Genetic structure in two meadow varieties ofEuphrasia stricta on the Baltic island of Gotland (Sweden) and implications for conservation

The annual hemiparasiteEuphrasia stricta occurs on Gotland in two early-flowering meadow varieties.E. stricta var.suecica is on the Swedish red-list as endangered, occurring in Sweden only on the Baltic island of Gotland. It probably has near relatives east of the Baltic proper. The other variety,E. stricta var.tenuis, has a wider distribution occurring almost all over Sweden, but is declining in abundance. Both varieties have close morphological similarities and habitat preferences, raising questions about which level conservation efforts should be focused on, varieties or populations. In this study we describe the genetic structure between and within these two varieties using amplified fragment length polymorphism, AFLP.F _ST between varieties is 0.14, and between populations within the varietiesE. stricta var.suecica and var.tenuis F _ST is 0.60 and 0.26 respectively. The partitioning of gene diversity to different levels shows that 14% of the genetic diversity occurs between varieties, 42% between populations within varieties, and 44% within populations. Significant genetic differentiation was detected between varieties, populations and subpopulations within populations using a constrained principal coordinate analysis. We suggest that all of the existing populations of these two varieties on Gotland should be preserved, since they are few (6E. stricta var.suecica and 5E. stricta var.tenuis) and much of the genetic diversity is partitioned between populations.