Festuca dertosensis (Poaceae), an overlooked fescue from the NE Iberian Peninsula

A new species of Festuca L. (Poaceae) is described from the southern mountains of Tarragona (Catalonia, Spain). The new taxon belongs to the F. rubra aggregate, and superficially resembles plants of the F. trichophylla group. Its leaf anatomy, however, suggests a closer relationship with F. rubra and, in particular, F. heterophylla. Although sharing some features with F. paucispicula, a sympatric taxon, there are sufficient differences to warrant its separation from this local endemic. A comparative table and key are provided to assist in the identification of this overlooked fescue, and its relationship to other species present in the area is discussed, with special attention paid to species sharing a similar distribution. Mitosis studies have been carried out to determine the chromosome number, and the results suggest a decaploid, with a chromosome number of 2n = c. 70