Relationship of alien species continues in a foreign land: The case of and Australian (Proteaceae) in South African Fynbos.

Fungal invasions only recently started to receive more attention in invasion biology. This is largely attributed to little or non-existent information about these inconspicuous organisms. Most invasion hypotheses focus on factors that increase invasion success; few try to explain why invasions fail. Here we hypothesize that a host-pathogen relationships can limit the invasiveness of an alien plant species in a novel range. To test this, we investigate whether the invasiveness of the Australian genus of Proteaceae, in South Africa is determined by the alien and major invasive phytopathogen, . The presence of in root and soil was evaluated using morphological and molecular techniques. Isolates were cultured onto selective media and polymerize chain reactions and internal transcribing spacers were used for identification. Acetone leaf extracts of 11 spp. were screened for antimicrobial activity against , using the minimum inhibitory concentration assay. A total of 3840 individuals from seven localities were surveyed. was consistently isolated from species root and soil samples. Out of the 12 species that were screened for antimicrobial activity, four introduced species, , , , and and the invasive and exhibited relatively high antimicrobial activity against (strain 696/12). We show that the phytopathogen in the native range has similar impact in the novel range and in doing so may limit invasion success of species with low antimicrobial activity.