Evolutionary dynamics of lichen-forming algae fungi and natural products

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The algal and fungal components that interact to produce a lichen association, form a complex thallus unlike either of the two symbiotic partners alone. Morphological changes in the thallus have been reported in nature and correlated with changes in environmental conditions. The ability of lichens to adapt to changing conditions is instrumental to their ability to survive especially under the current climate change in the north where members of the Reindeer lichens dominate and form an important component of the winter diet for large mammals. It is difficult to study morphological changes in lichens under controlled culture conditions because lichens are so difficult to grow in culture. But one phenotypic feature that is readily measured in culture is the production of natural products (secondary metabolites). The genes for these metabolites have been described making gene expression a measurable phenotype with changes in culture conditions that reflect changes in environmental conditions. The general goal of this research program is to understand the evolutionary relationships among species of lichen-forming fungi, and how the symbionts are affected by changes in environmental conditions. This will shed light on the mechanisms that drive biodiversity in lichens. One PhD student is studying the evolutionary relationships among members of the genus Ramalina with respect to evolution of the secondary metabolites produced by members of the genus. Another PhD student is examining evolution of the Reindeer lichens (Cladonia sect. Cladina) to better understand sexual reproduction and the ability of this group of lichens to adapt to changing environmental conditions. The selection of algae adapted to the habitat by lichen fungi is thought to be a strategy for survival as the fungal spores are dispersed to different habitats. Two MSc students will examine algal selection in an aquatic lichen and a terrestrial lichen to understand how these species might adapt to changes in water levels or pollution levels or to changes in ambient light and temperature. A better understanding of adaptation and environmental regulation of secondary metabolites may provide better pharmaceutical compounds without depleting our natural resources.