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 evaluatedbased on morphometric and micromorphological approaches. Here, we studied 21 populations fromfour 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 recognizablebased on overall morphometry and SEM analysis, respectively. On the contrary, L. arcusangeli (endemicto 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 welldistinct for their habit and flower features. Accordingly, by integrating all the available information, allfour species are well supported on morphological grounds.