemic, threatened, and extinct species diversity in European countries. Biological Conservation, 164, 90-97.
Guo, Q. (2014) Species invasions on islands: searching for general patterns and principles. Landscape Ecology, 29, 1123-1131.
Guo, Q. & Symstad, A.M.Y. (2008) A two-part measure of degree of invasion for cross-community comparisons. Conservation Biology, 22, 666-672.
Guo, Q. & Ricklefs, R.E. (2010) Domestic exotics and the perception of invasibility. Diversity and Distributions, 16, 1034-1039.
Jiang, H., Fan, Q., Li, J.-T., Shi, S., Li, S.-P., Liao, W.-B. & Shu, W.-S. (2011) Naturalization of alien plants in China. Biodiversity and Conservation, 20, 1545-1556.
Kueffer, C., Daehler, C.C., Torres-Santana, C.W., Lavergne, C., Meyer, J.-Y., Otto, R. & Silva, L. (2010) A global comparison of plant invasions on oceanic islands. Perspectives in Plant Ecology, Evolution and Systematics, 12, 145-161.
Long, J.D., Trussell, G.C. & Elliman, T. (2009) Linking invasions and biogeography: isolation differentially affects exotic and native plant diversity. Ecology, 90, 863-868.
Lonsdale, W.M. (1999) Global patterns of plant invasions and the concept of invasibility. Ecology, 80, 1522-1536.
Mac, M.J., Opler, P.A., Puckett Haecker, C.E. & Doran, P.D. (1998) Status and Trends of the Nation’s Biological Resources. U.S. Department of the Interior, U.S. Geological Survey, Reston.
McGeoch, M. A., Butchart, S. H., Spear, D., Marais, E., Kleynhans, E. J., Symes, A., ... & Hoffmann, M. (2010). Global indicators of biological invasion: species numbers, biodiversity impact and policy responses. Diversity and Distributions, 16: 95-108.
Mooney, H.A. & Drake, J.A. (1986) Ecology of Biological Invasions of North America and Hawaii. Springer-Verlag, New York.
Sax, D.F., Gaines, S.D. & Brown, J.H. (2002) Species invasions exceed extinctions on islands worldwide: a comparative study of plants and birds. The American Naturalist, 160, 766-
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783.Vitousek, P.M., D'antonio, C.M., Loope, L.L., Rejmanek, M. & Westbrooks, R. (1997)
Introduced species: a significant component of human-caused global change. New Zealand Journal of Ecology, 21, 1-16.
Wu, S.-H., Hsieh, C.-F., Chaw, S.-M. & Rejmánek, M. (2004) Plant invasions in Taiwan: insights from the flora of casual and naturalized alien species. Diversity and Distributions, 10, 349-362.
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Fig. S1. World map showing the locations of the 189 mainland areas and islands across the globe used in this study.
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Land area (km2)
100 101 102 103 104
Exotic fraction
10-2
10-1
100
USAr2 = 0.39P = 0.0001
Chinar2 = 0.30P = 0.004
Europer2 = 0.003P = 0.94
Fig. S2. Negative land area-exotic fraction relationships in the USA (across states) and China (across provinces) but not in Europe (across countries). These relationships are generally weaker than the population density-exotic fraction relationships across the three regions (see Fig. 3).
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0.0
0.2
0.4
0.6
0.8
1.0
50100
150200
250300
350400
100200
300400
500600
Exotic fraction
Popul density
Area
USA
0.02
0.04
0.06
0.08
0.10
0.12
100200
300400
500600
700
200 400600
800 10001200
14001600
Popul density
Area
0.00
0.05
0.10
0.15
0.20
0.25
50100
150200
250300
350
0 100 200 300 400500 600
700800
Popul density
Area
China Europe
Fig. S3. Joint effects of land area and population density on exotic fraction in the USA, China, and Europe. The units of area and population density are 1000 km2 and No. individuals km-2, respectively.
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Area (country/state/province km2)103 104 105 106 107
10-1
100
101
102
103
104
USA: r2 = 0.49P = 0.001
China: r2 = 0.66P < 0.001
Population density (Indiv. km
-2)
Europe: r2 = 0.03P > 0.05
Fig. S4. Relationships between land area and human population density in USA, China, and Europe. Note that, for Europe, extremely small countries, such as Vatican City and San Marino, and very big countries, such as Russia, are excluded to increase the comparability of the unit areas in all three regions. The average population density for the data points in China, Europe, and USA are 145, 72.9, and 35 individuals per km2, respectively).
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