Genetic variation in relation to substratum preferences of Hypogymnia physodes

• Genetic variability and its relationship to substratum preferences within and among populations of the sorediate foliose lichen Hypogymnia physodes was investigated using sequence variation in the complete nrDNA internal transcribed spacer (ITS) region. A few samples of the putatively closely related, sorediate, H. tubulosa were also included. Samples were collected from each tree species in study sites in Estonia, Finland, and Sweden. In total, DNA sequences from 104 individuals of H. physodes and 16 of H. tubulosa were obtained. A group I intron situated at the end of the small subunit (SSU) of the nrDNA was detected in both species. Within-species variability was observed in both species: fifteen haplotypes were found for H. physodes and seven for H. tubulosa for the combined alignment of the intron and the ITS. Possible recombination within the total gene fragment was detected and hence the different regions (intron, ITS1, 5.8S, ITS2) were analysed separately. They show a different degree of variability both between each other and between the species. The number of haplotypes of H. physodes in the four regions are 5, 5, 1, and 5 and for H. tubulosa 5, 2, 1 and 2, respectively. A statistical parsimony estimation resulted in two unconnected networks; one containing all the samples of H. physodes and one containing all H. tubulosa samples. It was not possible to show different potentials of the different haplotypes for establishment on different substrata as the network of H. physodes indicates recombination within the ITS region which may be frequent enough to make this primarily clonally reproducing species to behave like a sexual species.

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