{{Short description|Genus of liverworts}} {{Automatic taxobox | image = Ptilidium_pulcherrimum.jpeg | image_caption = ''Ptilidium pulcherrimum'' | parent_authority = H.Klinggr., 1858<ref name="Klinggräff">{{cite book|last=Klinggräff |first=Hugo von|year=1858|title=Die höheren Cryptogamen Preussens|location=Königsberg|publisher=Wilhelm Koch|page=37}}</ref> | taxon = Ptilidium | authority = Nees, 1833<ref name="Nees">{{cite book|last=Nees von Esenbeck|first=C. G.|year=1833|title=Naturgeschichte der europäischen Lebermoose|volume=1|page=95}}</ref> | subdivision_ranks = Species | subdivision = ''Ptilidium californicum''<br/> ''Ptilidium ciliare''<br/> ''Ptilidium pulcherrimum'' |synonyms = ''Blepharozia'' {{Au|(Dumort.) Dumort.}}<ref>{{cite web |title=''Blepharozia'' (Dumort.) Dumort. |url=http://www.worldfloraonline.org/taxon/wfo-4000004794 |website=www.worldfloraonline.org |access-date=5 July 2023}}</ref> }}
'''''Ptilidium''''' is a genus of liverwort, and is the only genus in family '''Ptilidiaceae'''. It includes only three species:<ref name="Schuster I">{{cite book|last=Schuster|first=Rudolf M.|year=1966|title=The Hepaticae and Anthocerotae of North America|volume=I|pages=757–780|location=New York|publisher = Columbia University Press|isbn=0-231-03567-5}}</ref> ''Ptilidium californicum'', ''Ptilidium ciliare'', and ''Ptilidium pulcherrimum''. The genus is distributed throughout the arctic and subarctic, with disjunct populations in New Zealand and Tierra del Fuego. Molecular analysis suggests that the genus has few close relatives and diverged from other leafy liverworts early in their evolution.
==Description== The name of the genus comes from the Greek word ''ptilidion'' for "small feather", in reference to the multiply deeply divided leaves with fringed edges, which give the plant a "feathery" appearance. Unlike other leafy liverworts, the underleaves are not significantly smaller than the lateral leaves.<ref name="Bold 1987">{{cite book|last=Bold|first=Harold C.|author2=C. J. Alexopoulos |author3= T. Delevoryas |title=Morphology of Plants and Fungi|edition=5th|page=235|location=New York|publisher=Harper-Collins|isbn=0-06-040839-1}}</ref> The "flossy" appearance from the leaf edges, together with the characteristic yellowish-brown or reddish-brown color make the genus easy to recognize.<ref name="Porley">{{cite book|last=Porley|first=Ron|author2=Nick Hodgetts |year=2005|title=Mosses and Liverworts|location=London|publisher=Collins|isbn=0-00-220212-3|page=162}}</ref>
Like ''Ptilidium'', ''Blepharostoma'' and ''Trichocolea'' have deeply divided leaves with marginal cilia, however ''Ptilidium'' differs from these other two genera in that its leaf cells have bulging trigones (thickenings at the corners between cell walls).<ref name="Frye & Clark">{{cite journal|last=Frye|first=T. C.|author2=Lois Clark |year=1943|title=Hepaticae of North America. Part II.|journal=University of Washington Publications in Biology|volume=6|issue=2|pages=174, 195–201}}</ref>
The plants grow in dense mats, with stems growing either prostrate or ascending. Individual stems are once or twice pinnate, rarely with branches and only a few short rhizoids. The leaves are incubous and divided deeply into three to five portions, and edges of the leaf divisions are fringed with cilia. The underleaves are similar to the lateral leaves, but are slightly smaller. All species are dioicous, producing antheridia and archegonia on separate plants. The archegonia are terminal on a main stem. Mature sporophytes develop from within a large perianth with three distal folds.<ref name="Clark & Frye">{{cite journal|last=Clark|first=Lois|author2=T. C. Frye |year=1928|title=The Liverworts of the Northwest|journal=Publications Puget Sound Biological Station|volume=6|pages=132–133}}</ref>
The three species in the genus may be distinguished by the density of cilia along the leaf margin, depth of lobing in the leaf, width of the leaf base, and the substrate on which it is found growing. ''P. californicum'' has few cilia along the edge of its leaves and has underleaves lobed to about seven-eighths of their length. The other two species have many marginal cilia and underleaves lobed to no more than half their length. ''P. ciliare'' usually grows on soil and has leaf lobes that are 15–20 cells wide at their base. ''P. pulcherrimum'' usually grows on wood or rock, and has leaf lobes normally 6–10 cells wide at their base.<ref name="Frye & Clark" />
==Distribution== The genus ''Ptilidium'' has a boreal distribution, and is found in abundance in coniferous forests of Europe, Asia, and North America,<ref name="Tan 2000">{{cite book|last=Tan|first=Benito C.|author2=Tamás Pócs |year=2000|chapter=Bryogeography and conservation of bryophytes|page=406|editor1=A. Jonathan Shaw |editor2=Bernard Goffinet |title=Bryophyte Biology|location=Cambridge|publisher=Cambridge University Press|isbn=0-521-66097-1}}</ref> as well as in New Zealand<ref name="Allison">{{cite book|last=Allison|first=K. W.|author2=John Child |year=1975|title=The Liverworts of New Zealand|location=Dunedin|publisher=University of Otago Press|pages=44–45}}</ref> and Tierra del Fuego.<ref name="Schofield">{{cite book|last=Schofield|first=W. B.|year=1985|title=Introduction to Bryology|page=357|location=New York|publisher=Macmillan|isbn=0-02-949660-8}}</ref> Plants often grow attached to the bark of trees in the northern hemisphere, but may occur in rocks in mountain districts of New Zealand. At the more temperate ends of its range, plants are restricted to higher elevations.<ref name="Schuster I" />
