Tree Talk

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The recent reorganisation of the NZ members of the genus Kunzea has prompted this Tree Talk. David English recalls learning scientific names early in his botanical career and that then, kanuka was known as Leptospermum ericoides. It is now called Kunzea robusta. He tries to explain what this is all about.

What’s in a name? A name tells you what it is or who you are. Most often our first name and surname is enough to separate us from others. If by some chance you find someone else with the same name you need to add further information, like an address, to be certain you have found the person you are looking for.

It’s just the same for plants. They all need to be named too. But it is very important that one name describes only one type of plant. Describing and classifying plants is the science of taxonomy and is fundamental to the study of botany because it not only names and describes plants, but also shows evolutionary relationships.

Carl Linnaeus in the London Museum of Natural History

It was Carl Linnaeus, born in 1707 in Sweden, who is often thought of as the father of modern taxonomy, having devised what is known as binomial nomenclature in his 1735 book called Systema Naturae and Species Plantarum in 1753.

The binomial system of nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which often use Latin terms and it is also called the Latin name. The first name (capitalised) is the genus of the organism, the second (not capitalised) is its species. Similarly both parts are italicised when a binomial name occurs in normal text.

Today, a species is recognised as one of the basic units of biological classification. A species is often defined as the largest group of organisms capable of interbreeding and producing fertile offspring.

When H H Allan produced his Flora of New Zealand Vol 1 in 1961 it described 1,273 different species of flowering plants or Dicotyledons. This was the first compilation since 1925, when T F Cheesman’s Manual of NZ Flora described 1,184 dicotyledonous species. The recently published NZs Inventory of Biodiversity Vol 3, edited by Dennis Gordon, suggests a number significantly higher.

Why is this number of different species increasing? It’s not a case of rapid evolution but rather the fact that taxonomists now have access to more and more techniques over and above using plant appearance and floral structures to define similarities and differences. They now use cytology (cell structure and function), ecology (relationship of organisms to one another and their environment), hybridisation (the process of combining different varieties of organisms to create a hybrid), molecular phylogeny (the analysis hereditary molecular differences) as well as the comparison of chromosome numbers and other advanced techniques to make sure relationships are correctly expressed when plants are named.

Therefore it is not that more plants are being found, but rather that plants are being more accurately described.

Over time taxonomists have often been referred to as “lumpers” or “splitters” by their colleagues, depending on their personal approach to recognizing differences or commonalities between organisms. The taxonomy of kanuka is a good example of “lumpers” or “splitters” at work.

Early botanists such as Joseph Hooker (1867) and Thomas Cheeseman (1906) were clearly “lumpers” as they placed kanuka and manuka in the same genus Leptospermum. Later workers, particularly Peter de Lange, have not only placed kanuka in a separate genus (Kunzea) but have identified several species which make up what is called the kanuka complex. They could well be known as “splitters”.

However, in this case, being a “splitter” is not a derogatory term.

NZ botanist Peter de Lange has been working for 15 years on the taxonomy of kanuka using all modern techniques described above. However, he has not forgotten the more traditional techniques such as observation, measurement, recording and collection. He reports that for this study he collected and stored over 1,000 specimens – all carefully stored as herbarium specimens, mostly at Auckland University.

As a result of this work Peter de Lange has recently announced a complete revision of the genus Kunzea in New Zealand. You can download his findings in his paper called A revision of the New Zealand Kunzea ericoides (Myrtaceae) complex.

In summary, it has been confirmed that Kunzea ericoides is actually endemic (ie. only found naturally) to New Zealand but that the species is confined to the South Island. The plant so abundant in the North Island that we have known as K. ericoides is now K. robusta!

Kunzea ericoides
Kunzea robusta

It is reported that Trees for Survival students are well versed in being able to tell the difference between manuka and kanuka. But now they will need to learn a new scientific name Kunzea robusta.

The wonderful NZ Plant Conservation Network website lists the five new species of NZ Kunzea. Check it out and you can click on each image to see how taxonomists today describe plants. The site also has excellent photographs.

And so as far as botany is concerned it’s not just a case of thinking of a name like we do for our children – you can see how much work has to be done to make sure a plant has the correct name. It also takes more effort to learn the scientific names – it’s highly satisfying and worth it. That is until it’s changed!

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