Editing Lichen (section)

== Reproduction and dispersal ==

===Vegetative reproduction===
[[File:Lichen reproduction1.jpg|thumb|right|''Xanthoparmelia'' sp. with dark-colored reproductive structures (disc-like [[apothecia]]) at center, surrounded by a pale coloured vegetative [[thallus]].]]
Many lichens reproduce asexually, either by a piece breaking off and growing on its own ([[vegetative reproduction]]) or through the dispersal of [[Diaspore (botany)|diaspore]]s containing a few algal cells surrounded by fungal cells.<ref name=WIL/> Because of the relative lack of differentiation in the thallus, the line between diaspore formation and vegetative reproduction is often blurred. Fruticose lichens can fragment, and new lichens can grow from the fragment ([[vegetative reproduction]]). Many lichens break up into fragments when they dry, dispersing themselves by wind action, to resume growth when moisture returns.<ref name=Eichorn2005/><ref name=Cook1995/> ''Soredia'' (singular: "soredium") are small groups of algal cells surrounded by fungal filaments that form in structures called soralia, from which the soredia can be dispersed by wind.<ref name=WIL/> ''Isidia'' (singular: "isidium") are branched, spiny, elongated, outgrowths from the thallus that break off for mechanical dispersal.<ref name=WIL/> Lichen propagules ([[Diaspore (botany)|diaspores]]) typically contain cells from both partners, although the fungal components of so-called "fringe species" rely instead on algal cells dispersed by the "core species".<ref name="RaiBergman2002">{{cite book|author1=A. N. Rai|author2=B. Bergman|author3=Ulla Rasmussen|title=Cyanobacteria in Symbiosis|url=https://books.google.com/books?id=ZM8nzztrTbEC&pg=PA59|access-date=2 June 2013|date=31 July 2002|publisher=Springer|isbn=978-1-4020-0777-4|page=59|archive-url=https://web.archive.org/web/20131231221834/http://books.google.com/books?id=ZM8nzztrTbEC&pg=PA59|archive-date=31 December 2013|url-status=live}}</ref>

===Sexual reproduction===
[[File:Lichen reproduction.jpg|thumb|left|Disc-like [[apothecia]] (left) and [[thallus]] (right) on a [[foliose lichen]]]]

Structures involved in reproduction often appear as discs, bumps, or squiggly lines on the surface of the thallus.<ref name=SSFGCL/>{{rp|4}} Though it has been argued that sexual reproduction in photobionts is selected against, there is strong evidence that suggests meiotic activities (sexual reproduction) in ''Trebouxia''.<ref>{{Cite journal|last1=Law|first1=R.|last2=Lewis|first2=D. H.|date=November 1983|title=Biotic environments and the maintenance of sex-some evidence from mutualistic symbioses|url=http://dx.doi.org/10.1111/j.1095-8312.1983.tb01876.x|journal=Biological Journal of the Linnean Society|volume=20|issue=3|pages=249–276|doi=10.1111/j.1095-8312.1983.tb01876.x|issn=0024-4066}}</ref><ref>{{Cite journal|last1=Škaloud|first1=Pavel|last2=Steinová|first2=Jana|last3=Řídká|first3=Tereza|last4=Vančurová|first4=Lucie|last5=Peksa|first5=Ondřej|date=2015-05-04|title=Assembling the challenging puzzle of algal biodiversity: species delimitation within the genusAsterochloris(Trebouxiophyceae, Chlorophyta)|url=http://dx.doi.org/10.1111/jpy.12295|journal=Journal of Phycology|volume=51|issue=3|pages=507–527|doi=10.1111/jpy.12295|pmid=26986666|bibcode=2015JPcgy..51..507S |s2cid=25190572|issn=0022-3646}}</ref> Many lichen fungi reproduce sexually like other fungi, producing spores formed by [[meiosis]] and fusion of gametes. Following dispersal, such fungal spores must meet with a compatible algal partner before a functional lichen can form.

Some lichen fungi belong to the phylum [[Basidiomycota]] (''basidiolichens'') and produce [[mushroom]]-like reproductive structures resembling those of their nonlichenized relatives.

