9707714 Nash Lichens are symbiotic associations of a fungus and an alga, and they are usually identified and classified on the basis of the fungal organism in the partnership. They occur widely and at times abundantly on soil, rocks, and as epiphytes. The classification of the several thousands of species of lichens is complicated by their poor representation in museum collections and their small size, resulting in an emphasis on a few supposed "key" characters for discrimination. Unfortunately, it is now widely accepted that many of these key features have evolved multiple times, in different groups or lineages of lichens; thus, lichen classification requires more specimens and closer attention to the acquisition of new morphological and molecular characters. For the large lichen "flora" of the North American Sonoran desert and adjacent parts of California with a mediterranean type climate, Prof. Thomas Nash has assembled an international team of 50 or so specialists, students to senior researchers, to complete a taxonomic inventory of the suspected 1700 species of lichens. Four large and taxonomically troublesome genera, Arthonia, Buellia, Lecania, and Solenopsora, are the main targets for field work, museum study, and taxonomic revision; a fifth genus, Verrucaria, will receive preliminary study. This will be accomplished in conjunction with young European workers who have specialized on the mediterranean relatives of these groups, and who can test species limits and diagnoses against the variation to be found in the North American groups. The biodiversity and classification of lichens remain poorly known in most parts of the world, and the research tradition for their study has emphasized narrow national or regional studies by one or two specialists. Prof. Nash's international consortium of colleagues, focusing on a large desert region of North America, with taxonomic relatives in mediterranean climates of the world, promotes two modern approaches that promise to revolutionize the study of lichens. First, collaborative work by specialists drawn from an international pool of talent; second, a global perspective in comparisons of morphological and anatomical characters to assess the reliability of taxonomic features useful for identification and upper-rank classification.
