Inter-intraspecific variation of chloroplast DNA of European Plantago spp.

Abstract

Inter- and intraspecific chloroplast DNA variation in four species of Plantago (P. lanceolata, P. major, P. media and P. coronopus) were analysed by comparing DNA fragment patterns produced by seven restriction endonucleases. Plant material was collected in seven European countries. Only 21.3 per cent of the 409 restriction sites were shared by all four species. Phylogenetic analysis, performed by constructing the most parsimonious trees, showed that genetic differentiation in cpDNA was very high among P. lanceolata, P. coronopus and the species pair P. media and P. major, which were more closely related. At the intraspecific level, four restricted site mutations were detected. Most of the variation was due to numerous small length mutations, one of which (70 bp) discriminated between the two subspecies of P. major (i.e. ssp. major and ssp. pleiosperma). This mutation was used successfully to show that, in Denmark, cpDNA introgression occurs from pleiosperma into major in the areas where the two subspecies grow together, whereas previous studies of the same subspecies in the Netherlands suggested introgression in the reverse direction. In P. lanceolata, five distinct types of cpDNA genome could be distinguished, one of these being widely distributed. Therefore, DNA variation was present both between and within populations. In P. media, three distinct cpDNA genomes were found, one being specific to diploid and tetraploid material from the Pyrenees, suggesting multiple origins of the autotetraploids in this species. Whereas cpDNA variation was observed in the two outcrossing species of Plantago (P. media and P. lanceolata) no variation was detected in the two autogamous subspecies of P. major. This suggests that chloroplast DNA variation may be related to nuclear genome diversity.