Level and distribution of genetic diversity in the European species Nardus stricta L. (Poaceae) inferred from chloroplast DNA and nuclear amplified fragment length polymorphism markers

Abstract

The present level and distribution of genetic variation is defined by the interplay between gene flow, drift, inbreeding, mutations and selection and reflects both contemporary and historical processes (e.g. Pleistocene glaciations). Especially, the breeding strategy of a species is a dominant factor influencing the pattern of genetic diversity. In this study, using AFLP molecular markers and cpDNA sequences, I investigate neutral genetic variation of nuclear and chloroplast genomes of European populations of the grass Nardus stricta. The results of the present study indicate a lack of genetic variation in European N. stricta populations; there were no cpDNA variation detected and only the Austrian population had different AFLP pattern from other populations analyzed. In earlier studies, it has been suggested that N. stricta reproduces via agamospermy, and the observed lack of genetic variation strengthens this hypothesis about asexual reproduction in N. stricta. Also, given the lack of variation in both nuclear and chloroplast DNA it is likely that the present European populations of N. stricta come from one refugium only, but it is impossible to say which based on our data. However, nucleotide variability is not the only source of variation that results in phenotypic variation. Epigenetic variation might enable the wide geographical distribution of N. stricta and explain the observed lack of nucleotide variation. This might be interesting to investigate further. Even though AFLP is a high resolution technique, the resolving power of the techniques used should be carefully investigated. I strongly emphasize that these results are preliminary as they are only based on screening of a few populations. More populations need to be screened and possibly also more primer/restriction enzymes combinations before any conclusions can be drawn.