Cary for her diligent bibliographic work in compiling the majority of the references. Fruitful discussion and comments on the manuscript were provided by E. Leger, T. Rand, A. Dyer, J. Gaskin, K. Rice, and the V. Eviner lab. We also thank two anonymous reviewers whose comments substantially improved the manuscript.

Appendix See Table 6. Table 6 Dataset and references for the statistical analysis Species name Family Geographic rangea (GR) Habitat specificityb (HS) Local abundancec (LA) Life history Pollination syndrome Dispersal (biotic/abiotic) Specific dispersal Mating system Referenced Acacia ausfeldii Fabaceae S S D check details Perennial   Biotic Ant   Brown et al. ( 2003 ) XMU-MP-1 Acacia sciophanes Fabaceae S G S Perennial Biotic     Mixed Coates et al. ( 2006 ) Acacia williamsonii Fabaceae S S D Perennial   Biotic Ant   Brown et al. ( 2003 ) Agrostis hiemalis Poaceae

L G S Perennial         Rabinowitz and Rapp Selleckchem C646 (1979) and Rabinowitz and Rapp ( 1985 ) Alchemilla fontqueri Rosaceae S S S Perennial Abiotic Abiotic Wind Mixed Blanca et al. ( 1998 ) and Baudet et al. (2004) Alyssum nevadense Brassicaceae S G S Perennial Biotic Abiotic Ballistic   Blanca et al. ( 1998 ), Melendo et al. (2003) and Ivorra (2007) Arenaria nevadensis Caryophyllaceae S S S Annual Biotic Abiotic Ballistic Sexual Blanca et al. ( 1998 ), Melendo et al. (2003), Baudet et al. (2004), and Lopez-Flores et al. (2008) Armeria filicaulis subsp. trevenquiana Plumbaginaceae S S

S Perennial Biotic Both   Asexual Blanca et al. ( 1998 ), Melendo et al. (2003) and Baudet et Adenosine triphosphate al. (2004) Artemisia alba subsp. nevadensis Asteraceae S G S Perennial Abiotic Abiotic Ballistic   Blanca et al. ( 1998 ) and Melendo et al. (2003) Artemisia granatensis Asteraceae S G S Perennial Abiotic Abiotic   Asexual Blanca et al. ( 1998 ), Melendo et al. (2003), and Baudet et al. (2004) Artemisia umbelliformis Asteraceae L G S Perennial         Blanca et al. ( 1998 ) and USDA PLANTS Database (2009) Betula pendula subsp. fontqueri Betulaceae L S S Perennial         Blanca et al. ( 1998 ) and Flora Iberica (2009) Boopis gracilis Calyceraceae L S D Annual         Ghermandi et al. ( 2004 ) Brassica insularis Brassicaceae S S S Perennial Biotic     Sexual Hurtrez Bousses ( 1996 ) and Glemin et al. (2008) Centaurea gadorensis Asteraceae S G S Perennial Biotic Biotic Ant   Blanca et al. ( 1998 ), Melendo et al. (2003) and Lorite et al. (2007) Cephalanthera rubra Orchidaceae L G S Perennial Biotic     Mixed Blanca et al. ( 1998 ) and Brzosko and Wroblewska (2003) Chenopodium scabricaule Chenopodiaceae L S D Perennial         Ghermandi et al.