Host identity and functional traits determine the community composition of the arbuscular mycorrhizal fungi in facultative epiphytic plant species

The epiphytic vascular flora is scarce and mostly facultative in semiarid Mediterranean ecosystems, thus covering a wide range of taxonomic groups. But, differently to terrestrial conditions, little is known about the factors driving mycorrhizal communities in epiphytic environments. Here, we investigated the arbuscular mycorrhizal fungi (AMF) harboured by 41 plant species occurring in the trunks of Phoenix dactylifera. We wanted to ascertain if the arbuscular mycorrhizal symbiosis is a generalized trend and how host identity and plant functional traits shape mycorrhizal communities. Specifically, we tested the plant life-cycle (perennial versus annual), the plant life-form (herbaceous versus woody), the plant origin (exotic versus native), the plant family, and the plant species.The roots were examined by molecular and phylogenetic analysis. The plant affiliation to species or family strongly influenced the AMF assemblages. Plant life-form and plant life-cycle also shaped AMF interactions. The AMF community differed between annual and perennial species and higher AMF richness was detected in perennial plants. The indicator species analysis revealed three Operational Taxonomic Units belonging to the Glomeraceae, associated with annual species. However, the epiphytic plants associated with AMF irrespective of whether they were native or not, probably because here no functional differences derive from plant origin.