Abstract
A new diploid (2n = 18) species, Leucanthemum ligusticum, is described from siliceous outcrops in eastern Liguria (northwestern Italy). This species differs from L. pluriflorum—endemic to northwestern Spain, Galicia and Asturias—and L. monspeliense—endemic to northeastern Spain and central and southern France—mainly by longer petioles of basal and lower cauline leaves, shorter teeth of lower cauline leaves, and narrower ligulate florets and involucral bracts. This new species has western European affinities. Because L. ligusticum is diploid, it is one of the "basic units" of Leucanthemum and therefore a key species for inferring evolutionary relationships in this genus.