Summary• The chloroplast phylogeography of two peat mosses ( Sphagnum fimbriatum and Sphagnum squarrosum ) with similar distributions but different life history characteristics was investigated in Europe. Our main aim was to test whether similar distributions reflect similar phylogeographic and phylodemographic processes.• Accessions covering the European distributions of the species were collected and approx. 2000 bp of the chloroplast genome of each species was sequenced. Maximum parsimony, statistical parsimony and phylodemographic analyses were used to address the question of whether these species with similar distributions show evidence of similar phylogeographic and phylodemographic processes.• The chloroplast haplotypes of the currently spreading species S. fimbriatum showed strong geographic structure, whereas those of S. squarrosum , which has stable historical population sizes, showed only very weak geographic affinity and were widely distributed.• We hypothesize that S. fimbriatum survived the last glaciations along the Atlantic coast of Europe, whereas S. squarrosum had numerous, scattered refugia in Europe. The dominance of one haplotype of S. fimbriatum across almost all of Europe suggests rapid colonization after the last glacial maximum. We hypothesize that high colonizing ability is an inherent characteristic of the species and its recent expansion in Europe is a response to climate change.

No abstract

Propagule banks are assumed to be able to store considerable genetic variability. Bryophyte populations are expected to rely more heavily on stored propagules than those of seed plants due to the vulnerability of the haploid gametophyte. This reliance has important implications for the genetic structure and evolutionary potential of surface populations. A liverwort, Mannia fragrans, was used to test whether the bryophyte diaspore bank functions as a "genetic memory." If a diaspore bank is capable of conserving genetic variability over generations, the levels of genetic diversity in the soil are expected to be similar or higher than at the surface. Surface and diaspore bank constituents of two populations of M. fragrans were investigated. Genetic structure and diversity measured as unbiased heterozygosity were analyzed using three ISSR markers. Similar genetic diversities were found in the soil (H(s) = 0.067) and at the surface (H(s)= 0.082). However, more haplotypes and specific haplotype lineages were present in soil samples. The results suggest that the bryophyte diaspore bank has an important role in accumulating genetic variability over generations and seasons. It is postulated that the role of the diaspore bank as a "genetic memory" is especially important in species of temporarily available habitats that have long-lived spores and genetically variable populations.

Ecological factors affecting reproduction and dispersal are particularly important in determining genetic structure of plant populations. Polyoicous reproductive system is not rare in bryophytes; however, to date, nothing is known about its functioning and possible population genetic effects. Using the liverwort Mannia fragrans as a model species, the main aims of this study were to separate the relative importance of the components of the polyoicous reproductive system and to assess its consequences on the genetic structure of populations. High sex expression rates increasing with patch size and strongly female-biased sex ratios were detected. Additional input into clonal growth after production of sex organs was found in males compared to females. Similar clonal traits of the rare bisexual and asexual plants and preference toward newly colonized patches suggest that selection prefers colonizers that first develop organs of both sexes, hence ensuring sexual reproduction when no partner is present. Despite frequent spore production, ISSR markers revealed low genetic diversity, probably resulting from the effective clonal propagation of the species and frequent crossing between genetically identical plants. The presence of numerous rare alleles and unique recombinant haplotypes indicates occasional recombination and mutation. Effective spreading of new haplotypes is probably hampered however by large spore size. Since populations are small and isolated, such haplotypes are probably continuously eliminated by genetic drift. These results suggest that although both sexual and asexual reproductions seem to be effective, asexual components of the reproductive system play a greater role in shaping the genetic composition of the populations.

No abstract