Diversity, ecology and specificity in Antarctic lichens
The extreme climate conditions make Antarctica an environment where only the hardiest organisms can survive. The terrestrial vegetation communities of the ice-free areas of this continent (c. 2%) are mainly comprised of mosses, fungi and lichens, i.e. fungal species (mycobionts) which form a symbiotic association with algae or cyanobacteria (photobionts). Although Antarctica’s ecosystems represent some of the simplest in the world, it is increasingly becoming clear that their biodiversity is far greater than previously thought and that spatial variations in species diversity are complex, possibly reflecting regional to local variations in climate. However, the mechanisms that connect climate and life’s diversity and evolution in Antarctica are still poorly understood owing to limited taxon and climate data sampling in many areas of the continent. On this background, the current research project investigates the role of environmental (climatic) factors driving lichen diversity, distribution and evolution in Antarctica and adjacent South American regions, using saxicolous lecideoid lichens as a model system. This aim will be accomplished by integrating analytical approaches from molecular phylogenetics, ecological niche modelling (ENM), and morphology/anatomy on the basis of a worldwide unique collection of about 700 specimens with a focus on circum-Antarctic coverage. There are two major and specific issues addressed: (1) the identity, geographic distribution and phylogenetic relationships of the photobiont and mycobiont lineages in the target regions; and (2) the extent of specificity between these symbiotic partners and how this relates to their degree of environmental (climate-related) niche overlap. The research envisaged here has the potential to provide an unprecedented broad-scale view of the contribution of ecological (climate-related) processes to the origin and maintenance of species and lineage boundaries in lecideoid lichens and to the selectivity of mycobionts towards their photobionts throughout the southern Polar region. Whilst the focus is on lichens, resolving this latter and still controversial issue may have also wider implications for symbiosis research in general, as it explicitly tests ecological (climate-related) explanations for patterns of symbiotic distribution, diversity, and evolution in climatically heterogeneous environments.