| Summary: | The Northeast Asian endemic species of lichen-forming fungus <i>Umbilicaria krascheninnikovii</i> is herein discussed in the global context of biogeography and phylogeny of the <i>U. aprina</i> group. The name <i>U. krascheninnikovii</i> has been erroneously used by lichenologists for <i>Umbilicaria</i> spp. from high latitudes or altitudes worldwide, as there are omphalodisc apothecia and rough “crystals” of a necral layer on the upper surface. To test the monophyly and phylogenetic relationships within the <i>U. aprina</i> group, four independent DNA regions (<i>nrITS</i>/<i>5.8S</i>, <i>RPB2</i>, <i>mtLSU</i>, and <i>mtSSU</i>) were used for six rare species, including a dozen specimens of <i>U. krascheninnikovii</i> from its locus classicus in Kamchatka. The study is based on the phylograms obtained using maximum likelihood and a Bayesian phylogenetic inference framework. As a result of phylogenetic and biogeographic analyses, it was shown that <i>U. krascheninnikovii</i> is a neo-endemic of the areas of modern volcanism in Kamchatka, Japan, as well as in the Kurile Islands, where this species was recorded for the first time. The morphology of <i>U. krascheninnikovii</i> is herein described and illustrated. Increasing the role of the sexual process and reducing asexual thalloconidiogenesis are shown to be apomorphic traits in the <i>U. aprina</i> group. The combination of sexual and asexual reproduction provides adaptive advantages in changing environmental conditions.
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