Systematics of polyploid Dactylorhiza (Orchidaceae) - genetic diversity, phylogeography and evolution

Abstract: This thesis examines genetic variation in allotetraploids of the Dactylorhiza incarnata/maculata polyploid complex in different parts of Europe. The molecular markers used were AFLPs, allozymes, ITS, nuclear microsatellites and plastid DNA markers. The results showed that the Alps and Greece have served as refugia for the genus during Pleistocene glaciations. Immigration routes of D. majalis ssp. lapponica into Fennoscandia after the last ice age were described. One wave of immigration reached Scandinavia from the south and one from northeast via Finland. Gotland was recolonized from the east. A meeting zone was detected in northern Scandinavia. No genetic markers could clearly divide the allotetraploids of the complex into groups according to their current taxonomy. All allotetraploid derivatives should be considered as subspecies of D. majalis. Further, no markers separated the morphologically confluent “traunsteineri”, “lapponica” and “russowii”, and they were accordingly combined as: D. majalis ssp. lapponica. Greek allotetraploids should be treated as regional or local variants of D. majalis ssp. cordigera. The levels of genetic diversity in the allopolyploids were as high as in the diploids. In addition, unique alleles and haplotypes were found among the polyploids. Allotetraploid Dactylorhiza includes lineages retained from both old and new polyploidization events. Introgression involving both parental lineages was detected, as well as recent and old hybridizations between polyploid lineages. Finally, evidence of diploidization in the allotetraploids in terms of intergenomic recombination and gene conversion was found.

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