A focus for my research in 2014 has been preparing an account on the Gleicheniaceae fern family for the online Flora of New Zealand.
The Gleicheniaceae in New Zealand comprises nine species in the genera Dicranopteris (one species, restricted to central North Island thermal areas), Gleichenia (four species), and Sticherus (four species).
It is the Gleichenia tangle ferns that have required the most study. Determining their taxonomy – how many species are present, and what are their scientific names? – has been as complicated as their entangling fronds. But I think I’ve made some progress, which I’d like to share.
Tangle ferns made simple
When viewed from above, the tangle ferns in New Zealand look fairly similar to one another. (The exception is Gleichenia alpina, which has shorter branches.) But if you turn them over and look closely, you’ll see some marked differences.
Indeed, they are so different that you might be wondering what the trouble was…
Extra for experts
The problem is that some plants do not match the four pictured above. There are at least two reasons.
The first is that plants that have intermediate characteristics or combine the characteristics of Gleichenia dicarpa and Gleichenia microphylla are common.
As background, Gleichenia microphylla has green undersides to its frond segments, ultimate segments that are flat or recurved (but not pouched) and often have pointed apices, and spore capsules (sporangia) that occur in clusters of three or more. In contrast, Gleichenia dicarpa has white undersides to its frond segments, ultimate segments that are pouched or recurved with rounded apices, and spore capsules (sporangia) usually in clusters of only two. They also have different kinds of scales (the appendages that occur on the axes, and which are wider than hairs).
But plants with more or less flat ultimate segments that are whitish underneath also occur (as do some other combinations of characteristics). It is likely that these ‘intermediate’ plants are hybrids. But I have no independent proof of this.
The second reason is that there are (at least) two distinct morphologies in Gleichenia dicarpa.
In some plants of Gleichenia dicarpa, scales occur along the full length of the underside of the minor axes (technically, on the abaxial surface of the alpha costae). These plants also have minute scales on the underside of the frond segments (technically, on the abaxial surface of the ultimate segments). Such plants are dominant in the northern North Island, and also occur in the southern and eastern South Island, Stewart Island, and on the Chatham Islands, and they are scattered elsewhere in the North and South Islands. Interestingly, these plants are genetically heterogeneous.
But in most New Zealand plants of Gleichenia dicarpa, the scales on the underside of the minor axes (i.e., on the abaxial surface of the alpha costae) do not extend along the full length of the minor axes. And, there are no scales on the underside of the frond segments (i.e., the abaxial surface of the ultimate segments is glabrous).
So, not so simple…
How you can help
I am not sure what this means for Gleichenia dicarpa. But, I am very interested in observations or specimens of Gleichenia dicarpa from either
- south of Auckland that have scales occurring along the length of the underside of the minor axes; or
- north of Auckland that lack scales along the length of the underside of the minor axes.
Photos uploaded to the Ferns with Te Papa project in NatureWatch would be gratefully appreciated. And your photo might end up in the exhibition DeCLASSIFIED! Nature’s secrets exposed at Te Papa.
The online Flora of New Zealand
Are you interested in expert accounts of New Zealand’s plants? Then the Flora of New Zealand is for you!
Our treatment for the Gleicheniaceae is still in preparation. However, ten fern families are online. Five of these have downloadable pdfs. More are scheduled for release in February 2015.
pdf for the Osmundaceae, as an example of what is being prepared.
Previous posts on Gleichenia and Sticherus
I’ve posted before about our work on the Sticherus umbrella ferns and a new species of Gleichenia tangle fern.