The first attempt to artificially hybridize species of Potamogeton resulted in the hybrid P. perfoliatus × P. gramineus. The morphological features, reproductive behaviour and molecular markers of the offspring of this experimental hybridization were compared with those of the parental species and natural hybrids of the same assumed parentage. A phenotype corresponding to that of the natural hybrid P. × nitens was acquired from an experimental cross between P. perfoliatus and P. gramineus. All plants, both natural and artificial, of this hybrid were consistently sterile. They showed the ITS variants of both parental taxa, which is consistent with biparental inheritance of nuclear DNA. The experimental hybrid was used to test the maternal inheritance of chloroplast DNA in Potamogeton. Sequences of a chloroplast intergenic spacer (rpl20- rps12) were identical with those of the female parent. Then, the directions of the crosses resulting in the natural hybrids were investigated. Of five natural populations of P. × nitens, P. gramineus was the maternal parent of two and P. perfoliatus of three populations. The frequency of hybridization events and rise of hybrids are discussed.
The phylogeographical structure of the temperate shrub Rosa pendulina at 45 locations in Europe was studied using sequencing of a non-coding cpDNA region (trnL-trnF). Our study revealed a clear geographic structure of cpDNA haplotypes. Three main haplotypes were geographically widespread, but showed little overlap in their distributions, suggesting that postglacial expansion occurred from at least two distinct glacial refugia, probably located (1) at the edge of the Alps, N Apennines or Dinaric Alps, and (2) in the Balkan Peninsula or S Carpathians. All populations at locations in the Czech Republic and surrounding regions are of Carpathian origin. This finding disproved an Alpine origin of R. pendulina populations in the Šumava Mts (Czech Republic). A contact zone between Carpathian and Alpine migration routes of R. pendulina is probably located in the Danube valley.