Fast forward to 2016, and the situation has changed completely. In 2002/03 I started bryo recording in Brechfa Forest, discovering vast colonies of Colura on willows in the conifer plantations there. It proved to be widespread, and more or less ubiquitous in the upland-edge plantations of Wales, as Charles and Hilary are ably demonstrating in Neath - Port Talbot. However, it remains pretty scarce in Monmouthshire, and I have only seen it in VC35 on three occasions since that exciting day in 2001: twice in the west and once in the east. Graham asked me a couple of days ago whether it's still in the Yew Tree Wood, and I didn't know. Sure enough, it is - I revisited the site yesterday lunchtime and found Colura on several Ash trunks in the original area, alongside loads of Cololejeunea minutissima, Radula complanata and Metzgeria spp., plus a patch of Lejeunea cavifolia.
This rambling tale is a way of letting relative newcomers to bryology know how much things have changed, even during my bryological career!
'absence of evidence is not evidence of absence' or so they say. Is this a case of under recording or not recording in the right places or is it signs of a species that has been spreading? just s simple question from a newcomer !
ReplyDeleteMonmouthshire is pretty well recorded bryologically, albeit more in the 2000s than the 2010s: I have visited around 2/3 of the county's tetrads and have 'done' many conifer plantations. I'm sure that Colura is slightly overlooked in the county, but it's certainly nothing like as common here as it is in Charles' patch or in Carmarthenshire. This makes good climatic sense, because Colura is a desiccation- and frost-sensitive species that was until recently restricted to the ultra-Atlantic regions of Europe. It is spreading eastwards, but remains (almost) unknown in the southern half of England.
ReplyDeleteThere was an absence of evidence prior to 2000 though: south Wales was exceedingly under-recorded for bryophytes until then, and the apparent rarity of Colura was surely something of an artefact. Having said that, it has increased markedly in parts of Brechfa Forest in the last 10 years, so I suspect its initial colonisation (from Ireland) wasn't too long ago.
In her report, submitted in 1994, Martha Newton wrote 'C. calyptrifolia must be regarded as an extremely rare species everywhere except Western Scotland and Ireland, and this is certainly true of Wales'. I remember looking for it in the Nedd Fechan Valley in the late 1990s after reading that report (and not finding it) and then, later, Graham telling me that he and Sam had scrutinised an oak tree 'for some time' before they found it. H and I first saw it on some willows at the side of the River Neath in Glyn Neath, many years later - and with the same excitement that Sam describes. Sam's note in Field Bryology 82 (pp. 3-5) gives a very plausible explanation of the spectacular colonisation of Wales by this Hyperoceanic, southern temperate species - early pioneering colonisation by spores from Ireland finding suitable 'hyperoceanic' conditions in the vicinity of the constantly cool, humid conifer plantations. Neath Port Talbot has vast areas of contiguous Sitka forest which provide perfect conditions for Colura to exploit and spread, and there's lots of it there. So much so that local populations have gone way past the pioneer phase and are expanding their range with the force of their own propagule pressure. So, no longer limited by the arrival of long-distance propagules, the interesting question is how far will Welsh Colura go? In Neath Port Talbot it is not confined to conifer forests but is also found on trees near waterways. It will grow on almost any species of tree or shrub. H often finds it on heather. It will also grow on other surfaces (e.g. glass).
ReplyDeleteNo less phenomenal than the spread of Colura is the spread of Cololejeunea, which appears to be spreading further and wider.
Still seems to be rare in the Swansea area, though I'm sure more effort checking conifer forests would yield more records. Just checked and of the 264 records I have for Glamorgan, 240 have been provided by Charles and Hilary!
ReplyDeleteI've still not found it around Cardiff, perhaps not surprising given its apparent scarcity in Monmouthshire.
ReplyDeleteCharles - do you know whether those populations on willows along forestry rides survive when the Sitka is clear-felled?
That is a good question George, although I can't answer it from experience. As Sam has already said, Colura does not tolerate desiccation or frosting, and clear-felling might expose plants to those conditions, so you might think that colonies would then suffer. But, in very large plantations, the effect may not be as severe. Also, if the south Wales climate is becoming more hyperoceanic and, at the same time, if our Coluras are adapting to a new biogeographical range, then we may find them tolerating more exposed conditions. In that respect, the collection of bryophyte distribution data in south Wales, which we are all contributing to, is of great scientific value.
ReplyDeleteThanks for the nice answer Charles. Hopefully in time some re-surveys of known Colura trees in clearfell areas will provide some direct evidence as to whether they survive it, or not.
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