Friday, 13 May 2016

Green-winged and Early Purple Orchid - Questions, questions.

It has been an orchid week; I seem to have spent almost every moment looking at Green-winged orchids (Anacamptis morio) and Early purple orchids (Orchis mascula), but ended up with a several questions about their ecology and more. 

Today at Leafield, I looked at around 150 GWO in 2 separate pastures, looking at the colour variation, and preparing to get data on fruit set efficiency.   I counted the number of flowers on the spike of roughly 40% of the population - average 5.7, std dev around 2.0. One group were on a steep bank, the other on a more gentle slope, but there was no statistical difference between average number of flowers of the two groups. I will go back in around 6 to 8 weeks to count developing seed pods; literature suggests that because GWO provides no reward to pollinators then seed set efficiency will be low.   (That's the first question).  In fact I found very few pollinia had been removed, though they only came into flower a few days ago, and the bursicle (i.e. pouch) surrounding the pollinia was quite tough and difficult to burst; I did manage to extract one pollinia using my pen, but it was a struggle.   (The second question: is there an opportune time for pollinators to visit, perhaps well into flowering?)

GWO - Pollinia partly detached, Leafield
GWO Pollinia
GWO Pollinia removed, Leafield
At Leafield I found just a single white GWO variant (0.7% of the total), and one pinkish plant.   Elsewhere I estimated 1% at Bernwood Meadow in Oxfordshire, and Wink's Meadow in Suffolk, but found none at Martin's Meadow in Suffolk.   Sampling is an issue because they seem to grow in clusters; my method was to follow a path and count all the orchids within 1 metre of the path to avoid bias towards cluters or otherwise.  As an aside why is everyone drawn to the white and pale variants?  (That's not a question for follow up, just an observation!)

GWO - White variant

I went to Martin's Meadow because it is unusual in having populations of both EPO and GWO intermingled (co-location might be expected to be more common because they have similar habitats - EPO possibly tolerates shade, and might favour edge of woodland more).  Orchids are often promiscuous (for example Monkey and Lady orchid hybridising at Hartslock in Oxfordshire)but in the case of EPO and GWO  there is only one record of a putative hybrid between them since 1970 in the UK, according to 'Hybrid Flora of the British Isles' (Stace et al) .  Despite being taxonomically close and with non-specific pollinators the pollen of one does not pollinate the other.  (Another question, why, but fortunately quite a lot of literature on the subject).   

GWO - Bernwood Meadow

GWO - Bernwood Meadow

Mixed Populations of EPO and GWO (one plant shown, foreground), Martin's Meadow

EPO - Sidlings Copse

EPO - Sidlings Copse

Unsurprisingly, I found no hybrids at Martin's Meadow, and the warden there, Paul, has never seen any either.   The closest I came was a very robust EPO plant (the largest on the reserve) with it's usual colouration and all the other EPO traits except that the leaves were unspotted. It had not GWO traits.   I did find out that it can be very wet in Suffolk, and that my boots ship water.

Finally I am laying claim to a new GWO variety - Janus, for obvious reasons.

GWO var. Janus (!)

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