Good question! I asked one of my fluent Spanish speaking Dragon Fruit growing friends for help.
This was the best answer:
Dear Richard,
If I am not wrong, the consensual name for all the formerly called "Selenicereus megalanthus" is, since 2003, Hylocereus megalanthus ( its genetic proximity to the genus Hylocereus is much greater than with the genus Selenicereus).
Hylocereus triangularis, formerly cereus triangularis, or cactus triangularis, is an old name for hylocereus that has been widely applied in Latin America, France and Spain, especially to the yellow pitaya, but also to other clones of almost any subspecies (including the undatus). Britton et Rose designates as Hylocereus triangularis a subspecies of Jamaica that coincides descriptively with what is currently agreed Hylocereus trigonus.
Anyhow, taxonomy is a young science, and sometimes is a bit arbitrary... Maybe we need a botanist in the group :_).
In relation to Palora, it is a natural ecotype captured by Félix Zabala Haro in the jungle of the same canton (Morona Santiago province), and is very close to another yellow pitaya ecotype called, in Ecuador, "Pichincha" that is more similar to the Colombian pitaya but more productive and resistant to diseases. From northern Ecuador to northern Perú there are who knows how many wild ecotypes still to "domesticate". Many of them are spontaneous Megalanthus hybrids or retrohybrids with economic potential...
My theory about Palora is that it is a spontaneous retrohybrid. The slight wax coverage of the stems, its greater resistance and habit of vigorous growth, and its morphological similirarity makes me think that has yellow costaricensis genetics (less known but morphologically very similar to Cebra, orejona, etc).
When INTA starts its program of sellection of superior Costaricensis, the yellow clone in the essay was discarded in the process of selection because it loses the production trial (the winners were Cebra, Orejona, Lisa, Rosa and San Ignacio). But the yellow costaricensis are not difficult to find in Central America. And due to the total genetic compatibility, the migration of genes with the ability to improve the vigor and sun resistance of the megalanthus does not seem impossible.
Anyhow, the megalanthus are still a quite unknown genetic group. Probably, in the coming years, new megalanthus will emerge in the markets. Peru has yellow and red giants, Brazil has a yellow giant, etc...
Pitayaworld is an exciting universe ....
Ps: I'm sorry my english
Bauernhoff Drachenfrucht