Thursday, 26 January 2017

more Fissidens incurvus

Barry's record of the 'tall form' of Fissidens incurvus made me remember how utterly distinctive the Pembrokeshire colonies of this plant were.  The (not very good) photo above shows their very long, red setae and narrow, short-leaved shoots.  My Pembs Flora says:
"Five sites in Pembrokeshire support a strikingly different form of Fissidens incurvus to the one that frequents lane banks in the south of the county.  It has remarkably long red setae, and each patch includes sterile shoots with 9 to 15 pairs of short leaves.  All five colonies are on damp clay tracks or flushed areas in turf on clay, with associates that include Archidium alternifolium and Weissia spp.; a situation in which similar plants have been found by SDSB in Co. Clare (V.-c. H9). The taxonomic status of these plants is unclear, and they may be just habitat modifications, but their appearance is certainly distinctive.  It is possible that they represent F. incurvus var. tamarindifolius, which is differentiated by Frey et al. (2006) by virtue of its short, wide, distant leaves and is described as a Mediterranean taxon; it is listed as having 10–12 pairs of leaves by Cortini Pedroti (2001).  Var. tamarindifolius is no longer recognised as a valid taxon in Britain (Smith, 2004a), indeed Hill et al. (2006) reduce F. incurvus to a variety of F. viridulus and Hallingbäck et al. (2006) even include both F. incurvus and F. viridulus as synonyms of F. bryoides.  This may not be the final word on this complicated group."
The Flora Briofitica Iberica treatment of Fissidens was published in 2013 and has incurvus as a variety of F. viridulus, although the illustrations look like our classic incurvus and viridulus and nothing like the 'tall form'.  The most similar illustrated species is the non-British F. ovatifolius, but I don't think the leaf shape of that species matches our plants.  Maybe a friendly DNA Barcoder might take the 'tall form' on!

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