“…The literature on lichen metabolism has been largely focused on understanding the exchange of key nutrients between symbionts ( Lines et al, 1989 ; Kono et al, 2020 ; ten Veldhuis et al, 2020 ) and identifying lichen secondary metabolites and their biosynthetic pathways (i.e., metabolite profiling) ( Fahselt, 1994 ; Aubert et al, 2007 ; Elix and Stocker-Worgotter, 2008 ; Mittermeier et al, 2015 ; Bertrand et al, 2018b ; Brakni et al, 2018 ; Calcott et al, 2018 ; Kuhn et al, 2019 ; Goga et al, 2020 ; Figure 4 ). In the 1960s, observations of carbohydrate storage and translocation between the symbionts of Peltigera polydactyla ( Smith and Drew, 1965 ; Drew and Smith, 1967a , b ) together with a series of similar studies on other lichens ( Smith et al, 1969 ) established the foundations for studying the metabolic interplay in lichens.…”