Soil nutrient gradients drive phylogenetic clustering of arbuscular mycorrhizal fungi associated with Malva sylvestris across Moroccan drylands

Arbuscular mycorrhizal fungi (AMF) are ubiquitous in arid ecosystems, yet their distribution and community structure along spatial and ecological gradients remain insufficiently explored on a large regional scale. Here, we investigated the distribution pattern and phylogenetic structure of AMF community associated with Malva sylvestris L. along a 700 km a transect from the Atlantic coast to inland Morocco covering arid and semi-arid ecosystems. Amplicon sequencing of the LSU rDNA region of roots and rhizosphere soil samples across 13 sites revealed a highly diverse AMF assemblage spanning 10 families, with Entrophosporaceae, Sclerocystaceae, Septoglomeraceae, Domikaceae and Diversisporaceae predominating in root and soil biotopes. The most frequent taxa, Entrophospora furrazolae , E. infrequens , Dominikia aurea and D. iranica ; Funneliformis geosporum and F. coronatus and Rhizophagus irregularis , and R. invermaius occurred in over 80% of sampled sites. Community composition of AMF in the rhizosphere was mainly explained by the distance from the coastline, mean annual temperature (MAT), and precipitation, in addition to soil phosphorus (P) and nitrogen (N). Whereas roots-associated communities were more strongly shaped by soil total P and carbon, suggesting a strong resource-driven symbiotic interactions. Community phylogenetic structure (α-diversity) was primarily driven by soil physicochemical properties, particularly total P, and N, but not directly by climatic parameters such as precipitation and MAT. Net Relatedness Index (NRI) and Nearest Taxon Index (NTI) increased along soil P and N gradients in roots and rhizosphere, respectively, indicating a trait-based environmental filtering mechanism, whereby higher nutrient concentrations promote phylogenetic clustering of AMF communities. Additionally, βNTI of root-associated AMF communities was positively correlated with soil total P, whereas co-occurrence network degree, and closeness centrality displayed negative associations, suggesting that high P concentration enhances heterogenous selection, but simultaneously reduces network complexity and connectivity. Overall, this study advances our understanding of AMF ecology in dryland ecosystems and highlights the central role of soil nutrient gradients in shaping AMF phylogenetic structure and assembly processes across spatially heterogeneous habitats.