Starry breck-lichen (Buellia asterella)
|Size||Diameter: 10 - 15 mm|
Classified as Critically Endangered in the UK.
This particular lichen grows on chalky soil, forming small white rosettes with small black discs about 0.5 millimetres across on the upper surface. These are the spore-producing structures.
This species is found in Germany, France, Norway and Switzerland, but in the UK it is now known from only one site. This lies within the area of East Anglia known as Breckland, characterised by a low rainfall, and chalky, free-draining soils.
In Britain, the starry breck-lichen requires dry, sandy soil over chalk. It also needs a short, well-grazed open grass sward, preferably nibbled and disturbed by rabbits.
This lichen is one of many that grow on the surface of the soil rather than on a raised surface such as stone or on trees. Like most other lichens, it is slow-growing and needs a bare surface to form colonies.
This lichen has always been confined to the Brecklands of East Anglia where it was once found on four sites. Three of these had been disturbed by man's activities in the past. One was found on the site of 19th century flint mines, and on two, the ground had been disturbed by the digging of trenches to deter the landing of gliders during World War Two. It is now found on only one site, and may well be Britain's rarest lichen. It is believed a reduction in the rabbit population through myxomatosis and the ending of sheep grazing led to the loss of the open sward required by this species. On the main site, there is also a threat from pine seedlings, which are thought to have affected the microclimate of the site.
This lichen is listed in the UK Biodiversity Action Plans (UKBAPs), and is part of English Nature's Species Recovery Programme (SRP). A series of protective measures have been introduced to conserve this species and the unique habitat it grows in. A translocation of the lichen using transplanted plugs was undertaken on two sites away from the main one where conditions appeared favourable. So far, these transplants have survived, although they have not spread beyond the plugs. In the long term, it has been agreed that rabbit grazing be encouraged on these sites and the invasive pine seedlings be controlled. As the lichen also requires open ground, the turf has been stripped from several plots in the hope that it will re-colonise these areas over time, along with a suite of the mosses and rare flowering plants with which it is associated.
Information supplied by English Nature.
- Colonies: a group of organisms living together, individuals in the group are not physiologically connected and may not be related, such as a colony of birds. Another meaning refers to organisms, such as bryozoans, which are composed of numerous genetically identical modules (also referred to as zooids or 'individuals'), which are produced by budding and remain physiologically connected.
- Myxomatosis: a contagious viral disease in rabbits.
- Spore: microscopic particles involved in both dispersal and reproduction. They comprise a single or group of unspecialised cells and do not contain an embryo, as do seeds.