Patterns in plant–soil biota interactions could be influenced by the spatial distribution of species due to soil conditions or by the functional traits of species. Gypsum environments usually constitute a mosaic of heterogeneous soils where gypsum and nongypsum soils are imbricated at a local scale. A case study of the interactions of plants with arbuscular mycorrhizal fungi (AMF) in gypsum environments can be illustrative of patterns in biotic interactions. We hypothesized that (i) soil characteristics might affect the AMF community and (ii) there are differences between the AMF communities (modules) associated with plants exclusive to gypsum soils (gypsophytes) and those associated with plants that show facultative behavior on gypsum and/or marly-limestone soils (gypsovags). We used indicator species and network analyses to test for differences between the AMF communities harbored in gypsophyte and gypsovag plants. We recorded 46 operational taxonomic units (OTUs) belonging to nine genera ofGlomeromycota. The indicator species analysis showed two OTUs preferentially associating with gypsum soils and three OTUs preferentially associating with marly-limestone soils. Modularity analysis revealed that soil type can be a major factor shaping AMF communities, and some AMF groups showed a tendency to interact differently with plants that had distinct ecological strategies (gypsophytes and gypsovags). Characterization of ecological networks can be a valuable tool for ascertaining the potential influence of above- and below-ground biotic interactions (plant-AMF) on plant community composition.

The influence of flooding and salinity gradient on the arbuscular mycorrhiza (AM) fungal spore and root colonization level in Inula crithmoides was studied. One transect divided into five plots was established from shoreline (border) to inland in La Mata lagoon, Alicante, Spain. The plots with high salinity level and flooding showed a decreased spore number in soil, and a decrease in the percentage of mycorrhization. The number of mycorrhizal fungal propagules resulting from the most probable number (MPN) experiment was very low. Glomus geosporum was the most frequent fungal species in all plots.

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.