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The naming of a mistletoe

Tim Harris
13 January 2011
Blog team: 
Find out how collaboration between mistletoe experts and the Drylands Africa team in the Herbarium resulted in a new species of mistletoe being documented.

If you looked at the Kew website over Christmas you may have seen a story about a new mistletoe, Helixanthera schizocalyx. I was on the trip to Mt Mabu in 2008 during which this plant was found, and was also involved in writing the scientific paper in which the new species has been formally described. The scientific paper will be published in the next few months.

The events that lead up to this new species being described involved a large number of different people. While some species are only identified as new and different years after their pressed specimens enter a Herbarium, the number of specialists that looked at the pressed specimens from the trip to Mt Mabu in Mozambique meant that this mistletoe was described soon after returning from the expedition.

Mozambican botanists pressing plants in woodland on Mt Mabu (Image: RBG Kew)

On the trip to Mt Mabu, local guides living around the mountain were essential for navigating to its remotest parts. The project was lead by Jonathan Timberlake. Five Mozambican botanists worked alongside experts from three other countries. One such expert was Colin Congdon whose work specialises in butterfly-plant herbivory and pollination relationships. It was Colin who first realised that the mistletoe we were seeing could be a new species.

Back at the Herbarium

Once the pressed plants reached the Herbarium at Kew, Colin's immediate excitement was justified as longstanding mistletoe expert Roger Polhill agreed that certain plant specimens were sufficiently different from anything seen before to be judged a new species. Botanists may wonder whether they are dealing with a new species when the identification keys written for a particular group of plants do not match up with the particular combination of structures seen on a plant specimen, but in practice deciding that a group of specimens represent a new species usually depends on an expert knowledge of that group of plants. Despite this reliance on expertise, on average 2000 species are described each year by scientists around the world.

Having decided that the mistletoe material did represent a new species, work then began on taking the measurements and observations of the specimen necessary to write a formal description of the plant covering everything visible from general form to vegetative parts and detailed flower structures. I worked with Iain Darbyshire on this descriptive work, who like me is within the Drylands Africa Team in the Herbarium.

Naming the species

Perhaps surprisingly, deciding on a name for the new species did not take much time. Whilst new species are occasionally named after people (as was Mastigostyla woodii,) there is more often a tendency to name new species after the locality in which they are found or, as is the case for this mistletoe, after a relatively obvious feature of the plant that distinguishes it from species thought to be closely related. The name of this mistletoe relates to its calyx (the calyx is the outermost parts of the flower that protect the other parts when in bud). Whereas other Helixanthera species have a calyx shaped like a cup without any full-length splits, in this case the epithet 'schizocalyx' refers to the way this species has a split top to bottom.

Publishing a scientific paper in hardcopy is necessary for a new species to be validly publised. As well as a publishing company being involved, publishing a new species often requires us to ask one of Kew's talented botanical artists to make an illustration showing the novel features of the plant. So from the initial planning to go to a geographical area whose plants are poorly known to producing the glossy scientific paper giving all the evidence behind the decision to call it a new species, plenty of people have been involved.

This year starts with the task of identifying material from the expedition to southern Ethiopia. I will be using the recently completed Flora of Ethiopia to identify the newly collected material, and for the rarer groups the same process of looking a newly collected specimens alongside numerous specialists is just about to begin...

- Tim -


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