I’m a co-author of a just-published scientific paper examining the evolution and classification of the Arthropteris climbing ferns. The paper was a real international collaboration, involving authors from China, Netherlands, France, United Kingdom, and New Zealand.
It is unclear how many species there are of Arthropteris – probably somewhere between 10 and 20. They occur throughout the tropics of the Old World, extending to New Zealand and through the Pacific to Juan Fernández Islands.
My contribution was samples from New Zealand and Fiji. There is a single species in New Zealand, Arthropteris tenella, which also occurs in Australia. It was an important species for this study because it is the so-called type species of the genus Arthropteris; wherever this Australasian species is classified, the name Arthropteris must follow, so determining the relationships of this species is critical for establishing an appropriate circumscription of the genus Arthropteris.
Arthropteris tenella is known as jointed fern because the leafy segments of the frond are jointed to the frond stalk. In New Zealand, it is found through the lowlands of the North Island and northern South Island. It is often a low, climbing epiphyte on tree trunks, but sometimes scrambles over the ground.
Fiji is home to several species of Arthropteris, one of which is Arthropteris articulata. It differs in having a more-divided frond, and in that its reproductive structures have a protective covering; the reproductive structures of Arthropteris tenella are, by comparison, nakedly exposed.
One of the principal findings of our paper was that Arthropteris does not fit well within the family – Tectariaceae – in which it has been recently classified. This was both with regard to morphology and evolutionary relationships as inferred from DNA sequences. Because of this, some of my co-authors suggested that Arthropteris be classified in its own (and new) family, Arthropteridaceae.
Below are photos of a couple of Tectaria, from the Tectariaceae, for comparison. They are generally much bigger plants, that grow on the ground.