A study of the leaf anatomy in the species of the genus Festuca present in the Iberian Peninsula was made. A total of 68 taxa were included and 15 characters were measured in leaf cross-section. The major anatomical features of each taxonomic group were characterized, and some variability was observed in the taxa. The anatomical patterns observed were compared and discussed with the relationships suggested by the molecular analyses. The leaf outline, the presence or absence of complete girders, and the development degree of the bulliform cells were the main characters to differentiate among fescue species of the fine-leaved clade and those of the broad-leaved clade. The most useful character to segregate species groups within the different taxonomic sections was the arrangement of the sclerenchyma, and a remarkable variability of this character was found in the species of Festuca section Festuca, especially in those located in other lineages according to molecular markers. Most of the anatomical patterns were not exclusive of the sections or lineages, and only some taxa could be anatomically differentiated at species level based on a set of non-taxative characters. The discordant pattern observed in F. henriquesii, a species traditionally included in Festuca sect. Festuca that shared anatomical features with the species of "F. rubra complex", suggests its possible inclusion in the sect. Aulaxyper pending further taxonomic and phylogenetic analyses.
Keywords: Festuca; Iberian Peninsula; leaf anatomy; sclerenchyma arrangement.