Several weeks ago I talked about a fascinating plant parasite called Ghost Pipe. Here’s another, Indian Pipe, which derives nutrients from mycorrhizal fungi with which it is found. Although both of these plants belong to the same phylum, they occupy different plant orders. Ghost Plant belongs to a group which includes tea, blueberry, and azalea while Indian Pipe is a close relative of herbs such as mint, basil, and rosemary.
In a genealogical sense, these plants are only as closely related to each other as placental mammals are to marsupials. Although I cannot tell you how long ago their common ancestor may have lived, I am certain that it was photosynthetic and not an achlorophyllous parasite. So, parasitism evolved, independently and de novo, in each line. It is surely an effective way of making a living and there is every reason to expect the niche to have been exploited by species from vastly different groups. Plant form is constrained by the chemical and physical nature of life on this planet. That two, unrelated, forms should express the same solution to the complex question of survival is to be expected. It is simply an outcome of first principles.