[in Russian with English summary: ] Diversity of Aspicilia desertorum s. l. was studied in Bogdinsko-Baskunchakskiy reserve (Astrakhan region, Russia). The group comprises eight species in the region. Six of them include specimens with rusty-colored thalli. We found that trivalent iron in the cortex of the studied species is not a taxonomic character but has a connection with chemistry of the substrate and may act as a sun-screen, decreasing levels of UV-B reaching the photobiont. Key words: Aspicilia desertorum, iron accumulation, Megasporaceae, species delimitation, taxonomy.