Status of the fungus Parmelina quercina/carporrhizans in Great Britain

This project assesses the occurrence and distribution of two lichen species in the UK that were separated by molecular data and are of conservation concern.

Lichenized fungi (lichens) are sensitive to environmental change and are therefore used as bioindicators for monitoring the effects of air pollution, analyzing ecological continuity, and other applications. The appearance of species not previously known in Britain as well as the response to climate change of lichens with restricted distribution are relevant issues for conservation and site management.

In the lichen genus Parmelina, three species are listed for the British Isles (Smith et al. 2009, Lichens of Great Britain and Ireland): P. carporrhizans (=P. quercina), P. pastillifera and P. tiliacea. Parmelina carporrhizans is considered to be a rare species with a restricted distribution in coastal areas of Great Britain; in the last 50 years it is known only from the south and southwest of England, extending north on the west coast to the middle of Wales (Seaward 1995, Lichen Atlas of the British Isles). Consequently, P. carporrhizans is of conservation concern and is included on the UK BAP (Biodiversity Action Plan) list of priority species.

In the 1996 Red Data Book for British Lichens, and in the recent 2010 Red Data List for Wales, P. carporrhizans is categorized as “vulnerable.” Although it is still listed in 38 of the 10x10 km squares of the British Ordinance Survey, since 1960 it has only been recorded in 21 of these. A recent decline has been noted in some areas in southwest England and it is apparently extinct in counties east of Devon (Hampshire, Isle of Wight, Surrey, Sussex, Kent). The population density is also skewed, with 25% of its British population occurring at the northern edge of its range in Wales. Factors contributing to its current distribution and population numbers include climate change, historical sulphur dioxide pollution, and present day increases in nitrogen deposition.

Recent molecular work has called into question the synonmy of P. carphorrhizans with P. quercina, raising the possibility that both occur in the UK. Using DNA evidence, morphological characters, and distribution patterns, Argüello et al. (2007, Biol. J. Linn. Soc. 91: 455-467 and Lichenol. 39: 397-399) demonstrated that European collections of P. carporrhizans/quercina consist of two genetically distinct lineages, recognizing P. carporrhizans and P. quercina as separate species. However, an updated checklist of British lichens excluded P. quercina from the British Isles (Hawksworth et al. 2008, Lichenol. 40: 1-21), even though no British specimens were used in the study by Argüello et al.

In this project we will re-examine all available British vouchers of P. carporrhizans and P. quercina using both morphology and DNA analysis to determine which of these species is present in the UK. We will assess recent and historical distribution patterns of P. carporrhizans/quercina in Britain to evaluate possible response to climate change and other environmental factors. The results will contribute to the accuracy of the Checklist of Lichens of Great Britain and Ireland (published by the British Lichen Society) and inform conservation assessment and management plans for this priority BAP species.