["Pollinator specificity to a flower is akin to parasite specificity to a
host. Although there is a naturally selective trend toward greater
specificity, in the long term obligate relationships fail."]
Some idle speculation on my part (with no claim to any truth; just a desire to continue discussion):
While pollinator specificity does seem to cause vulnerability in species that have evolved it to a high degree; existing environmental conditions drive natural selection. So should a pollinator become extinct, it is only then that the vulnerability becomes an issue. Evolution is driven by specific pressures, not by speculation, possibility, or efficiency. Some traits are rendered valuable by the preexistence of other traits. Were consolidated pollen to have evolved in orchid ancestors for example, it may well have predisposed orchids towards some level of pollinator specificity (sort of like the chicken and the egg, which came first).
That orchids may exhibit specificity in their native habitat, but require only a pollinator of a particular size when cultivated is clear (my Prosthecia vittelina generally has most of its flowers pollinated, much to my dismay; and my Epidendrum fimbriatum, Nageliella purpurea and several Pleurothallids are successfully pollinated from time to time despite the small size and complex shape of the flowers).
In a stable environment, it does not seem as if there would be any reason for selection to minimize obligate relationships. Were this so, how would strategies such as pseudocopulation have evolved? Wouldn't all Angraecums have the shortest possible spurs, rather than long ones?
[' "Hyperspecialisation" is an
adaptive phenomenon that is probably being observed within a narrow
window of ecological/evolutionary time and is limited to only a few
orchid lineages (in this case, as other examples occur throughout other
groups of organisms).']
All species are observed within a narrow window of ecological/evolutionary time, and all are in some sort of flux. Individual species may well have a natural life span, given that everything else in the universe seems to, even the universe itself.
["Similarly, all of the species of a family (e.g., Orchidaceae) share a
basic degree of relatedness that may or not be expressed among
different groups of species. Indeed, consider the pollination
syndromes, where there are trends of selection for certain kinds of
pollinating capabilities: moths, bees, beetles, birds, bats, etc. I
think that these would illustrate the "brand loyalty" trend that you
are considering."]
Some genera seem to have pollinator type as the basis for their relatedness (i.e.. Ophrys, Porroglossum, Pleione, and many others). Other genera seem to show a broad range of pollinator types (i.e.. Epidendrum, Masdevallia, Dendrobium and others).
Pollinator specificity is one of the great (and endearing) aspects (or myths) of the Orchid family, and a great topic for speculation and research. Even if it turns out that most species do not exhibit any sort of fidelity, where it does exist it is pretty amazing.
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