Acacia longifolia, a species native to Australia, is an aggressive invasive in Mediterranean-type ecosystems worldwide. Its success in diverse habitats, expanding from coastal dunes to forests, is often attributed to its ability to establish interactions with a variety of microbes, including bacteria and fungi. This study investigates the seed and root-nodule microbiomes of A. longifolia to understand the roles these microbial communities play in its adaptation and invasive behaviour. Using high-throughput sequencing, we characterized the bacteriome and mycobiome associated with the plant, considering nodules and seeds, and the surrounding soil in three different locations in Portugal with different climate conditions (North, Center and South), and a comparison between two different habitats (Dune versus Forest). Our results reveal a dynamic interaction between A. longifolia and its microbial partners, supporting the importance of these plant-microbe interactions in nutrient acquisition and stress tolerance for A. longifolia, ultimately leading to their impact in an invaded ecosystem. The seed microbiome of A. longifolia was less diverse than for nodules but with more functions assigned, while nodules showed a broader diversity, assigned to more specific functions. Here we provide evidence for the role of seed microbiota in germination and seed-to-seedling transition along with the beneficial role of nodulation in development and seedling-to-sapling switch. We also propose a local signature for microbial communities as we found a dissimilarity in microbial partners when considering habitat, with dune communities showing a functional plasticity, aiding A. longifolia to cope in such nutrient-limiting environment. For forests, functions more related with plant and microbe associations are evidenced, possibly facilitating interspecific competition. These findings contribute to an understanding of the plant-microbe interactions and dynamics that underpin A. longifolia ecological success as an invasive plant.
