Most of the theory of community ecology has been developed studying the unitary organisms. Therefore, the applicability of established theory to modular organisms remains unclear. Here we present theoretical developments that allow the community ecology of modular organisms to be firmly embedded within the established community ecology frameworks of modern coexistence theory and movement ecology. Within modular organisms, our primary focus is on filamentous fungi. The interplay of space and movement of organisms is critical for community assembly and species coexistence. Several research areas such as metacommunity theory, modern coexistence theory, and movement ecology aim to describe this interplay for animals and plants. These disciplines have assembled theoretical knowledge about the persistence and dynamics of biological diversity that is intended to be universally applicable to living systems. Applying theoretical concepts largely developed for unitary macro-organisms to filamentous fungi is challenging given their modular, network-like body structure. Here, we reviewed relevant knowledge from modern coexistence theory, movement ecology, and fungal ecology and developed two concepts that enable the application of established community ecology to filamentous fungi. We named these concepts unit of community interactions (UCI) and active movement of fungi. The first concept provides an operational definition of individual and population that is central to modern coexistence theory, but is problematic for clonal/modular life forms. This concept is introduced in the first chapter of this thesis along with modern coexistence theory applied to fungal systems. In the second chapter, we introduce the concept of active movement in fungi, demonstrating how the framework of movement ecology can be applied to filamentous fungi at all relevant spatial scales. We show that in modular organisms, physiological and morphological movements have a coupled ecological function and can thus influence community assembly via processes predicted by movement ecology. We further demonstrate this in the third chapter, where we describe the development of an agent-based model of hyphal dispersal in micro-structured environments and provide an initial evaluation of the model.
