PlasticMulticell · Unravelling the mechanisms underlying the evolution of multicellular life

The transition from unicellular to multicellular life has fuelled biological diversity and complexity. Multicellularity has evolved repeatedly across the tree of life and within clades, such as the green algae, multicellularity has arisen independently numerous times. Why has multicellularity evolved so many times in some lineages, but not others? An untested idea is that multicellularity readily evolves from unicellular organisms that prolong their replicative (multicellular) life-stages under specific environmental conditions (“facultative multicellularity”). Here, I aim to investigate if facultative multicellularity has preceded the evolution of obligately multicellular life. I will use an integrated approach of empirical research with green algae and theoretical modelling that allows for a mutual exchange of expertise between the host group and me: (1) I will investigate if the genetic mechanisms that regulate facultative multicellularity have been under selection during the evolution of obligate multicellularity using comparative genomics and transcriptomics across eight origins of multicellularity in green algae; (2) I will investigate if obligate multicellularity evolves more readily from facultatively multicellular than from unicellular species using experimental evolution in green algae; (3) I will investigate if gene regulatory networks lead to developmental bias, favouring the evolution of obligate multicellularity from facultative multicellularity using theoretical evolutionary modelling. This project could significantly advance our understanding of the evolution of multicellular life by integrating mechanistic explanations of the molecular regulation of traits, cell behaviour, and development into evolutionary explanations. The project provides interdisciplinary training opportunities, where I will complement my theoretical background with a variety of experimental and molecular techniques.