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Cladonia pyxidata (L.) Hoffm.


Description and concept based in substantial part on notes in Aptroot, Sipman & van Herk (2001), Lichenologist 33: 271-283:
a "pixie-cup lichen" with funnel-shaped podetia tapering gradually towards the base, exterior variably clothed with corticate granules and sometimes also with small squamules, interior with conspicuous, disk-like, corticate granules (sometimes developing into squamules within the cup), soredia absent; basal squamules small, lacking pink tints, margins flat, smooth; apothecia brown, globose, more or less sessile on the podetial margins or on very short, stalk-like proliferations (<5mm). Distribution uncertain due to confusion with other species (see below) but evidently widespread, at least in the north and west, perhaps mostly in degraded, peaty habitats, but surprisingly able to grow on Hazel (Corylus) branches in high-Atlantic hazelwoods (noted on Jura, 2011).

Refs: Aptroot, Sipman & van Herk (2001), Lichenologist 33: 271-283; Smith et al. (2009), 334; Purvis et al. (1992), 200; Nordic Lichen Flora (2013) 5: 67, 105 (photo); Dobson (2005), 142 (photo); Dobson (2011), 149, 150 (photo); Whelan (2011), 78 (photo), probably also 76 (photo, as "C. pocillum"); Aptroot et al. (2011), 104-5 (photos); Krog et al. (1994), 166 (photo); Moberg & Holmåson (1984), pg. 145 (photo, verified by Aptroot et al.); Stenroos et al. (2011), 162 (photo); Wirth (1995), 1: 307 (lower photograph only, verified by Aptroot et al.); Wirth et al. (2004), 84 (photo - as Wirth 1995 and so verified by Aptroot et al.); Wirth, Hauck & Schulz (2013), 1: 386 (photo); Valcárcel et al. (2003), 166-7 (photo); Hinds & Hinds (2007), 200-201 (photo); Brodo et al. (2001), 267-8 (photo).

This species is part of a difficult complex with C. pocillum and C. monomorpha, interpreted here as characterised by conspicuous, discoid, corticate granules and lack of soredia within the podetia.

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C. pocillum has larger, often imbricated, basal squamules with similarly flat but distinctly abraded margins, squamules frequently tinted grey-pink, conspicuous and often ring-like apothecia, and preference for mesic or more base-rich situations.
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C. monomorpha has downwardly recurved, smooth margins to the basal squamules and typically rather blistered-like surfaces to the podetia; apothecia rather small, rounded and in clusters on taller (to 1cm) proliferations from the podetial margins. It is apparently restricted to acid, sandy heaths and dunes (overlooked or very rare and perhaps uncertain in the UK). The characters given in Dobson (op. cit.) do not accord with the original description.
 
Confusion of the complex with C. chlorophaea agg. is also all too easy. In mature but fresh podetia of C. pyxidata and its allies, the corticate nature of the granules is shown by their rather distinct surface sheen, but this is lost in older or dried-up material.

Although C. pyxidata has been considered to be common in Britain, it is probably over-recorded for C. pocillum and for coarsely sorediate states of C. chlorophaea agg. Aptroot et al. (2001) refered several published supposed illustrations to C. pocillum. Their interpretations of the analytical paintings in Galløe (1954), Natural History of the Danish Lichens, part IX, are highly instructive in understanding this complex. However, Ahti & Stenroos (in Nordic Lichen Flora (2013)) take a broader view of C. pyxidata and doubt its separation from elements of the C. chlorophaea complex. The extent to which stated diagnostic characters correlate needs further work; it may be that some are environmentally induced and future treatments may involve either further splitting or else lumping of taxa. Recent DNA results appear to be conficting, N. American work has shown presence of distinct clades, but other recent work favours a lumping approach (D. Hawksworth, pers.comm.). It is essential that further work includes detailed micro-morphometric work on each sample to enable reliable correlation with cladistical results.

FGBI: http://fungi.myspecies.info/lichens/cladonia-pyxidata

Cladonia pyxidata, podetia, close view
Cladonia pyxidata, colony
On peat amongst rocks, Gleniffer Braes, Renfrewshire, March 2009


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Uploaded July 2010, last updated January 2014