Comparative phylogeography of a lichen, its photobiont and its major carrier tree species

No taxa illustrate parallel evolution more dramatically than lichens, which are composite organisms created by the mutualistic association between a phototrophic algae and a fungus. I will study the evolutionary dynamics of lichen symbionts in a molecular phylogeography framework, focussing on the lace lichen (Ramalina menziesii), which represents an exciting model system for studying evolutionary dynamics of lichens. Glacial refugia proposed for animals and plants will be tested for their validity in R. menziesii and its symbiotic green algae (genus Trebouxia), and postglacial migration routes will be inferred. Because of the widespread distribution and the diversity of ecological niches occupied by R. menziesii, the genetic structure of its algal and fungal genome will provide valuable insight about how closely co-evolved is the mutualistic relationship that creates this lichen species. It will also be investigated how co-dependent or independent the lichen is from a major carrier tree by taking advantage of existing molecular data on the California Valley oak (Quercus lobata), thus contrasting the phylographical patterns of a weakly mutualistic species interaction (lichen versus carrier tree) with those of a strong mutualistic interaction (lichen fungus versus symbiotic green algae).