CALOPLACA-MARINA AND C-ROSEI, 2 DIFFICULT SPECIES IN NORTH-AMERICA

Caloplaca rosei Hasse and C. marina (Wedd.) Zahlbr. both grow on seashore rocks and are widely distributed along the North American west coast. Caloplaca marina occurs in Europe as well, but not on the North American east coast. Due to their similarities to one another and the lack of correctly determined specimens in herbaria, the two species have been very much misunderstood in North America. The present study, based on my own material and on herbarium material, was carried out to clarify their relationship and to establish whether or not the North American populations of C. marina are conspecific with those in Europe. A large set of morphological and anatomical characters was studied and analyzed using a computer-assisted principal components analysis. The results show that C. rosei and C. marina, even though closely related, are well separated by morphological traits such as continuity, areolation, and surface of the thallus, together with the shape, disk, and thalline margin of the apothecia. Within C. marina two subgroups could be recognized, corresponding well with their disjunct distribution on the two continents. The American population is designated C. marina subsp. americana Arup, differing from subsp. marina mainly in ecology but also having narrower spores and spore septum and a thicker hymenium.