Toropapa (Alseuosmia) is a genus of shrubs found only in New Zealand. Toropapa has been confusing botanists for over 100 years because they show extreme variation in leaf shape – even between plants considered to be the same species from a single location! Te Papa scientists Lara Shepherd and Leon Perrie, along with the Department of Conservation’s Andrew Townsend, recently returned from a fieldtrip collecting samples of toropapa.
The extreme variation in toropapa has made it very difficult for botanists to determine the exact number of species. Our fieldtrip was focused on Northland, which is the hotspot for toropapa leaf variation. Currently there are only three toropapa species recognised from Northland.
The photos below show the range of leaves we saw. How many species do you think there are?
To add to the confusion, the leaves of some toropapa plants show a remarkable resemblance to completely unrelated species, such as maire, porokaiwhiri (pigeonwood), ramarama, and horopito. A photo of one toropapa plant that I loaded on the citizen science platform NatureWatch even tricked several experts into thinking it was ramarama!
It has been suggested that this is a case of mimicry whereby palatable plants, in this case toropapa, mimic unpalatable plants to avoid being eaten by browsing animals.
We will now use the samples that we collected to study the genetics and morphology of toropapa. This will help us determine how many species there are and hopefully allow us to understand how mimicry has evolved in the genus.
This information will then be used to assess the threats facing each species and whether any of them require conservation management.
As well as the huge variation in toropapa leaf shapes and sizes we also noticed that the flowers varied in size, colour, and the level of ‘frilling’ at the tips of the petals.
The gallery below depicts the variation we saw.
We would like to thank the many locals and DOC staff who aided our fieldwork.