A name change for strap ferns

I recently co-authored a paper with Barbara Parris that investigated the scientific classification and naming of New Zealand’s strap ferns.

If you’ve spent any time in New Zealand’s forests, you will have almost certainly seen the common strap fern. It has simple, undivided fronds up to 20 cm long, but usually much less. It is widespread and can be abundant, growing at the base of tree trunks or on the ground, usually amongst mosses and liverworts. The other species are less frequently encountered.

Abstract of our paper in the New Zealand Journal of Botany.

Email me if you would like a pdf of our paper.

A cluster of individuals of common strap fern, Notogrammitis billardierei, previously known as Grammitis billardierei. Photo Leon Perrie. (c) Leon Perrie.

A cluster of individuals of common strap fern, Notogrammitis billardierei, previously known as Grammitis billardierei. Photo Leon Perrie. (c) Leon Perrie.

Reproductive structures on the frond underside of Notogrammitis billardierei. Photo Leon Perrie. (c) Te Papa.

Reproductive structures on the frond underside of Notogrammitis billardierei. Photo Leon Perrie. (c) Te Papa.

The 10 species of strap ferns in New Zealand have been classified in the genus Grammitis. All have small, simple, undivided fronds, and their reproductive structures are in a herring-bone pattern on the underside of the fronds. Although related, the comb fern differs from the strap ferns in having a lobed frond, and it was placed in a different genus, Ctenopteris, as Ctenopteris heterophylla.

Comb fern, Notogrammitis heterophylla, previously known as Ctenopteris heterophylla. Photo Leon Perrie. (c) Te Papa.

Comb fern, Notogrammitis heterophylla, previously known as Ctenopteris heterophylla. Photo Leon Perrie. (c) Te Papa.

Barbara had hypothesised that the New Zealand strap ferns and comb fern were misclassified in both Grammitis andCtenopteris. After looking closely at their external structures, she considered them to be closely related to one another but to be distantly related to the ‘true’ Grammitis and Ctenopteris (which are defined by the first species named as such). DNA analyses that I conducted supported Barbara’s hypothesis.

This left the New Zealand strap ferns and comb fern without a genus name, so Barbara coined Notogrammitis; noto being Greek for southern, and Grammitis being the genus in which the New Zealand strap ferns were previously (mis-) classified.

Notogrammitis also occurs in Australia, South America, South Africa, and many of the sub-Antarctic islands. There are 12 species in total, with 11 found in New Zealand (four of these are only found in New Zealand, while seven also occur elsewhere). However, our DNA results suggest there are almost certainly more species than currently recognised.

Te Papa’s collections of Notogrammitis.

Fortunately, the name change is simple for most species, with Notogrammitis being substituted for Grammitis (or Ctenopteris). For example, Grammitis billardierei and Grammitis pseudociliata have become Notogrammitis billardierei and Notogrammitis pseudociliata, respectively. However, there are a couple of discrepancies to watch for. Firstly, Grammitis magellanica has become Notogrammitis angustifolia. This is because although angustifolia is the oldest relevant species name, it could not be used for this New Zealand strap fern when it was classified in Grammitis as the combination Grammitis angustifolia had already been used for a completely different species. Secondly, Grammitis poeppigiana has become Notogrammitis crassior. This is because the type specimen of Grammitis poeppigiana actually belong to the species now called Notogrammitis angustifolia, and the species name crassior is the earliest that is based on a type specimen that actually belongs to the species we have previously (mistakenly) called Grammitis poeppigiana. Straightforward, huh?!

Changes to scientific names (should) reflect improved understanding of species’ evolutionary relationships. Although we might grumble about having to learn new names, it is the stark reality that current scientific classifications are still far from accurately portraying evolutionary history. In this case, the species in New Zealand are not closely related to true Grammitis, which have fronds with black margins and occur in the Pacific Islands, Africa, Madagascar, and the New World, or Ctenopteris, which is actually an older (and therefore not to be used) name for Prosaptia. Expect many more name changes as evolutionary relationships are determined with ever more accuracy.

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