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 c luster, and the termini of the large and small subunit genes, were amplifie d 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 Engla nd, Wales and central Spain established the 622 bp genotype as the most wid espread, and the 835 bp genotype as the next most frequent. The size differ ence was due to a group I intron at the 3' end of the small subunit. The re lative frequencies of the three genotypes were consistent between long esta blished sites in Spain and the UK. The frequencies of the different size cl asses were examined in the vegetatively reproducing populations recolonizin g 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 fr om recolonising sites where P. sulcata had previously been lost consisted o f a single genotype (622 bp). This technology provides a powerful tool for testing hypotheses relating to the individuality and population structure o f lichens, and has implications for lichen conservation.