One of the characteristics of the Orchid family is their ability to hybridise - produce seeds whose parents are of two different species. Some can even hybridise with species from a different genus. However this hybridisation may not happen that frequently, and many hybrids are infertile - basically they are one-offs. When they do appear however they can lead to much discussion. Is it a hybrid or are the unusual features in a specimen merely within the extremes of variation of a species? Or what is its parentage? This is not always the case. Species of the genus Dactylorhiza seem to delight in hybridising with each other and producing a range of individual plants with features of the parents in varying degrees, and often the offspring are as fertile as the parents. The hybrids can then back-cross with one or other of the parents (introgression) producing a spectrum of features between the two parents. At Buckley Common there are both Common Spotted Orchids and Northern Marsh Orchids, and hybrids of those two; Dactylorhiza x venusta. This hybrid is fertile and in my estimation the population of pure Northern Purple Orchids is falling and the hybrids are not only increasing, but seem to favour back-crossing with the Common Spotted Orchids. The flowering times may be critical here. The NMO flower first but overlap with the CSO. During that overlap they can hybridise. The hybrids are flowering across the range of the flowering time. Now if the colours, scents, etc of those with CSO features are more attractive to insects the hybrids and the CSOs will be pollinated in preference to the NMOs, and the NMOs which are pollinated are just as likely to be fertilised by pollen from a hybrid as another NMO. Will the Buckley Common population end up solely as hybrids with CSO features?

One definition of a species says that a species is often simply defined as a group of organisms capable of interbreeding and producing fertile offspring. This seems to fall down with Dactylorhiza due to this hybridisation. Either that or we have the Dactylorhiza species all wrong.

To be continued