Although Smith (1978) treated var. commutata as a valid
taxon, British bryologists have tended to regard it as merely
'a luxuriant form of the species which is found in sheltered,
nutrient-rich sites' (T.L. Blockeel in Hill et al. 1992: 262).
Hence it has often not been recorded separately and such
records are treated here as B. convoluta s. l.. Nevertheless,
Frahm & Ahmed (2004) suggested it has several distinctive
characters and deserves species rank, but occurrence of
numerous apparent intermediates must cast doubt on this and
Hill et al. (2008)
returned it to varietal rank (as var. sardoa).
Grows as scattered stems, short turfs, often
forming lawns, cushions or patches (tending to form rounded
cushions especially on walls). Habitat notes on B. convoluta s. l. from C&S are
as follows. On slightly acidic or more often basic or neutral
mineral soils (e.g. in arable fields: barley, stubble, flax,
daffodils, grass leys; gardens; bare patches in grassland;
short dune grassland; on disturbed ground, soil on top of
'hedge', soil heaps, banks, on old mine-spoil, in plant pots),
also on thin or compressed soil on paths, tracks, roadsides,
edge of gravel car parks, among marble chippings on graves, in
quarries, on old masonry or in crevices of walls. Also
directly on old concrete, mortar of walls, and old
asbestos-cement roofing material. Withstands desiccation well
on free-draining substrates and absent from permanently wet
sites. Tolerates sites close to cliff tops and subject to
salt-spray. Mainly in unshaded places, sometimes lightly or
moderately shaded and occasionally in heavy shade from trees
or walls. Single atypical records of it on moist old carpet
dumped on mine spoil (Tuckingmill), and on soil in crevice in
metal of old farm roller. Associates recorded include Amblystegium serpens
var. salinum,
Anthoceros
punctatus, Barbula
unguiculata, Bryum cf. algovicum, Bryum dichotomum, Bryum klinggraeffii,
Bryum rubens, Ceratodon purpureus,
Dicranella
schreberiana, Dicranella staphylina,
Didymodon acutus,
Didymodon
insulanus, Didymodon tophaceus,
Ditrichum gracile,
Trichodon
cylindricus, Fossombronia pusilla,
Microbryum
davallianum, Phaeoceros laevis, Pleurochaete
squarrosa, Pseudocrossidium
hornschuchianum, Riccia glauca, Riccia sorocarpa, Riccia subbifurca, Phascum cuspidatum
var.
cuspidatum, Tortula
truncata, Trichostomum
crispulum, Aphanes sp., Cerastium glomeratum,
Festuca rubra, Lamium pupureum, Plantago coronopus, Stellaria media, Veronica
persica.
Occasionally/frequently c.fr.: capsules immature
1-6, 9, 11, 12; dehiscing 6-8 [9]; dehisced [1 old], 6,
9-12.
