Comparison of rRNA genotype frequencies of Parmelia sulcata from long established and recolonizing sites following sulphur dioxide amelioration

The variable internally transcribed spacer (ITS) regions of the rRNA gene cluster, and the termini of the large and small subunit genes, were amplified from 231 specimens of the lichen-forming fungus Parmelia sulcata from the UK and Spain. Amplification products comprised three distinct size groups of 580, 622 and 835 base pairs (bp). Analyses of the collections from England, Wales and central Spain established the 622 bp genotype as the most widespread, and the 835 bp genotype as the next most frequent. The size difference was due to a group I intron at the 3' end of the small subunit. The relative frequencies of the three genotypes were consistent between long established sites in Spain and the UK. The frequencies of the different size classes were examined in the vegetatively reproducing populations recolonizing following the amelioration of sulphur dioxide air pollution. Populations of P. sulcata from long established sites where sulphur dioxide levels are known to have risen and then fallen contained two genotypes. Populations from recolonising sites where P. sulcata had previously been lost consisted of a single genotype (622 bp). This technology provides a powerful tool for testing hypotheses relating to the individuality and population structure of lichens, and has implications for lichen conservation.