There are an estimated 352,000 species of flowering plants, known as angiosperms. There are more than 1,000 species of gymnosperms, with conifers predominant amongst them. Thus, it should come as no surprise that parasites occur more frequently among flowering plants: 3 to 4,000 species suffer from them. Conversely, only a single parasitic gymnosperm is currently known.
It was discovered, a few decades ago, in the forests of New Caledonia. Its host is a fellow-member of the same conifer family as the parasite, the Podocarpaceae, Southern Hemisphere conifers. The host is the Falcatifoium taxoides shrub or tree, that rises up to 15 m (45 ft). It is also endemic to North Caledonia.
The parasite conifer (Parasitaxus usta) puny by comparison to its host, has a maximum height of 1-1.5 m (3-5 ft). Both inhabit dense humid forests, at elevations between 150 and 1.110 m (500 and 3,500 ft), predominantly above 800 m (2,600 ft).
The parasitic shrub is reddish in color, its branches are covered with small scales, it bears tiny 1-2 mm in length (at most 1/10 in) triangular leaves, helically arranged.
Whenever parasitism is discussed, the question is raised as to the benefits to the intruder and the damage to the host. In this case, given the difference in size, the damage is minimal. As for the parasite, installed as it is on the roots of its host, in a graft-like union of tissues, it enjoys a free lunch : it pumps nutrients — but water and nitrogen only — from its host’s roots.
A graft-like union of tissues : let me be more specific. The parasite uses woody root-like sinkers, to penetrate the host’s roots and bridge the two — but without a joint vascular system to circulate sap.
If the one is able to sponge on the other, it owes full benefits of that union to a third body. This is indeed a ménage à trois, involving also a fungus whose symbiosis with the host apparently renders possible the welcome rather than the rejection of the parasite. In addition, the fungus supplies scarbon to the parasite.
Parasitaxus lives on that very unusual arrangement: not quite what Emily Dickinson described for the human mind and heart:
The Mind lives on the Heart
Like any Parasite —
If that is full of Meat
The Mind is fat. —
But if the Heart omit
Emaciate the Wit —
The aliment of it
So absolute.