Islands of Biodiversity: Characterization of Lichen Flora in Antarctic Nunataks

Antarctic terrestrial photosynthetic biota is dominated by cryptogamic communities, which are largely restricted to scarce ice-free areas. Among these, nunataks constitute habitats of remarkable biogeographical interest, as they may harbor distinctive biotic assemblages worthy of investigation. This work presents a comprehensive assessment of lichen diversity on Antarctic nunataks. The lichen flora of four nunataks on the Hurd Peninsula (Livingston Island, maritime Antarctica) was investigated. Specimens were identified using an integrative approach combining morphological assessment and DNA barcoding. This survey revealed a high and potentially underestimated species richness, with 39 confidently identified and several additional taxa requiring further taxonomic resolution. A review of published records of lichen occurrence in nunatak and non-nunatak environments throughout Antarctica was used to evaluate patterns in taxonomic, biogeographical, and morphotype composition. This synthesis showed that nunataks support lower species richness than other ice-free environments. Most of their taxa occur in non-nunatak areas, consistent with patterns observed locally on the Hurd Peninsula. Floristic overlap seems greater in continental Antarctica, suggesting a stronger influence of nunatak-associated environmental constraints in the maritime region. These results underscore the ecological significance of nunataks as environmentally filtered habitats and highlight their relevance for understanding biodiversity patterns and community assembly in Antarctica's terrestrial ecosystems.