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

ABSTRACT The epiphytic vascular flora is scarce and facultative in semiarid Mediterranean ecosystems, thus covering diverse taxonomic groups. However, 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 31 plant species occurring in the trunks of Phoenix dactylifera . We wanted to ascertain if 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) and the plant species. The roots were examined by molecular and phylogenetic analysis of AMF community. The plant affiliation to species 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. IMPORTANCE Arbuscular mycorrhizal (AM) symbiosis has a decisive role in plant nutrient and water uptake by plants, with particular importance in stressful environments. Under semiarid conditions, the facultative epiphytic flora should cope with harsh conditions. While numerous studies have been conducted on factors driving terrestrial AM assemblages, the epiphytic environment remains unexplored. We offer new insights into composition of AM communities as shaped by epiphytic plant host identity and functional traits.