| Thirty-one saxicolous species of Buellia s.l. with one-septate ascospores were examined from the Greater Sonoran Desert Region. They are distinguished by thallus morphology, exciple anatomy, spore ultrastructure, secondary chemistry, ecology and distribution. As a result, seven new species are described. Other species are reported from the region for the first time and the synonymy of several taxa is resolved.; All species are traditionally included within the Physciaceae. Recent molecular evidence suggests that calicioid lichens are closely related to Buellia s.l. A comparison confirms that spore wall ultrastructure is identical in both groups. Iodine staining of the ascus in the light microscope corresponds well with the ascus ultrastructure. This Bacidia-type ascus is variable but common to all species. The prototunicate asci of calicioid Physciaceae may have evolved by reduction from this type.; Spore ontogeny of Buellia s.l. is a highly dynamic process. Four stages can be distinguished: (1) immature, (2) premature, (3) mature and (4) overmature. During these stages wall differentiation, septum formation and pigmentation develop independently. Wall thickenings result from endospore differentiation. They are most obvious in premature and mature spores, but usually become reduced with age. Exciple anatomy of Buellia s.l. is diagnostic and corresponds to some degree with pigmentation. Only B. mamillana has a thalline exciple, which soon becomes excluded. Other species lack a distinct thalline margin as observed in Rinodina s.l. Several inconspicuous species show some degree of substrate penetration but only Buellia sequax and B. vilis are chasmolithic. Pycnidia of all species are similar. A general transfer of taxa with filiform conidia into Amandinea is therefore not supported. Amandinea needs to be revised to include only species closely related to the type, Amandinea coniops .; A phylogenetic analysis of eighty species demonstrates that most generic segregates of Buellia s.l. are presently not well supported. Groups like Diplotomma s.str. or Hafellia may be recognized but even these are not strongly supported. The low support is inherent to the small amount of characters available. As a consequence, genera should only be accepted if classical concepts are re-evaluated with molecular tools. |
