I thought this was interesting — a post on the OrchidGuide Digest responding to the question about the very patchy distribution of orchid species in the wild.
“Along the gallery forest we found many species but always focally, meaning there were some kilometers, you could not see a single species, and then in another area at least 6-7 different species.”
Oliver Sparrow, a UK grower, had this to say:
“I have seen and written about the same phenomenon in the Himalayas. Some of it is the outcome of random events, but the statistics of our numbers suggested that this could not be the only reason. Two issues presented themselves:
1: Microclimate, which is particularly significant in the Himalayas, where areas tens of feet apart can get radically different conditions.
2: History, and specifically, the presence of “orchid trees” to seed the local environment. Essentially, one hub can seed many trees around it over the decades. As orchids always go for the topolimnon – the transition zone at the edge of things – they tend to be distributed linearly on a river bank, even though the seed distribution is a blob.
What I call ‘orchid trees’ are unusual old trees but not always big ones that are absolutely plastered with orchids, usually from several genera. One encounters these at random, and microclimate never seems an issue. I
guess at the following event. First, a creeper envelops the tree, bringing on a large number of shade-dwellers, such as ferns. The creeper dies, leaving a fern garden that is perfect as an orchid seed bed. Gradually, the ferns die away – or anyway fail to reproduce as well as when under cover – and the orchids are left as dominants.
It is also notable that some trees take countermeasures against epiphytes, by shedding bark discs and branches when the burden gets large. Such trees are usually orchid free, although neighbouring peers are heavily