Invasive Melinis minutiflora outperforms native species, but the magnitude of the effect is context-dependent
Impacts of invasive species are context-dependent owing to genetic differences in the invasive species, in the abiotic environment or the recipient biotas. Here, we tested how these factors affected the invasive grass Melinis minutiflora and its impacts on native plants in Hawai’i (USA) and in the Brazilian Cerrado under four environmental conditions. We sampled M. minutiflora and three native species from each studied region and conducted two equivalent greenhouse experiments. In each experiment, we manipulated shade, irrigation, soil nutrients, and interspecific competition. We found that M. minutiflora had low genetic polymorphism, and two distinct genetic clusters exist. Both clusters exist in Hawai’i and Brazil. Melinis minutiflora biomass was three-times greater in Brazil compared to Hawai’i. Both in Brazil and Hawai’i, M. minutiflora was affected by shade, irrigation, and competition. While in Brazil the identity of the competing native species did not matter for M. minutiflora, in Hawai’i the identity of the native species affected M. minutiflora when shade was applied. Brazilian native species were all affected by shading, two of them by competition with M. minutiflora, and one of them by fertilization. Two Hawaiian native plants were affected by shade and competition with M. minutiflora, whereas one native species was not affected by any of the experimental factors. In summary, both biotic and abiotic factors affected native and invasive species. However, in all cases native species were outperformed by the invader.
KeywordsBrazil Cerrado Hawai’i Invasion biogeography Invasion ecology Invasiveness Molasses grass
We thank Isabel Schmidt, Courtney Angelo, Mashuri Waite, Amy Tsuneyoshi, Travis Idol, Servillano Lamer, Sergio Tadeu Meirelles, and Agno Damasceno for assistance with field and greenhouse work. We thank Carlos Romero Martins, Clyde Imada and Neil Snow for grass specimens’ identification. The study was funded by Fundação de Apoio à Pesquisa de São Paulo (FAPESP) and Natural Grasslands Conservancy. We used the facilities of the University of Hawai‘I, Departments of Botany and NREM, in Hawai’i, and the Juquery State Park in Brazil. RDZ and ABS were supported by CNPq-Brazil.
RDZ analysed the data and wrote the manuscript. ABS, VRP, and CD designed and carried out the experiments. YPL, MP-F, and TCLL collected data and performed the genetic analyses. All authors revised the manuscript.
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