Why do scientific names change? Kiokio by any other name…

Why do scientific names change? Kiokio by any other name…

What is an appropriate amount of change in our scientific classification of life? Botany Curator Leon Perrie ponders this using the kiokio and its fern relatives as an example.

Do you want me, as a taxonomist, operating with the taxonomic equivalent of a surgical scalpel, or are you okay if I flail around with a chainsaw?

Whether I’m out-and-about with botanical societies or perusing social media about biodiversity, I regularly come across people complaining about changes in scientific names. To paraphrase, they ask “why did that name have to change?” I find that a particularly pertinent question, since my job as a plant taxonomist involves determining the appropriate scientific name for our plants, especially ferns in my case.

Who is kiokio?

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Kiokio is one of New Zealand’s most prominent ferns. It’s even at the centre of the $10 note! © Reserve Bank of New Zealand
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Kiokio is widespread and common, including being frequent on roadside cuttings. Te Papa
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Like most of its relatives in New Zealand, the spore-producing fronds of kiokio are not green and have much narrower segments.  Such different-looking fertile and sterile fronds means the group is usually easily distinguished. Te Papa

Kiokio has had the scientific name of Blechnum novae-zelandiae. But it has recently been suggested that this should change to Parablechnum novae-zelandiae. Why?

The reasons for taxonomic change

Increasing knowledge is the underpinning driver for change. Most taxonomists prefer scientific classifications that reflect the pattern of evolutionary relationships. That is, if a group is to be formally given a scientific name, all members of that group should be more closely related to each other than to entities outside the group.

“Monophyly” is the jargon, and, in providing an objective criterion for scientific classification, it is a basic tenet for most taxonomists. (Some taxonomists don’t use the monophyly criterion, preferring instead the it-is-a-scientific-group-because-I-say-so approach; this suffers from subjectivity and authoritarianism.)

Changes to scientific naming follow when investigations reveal that the current classification does not reflect evolutionary history. Given that we are far from knowing everything, a need for updating our scientific classification is not infrequent.

Having established a need for revision, the question becomes how to update the scientific classification so that it is consistent with the current understanding of evolutionary history.

Unfortunately, there are no objective criteria for what constitutes a genus or family or order, etc. in scientific classification. Instead, it is up to the taxonomist to interpret the available evidence (and then whether their suggestion is accepted or rejected by the community).

My taxonomic practice in such situations is to look for the solution that entails the least amount of change. This, I believe, is what the general users of taxonomic names want – certainly, that’s what I’ve heard you say!

But not all taxonomists follow a mandate of minimising-change. Some even make changes when the current scientific classification is consistent with the pattern of evolutionary history.

Such examples in ferns include the proposed segregation of Trichomanes filmy ferns, Cyathea tree ferns, and Botrychium – all changes not presently adopted by the Flora of New Zealand. The split of the Nothofagus southern beeches to give Lophozonia and Fuscospora in New Zealand is a recent prominent flowering plant example of changing names even when the evolutionary pattern did not conflict with the scientific classification.

How much change? The family tree of kiokio as a case study

Kiokio is part of the Blechnaceae family of ferns, and this is its global family tree of relationships based on DNA sequences.  Recent classifications have accepted seven or so genera. The numbers next to each name are the number of species in that group.
Note that species classified in Blechnum occur in multiple parts of the family tree; Blechnum as defined here is not monophyletic.
The red arrow points to the position of a group of ferns called Doodia. The closest relatives of Doodia are indicated by the horizontal blue lines towards the bottom of the figure; these have been classified in Blechnum, which means that these species of Blechnum are more closely related to Doodia than they are to other species of Blechnum; so close in fact, that they even hybridise.
The blue arrow points to two species that have been classified in Blechnum but which are more closely related to Stenochlaena and Salpichlaena.
Another issue not shown on this figure is that two Australian species traditionally called Pteridoblechnum are, like Doodia, nested within the bulk of Blechnum.
Te Papa
Subsuming Doodia (and Pteridoblechnum) into Blechnum, and recognising the two Blechnum species related to Stenochlaena as Telmatoblechnum fixes the definite problems with the classification (i.e., those which are strongly indicated in analyses of the DNA sequences).
Number of name changes: about 25.
Number of genera in the world: remains at 7.
Te Papa
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Doodia can be kept if what was Blechnum is split into many smaller, monophyletic genera. The numbers next to each name are the numbers of species in that group. Most are small. Kiokio would be in Parablechnum.
Number of name changes: about 180.
Number of genera in the world: 24.
Te Papa

