Trimenia – A living botanical dinosaur

Flowers of Trimenia moorei

The primitiveness of plants is a man-made concept – a way to ‘organize’ the world. Nevertheless, if a concept that a plant is primitive inspires one to appreciate the uniqueness of a species, the concept of primitiveness has done what it is meant to do.

To illustrate the magnitude of appreciation a concept such as primitiveness can engender, I quote the following blog post from the University of New England blog writing about how Professor William (Ned) Friedman from Boulder, USA, flew all the way to New South Wales, Australia for 2 days of fieldwork to find a species of primitive plant unique to north-eastern NSW. He is quoted as having said:

“There aren’t many places in the world I’d go for only two days,” he said. “But I’d come here for just one day.”

He was looking for Trimenia moorei, a vine species found only in the sub tropical rain forests of north-eastern NSW. Another 4-5 species of Trimenia occur in Southeast Asia and are much less well known.

I am fortunate to encounter Trimenia flowering in a glasshouse and I have had the pleasure of seeing this plant in New South Wales near Dorrigo.

I have written about Amborella trichopoda, the most primitive plant lineage that currently still exist on the planet. In the very coarsely made ‘phylogeny’ below, you can see how Trimenia fits in with the ‘primitive’ club.

|___________ Amborella
|______________ Water lilies (Nymphaea spp etc.)
|_____________________ Austrobaileyales (includes Trimenia)
|___________ (ALL OTHER FLOWERING PLANTS)

Magnolias and Laurels, once considered the most primitive groups, are in the “ALL OTHER FLOWERING PLANTS” group, and Trimenia comes before them in the Order Austrobaileyales.

Again, as with Amborella, an untrained eye would have failed to pick up anything particularly unique about Trimenia, but on closer inspect, one will find that this is something very strange with the flower construction.

The white petal-like structures are actually more accurately called bracteoles (bract-like structures) and it will soon be realized that as with Amborella, the distinction between sepals and petals in normal flower do not apply for these primitive plants.

The ecologist in me wants to think of what the interesting ecology that surrounds the plant. How does it fare alongside other groups of plants with which it co-occurs, that are comparatively young in an evolutionary sense. Is it doing something different from these younger plant lineages?

Those questions can wait.

Trimenia moorei, for want of a better description, is a living botanical dinosaur!

When one sees a dinosaur, one observes a moment of silence to be in awe.

Notes
Trimenia moorei belongs to the family Trimeniaceae and is a climber with opposite leaves. The leaves and stems particularly are covered in red-brown hairs. Veins of the leaves come out at almost right angles from the midrib. The inflorescence develops at the end of the shoots.
Trimenia moorei has been the subject of a number of detailed studies on their reproductive biology, in particular, the development of the female gametophyte (see link)

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