What is an ‘individual’ in lichen symbioses? An overview of alternative perspectives

Abstract

Lichens are multispecies consortia that visually and semantically masquerade as an ‘organism’, but beneath this illusion lies a fundamental challenge: how do we identify an ‘individual’ for our research? Our aim here is to offer a guide to some of the primary perspectives on individuality as they might apply to lichen symbioses, with an emphasis on the advantages, limitations and best use contexts for each. We introduce three perspectives of individuality that are relevant to the study of lichen symbioses: morphological, physiological and evolutionary individuality. By describing how each framework applies to lichen symbioses, we aim to clarify how individuality is realized in practice, and why these distinctions matter, not just for philosophical debates, but for empirical questions about diversity, biology and evolution. The goal is to emphasize why these different perspectives are relevant to our current research applications in lichenology, and how engagement with these ideas can challenge our current understanding of the symbiosis in constructive ways.