Pohlia scotica – a neglected endemic moss

Article
Pohlia scotica – a neglected
endemic moss
Gordon Rothero tells us why, where,
and how to look for this ‘forgotten’
endemic
rFigure 1. A patch of Pohlia scotica showing the somewhat ‘spikey’ appearance when wet. G. Rothero
W
e do not have many endemic species
in the British Isles so it seems a little
odd that one that we do have has
been rather neglected. The reasons for this are
probably fairly obvious and are related firstly to
the fact that it is a Pohlia, quite a difficult genus,
and secondly that an endemic, weedy Pohlia just
seems so unlikely.
Pohlia scotica was first described by Alan
Crundwell (1982) from material collected in
1964 by the River Orchy in Argyll and from a
few other sites in much the same area of Argyll
and the west of Perthshire, all collected in the
1970s and early 1980s. Immediately following
the appearance of Crundwell’s paper a number
of other records were made, mostly by Martin
Corley and David Long, the last being made in
1986. One of these records came from the remote
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Corriemulzie in Easter Ross, thus markedly
increasing the known range of this moss and
indicating, perhaps, that it should be looked for
in the intervening hill country. However, after
this, Pohlia scotica seems to have dropped off the
bryological radar.
I had paid homage to the moss at its site on
Loch Tulla, a convenient 20m or so from the
road, but it was not until I started recording for
the Flora of Assynt that I found it for myself. In
2001, in the wonderful, empty country north of
Canisp, Ian Evans and I were examining a dead
Red-throated diver on the shore of a small loch
and nearby was a patch of a nondescript Pohlia in
the gravel and this proved to be Pohlia scotica, the
first new site for 15 years. Not long after this, the
boom in small scale hydro-electric schemes in
Scotland started to take off and I was employed
rFigure 2. A leaf of Pohlia scotica showing the narrow triangular shape and the recurved leaf margins. G. Rothero
to look at the bryophytes on a number of sites.
This sort of surveying involves looking at riparian
bryophytes in rather more detail than when just
square-bashing and the work has resulted in
a further nine sites for Pohlia scotica. The sites
I have been looking at are quite widespread in
the west of Scotland and reinforce the idea that
Pohlia scotica is still under-recorded. Crundwell
expressed the likelihood of this possibility
elegantly: “A not particularly striking sterile
Pohlia that looks as though it may be material
without bulbils of a species that normally has
them, is unlikely to be collected in proportion to
its frequency.”
Apart from its small size, it is not a difficult
plant to recognise. In the field it is most similar to
Pohlia drummondii without bulbils but the leaves
are narrower and more triangular than in that
species. In Pohlia scotica the leaves taper almost
from the base to a rather narrow point and are
erect and little changed when dry, giving the plant
a ‘spiky’ look (Fig. 1). In Pohlia drummondii the
leaves are usually broadest about a quarter of the
way up the leaf and taper to a broader point and
are somewhat incurved when dry. Pohlia scotica
is a little like Pohlia filum but in that plant the
leaves are more erect and appressed against the
stem so that the plants look narrow. Apart from
the lack of bulbils the most obvious difference,
which is just about visible with a x20 lens, is that
both leaf margins in Pohlia scotica are narrowly
recurved from near the base right up to the
apex in most leaves (Fig. 2), whereas in Pohlia
drummondii and P. filum the margins are usually
plane or with just a hint of a recurved margin
in the lower half of some leaves. This character
is easily confirmed under the microscope. The
illustrations in Smith’s flora (2004) and also used
in the original paper, are good, showing the leaf
characters and habit quite well.
The habitat for all the records is fairly consistent
(Fig. 3), with the plant occurring in the fine
gravel that accumulates in the interstices of rocks
in the inundation zone of larger burns, lochs
and, in the case of the River Orchy, a large river.
This is a very dynamic habitat and one which
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Article
wFigure 2.The shoot tips of
Sematophyllum demissum
characteristically curve upwards and
away from the main colony mat.
D. A. Callaghan
Sematophyllum
demissum in Wales
Des Callaghan reports
on the status and conrFigure 3.The habitat of Pohlia scotica (large green cushion, lower middle), here in a gravel-filled pocket in granite slabs by a
large burn. G. Rothero
must change to some degree with every spate, so
it should be expected that Pohlia scotica will move
around. In this habitat it is often accompanied
by other ruderal and riparian species like Nardia
scalaris, Diplophyllum albicans, Pellia epiphylla,
Solenostoma hyalinum, Scapania undulata and
occasionally Pohlia drummondii. The largest and
probably most persistent population I have seen
is in gravel on the shallow margin of Loch Tulla,
right beside the A82; here the site is kept open
by the fluctuating loch level and the considerable
wave action. Although there is constant erosion,
the transport and re-deposition of gravel probably
occurs only over a limited area so bits of the moss
remain. Like the bulbiferous Pohlias to which it
is presumably related, it is a ruderal species but
it does not seem to have specialised propagules;
in one collection there do seem to be some
fragile deciduous branches but fragmentation in
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its harsh habitat is probably the main means of
persistence and spread.
Given its ruderal lifestyle, its widespread (if
apparently rare) occurrence in Scotland and the
frequency of its riparian habitat in upland areas,
it is difficult to believe that Pohlia scotica will not
turn up elsewhere in the British mountains and
in Scandinavia.
References
Crundwell, A.C. (1982) Pohlia scotica, a new species from the
Western Highlands of Scotland. Journal of Bryology 12: 7-10.
Smith, A.J.E. (2004) The moss flora of Britain and Ireland. 2nd.
ed. Cambridge University Press, Cambridge.
Gordon Rothero
Dunoon, Argyll, Scotland
e [email protected]
servation of one of our
rarest oceanic species
Introduction
ematophyllum demissum is a rare plant
in the British Isles, confined to Wales
(Caernarvonshire and Merionethshire)
and SW Ireland (North Kerry, South Kerry, West
Galway and West Cork), with a notable absence
from Scotland (Fig. 1). In Wales, it is considered
a national priority for biodiversity conservation
under Section 42 of The Natural Environment
and Rural Communities Act 2006 (as amended)
and is categorised as ‘Vulnerable’ on the national
Red List (Bosanquet & Dines, 2011).
The purpose of the present study is to
provide a review of Sematophyllum demissum in
Wales, with a particular focus on its status and
distribution within sites. This is largely based on
fieldwork that was undertaken over twelve days,
during 24 April, 26 April and 7-16 June 2014,
when S. demissum was searched for within areas
S
from which it has or may have been recorded
but for which recent information is lacking
or incomplete. The sites included Ceunant
Llennyrch (SH6639), Coed Gerddi-bluog
(SH6129), Cwm Bychan (SH6431), Ganllwyd
(SH7224), Garth Gell (SH6819), Hafod
Rhisgl (SH6552), Parc Hafod-y-llan (SH6250),
Pont Aberglaslyn (SH5946) and Tyn y Groes
(SH7323). Sites known to support the species
but which have been surveyed by the author
recently were not covered, including Coed
Crafnant (SH6128; Callaghan, 2014a), Coed
Graig Uchaf (SH6426; Callaghan, 2014b) and
Coed y Rhygen (SH6836; Callaghan, 2013b).
When the moss was found, a waypoint
was logged with a Garmin GPSMAP 62s
unit, providing a positional accuracy of about
5-10m in the present survey conditions. At all
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