Johannes Le Roux1,2, Staci Warrington2, Jan-Hendrik Keet3, Cang Hui2 and Allan Ellis3
1Department of Biological Sciences, Macquarie University, Sydney, Australia
2Centre for Invasion Biology, Stellenbosch University, Stellenbosch, South Africa
3Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa
Plants interact with many soil microbes. For non-native plants, interactions with both mutualistic and antagonistic soil microbes can significantly impact their invasivesness. This, however, is dependent on the eco-evolutionary experiences of both interacting partners. We will illustrate that invasions by Australian acacias in South Africa’s hyper-diverse fynbos biome are often characterized by co-invasions with their nitrogen-fixing rhizobium mutualists from Australia. DNA barcoding and functional analyses of rhizobia revealed that acacias enrich and homogenise invaded soils for these mutualists, leading to positive plant-soil feedbacks. Homogenization of rhizobial communities in invaded soils was, to some degree, mimicked by other bacterial taxa, i.e. whole soil microbiomes. Next generation sequencing data of whole soil microbiomes illustrated that pristine (uninvaded) fynbos soils are characterized by high microbial community turnover, possibly reflecting high turnover in above-ground plant community components. This signal was diluted by the presence of dense monotypic acacia infestations, even over large spatial scales. We will discuss the implications of our findings for the restoration of acacia-invaded fynbos regions.