Draft talk:Lichen

Etymology

 * various acceptable pronunciations, first use of word

Taxonomy

 * review (2020): "Three challenges to contemporaneous taxonomy from a licheno-mycological perspective"
 * A. Explanation of composite organism
 * review (2020): "Lichens redefined as complex ecosystems"
 * suggested redefinition of lichen: a self-sufficient ecosystem formed by the interaction of a thallus-forming fungus, an extracellular arrangement of one or more photosynthetic partners, and a variable number of other microorganisms.
 * proposal of modified definition of lichen, "integrating aspects put forward by Ainsworth et al. (1971), Hawksworth (1988), Honegger (1991, 2012), Goward (1994), Kirk et al. (2008), and Hawksworth and Grube (2020)."
 * "A lichen is a stable, self-supporting association of a fungus or fungal-like organism, the primary mycobiont, and a morphologically undifferentiated, unicellular to filamentous alga and/or a cyanobacterium, the primary (and secondary) photobiont, along with obligately associated elements of the fungal and bacterial microbiome contained therein. The phenotype of the mycobiont in the lichenized state (the exhabitant) typically functions as a greenhouse around the photobiont (the inhabitant), the mechanical, physiological and evolutionary properties of the symbiosis thereby exhibiting analogies with agriculture."
 * B. Where lichens fit in the "tree of life"
 * C. Why they're named for fungal partner
 * some background info here (in section "What are lichens and how should they be named?")
 * D. How often lichen lifestyle has evolved
 * note duplication of this with "Lichen evolution" later. I think here, mention of lichenization should be brief and to the point, with more information in later section.
 * E. Percentage of fungal species that have this lifestyle
 * review (2018): "Fungal diversity in lichens: from extremotolerance to interactions with algae"
 * F. Number of classes, orders, genera and species included
 * lichen #'s as of 2017: "the number of lichenized species is now tabulated at 19,409 and the number of fungal genera, families, and orders including lichens at 1,002, 119, and 40, respectively"
 * largest genera are Xanthoparmelia (820 species), Lecanora (550 species), Arthonia, Cladonia, and Pertusaria (several hundreds of species each)
 * the largest families, in terms of number of species and genera, are the Parmeliaceae (2765, 77 genera), Graphidaceae (2161, 79 genera), Verrucariaceae (943 spp., 43 genera), Ramalinaceae (916 spp., 43 genera), and the Lecanoraceae (791 species, 25 genera)
 * average number of species per genus is 19.5, and 256 genera contain a single species
 * section: "Species concepts and their application in lichenized fungi")
 * Review (2011): "Goodbye morphology? A paradigm shift in the delimitation of species in lichenized fungi"

Range and habitat

 * A. Where they're found on the planet
 * The highest reported elevation for a lichen is 7400 m, in Makalu (Nepal); these are the rock- and soil-dwelling crustose lichens Carbonea vorticosa, Pertusaria bryontha, and Lecanora polytropa. For comparison, the highest recorded elevation for a plant is 6400 m.
 * B. Percentage of earth's surface covered
 * Could mention this (2020) study in a discussion about lichen biomass: "The weight of the crust: Biomass of crustose lichens in tropical dry forest represents more than half of foliar biomass"
 * C. Various substrates used (including endolithic, within plant parts, etc.)
 * Corticolous
 * Terricolous
 * Saxicolous
 * Foliicolous
 * Misc. substrates
 * D. Extremes tolerated
 * review (2008): "Desiccation-Tolerance in Lichens"
 * review (2021): "Advances in Understanding of Desiccation Tolerance of Lichens and Lichen-Forming Algae"
 * review (2017): "Adaptation of Lichens to Extreme Conditions"
 * E. Restricted vs widespread
 * F. Bipolar
 * review (2017): "Past, present, and future research in bipolar lichen-forming fungi and their photobionts"
 * G. Marine / freshwater
 * source (2020): "Coastal Lichens"
 * F. Bipolar
 * review (2017): "Past, present, and future research in bipolar lichen-forming fungi and their photobionts"
 * G. Marine / freshwater
 * source (2020): "Coastal Lichens"
 * source (2020): "Coastal Lichens"

Composition

 * A. Explanation of component parts
 * 1. Mycobiont
 * 2. Photobiont
 * (2019) "...the known photobionts are only about 156 species from 56 genera"
 * i. Algal - including most common genera, % of lichens containing algal partners
 * review (2021): "Lichen algae: the photosynthetic partners in lichen symbioses"
 * ii. Cyanobacterial - including most common genera, % of lichens containing cyanobacterial partners
 * source (2015): "Cyanolichens"
 * source (2017, book chapter): "Symbiotic Cyanobacteria in Lichens"
 * 3. Yeast - briefly when and how they discovered this was an integral partner for some species
 * this (2017) review summarizes knowledge of yeasts in lichen (maybe too dated for use)
 * source (2022): "The yeast lichenosphere: high diversity of basidiomycetes from the lichens Tephromela atra and Rhizoplaca melanophthalma"
 * 4. UNPOs: Unicellular, Non-Photosynthesizing Organisms (not traditionally recognized as lichen symbionts), part of of 3-D biofilms some lichens make
 * B. Bipartite vs tripartite lichens - % of each, with explanation of advantages conferred
 * B. Bipartite vs tripartite lichens - % of each, with explanation of advantages conferred

