Dicranideae

 Racomitrium lanuginosum, photographed by Stuart Dunlop.

Belongs within: Bryophyta.
Contains: Pottiaceae, Erpodiaceae, Calymperaceae, Ephemeraceae, FissidentaceaeLeucobryum, Dicranaceae, Ditrichaceae, Rhabdoweisiaceae, Trematodon, Seligeriaceae, Racomitrioideae, Grimmia, Schistidium.

The Grimmiales is an order of mosses found growing on rocks. A close relationship between Ptychomitrium and Grimmiaceae, but not Scouleriaceae, is supported by molecular phylogenetic analysis (La Farge et al. 2000). Members of the Grimmiaceae usually grow in dense tufts or cushions on rocks (Dixon 1924).

Southern moss
Published 6 July 2009
There don’t seem to be any images of Ptychomitrium muelleri available online, so here’s another Ptychomitrium species, P. gardneri from China. Photo by Li Zhang.

Mosses are often treated as the poor relation in plant diversity. Popular presentations of plant evolution often tend to have even more of a Scala Natura-esque slant to them than presentations of animal evolution, and so mosses and other non-vascular plants get glossed over as mere stepping stones to their more upright “descendants”, if they even warrant a mention at all. This is, of course, complete rubbish—mosses have a very respectable diversity of species (about 10,000, according to Tree of Life). I’ve met a few moss researchers over the years, and a more devoted following a taxon could not hope for.

Ptychomitrium muelleri is a haplolepidous moss of the family Ptychomitriaceae (I’ll explain what that means in a minute). It grows to a maximum height of one and a half centimetres, and if the type specimens are any indication, prefers to grow on rocks. Ptychomitrium mosses seem to be found more or less worldwide, but Ptychomitrium muelleri itself is found in south-eastern Australia, New Caledonia, southern South America and southernmost Africa. What is interesting about this species’ distriution is that it was thought to be endemic to Australia until very recently when Cao et al. (2001) established that species described from each of the other localities were conspecific with P. muelleri. As a result, P. muelleri has what might be described as a classic “Gondwanan” distribution, but I rather doubt that Gondwana had anything to do with it. After all, moss spores are very light and extremely easily dispersed, and surely it is no coincidence that all the localities where P. muelleri can be found lie roughly along the same wind belt.

The diagram of a moss life cycle above has been stolen from Palaeos.com. For the nonce, the important details are these—mosses, like other plants, are multicellular at both the haploid and diploid stages of the life cycle, but unlike vascular plants, the larger, dominant stage of the life cycle is the haploid gametophyte. When a female gametophyte is fertilised, the diploid sporophyte remains attached to the gametophyte and grows a spore-filled capsule that eventually breaks open (after the loss of the protective calyptra) to release the spores. Around the mouth of the capsule is a ring of “teeth”, the peristome. In basal mosses, the peristome is made up of entire cells, but in the class Bryopsida, the arthrodontous mosses (which includes the larger part of the mosses), the teeth are reduced to cell wall remnants. Most of the bryopsid lineages have two rows of teeth in the peristome, an outer and an inner, but Ptychomitrium belongs to a group called the Haplolepideae or Dicranidae which have only the inner row of teeth. The haplolepidous mosses form a monophyletic clade within the Bryopsida.

Ptychomitrium polyphyllum from Scotland, showing the calyptra on the left capsule and the exposed peristome on the right. Photo from here.

Most of the features separating moss taxa are microscopic and relate to such things as cell arrangement (which is my weaselly method of saying that I don’t understand a word of them), but Ptychomitrium is distinguished by having a mitrate calyptra with characteristic lobes around the lower edge (Hernández-Maqueda et al., 2008, compare it to a Hawaiian skirt). Ptychomitrium muelleri has (amongst other features) lingulate (tongue-shaped, I’m guessing) leaves with smooth margins, and ovoid capsules.

