GENETIC DIVERSITY OF MELICA TRANSSILVANICA SCHUR (POACEAE)AT ITS NORTHERN RANGE LIMIT

摘要

Geographically marginal populations are expected to have low genetic variability, which potentially can affect their viability. In Poland Melica transsilvanica Schur reaches the northern limit of its continuous geographical range. Genetic diversity and population genetic structure were analyzed in 15 of its marginal and more central populations using AFLP5. Overall, genetic diversity parameters did not differ significantly, and comparable pat-terns of genetic variation were found in central and marginal populations. All AFLP phenotypes were unique to particular populations. Unique alleles were fixed in some central and some marginal populations. The percent-age of polymorphic loci varied from 1.30 to 5.19 (3.24 average) in central populations and from 0.43 to 5.63 (2.36 average) in marginal ones. Hierarchical analyses of molecular variance (AMOVA) for each species/region combination revealed highly significant differentiation between populations and showed similar partitioning of molecular variance in marginal and central populations of M. transsilvanica (diversity between populations: 93.24% and 93.18%, p < 0.001, respectively). The scattered distribution of suitable species habitats and the pre-dominant selfing breeding system of the species strengthen the effect of selection pressure on fixation of unique loci in individual populations. Marginal populations of M. transsilvanica with unique alleles considerably expand the genetic variation of the species and are therefore valuable for conservation of genetic diversity.