CEB Committe on Evolutionary Biology

Spotlight : Matthew Nelsen

Matthew Nelsen

Matt getting “up close and personal” with some lichens in Madre de Dios, Peru (August 2008). Photo by Robert Lücking.

I am interested in the evolutionary origins and diversification of symbiotic associations. For my dissertation, I am focusing on the evolution of the lichen symbiosis. Lichens are symbiotic associations between fungi (mycobiont) and green algae and/or cyanobacteria (photobiont). In lichen associations, the photobiont essentially “feeds” the mycobiont photosynthetically-derived sugars; in return, the mycobiont provides shelter for the photobiont, and protects them from UV light, herbivores and desiccation. These lichen associations dominate 8% of the earth’s surface, and play important roles in nutrient cycling, soil stabilization and as food sources for diverse organisms. As a result of their diversity (17,500 fungal species = ~20% of all fungi) and overall abundance, this type of association is considered one of the most successful among the fungi.

My dissertation concentrates on four interconnected questions (1) How frequently has lichenization evolved, and when in time did this occur? (2) Do symbiont-switches occur randomly, or are switches between certain symbionts more likely? (3) Did lichen-forming algal lineages originate synchronously with lichen-forming fungal lineages? (4) How has the transition to the lichen-forming state influenced the morphological evolution of fungi? To address these questions, I am sequencing DNA from a broad range of fungi and algae from all over the world (especially those in the tropics). By reconstructing the evolutionary history of these lineages from DNA sequences, I am better able to understand how these lichen-forming fungi and algae are related to each other and to non-lichenized fungi and algae. I am then using a molecular clock approach (together with fossil data) to determine when in time these lichen associations formed. Coupling these approaches with morphological data from extant species allows to then gain a better understanding how lichens have diversified. Addressing these questions will provide insight into the roles symbiosis has played in evolution, and elucidate the evolutionary dynamism and consequences of the lichen symbiosis.

For more information about me, please see my website and The Featured Scientist Section of the Facebook page for the DNA Discovery and Pritzker Lab at the Field Museum

Connect with Matthew Nelsen.