Worldwide concerns over the prevalence and impact of alien plant species have stimulated interests in determinants of plant invasion into native communities. Success of alien plant species is often attributed to high competitive ability. However, not all alien species become invasive, and not all natives are vulnerable. Here, we quantified competition in 48 pairs of annual native and naturalized alien species that are either common or rare in Germany.
Results/Conclusions
Overall, alien species were not more competitive than natives. However, common alien species (i.e. invasive alien species), although strongly limited by intraspecific competition, were more competitive than rare natives. This is because alien species had higher intrinsic growth rates (i.e. growth rates in absence of competition) than native species, and common species had higher intrinsic growth rates than rare species. In addition, interspecific competition was not related to status or commonness. Our work highlights the importance of including commonness in understanding invasion success. It suggests that variation among species in intrinsic growth rate is more important in competitive ability than inter- or intraspecific competition, and thus contributes both to invasion success and rarity.