ABSTRACT
Pestalotioid fungi were isolated in pure culture from symptomatic plants of Callistemonlaevis, C.viminalis, Lumaapiculata (marketed as "Myrtusluma"), Myrtuscommunissubsp.tarentina, and M.communisvar.microphylla (M.communis 'Microphylla'), showing twig canker, dieback and defoliation. The isolates were identified to species by ITS, tef1 and tub2 sequences, which revealed the presence of six species of Neopestalotiopsis (N.camelliae-oleiferae, N.hispanica, N.iberica, N.rosae, N.rosicola, and N.zakeelii) and one species of Pestalotiopsis (P.biciliata). While most species were isolated only once or twice, the majority of isolates belonged to N.rosae (13) and N.hispanica (8). Pathogenicity was investigated by pathogenicity tests on all hosts, which confirmed the pathogenicity of all Neopestalotiopsis species on at least some of the hosts tested, while P.biciliata did not cause any disease symptoms. Neopestalotiopsishispanica and N.rosae caused symptoms in all hosts of the present study, while the other Neopestalotiopsis species tested showed no symptoms on Lumaapiculata.
ABSTRACT
BACKGROUND: Fungi and ants belong to the most important organisms in terrestrial ecosystems on Earth. In nutrient-poor niches of tropical rainforests, they have developed steady ecological relationships as a successful survival strategy. In tropical ant-plant mutualisms worldwide, where resident ants provide the host plants with defense and nutrients in exchange for shelter and food, fungi are regularly found in the ant nesting space, inhabiting ant-made dark-colored piles ("patches"). Unlike the extensively investigated fungus-growing insects, where the fungi serve as the primary food source, the purpose of this ant-fungi association is less clear. To decipher the roles of fungi in these structures within ant nests, it is crucial to first understand the dynamics and drivers that influence fungal patch communities during ant colony development. RESULTS: In this study, we investigated how the ant colony age and the ant-plant species affect the fungal community in the patches. As model we selected one of the most common mutualisms in the Tropics of America, the Azteca-Cecropia complex. By amplicon sequencing of the internal transcribed spacer 2 (ITS2) region, we analyzed the patch fungal communities of 93 Azteca spp. colonies inhabiting Cecropia spp. trees. Our study demonstrates that the fungal diversity in patches increases as the ant colony grows and that a change in the prevalent fungal taxa occurs between initial and established patches. In addition, the ant species significantly influences the composition of the fungal community in established ant colonies, rather than the host plant species. CONCLUSIONS: The fungal patch communities become more complex as the ant colony develops, due to an acquisition of fungi from the environment and a substrate diversification. Our results suggest a successional progression of the fungal communities in the patches during ant colony growth and place the ant colony as the main driver shaping such communities. The findings of this study demonstrate the unexpectedly complex nature of ant-plant mutualisms in tropical regions at a micro scale.