Lichen material from the Iberian Peninsula of Melanelia commixta, M. hepatizon and M. sorediella has been studied and compared on the basis of morphology, chemistry, habitat and distribution. The new combination Melanelia sorediella is proposed and Cetraria commixta f. sorediella is lectotypified. Chemotypes I and III have been detected in M. commixta. Melanelia sorediella is characterized mainly by the formation of pycnoisidia and soralia-like structures in the lamina and margins of the thallus and by the absence of pseudocyphellae and apothecia. The pycnoisidium is here described as a combination of isidia-like proliferations of the thallus surface containing pycnidia, carrying algae and acting as vegetative symbiotic propagules. Non detached pycnoisidia grow into lobuli in central parts of the thallus, regenerating it. Pycnoisidia, soralia-like areas and lobuli are formed as a consequence of pycnidia development. Melanelia sorediella is morphologically and chemically close to M. commixta and is currently known from mountains of central and south-west Europe where it grows on acid rocks. In south-western Europe, the meridional limit of the distribution of the three species studied seems to be located in the mountains of the central part of the Iberian Peninsula (Sistema Central Ibérico). Relevant data on the three species are provided and a key is also included.