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? 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 Kiokio is widespread and common, including being frequent on roadside cuttings. Te Papa 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 PapaKiokio 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 changeIncreasing 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.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?
More readingBotany Curator
I specialise in the taxonomy (i.e., naming) and evolution of New Zealand’s ferns, often using DNA analyses to address issues that can’t be resolved by consideration of the external features of the plants alone. I enjoy exploring new places, even if it is only to see plants I’ve never before encountered in the wild!
2018-08-31
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