Friday, 28 November 2014

Cololejeunea and Colura in Glamorgan

Cololejeunea miutissima (Minute Pouncewort), Afan Forest

After reading Graham's excellent update on Breconshire bryophytes, and particularly his comments on Cololejeunea minutissima, I thought it might be a good idea to review the apparent, current status of these two liverworts in VC41, at least according to Map Mate records.
Hilary and I encounter Cololejeunea quite a lot in NPT, and it's beginning to look as if it is distributed widely in the county. The apparent gaps in its distribution are probably more a reflection of recorder effort than anything else. You are as likely to see it on a tree in a park as on willow in a conifer plantation and I think we should look for it in every tetrad.

Cololejeunea minutissima is easy to identify particularly when it's in fruit. The perianths resemble the heads of a small Phillips screwdriver (fairly clear in photograph above). But even when it's not in fruit, the dense clusters, sometimes forming little mounds, are very distinctive. The rise and rise of this species in South Wales is very significant.
The rise and rise of Colura calyptrifolia is also significant.

Much of the distribution of Colura shown in the map above corresponds with the distribution of Sitka Spruce plantation in NPT. Sam's highly plausible theory that mature conifer forests provide the cool, moist conditions that this hyperoceanic liverwort enjoys, and also have acted as very effective traps for spores than have rained in on westerly weather fronts, goes  a long way in explaining the phenomenal expansion of this species' range in South Wales. Hilary searches diligently for Colura almost everywhere we go, so the gaps in its distribution in NPT at the very least suggest that it is rarer in lowland squares away from plantations. The exception seems to be areas in the vicinity of Crymlyn Bog and the nearby Tennant Canal where it occasionally grows on willows. It's apparent rarity in Gower is interesting; Barry tells me that he has searched for it, without success, in suitable places. In contrast, Cololejeunea minutissima, another hyperoceanic species, seems to be more common in lowland areas and its distribution does not correspond specifically with the occurrence of conifer plantation.
As the density of Colura increases in and around plantation areas, the increased propagule pressure may  generate a second phase of expansion. This may already be happening in areas of mid and east Glamorgan. 
Colura is often found on willows, particularly Salix cinerea, but it can be found on virtually any tree (conifer or hardwood, including Buddleja) in suitable locations. It also grows on Ulex spp., Calluna vulgaris and Vaccinium myrtillus in NPT, which are common hosts for it in Ireland. It has even been recorded growing on glass.
As the data base of records for South Wales bryophytes increases, I think it will reveal some very interesting and detailed patterns in the distribution of species like Cololejeunea and Colura. Since they are both bellwether species, whose current range expansions are indicating significant changes in our climate, we shouldn't underestimate the wider value of our efforts. 


  1. I fully agree that our data are really valuable, but the lack of baseline data is a slight problem. Nobody recorded in NPT plantations until you! My only potentially useful observation was in the Afon Pib valley in Brechfa Forest where I got Colura new to VC44 in 2003. I returned in 2013 and I'm sure there was a lot more: 1000s of tufts on every willow rather than 100s on a few. However I didn't note the abundance precisely and my perception may have have changed. I have no doubt there has been a phenomenal increase though, even in the last 15 years.

    The Atlas, published today I believe, shows many epiphytes increasing on a national scale. These observations are more robust, but even with them there are few instances where a site was really well recorded pre and post the changes.

  2. C. minutissima is certainly common around Cardiff, even in urban woodlands. I've yet to record Colura in my local area, but as I have yet to visit the conifer plantations on the north Cardiff ridgeway this isn't surprising.

    The increase in epiphytes in the last couple of decades does seem really remarkable. The Flora of Glamorgan says of Cryphaea heteromalla " a few scattered localities..." and now it is on almost every mature Norway Maple, Sycamore and Ash in Cardiff.

  3. We may not have the baseline data for Colura Sam, but at least we know that mature conifer plantation is a relatively recent phenomenon in South Wales. A tenuous link perhaps, but hopefully our data will eventually be good enough to generate good coincidence maps. The general increase in epiphytes is also really interesting and l'm looking forward to seeing the new atlas. I suspect that cleaner air has at least played a part. George's comment on Cryphaea heteromalla is very apt and I would also include Ulota phyllantha among the local cohort of epiphytes that appear to be increasing in abundance. Several lichen epiphytes have also exhibited a similar renaissance to my mind, Flavoparmelia caperata, Parmelia perlata and Ramalina fastigiata to name just a few., but most would attribute that to lower levels of sulphur dioxide in the atmosphere.

  4. Radula was also described as rare in Roy's Flora. It and Cryphaea are too obvious to have been missed if they were anything like as ubiquitous as they now are. I am certain there has been change, and have written about that in Field Bryology.