A molecular assessment of ectomycorrhizal fungal communities associated with North African Alnus glutinosa forests

The diversity and biogeographic patterns of ectomycorrhizal fungi (EcMF) remain underexplored in many parts of the world, particularly in southern temperate ecosystems. Here, we present the first molecular characterization of EcMF communities associated with North African populations of <i>Alnus glutinosa</i> (L.) Gaertn., commonly known as black alder. Root samples over multiple sampling periods were collected from three sites in and around El Kala Biosphere Reserve, northeastern Algeria, and analysed using high-throughput sequencing targeting the full ITS region. We identified 101 EcMF operational taxonomic units (OTUs), representing two phyla, two classes, seven orders, 15 families, and 18 genera-predominantly Basidiomycota (98.6%). The genera <i>Lactarius</i>, <i>Tomentella</i>, and <i>Inocybe</i> consistently dominated across all sites. Community richness and diversity varied significantly among sites. Organic matter content and site identity significantly influenced EcMF community composition, whereas seasonality and other edaphic parameters showed no detectable effects. Comparative phylogenetic analysis revealed minimal overlap with EcMF communities from European, Asian, or American <i>Alnus</i> populations. These findings demonstrate that southern marginal populations of <i>A. glutinosa</i> harbour exceptionally rich and potentially unique EcMF assemblages, likely shaped by relative aridity, geographic isolation, and host lineage divergence. Our study highlights the critical importance of incorporating biogeographically peripheral ecosystems into global fungal diversity assessments, particularly in historically and environmentally distinctive regions.