Monday, 15 June 2009

Dactylorhiza orchids

The main flush of Dactylorhiza orchids has appeared. These are always at their best when the lowest rank of flowers has just newly opened.

For years, there has been a huge debate about the number of species and descriptions of the species and hybridisation. It is known that they hybridise and back-cross, so I suggest that most specimens are an intermediate 'hybrid' amongst 3 key 'species' in our location: Common Spotted Orchid (CSO), Heath Spotted Orchid (HSO) and Northern Marsh Orchid (NMO). Given that these 'species' hybridise so regularly, I can't see any uncorrupted ones being possible, so I rather think that we are taking a few distinguishing characteristics and lumping individuals into one bucket or another, depending on what we see.

This one shows the main features of 'CSO'...tall spike, three very clear lobes to the base of the flower, very little frilling:

This one shows more influence of 'HSO', with much frillier lips and a slightly shorter spike.

This would appear to have some NMO influence...much darker markings and a still shorter spike:

I'll leave the next few to your own imagination.

The lower left flower in this specimen shows the nectar hole being clearly indicated by the purple lines, which act as a guide for insects. The hole suggests that these species need a long-tongued insect like a butterfly or bee to pollinate them. Pollination is carried out via the pair of brown pollinia which attach pollen to the back of the pollinating insect.

This last one, however, shows a nice feature. The flowers form 'upside down', and only then do they rotate to their final position.

That last one would be pure 'CSO' if it wasn't for the (very) short spike.

Late edit:

Gill mentioned in her comments that the inverted flower looks more developed than usual. This is true. A close look reveals that the 'lower' lip has developed too quickly and has jammed against the flower above it. This combination of features will prevent the flower from passing on any pollen, so this is the end of the line for that combination.


Gill said...

I've never seen one with the flower as fully open as that but still upside down** - I'd keep an eye on that spike because I suspect it may have a faulty "switch" and the flowers may well remain upside down, which will presumably confuse the insects!

** I believe in fact this is technically right way up and the mature flower is upside down, but that's semantics! Cerainly the flower stalk is twisted which is quite clear in some specimens.

Stuart said...

I took a closer look at the original shot, and the flower has jammed against the higher flower stalk. That flower won't pass its pollen on, so that's one little evolutionary attempt down the drain.

New picture added.

Gill said...

Nice spot.

"so that's one little evolutionary attempt down the drain" yes and no - I guess the other flowers on the same spike will be OK and have the same genetic make-up. Also, maybe some bees fly upside down :-)