Schuster (1984) proposed that the disjunct distribution of ''Ptilidium ciliare'' between the northern and southern hemispheres could be explained by migration of the Indian Plate from Gondwana.<ref name="Schuster 1984">{{cite book|last=Schuster|first=Rudolf M.|year=1984|chapter=Phytogeography of the Bryophyta|title=New Manual of Bryology|location=Nichinan, Miyazaki, Japan|publisher=The Hattori botanical Laboratory|pages=514–516, 601}}</ref> In this hypothesis, ''P. ciliare'' is a species originally native to Gondwana, and sterile populations existing in modern New Zealand and Tierra del Fuego are relicts of this earlier distribution. The other two species of ''Ptilidium'' are thus believed to be later descendants. Schuster's hypothesis is partially based upon a belief that ''Ptilidium'' is related to the genera ''Mastigophora'' and ''Dendromastigophora'', both of which are largely restricted to the southern hemisphere. However, this relationship is not supported by modern molecular analysis, which places ''Mastigophora'' in an entirely different part of the liverwort phylogeny.<ref name="Forrest 2006" /> Instead, ''Ptilidium'' is now believed to be part of an isolated clade allied only to two East Asian endemics, and it is thus more likely that the sterile populations of ''Ptilidium'' in the southern hemisphere reflect long-distance dispersal of plant fragments. ''Ptilidium ciliare'' is tolerant of desiccation and is ubiquitous in the Arctic, but rarely produces spores, and it is therefore believed to spread by means of such fragments.<ref name="Schuster 1984" />
==Phylogeny== {| align="left" width="30%" style="text-align:left; padding:2.5px; background:#fff" |- style="background:#fff; padding:2.5px"| | {{clade| style=font-size:90%;line-height:75% |1={{clade |1={{clade |1={{clade |1={{clade |1='''Leafy II''' (2600 spp) |2={{clade |1='''''Ptilidium''''' |2={{clade |1=''Neotrichocolea'' |2=''Trichocoleopsis'' }} }} }} |2='''Leafy I''' (1800 spp) }} }} |2={{clade |1={{clade |1=''Pleurozia'' |2={{clade |1=Metzgeriaceae |2=Aneuraceae }} }} }} }} }} |}
The diagram at left summarizes a portion of a 2006 cladistic analysis of liverworts based upon three chloroplast genes, one nuclear gene, and one mitochondrial gene.<ref name="Forrest 2006">{{cite journal | last = Forrest|first = Laura L. |author2=Christine E. Davis |author3=David G. Long |author4=Barbara J. Crandall-Stotler |author5=Alexandra Clark |author6=Michelle L. Hollingsworth | year = 2006 | title = Unraveling the evolutionary history of the liverworts (Marchantiophyta): multiple taxa, genomes and analyses | journal = The Bryologist|volume = 109|issue = 3|pages = 303–334 | doi = 10.1639/0007-2745(2006)109[303:UTEHOT]2.0.CO;2}}</ref><ref name="Davis">{{cite journal|last=Davis|first=E. Christine|year=2004|title=A Molecular Phylogeny of Leafy Liverworts (Jungermanniidae: Marchantiophyta)|series=Molecular Systematics of Bryophytes|journal=Monographs in Systematic Botany|volume=98|pages=61–86|publisher= Missouri Botanical Garden Press}}</ref> The genus ''Trichocoleopsis'' was not included in the original broad analysis, but is the sister taxon of ''Neotrichocolea'' according to a more narrowly focussed study utilizing six chloroplast genes, two nuclear genes, and a mitochondrial gene.<ref>{{cite journal|doi=10.3417/2006071|last=Yang|first=Liu|author2=Yu Jia |author3=Wei Wang |author4=Chen Zhi-Duan |author5=Davis, Christine E. |author6= Qiu Yin-Long |year=2008|title=Phylogenetic relationships of two endemic genera from East Asia: ''Trichocoleopsis'' and ''Neotrichocolea'' (Hepaticae)|journal=Annals of the Missouri Botanical Garden|volume=95|issue=3|pages=459–470|issn=0026-6493}}</ref>
The genus ''Ptilidium'' is sister to the ''Trichocoleopsis''-''Neotrichocolea'' clade. This combined clade, in turn, attaches at the base of a large clade (2600 species) designated "Leafy II". That clade, together with "Leafy I" (another 1800 species) and ''Pleurozia'' constitute the Jungermanniales, as traditionally defined. ''Ptilidium'', ''Neotrichocolea'', and ''Trichocoleopsis'' thus sit at the base of the Jungermanniales, at a point where the two major groups of leafy liverworts diverge from each other. {{-}}
==Gallery== <!-- Please do not add images to this gallery simply because the image exists. The collection of images below was selected to illustrate key structures described within the article. Additional images are better placed among the article text or uploaded to Commons. --> <gallery> File:Ptilidium ciliare blatt.jpeg |{{center|Magnified view of the stem of ''P. ciliare'', showing the lateral leaves with deep lobing and marginal cilia.}} File:Ptilidium ciliare laminazellen.jpeg |{{center|Higher magnification of the leaf surface, showing the ''trigones''–cell wall thickenings in the corners between neighboring cells.}} </gallery>
==References== {{Reflist|2}}
==External links== *{{Wikispecies-inline}} *{{Commons category-inline|Ptilidium}}
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Category:Ptilidiales Category:Liverwort genera