Reproductive isolation between hybridizing orchids

The potential for gene exchange between species with different ploidy levels has long been recognized, but only a few studies have tested this hypothesis in situ and most of them have focused on not more than two co-occurring species.

De hert et al  examine hybridization patterns in three species of the genus Dactylorhiza (Orchidaceae; diploid D. incarnata and D. fuchsii, and allotetraploid D. praetermissa). Morphometric and molecular analyses indicate that the majority of hybrids are F₁ hybrids.

Crossing experiments show strong post-zygotic barriers and high sterility of the hybrids; however, the presence of triple hybrids indicates that in some cases hybridization may extend the F₁ generation.