DOI: 10.5061/dryad.b47g160
title: Data from: Importance of soil legacy effects and successful mutualistic interactions during Australian acacia invasions in nutrient poor environments

description: Non-native plants often alter environments they invade, favouring their
 own performance through positive feedbacks. Plant-soil interactions
 represent one such mechanism, but their complexity (e.g. invader-induced
 changes in soil nutrients, microbial communities, etc.) makes inferences
 of the precise mechanisms that benefit invaders difficult. Here we aimed
 to determine: 1) whether invasion by Australian acacias (genus Acacia L.)
 changes nitrogen-fixing soil microbial community diversity and structure,
 and 2) the importance of available rhizobial partners and overall
 invader-induced soil changes as significant facilitators of acacia
 performance. We sampled soils from various invaded and nearby uninvaded
 areas in South Africa’s Core Cape Subregion and, using next generation
 sequencing data, compared nitrogen-fixing soil microbial communities
 between invaded and univaded soils. We then determined the relative
 importance of soil status (invaded vs. uninvaded), in conjunction with the
 rhizobial addition, to the performance of invasive acacias under common
 garden conditions. Next generation sequencing data revealed that invaded
 soils generally harboured lower nitrogen-fixing microbial diversity and
 were compositionally more homogenous, compared to uninvaded soils.
 Bradyrhizobium strains, the most common known rhizobial associate of
 acacias, were more abundant in invaded than uninvaded sites. Our
 greenhouse experiments found significantly reduced growth performances of
 acacias in uninvaded relative to invaded soils for most species by site
 comparisons, and almost no influence of additional rhizobial inoculum
 However, the overall relationship between nodulation and growth kinetics
 was much steeper for plants grown in uninvaded soils compared to invaded
 soils. Despite invasive acacias homogenising nitrogen-fixing microbial
 community composition and reducing diversity, it appears that mutualist
 availability poses no significant barrier to acacia establishment.
 Although acacia-induced changes to soil conditions enhance plant
 performance, our successful nodulation seems important to early growth
 performance of acacias when encountering novel soil conditions. We provide
 evidence that invasions by Australian acacias affect the diversity and
 structure of soil rhizobial communities. Although overall soil changes
 benefit their performance independent of rhizobia addition, forming
 successful mutualistic interactions is critical during the establishment
 phase under novel environmental conditions. Taken together, our results
 indicate that interactions between soil abiotic and biotic conditions work
 in concert to enhance invader performance though positive feedbacks.
description: Datasets-for-Le-Roux-etal-JEcolSoil nodC derived rhizobial communities for three sites invaded by acacia species and nearby univaded areas of three nearby sites, data collected in greenhouse experiment using invaded and unvindaded soils from five sites, with all soil samples collected at the Core Cape Subregion, South Africa.