Life on Earth includes both very simple and rather complex organisms. The central question motivating this research is how do simple organisms evolve into complex organisms? The origin of organisms composed of more than one cell (i.e., multicellular organisms) was one of a few major events in the history of life that created new opportunities for more complex biological systems, such as plants and animals, to evolve. However, understanding how and why this kind of complexity has increased in some lineages remains a major challenge for evolutionary biology. The challenges posed by the evolution of multicellularity, in the evolution of mechanisms for sharing labor and cooperating among the cells within an organism, underlie many medical conditions and are foundational in understanding genotype to phenotype relationships. This project will also develop novel curriculum materials for teaching high school students about cellular differentiation and the challenges of multicellularity.
The goal of this research is to experimentally evolve multicellularity in the single-celled green alga Chlamydomonas reinhardtii. C. reinhardtii is an established model system with a well-developed set of genetic tools. Its relatives among the volvocine algae range from species having single cells to those having tens of thousands of cells of different cell types. Generation of a novel origin of multicellularity in the lab will enable direct comparison of multicellular descendants to their unicellular ancestors. Twelve replicate populations will be evolved in the presence of a filter-feeding predator, conditions known to favor multicellularity. Genetic changes that occur over the course of these experiments will be tracked to reveal the genetic basis of multicellularity and the evolutionary processes giving rise to those changes. Experimental data will be compared with the evolutionary and genetic routes by which multicellularity evolved in the volvocine algae. Finally, the role of environmentally induced developmental changes in the evolution of multicellularity will be evaluated.