Most lichen fungi belong to [[Ascomycetes]] (''ascolichens''). Among the ascolichens, [[spore]]s are produced in spore-producing structures called ''[[ascomata]]''.<ref name=SSFGCL/> The most common types of ascomata are the ''[[apothecium]]'' (plural: apothecia) and ''[[perithecium]]'' (plural: perithecia).<ref name=SSFGCL/>{{rp|14}} Apothecia are usually cups or plate-like discs located on the top surface of the lichen thallus. When apothecia are shaped like squiggly line segments instead of like discs, they are called ''lirellae''.<ref name=SSFGCL/>{{rp|14}} Perithecia are shaped like flasks that are immersed in the lichen thallus tissue, which has a small hole for the spores to escape the flask, and appear like black dots on the lichen surface.<ref name=SSFGCL/>{{rp|14}}

The three most common spore body types are raised discs called ''[[Ascocarp|apothecia]]'' (singular: apothecium), bottle-like cups with a small hole at the top called ''perithecia'' (singular: perithecium), and ''pycnidia'' (singular: pycnidium), shaped like perithecia but without asci (an [[ascus]] is the structure that contains and releases the sexual spores in fungi of the [[Ascomycota]]).<ref>{{cite web | url=http://www.earthlife.net/lichens/reproduction.html | title=Lichen Reproductive Structures | author=Ramel, Gordon | access-date=22 August 2014 | archive-url=https://web.archive.org/web/20140228111310/http://www.earthlife.net/lichens/reproduction.html | archive-date=28 February 2014 | url-status=dead }}</ref>

The apothecium has a layer of exposed spore-producing cells called ''[[ascus|asci]]'' (singular: ascus), and is usually a different color from the thallus tissue.<ref name=SSFGCL/>{{rp|14}} When the apothecium has an outer margin, the margin is called the ''exciple''.<ref name=SSFGCL/>{{rp|14}} When the exciple has a color similar to colored thallus tissue the apothecium or lichen is called ''lecanorine'', meaning similar to members of the genus ''[[Lecanora]]''.<ref name=SSFGCL/>{{rp|14}} When the exciple is blackened like carbon it is called ''lecideine'' meaning similar to members of the genus ''[[Lecidea]]''.<ref name=SSFGCL/>{{rp|14}} When the margin is pale or colorless it is called ''biatorine''.<ref name=SSFGCL/>{{rp|14}}

[[File:Pilophorus acicularis 109164.jpg|thumb|right|Crust-like thallus with [[pseudopodetia]]]]
A "[[podetium]]" (plural: [[podetia]]) is a lichenized stalk-like structure of the fruiting body rising from the thallus, associated with some fungi that produce a fungal [[apothecium]].<ref name=ASLGPZ/> Since it is part of the reproductive tissue, podetia are not considered part of the main body (thallus), but may be visually prominent.<ref name=ASLGPZ/> The podetium may be branched, and sometimes cup-like. They usually bear the fungal [[pycnidia]] or [[apothecia]] or both.<ref name=ASLGPZ/> Many lichens have [[apothecia]] that are visible to the naked eye.<ref name=WIL/>

Most lichens produce abundant sexual structures.<ref name=Murtagh/> Many species appear to disperse only by sexual spores.<ref name=Murtagh>{{cite journal |vauthors=Murtagh GJ, Dyer PS, Crittenden PD |title=Sex and the single lichen |journal=Nature |volume=404 |issue=6778 |page=564 |date=April 2000 |pmid=10766229 |doi=10.1038/35007142 |bibcode=2000Natur.404..564M |s2cid=4425228 }}</ref> For example, the crustose lichens ''Graphis scripta'' and ''Ochrolechia parella'' produce no symbiotic vegetative propagules. Instead, the lichen-forming fungi of these species reproduce sexually by self-fertilization (i.e. they are [[homothallic]]). This breeding system may enable successful reproduction in harsh environments.<ref name=Murtagh/>

''Mazaedia'' (singular: mazaedium) are apothecia shaped like a [[Pin#Straight pins|dressmaker's pin]] in [[pin lichen]]s, where the fruiting body is a brown or black mass of loose ascospores enclosed by a cup-shaped exciple, which sits on top of a tiny stalk.<ref name=SSFGCL/>{{rp|15}}