Sunday, 16 November 2014

Campylopus introflexus (Heath Star-moss)

Campylopus introflexus (Heath star-moss)

You may have ambivalent feelings for this alien bryophyte, but it is rather beautiful and it has a remarkable natural history in Britain. Its native range is in the southern hemisphere where it is represented in Australia, South Africa and South America. It was first recorded in Britain in Sussex  in 1941, perhaps arriving with horticultural imports. It remained unfamiliar to British bryologists in the 1950s -   it wasn't included in the first edition of Vernon Watson's 'British Mosses and Liverworts', but now it is one of the most common bryophytes in Britain, In fact in an article I wrote for British Wildlife a few years ago I suggested that it was the most successful alien plant in the British Flora. I still stick by that, because its range expansion in just 70 years is truly remarkable. How has it been able to do this?  Two of its attributes have given it an enormous advantage as a recent colonist. Firstly it has very wide ecological tolerance in terms of climate, soil reaction and substrate. It can colonise peat, gravel, coal spoil, mine spoil and, under suitable conditions, sand, slate and rock. It seems fairly indifferent to soil pH. In Denmark it is one of the most successful colonists on calcareous grey dunes. and, closer to home, it is one of the first colonists of the bare peaty ground that is exposed after Sitka Spruce is clear-felled or when heathland is burned. Secondly it has a formidable dispersal strategy. It often produces abundant fruit (even though it is dioecious) and the small spores (10-14 microns) are capable of dispersal over huge distances. As an example of this, plants had colonised the Faroe Islands before they were recorded in mainland Scandanavia. It has conquered western Europe and it is galloping across central Europe as we speak! And it has already made significant inroads into North America. Local dispersal is also very effective via broken leaf tips, a strategy not very different to that used by other Campylopus species.
Campylopus introflexus is a primary colonist capable of smothering large areas of bare ground, so I guess it must have an impact as an alien. But I'm not aware of any meaningful studies that have been undertaken to measure its affects on native bryophyte biodiversity. I love the way the capsules are buried in the leaves (again like other Campylopus species) and the fascinating movement of its hairpoints - when plants dry out you can watch it happening. I presume the deflexed hair points help to decrease the short-wave radiation load in hot weather. Who knows. Just because we can now land a fridge on a comet 350 million miles away, we shouldn't stop asking these little mossy questions.


  1. Fascinating stuff Charles, I never realised it was that recent an invader. I can add wood to your list of substrates. There was a colony on the salt-sprayed Pitch Pine decking of Mumbles Pier (laid in 1955) which I think has recently been replaced and it loves growing on coir rolls which are used as living revetment.

  2. In urban Cardiff it is quite scarce, but I've found it in small quantity in a few tetrads, with habitats including tree stumps in the city parks and the base of a Scots Pine tree. At Cosmeston it is common on the thatched roofs in the Mediaeval village.

  3. PS. You've not been investing in some macro kit by any chance - lovely photo.

  4. Really interesting that you've seen it on wood subject to salt spray Barry. That really does push it's ecological tolerance up a notch. What a plant!
    Yes, I used a 60mm macro for the shot, which is also cropped a bit. It's fairly standard kit for most of my bryo photos, including shots down the microscope.