Diversity of Lichen Photobionts: Their Coevolution and Bioprospecting Potential

Saini, Khem Chand; Nayaka, Sanjeeva; Bast, Felix

doi:10.1007/978-981-13-8487-5_13

Cited by 15 publications

(12 citation statements)

References 93 publications

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“…A merely functional definition, as a symbiosis between a heterotrophic fungus (or fungus-like organism) and a photosynthetic component, would be imprecise, as it would not discriminate between lichens one one hand and ecto-and endomycorrhiza, bryophilous fungi, mycophycosymbioses, and endosymbiotic associations, such as in Geosiphon pyriformis, all of which are not considered lichens (Hawksworth and Hill 1984;Hawksworth 1988). A taxonomic or phylogenetic definition, as a symbiosis between a fungus and an alga or cyanobacterium, would also be challenging, as fungi in the sense of the International Code of Nomenclature for algae, fungi and plants [ICNafp (Shenzen); Turland et al 2018;May et al 2018] are not a natural group, encompassing at least three kingdoms, and the known lichen photobionts represent two domains and three kingdoms (Friedl and Büdel 2008;Saini et al 2019). Given extant lichens, one could specify the fungal component as a member of the kingdom Fungi, but what would a theoretical association involving a member of the Oomycota then constitute and how could one exclude that associations with other fungal-like organisms might exist or might have existed in the past?…”

Section: What Are Lichens and How Should They Be Named?mentioning

confidence: 99%

Species in lichen-forming fungi: balancing between conceptual and practical considerations, and between phenotype and phylogenomics

2021

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Lichens are symbiotic associations resulting from interactions among fungi (primary and secondary mycobionts), algae and/or cyanobacteria (primary and secondary photobionts), and specific elements of the bacterial microbiome associated with the lichen thallus. The question of what is a species, both concerning the lichen as a whole and its main fungal component, the primary mycobiont, has faced many challenges throughout history and has reached new dimensions with the advent of molecular phylogenetics and phylogenomics. In this paper, we briefly revise the definition of lichens and the scientific and vernacular naming conventions, concluding that the scientific, Latinized name usually associated with lichens invariably refers to the primary mycobiont, whereas the vernacular name encompasses the entire lichen. Although the same lichen mycobiont may produce different phenotypes when associating with different photobionts or growing in axenic culture, this discrete variation does not warrant the application of different scientific names, but must follow the principle "one fungus = one name". Instead, broadly agreed informal designations should be used for such discrete morphologies, such as chloromorph and cyanomorph for lichens formed by the same mycobiont but with either green algae or cyanobacteria. The taxonomic recognition of species in lichen-forming fungi is not different from other fungi and conceptual and nomenclatural approaches follow the same principles. We identify a number of current challenges and provide recommendations to address these. Species delimitation in lichen-forming fungi should not be tailored to particular species concepts but instead be derived from empirical evidence, applying one or several of the following principles in what we call the LPR approach: lineage (L) coherence vs. divergence (phylogenetic component), phenotype (P) coherence vs. divergence (morphological component), and/or reproductive (R) compatibility vs. isolation (biological component). Species hypotheses can be established based on either L or P, then using either P or L (plus R) to corroborate them. The reliability of species hypotheses depends not only on the nature and number of characters but also on the context: the closer the relationship and/or similarity between species, the higher the number of characters and/or specimens that should be analyzed to provide reliable delimitations. Alpha taxonomy should follow scientific evidence and an evolutionary framework but should also offer alternative practical solutions, as long as these are scientifically defendable. Taxa that are delimited phylogenetically but not readily identifiable in the field, or are genuinely cryptic, should not be rejected due to the inaccessibility of proper tools. Instead, they can be provisionally treated as undifferentiated complexes for purposes that do not require precise determinations. The application of infraspecific (gamma) taxonomy should be restricted to cases where there is a biological rationale, i.e., lineages of a species complex that show limited phylogenetic divergence but no evidence of reproductive isolation. Gamma taxonomy should not be used to denote discrete phenotypical variation or ecotypes not warranting the distinction at species level. We revise the species pair concept in lichen-forming fungi, which recognizes sexually and asexually reproducing morphs with the same underlying phenotype as different species. We conclude that in most cases this concept does not hold, but the actual situation is complex and not necessarily correlated with reproductive strategy. In cases where no molecular data are available or where single or multi-marker approaches do not provide resolution, we recommend maintaining species pairs until molecular or phylogenomic data are available. This recommendation is based on the example of the species pair Usnea aurantiacoatra vs. U. antarctica, which can only be resolved with phylogenomic approaches, such as microsatellites or RADseq. Overall, we consider that species delimitation in lichen-forming fungi has advanced dramatically over the past three decades, resulting in a solid framework, but that empirical evidence is still missing for many taxa. Therefore, while phylogenomic approaches focusing on particular examples will be increasingly employed to resolve difficult species complexes, broad screening using single barcoding markers will aid in placing as many taxa as possible into a molecular matrix. We provide a practical protocol how to assess and formally treat taxonomic novelties. While this paper focuses on lichen fungi, many of the aspects discussed herein apply generally to fungal taxonomy. The new combination Arthonia minor (Lücking) Lücking comb. et stat. nov. (Bas.: Arthonia cyanea f. minor Lücking) is proposed.

