Invasive Nicotiana glauca shifts the soil microbial community composition and functioning of harsh and disturbed semiarid Mediterranean environments

Abstract

Exotic invasive plants have been reported to alter the soil microbial community composition and function in order to facilitate their further invasion. These changes in the soil microbiome could be influenced also by the characteristics of the soil and sites. We hypothesised that (i) the invasion of Mediterranean semiarid ecosystems by the woody shrub Nicotiana glauca (tree tobacco) would promote a specific rhizosphere microbial community with particular functions and (ii) the rhizosphere microbial community associated with the invasive plant would be independent of the edaphic characteristics of the invaded site. We tested these hypotheses by comparing the rhizosphere microbial community of N. glauca with that of the native plant community at four sites covering a broad range of distinctive edaphic characteristics, including two human-disturbed environments and two naturally harsh Mediterranean environments (one saline and one gypsum soil). The soil microbial community composition was analysed using Illumina MiSeq sequencing and the rhizosphere microbial function was predicted by PICRUSt and FUNGuild. Our results suggest that the composition of the rhizosphere bacterial and fungal communities differed between N. glauca and the dominant native plant species and according to the soil characteristics. The metabolic functions of indicator taxa also differed between the invader and the dominant native plant species. In particular, the functions involved in the metabolism of carbon (C) and sulphur (S) compounds were overrepresented in the rhizosphere community of the invader. In conclusion, invasive N. glauca shifts the soil microbial community composition and its function related to C and S cycling in semiarid Mediterranean environments, including soils affected by salinity and gypsum.