Morphology

 * A. External appearance (i.e. lichen growth forms) - explanation of macrolichen vs microlichen
 * 1. Crustose (including leprose)
 * 2. Foliose
 * 3. Fruticose (including byssoid)
 * 4. Squamulose
 * B. External non-reproductive structures
 * 1. Thallus
 * 2. Cortex
 * 3. Cephalodia
 * 4. Rhizines
 * 5. Cilia
 * C. External reproductive structures
 * 1. Ascus
 * 2. Pycnidia
 * 3. Isidia
 * 4. Podetia
 * D. Colours
 * E. Size and growth rate (here? or in section about lichenometry? or both?)
 * Review (2010): "Growth of crustose lichens"
 * Review (2011): "Growth of foliose lichens"
 * 2. Pycnidia
 * 3. Isidia
 * 4. Podetia
 * D. Colours
 * E. Size and growth rate (here? or in section about lichenometry? or both?)
 * Review (2010): "Growth of crustose lichens"
 * Review (2011): "Growth of foliose lichens"
 * D. Colours
 * E. Size and growth rate (here? or in section about lichenometry? or both?)
 * Review (2010): "Growth of crustose lichens"
 * Review (2011): "Growth of foliose lichens"

Anatomy and physiology

 * A. Internal organisation
 * B. Symbiosis
 * review (2018): "Relative symbiont input and the lichen symbiotic outcome"
 * review (2022): "Evolutionary biology of lichen symbioses"
 * (2022): "A call to reconceptualize lichen symbioses"
 * review (2023): "Chronicle of Research into Lichen-Associated Bacteria"
 * review (2023): "How to build a lichen: from metabolite release to symbiotic interplay"
 * review (2021): "Towards a Systems Biology Approach to Understanding the Lichen Symbiosis: Opportunities and Challenges of Implementing Network Modelling"
 * review (2020): "The Lichens’ Microbiota, Still a Mystery?"
 * review (2023): "Is lichen symbiont mutualism a myth?"
 * C. Nitrogen fixation
 * review (2010): "Ammonium and nitrate tolerance in lichens"

Chemistry

 * A. Biosynthetic pathways to lichen products
 * review (2017): "Secondary metabolism in the lichen symbiosis"
 * B. Categories of lichen products
 * C. Detection of lichen products
 * 1. Spot tests
 * 2. Microcrystallization
 * 3. Analytical chemistry techniques
 * review (2011): "Advanced methods for the study of the chemistry and the metabolism of lichens"
 * 3. Analytical chemistry techniques
 * review (2011): "Advanced methods for the study of the chemistry and the metabolism of lichens"
 * review (2011): "Advanced methods for the study of the chemistry and the metabolism of lichens"

Ecology

 * A. ecological significance of lichens in ecosystems
 * review (2023): This review highlights the growing understanding of lichen ecophysiology and its importance in predicting responses to climate change, emphasizing the role of water content, vapour pressure differential, and symbiont dynamics.
 * review (2023): "Functional Traits in Lichen Ecology", discussing how "functional traits" (see functional ecology) influence lichen community structure and function, and the development of life-history strategies
 * B. Role in nutrient cycles
 * review (2007); how lichens contribute to biogeochemical cycling (i.e., biogeochemistry)
 * review (2000): "Weathering of rocks induced by lichen colonization"
 * review (2017): "How lichens impact on terrestrial community and ecosystem properties"
 * C. Interactions with other (non-human) organisms
 * source (1994): "Lichens as nesting material for northern flying squirrels in the northern Rocky Mountains"
 * review (2017): "Microbial communities of lichens"
 * source (1999): "A Review of the Behavior and Ecology of the Northern Parula (Parula americana) With Notes From Oklahoma and Texas"
 * Coenogonium linkii, a common filamentous lichen of Neotropical lowland rainforests, is inhabited by several species of terrestrial diatoms. They grow between the thallus filaments on extracellular material of the mycobiont. It's probably an example of commensalism.
 * source (2011): Endozoochory is significant for seed plant dispersal, but its role in dispersing lichen has been largely unexplored until a study demonstrated that lichen fragments can survive and regenerate after passing through the digestive systems of snails, suggesting that gastropods may be vital, previously overlooked vectors for lichen dispersal.

