Botanist Leon Perrie recently posted about the desirability of minimising taxonomic name changes. He writes here about the need to change the name of a fern to reflect its newly discovered evolutionary relationships.
I like to use “pig ferns” as a colloquial name for the genus Hypolepis. It’s memorable. And it reflects that many of the species flourish in disturbed habitats, which nowadays includes those created by wild pigs when they rip up our forests.
One of the species has been called Hypolepis distans. It is common particularly in the north and west of the country. But it’s apparently not so prominent that it has a recorded colloquial name in either te reo Māori or English.
In any case, Hypolepis distans has long been regarded as morphologically and cytologically anomalous alongside the other Hypolepis species. Te Papa’s Patrick Brownsey first wrote about this in 1983.
Evolutionary relationships
Earlier this year, overseas researchers described a new genus, Hiya, for three species of Asian and American ferns that had previously been attributed to Hypolepis. They did this because analysis of DNA sequences showed that the species put into Hiya were only distantly related to ‘true’ Hypolepis. Indeed, Hiya is actually more closely related to very different-looking ferns like mātā (Histiopteris incisa) and ring fern (Paesia scaberula) than to Hypolepis.
The Australasian Hypolepis distans is a long way from Asia or the Americas, but given that we already knew it was odd, a few of us at Te Papa thought we better check how it fitted into this new understanding of evolutionary relationships. Was Hypolepis distans more closely related to Hiya, ‘true’ Hypolepis, or something else entirely?
Our analysis of DNA sequences strongly indicated that Hypolepis distans was most closely related to the species that had been moved to Hiya. Consequently, we’ve made the new name Hiya distans, and recommend that this now be used as it is a better reflection of evolutionary relationships. In this case, splitting Hypolepis involves fewer taxonomic name changes than the alternative of lumping together several long-recognised genera.
Our New Zealand Journal of Botany paper advocating for the recognition of Hiya distans
My blog post on minimising taxonomic name changes
The name Hiya
The authors who coined the name Hiya for these ferns were inspired by the name of the imperial guards of China’s Qing dynasty. It’s a reflection of the prickly frond stalks of the Asian and American species; Hiya distans, though, is not prickly.
The Qing dynasty is much more recent compared to the Qin dynasty’s Terracotta Warriors, some of whom are visiting Te Papa soon.
Terracotta Warriors: Guardians of Immortality exhibition info
Wikipedia page about the hiya imperial guards of the Qing dynasty
In a completely different cultural context, one of my co-authors (not Patrick) quickly cottoned on to the similarity of the name Hiya to the chorus of Outkast’s Hey Ya!, to the extent that for her the genus name is only sung, never spoken. You can be the judge as to whether such musical representation is helpful. Note that the video contains some obscene language.
Hiya distans presumably now escapes the “pig fern” moniker of Hypolepis, which is not a bad outcome since its liking for wetland habitats meant it wasn’t a particularly apt description for this particular species.
Electronic flora of New Zealand
The adoption of Hiya distans renders our chapter on the Dennstaedtiaceae out-of-date, and it was only published in June 2018! Science marches on.
Electronic Flora of New Zealand page for Hypolepis / Hiya distans
eFloraNZ chapter for the Dennstaedtiaceae ferns [PDF, 11.4MB]
We’ll make the update once we’ve finished all of the fern and lycophyte families in New Zealand. With the recent publication of chapters on Davalliaceae, Cystopteridaceae, Athyriaceae, and Isoetaceae, there are only the Lycopodiaceae, Blechnaceae, Dryopteridaceae, and Pteridaceae to go.
eFloraNZ chapter for the Davalliaceae ferns [PDF, 3.8MB]
eFloraNZ chapter for the Cystopteridaceae ferns [PDF, 2.5MB]
eFloraNZ chapter for the Athyriaceae ferns [PDF, 5.2MB]
eFloraNZ chapter for the Isoetaceae lycophytes [PDF, 2.5MB]
Leon, I understand your point. In one sense any sister species or sister taxon relationship is based only only the sampled taxa, and even if all known taxa are sampled, others might exist or others existed in the past that could be interposed within the phylogeny. My perspective was that since there was another species known to exist, but not sampled, it might have been better to view the relationships as potential sister species contingent upon future sampling of the other known species. But that’s just a personal choice and does not affect the phylogenetic result. If a sister species designation is preferred in the context of sampled taxa that is an alternative choice. Here the matter is very minor, but I have run into this conundrum on a larger scale such as for the Galapagos where studies identify, for example, a sister group relationship with Ecuador, but do not sample members of the group in Central America that may result in a substantial change in the geographic relationship.
Understood. Perhaps it would have been better that the sister species relationship would have been treated as provisional pending scrabristipes since there are two alternative possibilities. It will be interesting to see how that resolves in the future. But not a big deal. The distribution overall is an absolute classic as I am sure you know, and the Caribbean centered range of nigrescens makes perfect sense in light of that.
John – I’m not sure you do understand. In the context of the species sampled in the phylogenetic analysis, the sister relationship is clear, and our description in the context of describing the phylogenetic tree is correct.
Example: in a phylogenetic analysis that resolves {silver fern { kauri {pohutukawa, kowhai}}}, kowhai and pohutukawa are sister species in the context of the species sampled for that analysis. But you shouldn’t assume that pohutukawa and kowhai are sister species in ‘real’ life, because of unsampled species.
In our Discussion, we do not talk about a sister relationship of Hiya distans and Hiya brooksiae, but say they have a “close” relationship, with the significance of that being that Hiya distans is more closely related to the type species of Hiya (i.e., Hiya brooksiae) than it is to the type species of Hypolepis sensu stricto. The phylogenetic position of Hiya scabristipes is irrelevant to determining the relationship of Hiya distans to either of these type species.
The placement within Hiya is also a nice addition to the Pacific biogeography and origin of the genus. The only problematic aspect of the study is that a sister species relationship was asserted between H distans and H. brooksiae but the phylogeny shown in Fig. 1 does not include Hiya scabristipes – or did I miss something?
The description of a sister species relationship between Hiya distans and H. brooksiae is in the context of the Results of the species sampled/analysed with DNA sequences. Previously, from morphology, Hiya scrabristipes has been hypothesised to be closely related to H. brooksiae, but no-one has yet obtained DNA data from Hiya scrabristipes.