This list is now in-complete because the BSBI have updated their database to include many more plants, which now includes about twice as many inter-genera hybrids (aka inter-specific) as before. But anyway, this list may change as taxonomists tackle the implied inconsistencies in taxonomy which inter-genera hybrids imply: the taxonomy is probably wrong. This list should not really exist at all ...
A cross-hybrid between two plants in differing Genera is shown with a large and leading cross, as in:
It may simply reflect a possibility that the species has been placed in the wrong Genus; several plants that hybridize but were previously in differing genera have been moved into the same genus. The species in this inter-genus category may subsequently be moved by taxonomists, but the Author suspects that it may never be possible to eliminate all taxonomic artefacts such as this without placing each species, all alone, into an entirely separate family. Doing so would thereby defeat the purpose of taxonomy: to classify into like-groups. The Author poses the reader a question: how would they chose to classify the touching strands of wool in a ball of cotton-wool into groups? The Author declares it almost impossible. The Author likens the relationships between different plants in an analogous way to a ball of cotton-wool (only in the case of plants, there is not just one parameter to classify [as in the 'touching strands'] but a whole plethora of diametrically-opposing parameters).
The enormous difficulty of the problem is reflected in the way that taxonomists regularly shuffle the species between genera and genera between families, often ending up placing one species into its very own genera all on its own and then placing that into a new family that they have just invented specifically for the very purpose; thereby having admitted defeat: unclassifiable (or possessing no known relatives).
The species name of inter-genera hybrids is usually a contraction of the Genus names of the two species in question; inter-genera hybrids between Dactylorhiza and Gymnadenia are called Dactylodenia. It seems that the names are chosen from bits of the genera names when the genera are arranged in alphabetical order, although where the red partial should end and the blue partial should begin seems entirely arbitrary unless you know the language latinogreek:-) Thus the 'D' of Dactylorhiza comes before the 'G' of Gymnadenia resulting in Dactylodenia (and not Gymnarhiza). Three genera and four-genera hybrids are likewise a mish-mash between 3 or 4 genera chosen from small sections of the genera names. Or so your Author thinks...
However, since Inter-genera hybrids are usually sterile, unable to propagate sexually (although they may spread vegetatively), this might put a spanner in the works for those taxonomists who think that the two genera involved should be amalgamated into just one genera, calling perhaps instead for a sub-genera to be introduced?
In fact, even hybridisation between differing plants in the same genera often results in either sterile or partially sterile hybrids. Sterile hybrids cannot reproduce again, so the process just stops there. But in some genera of flower, such as in Evening-primroses (and about a dozen other genera) the hybrids are fertile and can hybridise either with one another or back with either parent. This can produce so-called
The hybridisation process occurs by the same mechanism as between the same flowers: by transfer of pollen from anther to style. For some species either from the same flower, or flower to flower on the same plant, or from one plants' flower to another plants' flower; it can depend on the species we are talking about.
|BSBI DISTRIBUTION MAPS OF INTER-GENERA HYBRIDS|