Lighthouse Island has already been the subject of fairly comprehensive lichen surveys (Seaward 1997, Simms in press), with 120 species recorded to date. However, Mew Island (Grid ref. 33/6086), the most westerly of the three Copeland Islands, has not previously been visited by a lichenologist. Furthermore, it lies almost entirely in a different 10km square from the other two islands and hence is of significance in the context of the British Lichen Society's long-running lichen mapping project. Aside from this the island's lichen flora is of interest as a self-contained entity and also for comparison with the more habitat-diverse Lighthouse Island. A 4-hour visit was made to the island on July 7th 1999 to survey the lichens. The weather was mild but overcast with light rain, though this did not greatly affect the survey. Geologically, Mew Island is very similar to Lighthouse Island, comprising near vertical beds of Ordovician greywacke and slatey siltstone with the same southwest-northeast strike as prevails across the region. Topographically, the island is very subdued, rising to less than 10 metres above O.D. at its north-east end adjacent to the light house buildings. Although rock exposures are abundant, none of the crags are more than 2-3 metres high. The island is dissected by several narrow tidal channels, presumably eroded along minor faults. The absence in recent years of rabbits or sheep has led to the growth of rank grass, bracken and brambles which are encroaching on many of the smaller crags. Seaweed growth in the intertidal zone is luxuriant and so several of the characteristic intertidal lichen species proved difficult to find. Lichen growth is most luxuriant on the rock exposures immediately above high water, where waves prevent the establishment of a significant soil cover or the encroachment of scrub vegetation.
At the north-east end of the island are numerous buildings associated with the lighthouse. These are mostly in good repair and hence offer few additional habitats for lichens. There are several fairly extensive concrete walkways which cross the island between the lighthouse buildings and landing stages on the north, north-east and south-west corners of the island; these support a number of mildly calcicolous species not otherwise present on the island. The opportunities for corticolous and lignicolous species are very restricted. Wooden railings on a small bridge crossing one of the tidal channels are too recent to have been colonised by any lichens yet, while the few pieces of wood found elsewhere also did not support any lichens. A few small sycamore saplings (Acer pseudoplatanus) are present in a small hollow a short distance south-west of the lighthouse buildings but yielded only two epiphytic species. A total of only 59 species was recorded, barely half that of nearby Lighthouse Island. To a significant extent this may be due to a markedly lower habitat diversity on Mew Island. As already mentioned, there are virtually no opportunities for corticolous or lignicolous species. The significantly lower relief of Mew Island is also a factor, with several species found on the crags of Lighthouse Island being absent from Mew. Even in the intertidal zone, the recorded diversity is lower while there appears to be a much denser cover of algae.
Total species list:
Acarospora fuscata locally common in supralittoral Anaptychia runcinata abundant in supralittoral Aspicilia calcarea locally common on concrete Asicilia leprosescens common on supralittoral bird-perch rocks Caloplaca citrina on mortar Caloplaca crenularia concrete, presumably on non-calcareous clasts Caloplaca flavescens on concrete Caloplaca marina abundant in supralittoral Caloplaca thallincola common in supralittoral Caloplaca verruculifera common on supralittoral bird-perch rocks Candelariella aurella on concrete Candellariella vitellina common on supralittoral bird-perch rocks Cladonia chlorophaea in crevice in supralittoral Cladonia furcata at margin of grass and rock Collema auriforme on concrete Collema crispum on concrete Collema tenax on concrete Diploicia canescens occasional on nutrient-enriched siltstone Graphis scripta on Acer pseudoplatanus Lecanora campestris on concrete and in supralittoral Lecanora crenulata on concrete Lecanora dispersa abundant on concrete Lecanora gangaleoides occasional in supralittoral Lecanora helicopsis abundant in supralittoral Lecanora muralis locally abundant in supralittoral Lecanora poliophaea locally common in supralittoral Lecanora polytropa common in supralittoral Lecanora rupicola abundant in supralittoral Lecidella asema abundant in supralittoral Lecidella elaeochroma on Acer pseudoplatanus Lepraria incana at margin of grass and rock Lichina confinis occasional in intertidal Ochrolechia parella abundant in supralittoral Opegrapha saxatilis concrete on wall Parmelia fuliginosa common in supralittoral Parmelia perlata occasional in supralittoral Parmelia saxatilis occasional in supralittoral Parmelia sulcata occasional in supralittoral Pertusaria pseudocorallina abundant in supralittoral Phaeophyscia orbicularis on concrete Physcia adscendens occasional in supralittoral Physcia caesia locally abundant in supralittoral Physcia tenella occasional on wall Porpidia cinereoatra occasional in supralittoral Pyrenocollema halodytes occasional on barnacles in intertidal Ramalina cuspidata common in supralittoral Ramalina siliquosa abundant in supralittoral Ramalina subfarinacea abundant on greywacke near light house Rhizocarpon geographicum occasional in supralittoral Rhizocarpon richardii occasional in supralittoral Scoliciosporum umbrina on concrete Tephromela atra abundant in supralittoral Toninia aromatica occasional on concrete Verrucaria macrostoma var. furfuracea occasional on concrete Verrucaria maura abundant in intertidal and low supralittoral Verrucaria mucosa common in intertidal Xanthoria candelaria locally common in supralittoral Xanthoria ectaneoides abundant in supralittoral Xanthoria parietina abundant in supralittoralA number of species which are common on Light House Island are inexplicably absent from Mew. Although a specific search was made for a number of these taxa, it is still quite possible that they have merely been overlooked. They include the following species:
Buellia aethelea Buellia stellulata Buellia subdisciformis Lecanora actophila Parmelia caperata Parmelia loxodes Porpidia tuberculosa Rhizocarpon obscuratum Trapeliopsis granulosa.
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