The pioneer lichen Placopsis in maritime Antarctica: Genetic diversity of their mycobionts and green algal symbionts, and their correlation with deglaciation time

Resumen:
Since ice-free areas in Antarctica are predicted to increase by up to 25% before the end of this century, lichens such as the genus Placopsis will be important colonizers of these newly available grounds and will still be present in later successional stages of the lichen community. The main symbionts of Placopsis species are examined for 56 specimens collected from the South Shetland Islands, Antarctica using molecular (fungal and algal nrITS, fungal RPB1, algal rbcL sequences) and morphological methods. The specimens were collected from soils with different deglaciation times. Eight uni-algal photobiont cultures were obtained and analysed from two specimens. Placopsis antarctica and P. contortuplicata proved to be monophyletic and are sister species, only the former producing vegetative diaspores (soredia). Both share the same photobiont pool and are lichenized with two closely related species, Stichococcus antarcticus and S. allas. Two haplotypes of S. antarcticus are restricted to areas deglaciated for more than 5000 years and the volcanic Deception Island indicating a shift in the photobionts of Placopsis in the course of the soil and lichen community development. These photobiont haplotypes exhibit different ecological preferences, possibly leading to adaptation of the symbiotic entity to changing environmental conditions.

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