Lichen algae: the photosynthetic partners in lichen symbioses

William B Sanders,Hiroshi Masumoto

doi:10.1017/s0024282921000335

William B Sanders, Hiroshi Masumoto

Open Access

https://doi.org/10.1017/s0024282921000335

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Abstract

AbstractA review of algal (including cyanobacterial) symbionts associated with lichen-forming fungi is presented. General aspects of their biology relevant to lichen symbioses are summarized. The genera of algae currently believed to include lichen symbionts are outlined; approximately 50 can be recognized at present. References reporting algal taxa in lichen symbiosis are tabulated, with emphasis on those published since the 1988 review by Tschermak-Woess, and particularly those providing molecular evidence for their identifications. This review is dedicated in honour of Austrian phycologist Elisabeth Tschermak-Woess (1917–2001), for her numerous and significant contributions to our knowledge of lichen algae (some published under the names Elisabeth Tschermak and Liesl Tschermak).

Highlights

The principal components of the lichen symbiosis are fungus and alga. Their intimate trophic relationship remains central to the lichen concept, despite our growing appreciation that other microorganisms harboured within the thallus might play significant roles (Lakatos et al 2004; Grube & Berg 2009; Bates et al 2011; Grube et al 2015; Spribille et al 2016; Muggia & Grube 2018; Mark et al 2020; Smith et al 2020; Tzovaras et al 2020)
The lichenforming fungi typically build distinctive vegetative tissues and characteristic sexual structures, providing numerous biological features for study and significant clues about phylogenetic relationships, which are relatively well delimited at broader taxonomic levels (Jaklitsch et al 2016; Lücking et al 2017a)
It is evident that a small number of very prominent photobiont genera (Asterochloris, Nostoc, Rhizonema, Trebouxia, Trentepohlia) each partner with many hundreds or thousands of lichen-forming fungal species; a number of others (e.g. Coccomyxa, Elliptochloris, Heveochlorella, Symbiochloris) are lichenized by many dozens or hundreds of different mycobiont species, while much of the remainder participate in only a small number of known lichen associations

Summary

Introduction

The principal components of the lichen symbiosis are fungus and alga. Their intimate trophic relationship remains central to the lichen concept, despite our growing appreciation that other microorganisms harboured within the thallus might play significant roles (Lakatos et al 2004; Grube & Berg 2009; Bates et al 2011; Grube et al 2015; Spribille et al 2016; Muggia & Grube 2018; Mark et al 2020; Smith et al 2020; Tzovaras et al 2020). Most mycobiont species appear to be fairly selective; they tend to partner with a limited range of strains or species within a single photobiont genus, but to differing degrees.

Results

Conclusion