Invasive Carpobrotus taxa reshape rhizosphere microbiome across native and non-native ranges

Invasive alien plants pose a significant threat to coastal ecosystems worldwide, with Carpobrotus taxa being among the most damaging. One of the most notable environmental consequences of plant invasions in coastal ecosystems is the modification of both abiotic and biotic soil properties. In this research, we investigated the impact of Carpobrotus taxa, representing distinct population genetic clusters in their native and non-native ranges, on soil abiotic characteristics, and the diversity of soil microorganisms. We sampled soils at 17 sites with Carpobrotus present vs absent, located in three regions: Southern Europe and California (non-native range) and South Africa (native range). We compared the pH, nutrient content, and diversity and composition of prokaryotic and fungal communities in soils from different regions as well as plots with and without Carpobrotus. We found substantial variation in soil abiotic properties and microbial diversity and composition between the studied regions, suggesting a strong influence of the regional context. Regardless of origin (i.e., native or non-native) or the population genetic cluster, Carpobrotus presence caused significant changes in soil chemical properties and microbial communities but the type and direction of the changes varied across regions. For example, pH declined under Carpobrotus in California but not in the other regions, whereas % organic matter increased in the other regions but not in California. Understanding the context-dependent effects is crucial for predicting the ecological impacts of these invasive taxa.