Interspecific hybridization as a source of new species in orchids of the genus Dactylorhiza

The Palaearctic genus Dactylorhiza includes 8 diploid,10 autotetraploid,and about 40 allopolyploid species. Most of the latter derived by multiple crosses in space and time between the diploid (2n=40) D.saccifera s.l. and either D.incarnata s.l. or D.euxina; they have 4x=80 and reproduce sexually (Allotetraploid Marsh Orchids,AMOs). AMO species are differentiated morphologically, ecologically and genetically, have distinct ranges and show different combinations of alleles from local races of their parental species. Hybridization between D.saccifera s.l. and D.incarnata s.l. also gave origin to a few allotriploid taxa, as yet undescribed, with apomictic reproduction and clonal structure. Other Dactylorhiza hybrid species originated from crosses between the diploid (2n=40) D.romana and D.sambucina. They include: 1) the apomictic allotriploid D.insularis (3x=60), which combines two genomes of D.romana and one of D.sambucina, and had a single origin in an Iberian hybrid zone; 2) the sexual allotetraploid D.cantabrica, which combines two genomes of each parental species, and had a single quite recent origin, as indicated by its very restricted range, much smaller than that of D.insularis. The ecological and evolutionary success of Dactylorhiza hybrid species is considered, with particular regard to their mode of reproduction, environmental adaptations, and competitive success