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Section: What Are Lichens and How Should They Be Named?mentioning

confidence: 99%

Species in lichen-forming fungi: balancing between conceptual and practical considerations, and between phenotype and phylogenomics

2021

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“…Both fungus and alga must adapt, at least to some extent, to be compatible symbionts. For some authors, such mutual adaptation constitutes coevolution (Ahmadjian 1987;Saini et al 2019); for others, coevolution supposes parallel cladogenesis in partners' phylogenies, a criterion not generally met by lichen symbioses analyzed in this regard (Piercey-Normore & DePriest 2001; Stenroos et al 2006). However, it has been argued that focusing exclusively on this fine scale ignores broader patterns of co-adaptation, whereby 'guilds' of different mycobionts share common pools of photobionts to mutual advantage (Rikkinen 2003(Rikkinen , 2013.…”

Section: The Algal Role In Lichen Symbiosismentioning

confidence: 99%

Lichen algae: the photosynthetic partners in lichen symbioses

Sanders

Masumoto

2021

The Lichenologist

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A 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).

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“…Four groups of species were distinguished: lichens containing green algae (Asterochloris, Trebouxia, Stichococcus and others), lichens with Trentepohlia s.l., lichens with cyanobacteria (Nostoc) and non-lichenized taxa lacking photobionts commonly examined by lichenologists, i.e., species of Chaenothecopsis, Microcalicium and Mycocalicium. Trebouxia and other green algae are the most common photobionts in lichen symbioses [62,63], and they can colonize numerous environments and tolerate dry and insolated conditions [64]. Trentepohlia photobionts have a particular adaptation to environments with higher temperatures and humidity levels [65,66].…”

Section: Morphological and Anatomical Traits Consideredmentioning

confidence: 99%

“…Trentepohlia photobionts have a particular adaptation to environments with higher temperatures and humidity levels [65,66]. Cyanobacterial photobionts are desiccation-tolerant, but most of them require liquid water for rehydration [63,64].…”

Section: Morphological and Anatomical Traits Consideredmentioning

confidence: 99%

Composition and Specialization of the Lichen Functional Traits in a Primeval Forest—Does Ecosystem Organization Level Matter?

Łubek

Kukwa

Jaroszewicz

et al. 2021

Forests

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Current trends emphasize the importance of the examination of the functional composition of lichens, which may provide information on the species realized niche diversity and community assembly processes, thus enabling one to understand the specific adaptations of lichens and their interaction with the environment. We analyzed the distribution and specialization of diverse morphological, anatomical and chemical (lichen secondary metabolites) traits in lichen communities in a close-to-natural forest of lowland Europe. We considered these traits in relation to three levels of forest ecosystem organization: forest communities, phorophyte species and substrates, in order to recognize the specialization of functional traits to different levels of the forest complexity. Traits related to the sexual reproduction of mycobionts (i.e., ascomata types: lecanoroid apothecia, lecideoid apothecia, arthonioid apothecia, lirellate apothecia, stalked apothecia and perithecia) and asexual reproduction of mycobionts (pycnidia, hyphophores and sporodochia) demonstrated the highest specialization to type of substrate, tree species and forest community. Thallus type (foliose, fruticose, crustose and leprose thalli), ascospore dark pigmentation and asexual reproduction by lichenized diaspores (soredia and isidia) revealed the lowest specialization to tree species and substrate, as well as to forest community. Results indicate that lichen functional trait assemblage distribution should not only be considered at the level of differences in the internal structure of the analyzed forest communities (e.g., higher number of diverse substrates or tree species) but also studied in relation to specific habitat conditions (insolation, moisture, temperature, eutrophication) that are characteristic of a particular forest community. Our work contributes to the understanding of the role of the forest structure in shaping lichen functional trait composition, as well as enhancing our knowledge on community assembly rules of lichen species.

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Diversity of Lichen Photobionts: Their Coevolution and Bioprospecting Potential

Cited by 15 publications

References 93 publications

Species in lichen-forming fungi: balancing between conceptual and practical considerations, and between phenotype and phylogenomics

Species in lichen-forming fungi: balancing between conceptual and practical considerations, and between phenotype and phylogenomics

Lichen algae: the photosynthetic partners in lichen symbioses

Composition and Specialization of the Lichen Functional Traits in a Primeval Forest—Does Ecosystem Organization Level Matter?

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