What this means for kiokio and its New Zealand relatives

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Overview of the diversity of the 22 indigenous species of Blechnaceae ferns in New Zealand. The contiguous images indicate related sets of species. The species not shown all have very close relatives above; for instance, kiokio (Blechnum novae-zelandiae) is very closely related to B. procerum and B. triangularifolium. Some of these groups are obvious from their external appearances, such as the kiokio group. But others are not, such as the group of B. nigrum, B. vulcanicum, and B. fluviatile at top-centre. Te Papa
Most of the New Zealand species have previously been classified in Blechnum.  The exceptions were four species, including rasp fern, placed in Doodia. Te Papa
With the approach of minimising change while still reflecting the pattern of evolutionary history, all of New Zealand’s Blechnaceae ferns are classified as Blechnum, in one big monophyletic group. Te Papa
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An alternative suggestion is to keep Doodia as a distinct genus and divide what was Blechnum into many smaller monophyletic genera.  In this scenario, there are seven genera in New Zealand, and Blechnum is not one of them.  The four species of Doodia would remain there, but all of the other New Zealand Blechnaceae ferns change to different genera. Te Papa

Taxonomists serve … who?

The taxonomists who proposed the wholesale name changes for kiokio’s relatives justified it by saying that “Smaller genera, having stronger morphological and molecular support, are easier to study, allow for recognition of phytogeographical patterns, clarify relationships, and point the way toward other interesting avenues of research, involving character and character state evolution, chromosomal repatterning, reproductive biology, and ecological issues; they also facilitate more detailed monographic work.”

This sounds to me like the changes were made to benefit the tiny number of specialists who study this group, at the expense of the vastly more numerous ‘regular’ users of scientific names having to make a whole lot of change.

Moreover, the actual benefit is arguably minimal, since all of those fields of study can continue whatever the classification, especially as most are undertaken by specialists well-versed in understanding evolutionary history and coping with different or layered systems of names (e.g., informally named groupings).

Some experts appear to delight in changing scientific names. Perhaps it allows them to show off their superior knowledge. But is change-for-change’s-sake good for the vast community of non-taxonomists who use scientific names?

A global group of experts on the scientific classification of ferns and lycophytes (collectively “pteridophytes”) recently came together to find consensus – the PPG or Pteridophyte Phylogeny Group. I liked their approach with families, which involved voting.

The genera, though, were handled by self-selected subcommittees who generally specialised in that particular group; personally, I felt several of them recognised too many genera in ‘their’ group, with the attendant change. I’m not clear whether these instances of arguably unnecessary change will be broadly adopted.

What do you think?

Do you think taxonomists should try to minimise changing the scientific classification while still reflecting evolutionary history?

Please leave a comment below – I’d appreciate hearing from you, whether you’re someone who uses scientific names without really understanding where they come from, or you’re a professional taxonomist.

Do you want me, as a taxonomist, operating with the taxonomic equivalent of a surgical scalpel, or are you okay if I flail around with a chainsaw?

