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-

1

123456789

10111213141516171819202122232425262728293031323334353637383940414243444546

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.

2

47484950515253

Fig. S1. World map showing the locations of the 189 mainland areas and islands across the globe used in this study.

3

54555657

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).

4

58596061

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.

5

626364

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).

6

65666768697071727374