Evolution of lichens

 * A. Fossil lichens
 * this (2018) source has a large discussion on both lichenization and lichen fossils. "This leaves 190 accepted lichen fossils, most of which (90%) are from Paleogene amber."
 * review (2009): photobionts do not co-evolve along with their mycobiont counterparts
 * B. Lichenization
 * source (2005): "Lichen-like symbiosis 600 million years ago"
 * review (2016): "Lichenized Fungi and the Evolution of Symbiotic Organization"
 * study (2020): "The macroevolutionary dynamics of symbiotic and phenotypic diversification in lichens"
 * study (2020): "The macroevolutionary dynamics of symbiotic and phenotypic diversification in lichens"

Uses (by humans)

 * lots of documented commercial and ethnic uses of lichens in India, and Nepal
 * A. Biomonitoring
 * review (2021): "A systematic review on biomonitoring using lichen as the biological indicator: A decade of practices, progress and challenges"
 * review (2022): lichens as a biomonitoring tool for environmental radioactivity
 * review (2023): as bioindicators for monitoring nitrogen pollution
 * review (2023): "Lobaria pulmonaria (L.) Hoffm.: The Multifaceted Suitability of the Lung Lichen to Monitor Forest Ecosystems"
 * review (2019): "Antarctic Studies Show Lichens to be Excellent Biomonitors of Climate Change"
 * B. Dyes
 * source (2001): "Lichen Dyes: The New Source Book"
 * C. Medicines
 * review (2022): ethnopharmacological uses and potential as sources of drug leads
 * review (2023): "Lichen Depsides and Tridepsides: Progress in Pharmacological Approaches"
 * review (2021): "Ethnolichenology—The Use of Lichens in the Himalayas and Southwestern Parts of China"
 * review (2019, book chapter): "Lichens Used in Traditional Medicine"
 * 52 different genera of lichens are used in traditional medicines, Usnea is the most common
 * D. Food
 * (2020) "A Review on Trends and Opportunity in Edible Lichens"
 * E. Perfumes
 * review (2009): "Lichen extracts as raw materials in perfumery. Part 1: oakmoss"
 * review (2009): "Lichen extracts as raw materials in perfumery. Part 2: treemoss"
 * F. Crafts
 * G. Lichenometry
 * Lichenometry is a geochronological method that estimates the age of exposed rock surfaces by measuring lichen growth rates, predominantly applied in high latitude and mountainous environments. This dating technique, though innovative in its approach, encounters several limitations and challenges. One of the primary issues is the variability in growth rates of lichens, which can be influenced by environmental factors such as climate, altitude, and substrate type. This variability often leads to inaccuracies in age estimation, making lichenometry less reliable compared to other dating methods. While age estimates obtained by lichenometry should be interpreted with caution, it can provide valuable information when combined with other dating techniques, contributing to a more comprehensive understanding of geological and historical timelines.
 * G. Lichenometry
 * Lichenometry is a geochronological method that estimates the age of exposed rock surfaces by measuring lichen growth rates, predominantly applied in high latitude and mountainous environments. This dating technique, though innovative in its approach, encounters several limitations and challenges. One of the primary issues is the variability in growth rates of lichens, which can be influenced by environmental factors such as climate, altitude, and substrate type. This variability often leads to inaccuracies in age estimation, making lichenometry less reliable compared to other dating methods. While age estimates obtained by lichenometry should be interpreted with caution, it can provide valuable information when combined with other dating techniques, contributing to a more comprehensive understanding of geological and historical timelines.
 * Lichenometry is a geochronological method that estimates the age of exposed rock surfaces by measuring lichen growth rates, predominantly applied in high latitude and mountainous environments. This dating technique, though innovative in its approach, encounters several limitations and challenges. One of the primary issues is the variability in growth rates of lichens, which can be influenced by environmental factors such as climate, altitude, and substrate type. This variability often leads to inaccuracies in age estimation, making lichenometry less reliable compared to other dating methods. While age estimates obtained by lichenometry should be interpreted with caution, it can provide valuable information when combined with other dating techniques, contributing to a more comprehensive understanding of geological and historical timelines.


 * H. Misc.
 * review (2015): lichens as biosorbents for bioremediation

Conservation

 * Review (2009): "Conservation strategies for lichens: insights from population biology"
 * Aspects of lichen conversation in US and Canada (2019)

Threats

 * A. Climate change
 * review (2019): "Climate Change, Bioclimatic Models and the Risk to Lichen Diversity"
 * study (2023): "Towards an understanding of future range shifts in lichens and mosses under climate change"
 * B. Pollution
 * review (2020): Impact of nitrogen pollution from agricultural practices on lichens
 * C. Habitat destruction
 * review (2016): "Does rock climbing threaten cliff biodiversity?"
 * D. Overgrazing
 * review (2022) on reindeer (caribou) diet, "...Our results indicate that in the winter caribou primarily consume lichen"
 * D. Overgrazing
 * review (2022) on reindeer (caribou) diet, "...Our results indicate that in the winter caribou primarily consume lichen"