Seed morphological variation in four closely related Linaria species (Plantaginaceae) endemic to the Tyrrhenian area

Seed features are a useful and relevant source of taxonomic information, especially when evaluated based on morphometric and micromorphological approaches. Here, we studied 21 populations from four out of the five species of the Mediterranean Linaria purpurea group (Plantaginaceae). Linaria capraria (endemic to Tuscan Archipelago) and L. cossonii (endemic to Sardinia and Tunisia) are easily recognizable based on overall morphometry and SEM analysis, respectively. On the contrary, L. arcusangeli (endemic to southern Sardinia) and L. purpurea (endemic to peninsular Italy and Sicily) show very similar seeds, whose features do not guarantee a reliable identification, although these two species are otherwise well distinct for their habit and flower features. Accordingly, by integrating all the available information, all four species are well supported on morphological grounds.