A case study from Australia on five acacias and their associated soil microbial communities across non-native and native range populations

Although Australian acacias are one of the most notable invaders world-wide, relatively little is known about the role of soil microbial communities in their invasion success both globally and locally. In Australia, acacias have also become invasive or naturalized when introduced into novel locations across states. However, the relative importance of soil biota, particularly beneficial rhizobial and fungal communities, in the invasion success, remains unknown. We comprehensively examined the role of soil biota on the invasion success of four Acacia spp. (A. cyclops, A. longifolia, A. melanoxylon and A. saligna) and a close relative Paraserianthes lophantha in Australia. Soil and seed samples were collected from respective five native and non-native range populations of each species across four states (i.e. New South Wales, Victoria, South Australia and Western Australia). To assess the role of soil biota on plant performance we used (i) plant-soil feedback experiment to assess the net effect of soil microbiota on plant performance and (ii) 454 sequencing to identify the bacterial and fungal communities in the nodules and soils. Although some variation in microbial composition across the non-native and native populations was found, this did not translate into improved growth in the non-native range suggesting that other abiotic and biotic components (e.g. human imposed artificial selection, herbivory) may contribute more strongly to the invasion success of these acacias in non-native populations in Australia. Interestingly, we found that seed origin had stronger effect on plant performance than soil biota