Epsilon Open Archive

Abstract

Genetic diversity is a prerequisite for evolutionary change. The conservation of genetic diversity within species is therefore important in order to ensure the potential for future adaptation in a changing environment. Genetic variation for traits of adaptive importance may be measured by observation of phenotypic variation in common garden experiments. Genetic variation can also be assessed using molecular markers. Ulmus laevis Pall. is a broadleaved riparian tree with a central and eastern European distribution. Ulmus laevis populations tend to be small, and many are thought to be at risk of losing genetic diversity via random drift. The aim of this study was to assess the amount and distribution of variation in U. laevis populations, using both quantitative and molecular genetic approaches. Five U. laevis populations from the north and west of the species range were included in a common garden experiment in which quantitative adaptive traits were assessed over two growth periods. Considerable genetic diversity was recorded, both among and within populations, and the populations also varied in the amont of genetic diversity they possessed. Three of the same populations were included in a phytotron-based experiment to test the effect of drought stress on the expression of quantitative genetic variation. Treatment effects were relatively small, but the genetic variation recorded within populations and families again appeared substantial. For the analysis of molecular genetic variation, two molecular marker systems were used: nuclear microsatellites and chloroplast DNA PCR-RFLPs. Microsatellites were developed for U. laevis and tested for utility in other Ulmus species. Seven populations were assessed using the two marker systems. Moderate levels of population differentiation were observed for the microsatellite loci. Chloroplast DNA diversity in the study area was very low, with only three haplotypes observed across all populations. A broad concordance was observed between allelic richness at the microsatellite loci, and the level of quantitative genetic variation within populations.