A new Armillaria mellea variant from tops of coastal sand dunes in southern Spain

An atypical ecological variant of Armillaria mellea, growing on coastal sand dunes in southern Spain associated with Retama monosperma, is described and illustrated based on morphological, ecological and molecular evidence. Both macro and micro-morphological features, combined with ecological data, support the segregation of these populations from typical A. mellea collections. Sequencing of the D1-D2 domains of the 28S rRNA gene and the ITS region suggests their strong affinities with A. mellea. Although the molecular data do not support their segregation as a different taxon, they illustrate the wide morphological and ecological variability within this species. Phylogenetic trees provide additional insights on the geographical diversity within the A. mellea complex, showing four distinct groups with different geographic origins: Asia, East North America, West North America, and Europe.