Abstract

Understanding why alien species become dominant in recipient communities requires a biogeographical perspective comparing the ecology of native and introduced populations. The genus Centaurea (Asteraceae) is well-known in invasion ecology because several aggressive invaders, including Centaurea melitensis L., belong to this genus. We compared the competitive ability of C. melitensis individuals from Spain (native range) and Chile (invaded range) when competing against Helenium aromaticum (Hook.) L.H. Bailey, a native relative from Chile. We performed germination bioassays and common garden competition experiments to compare: (1) the germination capacities of C. melitensis (Spain and Chile) and H. aromaticum (2) the potential allelopathic effect of leaf lixiviates of C. melitensis (Spain and Chile) on the seed germination of H. aromaticum, (3) the ability of C. melitensis from both origins to reduce the growth of H. aromaticum. No significant differences in the capacity of seed germination were found among C. melitensis from Chile and Spain and the native H. aromaticum. However, the seed germination of H. aromaticum was inhibited by the presence of C. melitensis leaves from Chile and Spain. Also, the biomass of H. aromaticum was reduced in the presence of C. melitensis, regardless of their origin. Our results demonstrate the competitive superiority of the invasive C. melitensis over H. aromaticum, but we found no evidence of an evolutionary increase in the competitive ability of the invader populations. Therefore, at least part of the invasive potential of C. melitensis seems to be acquired by selective processes in their original range.