Systematics of Dicranideae
<==Dicranideae [Dicrananae]S04
    |--Pottiales [Hyophilales, Hyophiloideae, Trichostomales]SK02
    |    |--PottiaceaeSK02
    |    |--ErpodiaceaeSK02
    |    |--CalymperaceaeSK02
    |    |--EphemeraceaeSK02
    |    |--Bryobartramia Sainsbury 1948 [Bryobartramiaceae]SK02
    |    |    `--B. novae-valesiae (Broth. ex Roth) Stone & Scott 1973 (see below for synonymy)SK02
    |    |--Viridivellus Stone 1976 [Viridivelleraceae]SK02
    |    |    `--V. pulchellum Stone 1976SK02
    |    `--Cinclidotus Palisot de Beauvois 1805 [=Cicclidotus; Cinclidotaceae, Cinclidoteae]OZB-O03
    |         |--C. aquaticus [=Harrisonia aquatica]OZB-O03
    |         |--C. fontinaloides (Hedw.) Beauv. 1805S04 (see below for synonymy)
    |         `--C. riparius (Host ex Brid.) Arnott 1827S04 [incl. C. nigricansOZB-O03]
    |--Dicranales [Dicranoidae]SK02
    |    |--FissidentaceaeOZB-O03
    |    |--Schistostega Mohr 1803S04 [Schistostegaceae, Schistostegales, SchistostegineaeOZB-O03]
    |    |    `--S. pennata (Hedw.) Weber & Mohr 1803S04 [incl. Mnium osmundaceumD24, S. osmundaceaS04]
    |    |--Leucobryaceae [Leucobryineae]OZB-O03
    |    |    |--LeucobryumSK02
    |    |    `--ExodictyonB57
    |    |         |--E. dentatumB57
    |    |         `--E. subscabrumSK02
    |    `--DicranineaeOZB-O03
    |         |--DicranaceaeSK02
    |         |--DitrichaceaeOZB-O03
    |         |--RhabdoweisiaceaeS04
    |         `--Bruchiaceae [Trematodonteae, Trematodontoideae]OZB-O03
    |              |--TrematodonO02
    |              `--Bruchia Schwägr. 1824O02, SK02
    |                   |--B. brevipes Harv. ex Hooker 1840SK02
    |                   |--B. eckloniana Müll.Hal. 1848SK02
    |                   `--B. queenslandica Stone 1977SK02
    `--GrimmialesSK02
         |--SeligeriaceaeOZB-O03
         |--Scouleriaceae [Scoulerioideae]SK02
         |    |--Scouleria patagonicaD03
         |    `--Tridontium Hooker ex Hooker 1840SK02
         |         `--T. tasmanicum Hooker ex Hooker 1840 (see below for synonymy)SK02
         |--Ptychomitriaceae [Ptychomitrieae, Ptychomitrioideae]S04
         |    |--Glyphomitrium (Dicks.) Brid. 1819S04
         |    |    `--G. daviesii ((Dicks.) Brid. 1819S04 [=Bryum daviesiiD24]
         |    |--Campylostelium Bruch & Schimp. in Bruch, Schimp. & Gümbel 1846S04
         |    |    |--C. brachycarpum (Noguchi) Iwatsuki et al. 1999 [=C. saxicola var. brachycarpum Noguchi 1950]OZB-O03
         |    |    `--C. saxicola (Weber & Mohr) Bruch & Schimp. in Bruch et al. 1846S04 (see below for synonymy)
         |    `--Ptychomitrium Fürnr. 1829SK02
         |         |--P. australe (Hampe) Jaeger 1874 (see below for synonymy)SK02
         |         |--P. laxifolium (Müll.Hal.) Paris 1900 [=Brachysteleum laxifolium, Glyphomitrium laxifolium]SK02
         |         |--P. ligulatumD03
         |         |--P. mittenii Jaeger 1874 (see below for synonymy)SK02
         |         |--P. muelleri (Mitt.) Jaeger 1874 (see below for synonymy)SK02
         |         |--P. polyphyllum (Sw.) Bruch & Schimp. in Bruch et al. 1839S04 (see below for synonymy)
         |         `--P. tortulaN02
         `--GrimmiaceaeSK02
              |--RacomitrioideaeOZB-O03
              `--Grimmioideae [Coscinodontoideae]OZB-O03
                   |--GrimmiaSK02
                   |--SchistidiumOZB-O03
                   |--JaffueliobryumOZB-O03
                   |--CosconodontellaOZB-O03
                   |--AligrimmiaOZB-O03
                   |--Hydrogrimmia (Hagen) Loeske 1910OZB-O03
                   |    `--H. mollis (Schimp.) Loeske 1910 [=Grimmia mollis; incl. G. mollis f. aquatica]OZB-O03
                   `--Coscinodon Spreng. 1804OZB-O03, S04
                        |--C. cribrosus (Hedw.) Spruce 1849S04 [=Grimmia cribrosaS04; incl. C. pulvinatusOZB-O03]
                        |--C. humilisD24
                        `--C. petersoniD24