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7 Comments

  1. Unfortunately I am (as you will probably have realised) “past my use-by date”, and the complexities of the proposed PhyloCode are beyond me. However a quick look at your reference reminds me of an old medical students joke. When I studied at Melbourne University in the early 50’s the medical students gained an MB, BS (something like Batchelor of Medicine, Batchelor of Surgery). Then if they went on to further studies they might add PhD, and all these letters stood for “More bloody bullshit, piled higher and deeper”. I suspect that in another generation scientists will come at last to accept that living things are not designed to fit into tidy boxes, but that the characteristics of every individual specimen are defined by it’s own unique collection of genes, and they will devise some new more flexible system to handle this variability.

    Something like 40 years ago the Melbourne Zoo built a new state of the art enclosure to house Orang Utangs (roughly ‘Old Man of the Bush’ in the local language) and brought over a local woman who was an expert carer to help look after the initial consignment of animals (from Borneo?). When I compared her face with those of the Orang Utans there was a strong similarity, and it was difficult not to believe that they shared some of their genes, regardless of what the theory of the day said about the impossility of this.

    And despite all my skepticism the Cybec Foundation, which I founded, still supports the Jim Willis Studentship at our National Herbarium. This fulfills a valuable role as it enables interested students to spend the summer vacation working a project in systematic botany, so they can find out whether it is really what they want to do, before they commit to spending three years or so studying for a PhD. See: https://www.rbg.vic.gov.au/about-us/job-opportunities/jim-willis-studentships

  2. I became interested in botany as a small boy, and met Jim Willis (Assistant Government Botanist at the National Herbarium, Royal Botanic Gardens of Victoria) in 1944, when I was 10. I had been introduced to botany by an older boy at the Mt. Dandenong State School, which had one room, one teacher, and maybe 20 pupils ranging from Grade 1 to Grade 8. I was particularly interested in the local ferns (a number of which we shared with NZ) and learnt all the scientific names, but unfortunately most of these had been changed (usually on extremely dubious grounds) before I finished school, so I have an extremely jaundiced view of systematic botanists. It is nice to think that we can have a tidy system of names which tell us all about a plant and just where it fits into the scheme of things, but living things do not fit into tidy boxes, and everyone (but systematic botanists) wants each plant to have a handle which they can learn once, and will unambiguously identify it to anyone who is interested.

    In my opinion we should accept that we should give each plant a handle, which will reliably identify it, and use some other system to try to specify it’s relationships.

    There is a series of articles on this subject at: http://corybas.com/index.php?ident=11100
    (See also: http://corybas.com/index.php?ident=10X0D )

  3. Hi Leon,
    I am not a professional but have had a lot to do with the natural sciences over the years. As a younger person my family lived on a farm south of Port Waikato and there was a host of things to keep a young naturalist happy. I took a keen interest in collecting ferns and orchids before naming was important. Then came shells and fossils with a club behind me these names and their changes confused me somewhat.
    I agree with Ann that it would be nice to lump as many as one can to a single name but over the years I have learnt that science evolves, new things are found, new techniques are discovered( like DNA). But the one thing that does annoy me is the personal bias that seems to creep into some writers manuscipts.
    Sorry about the rant but yes I would prefer a scalpel with the careful research behind it.

    Cheers
    Al

    1. Leon Perrie
      Author

      Thanks Al for your comments.

  4. Yes, I do think taxonomists should try to minimise changing the scientific classification while still reflecting evolutionary history. I think your argument above is sound.
    And I know this isn’t scientific but a euphonious name is much easier and more pleasant to remember than some of the new names which are just plain ugly. I am thinking of Helichrysum bellidioides (pretty sun gold) whose generic name became Anaphalioides (which doesn’t mean much to me)
    Anyway I am glad you incline to the ‘lumpers’ , Leon, and not to the splitters’ !
    Cheers
    Ann Graeme

    1. Leon Perrie
      Author

      Hi Ann,
      Thanks for your comment. Yes, it is an inclination to lumping, seemingly, but I will split when that produces the least amount of change. (We’ve got an example coming up in Lastreopsis, where some “Lastreopsis” are actually more closely related to Rumohra. Lumping would result in over 100 name changes globally; splitting only about 20-30.)
      Kind regards,
      Leon

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