The Hebe is dead, long live the hebe.
For anyone with a smidgeon of taxonomical knowledge, or even a passing interest in plant names, the subtleties of this statement will be self explanatory. Hebe, in italics, with a capital H looks like the name of a botanical genus, hebe does not.
And it was down this corridor of many doors that we were led last night by Ken Thompson, research fellow at Sheffield University, author of several books and columnist for The Telegraph. Surrey PH group have been flooded out of their normal meeting venue and the replacement location at RHS Wisley was cosy for the large group which met to hear Ken speak on how DNA research is remodelling our understanding of plant relationships.
Previously plants were categorised using the ‘looks similar’ approach and some families such as the Fabaceae/Leguminosae are happy fits with this method. However many plants which look similar – bay, spotted, cherry and spurge laurel all have very similar leaves – have no relationship with each other at all. Environmental niches in different parts of the world have been filled with the same type of plant. Pitcher plants – the Nepenthes of Borneo, the Sarracenia of N America and the Cephalotus of Australia all look similar and have adapted to their environments in the same way, but are not even distantly related. And some plants have lost the characteristics of what makes them look like a family member – duckweed is a member of the Araceae family but looks nothing like the familiar arum, so much so that it used to be categorised as a separate family.
20 or so years ago DNA profiling began to be used to look at how plants have evolved from each other. The more differences that occur in their DNA, the longer ago they diverged. This tree of relationships shows how plants are now believed to be related as a result of DNA analysis.
Willows are more closely related to violets than oaks; mistletoe, carnations and beets all share a branch; begonias and cucumbers are ‘close cousins’. For a better look at this tree, follow the link to the US Botanic Garden website and marvel at the close relatives of mustard, coffee and currants.
Results of these analyses are what we are encountering as name changes.
The Malvaceae family used to contain Malva and Lavatera but DNA analysis has shown that this is an erroneous distinction. They are all now called Malva – keeping the name which serves as a type specimen defining the features of that particular family.
The yellow Welsh poppy has many similarities with Meconopsis, those lovely, hard to grow, blue poppies and so were given the name Meconopsis cambrica. However DNA studies show that they are not particularly close and the Welsh poppy is now Papaver cambricum.
The Scrophulariaceae or foxglove family has ejected Digitalis (the foxglove, now in Plantaginaceae) but welcomed Buddleja into its fold. Entomolgists had already suggested this connection – moths eat both Verbascum and Buddleja.
Herbaceous Veronica gave its name to the very similar woody New Zealand Veronica but the latter was renamed as Hebe. Eventually this new name was accepted and along comes DNA which proves that they should all be called Veronica – relegating hebe to a common name.
Ken concluded by telling us that previously relationships were a matter of opinion; with the advent of DNA mapping our children and grandchildren should no longer be subject to name changes. However as the work is only done on a small section of the DNA there will still be potential for changes long into the future.
Fascinating stuff. Google ‘Angiosperm Phylogeny Group’ to read more.