Bryobartramia novae-valesiae (Broth. ex Roth) Stone & Scott 1973 [=Trachycarpidium novae-valesiae; incl. B. robbinsii]SK02

Campylostelium saxicola (Weber & Mohr) Bruch & Schimp. in Bruch et al. 1846S04 [=Dicranum saxicolaD24, Glyphomitrium saxicolaD24; incl. Grimmia geniculata Schwägrichen 1811OZB-O03]

Cinclidotus fontinaloides (Hedw.) Beauv. 1805S04 [=Guembelia fontinaloidesOZB-O03, Racomitrium fontinaloidesOZB-O03; incl. Cinclidotus minorOZB-O03]

Ptychomitrium australe (Hampe) Jaeger 1874 [=Brachysteleum australe, Glyphomitrium australe; incl. Ptychomitrium acutifolium, Brachysteleum acutifolium, Glyphomitrium acutifolium, G. adamsonii, Brachysteleum adamsonii, Ptychomitrium adamsonii]SK02

Ptychomitrium mittenii Jaeger 1874 [=Brachysteleum mittenii, Glyphomitrium mittenii; incl. G. serratum, Brachysteleum serratum, Ptychomitrium serratum (preoc.)]SK02

Ptychomitrium muelleri (Mitt.) Jaeger 1874 [=Glyphomitrium muelleri, Brachysteleum muelleri; incl. B. commutatum, Glyphomitrium commutatum, Ptychomitrium commutatum, Brachysteleum howeanum, Glyphomitrium howeanum, Ptychomitrium howeanum, P. howei (l. c.), Brachysteleum microblastum, Glyphomitrium microblastum, Ptychomitrium microblastum (Müll.Hal.) Paris 1900]SK02

Ptychomitrium polyphyllum (Sw.) Bruch & Schimp. in Bruch et al. 1839S04 [=Bryum polyphyllumD24, Glyphomitrium polyphyllumD24, Trichostomum polyphyllumSK02]

Tridontium tasmanicum Hooker ex Hooker 1840 [=Dichodontium tasmanicum, Dicranum tasmanicum, Didymodon tasmanicus; incl. Glyphomitrium latifolium, Ptychomitrium latifolium]SK02

*Type species of generic name indicated

References

[B57] Bartram, E. B. 1957. Additional Fijian mosses, III. Journal of the Washington Academy of Sciences 46 (12): 392–396.

Cao, T., S. Guo & Y. Zhang. 2001. Distribution of Ptychomitrium muelleri (Bryopsida), with its synonyms. The Bryologist 104 (4): 522–526.

[D24] Dixon, H. N. 1924. The Student’s Handbook of British Mosses 3rd ed. V. V. Sumfield: Eastbourne.

[D03] Dusén, P. 1903. Patagonian and Fuegian mosses. In: Scott, W. B. (ed.) Reports of the Princeton University Expeditions to Patagonia, 1896–1899 vol. 8. Botany pp. 63–126. The University: Princeton (New Jersey).

Hernández-Maqueda, R., D. Quandt, O. Werner & J. Muñoz. 2008. Phylogeny and classification of the Grimmiaceae/Ptychomitriaceae complex (Bryophyta) inferred from cpDNA. Molecular Phylogenetics and Evolution 46 (3): 863–877.

[N02] Negi, H. R. 2002. Abundance and diversity of moss communities of Chopta-Tunganath in the Garhwal Himalaya. Journal of the Bombay Natural History Society 99 (3): 418–433.

[OZB-O03] Ochyra, R., J. Żarnowiec & H. Bednarek-Ochyra. 2003. Census Catalogue of Polish Mosses. Institute of Botany, Polish Academy of Sciences: Cracow.

[S04] Smith, A. J. E. 2004. The Moss Flora of Britain and Ireland 2nd ed. Cambridge University Press.

[SK02] Streimann, H., & N. Klazenga. 2002. Catalogue of Australian Mosses. Flora of Australia Supplementary Series 17. Australian Biological Resources Study: Canberra.

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