Hierarchical Transition Via Individuation, Not Integration: How the Filamentous Fungi Challenge the Standard Model

Abstract

In this project I expand the current model of hierarchical transition to include transition by individuation in addition to transition by integration and I apply my model of transition by individuation to the evolution and development of the filamentous fungi. I accomplish this in two parts. In the first section, I defend a general Hierarchy Thesis: A differentiated hierarchical whole can arise not only through the integration of individuated parts but also by the individuation of parts within an integrated whole. I elaborate an expanded model of hierarchical transition and discuss the relevance of part-level selection and part-hood regulation for different modes of transition. In the second section, I defend a Mycology Thesis: The filamentous fungi have evolved a developmental cellularization process to meet ecological and reproductive demands for coenocytic growth in early development and cellularization in later development. I elaborate the origins and evolution of the filamentous fungi and argue that this history provides cases of hierarchical transition via individuation in both phylogeny and ontogeny. The project provides an expanded evolutionary-developmental framework for hierarchical transition and a framing narrative for the evolutionary development of filamentous fungi, an evolutionarily significant and ecologically ubiquitous group, and has implications for the study of similar organisms outside Fungi and of hierarchical transition in general.