Genetic diversity of sterile culturedTrebouxiaphotobionts associated with the lichen-forming fungusXanthoria parietinavisualized with RAPD-PCR fingerprinting techniques

Abstract

AbstractPhotobiont diversity within populations ofXanthoria parietinawas studied at the species level by means of ITS analyses and at the subspecific level with fingerprinting techniques (RAPD-PCR) applied to sterile cultured algal isolates. Populations from coastal, rural and urban sites from NW, SW and central France and from NE Switzerland were investigated. Between 8 and 63 samples per population, altogether 150 isolates, were subjected to phenetic and ordination analyses. Epiphytic samples ofX. parietinaassociated with different genotypes ofTrebouxia decoloransbut saxicolous samples containedT. arboricola. For comparison theT. gelatinosaphotobiont of a small population ofTeloschistes chrysophthalmus(4 samples) was investigated. ITS sequences ofT. decoloransisolates from different geographic locations were largely similar. In all populations a surprisingly high diversity of genotypes was observed inTrebouxiaisolated from lichen thalli growing side by side. AsTrebouxiaspp. are assumed to be asexually reproducing haplonts, the genetic background of this diversity is discussed. Fingerprinting techniques are a powerful tool for obtaining valuable insights into the genetic diversity within the algal partner of lichen-forming fungi at the population level, provided that sterile cultured isolates are available.