Biosystematicsis the science of studying biodiversity and its relationships in nature. Itaims to divide the biodiversity into monophyletic taxa of different gradesbased on their relationships, such as species, genera, families, orders,classes, phyla, and kingdoms.

Homologousbiosystematics is to comb diverse organisms in nature into different classes ofmonophyletic taxa according to their homologous characteristics. The homologouscharacteristics are inherited from both the genotype and phenotype of the sameancestor, and they have been associated with divergent evolution. In this book,the author presents the result of a homology analysis of homologouscharacteristics in the specimens of the Umbilicariaceae from the world. Itcontains an introduction, biosystematics, and taxonomy, which contains 125 speciesrespectively belonging to the genera Lasallia and Umbilicaria including 34 newspecies with one new form and one new name. Each species has one or more colorphotographs attached. The references cited and index of scientific names fortaxa are also attached.