Lichens from the genus Umbilicaria were collected across a 5,000-km transect through Antarctica and investigatedfor DNA sequence polymorphism in a region of 480–660 bp of the nuclear internal transcribed spacer region ofribosomal DNA. Sequences from both fungal (16 ascomycetes) and photosynthetic partners (22 chlorophytes fromthe genus Trebouxia) were determined and compared with homologs from lichens inhabiting more temperate,continental climates. The phylogenetic analyses reveal that Antarctic lichens have colonized their current habitatsboth through multiple independent colonization events from temperate embarkation zones and through recent longrangedispersal in the Antarctic of successful preexisting colonizers. Furthermore, the results suggest that relichenization— de novo establishment of the fungus-photosynthesizer symbiosis from nonlichenized algal and fungal cells—has occurred during the process of Antarctic lichen dispersal. Independent dispersal of algal and fungalcultures therefore can lead to a successful establishment of the lichen symbiosis even under harsh Antarctic conidtions.
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