Genetic diversity in the rare orchid, Gymnadenia odoratissima and a comparison with the more common congener, G-conopsea

Patterns and levels of genetic diversity may have significant influence on the long term persistence of local populations and revealing such information is important in protecting rare species. In this study we investigated the genetic pattern in five microsatellite loci within five Swedish populations of the rare orchid species Gymnadenia odoratissima. The geographic distribution of G. odoratissima is restricted to Europe and in Scandinavia it is only found in three provinces in southern Sweden; Ostergotland, Vastergotland and on the island of Gotland. Compared with the more widespread congener G. conopsea our results indicate lower levels of genetic variation within and higher degrees of genetic differentiation among populations of G. odoratissima (H-EL = 0.6-0.8 in G. conopsea and 0.3-0.7 in G. odoratissima; F-ST over all populations = 0.06 in G. conopsea and 0.19 in G. odoratissima). Also, we found a clear distinction among mainland and island populations of G. odoratissima where populations on the island of Gotland seem to exhibit higher levels of gene flow and intragenetic variation, probably as a result of a larger number of existing populations. Future conservation of this species should focus on facilitation on colonisation events, especially on the mainland, and preservation of the genetically more variable Gotland populations.