How many species of the confusing shrub toropapa are disguised in the bush?

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.

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Left: Toropapa, Omahuta. Photo by Leon Perrie. Te Papa. Right: Black maire (Nestegis cunninghamii). Photo by John van den Hoeven

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Left: Toropapa, Herekino. Photo by Leon Perrie. Te Papa. Right: Tawheowheo (Quintinia serrata). Photo by Sunita Singh

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Left: Toropapa, Herekino. Photo by Leon Perrie. Te Papa. Right: Pigeonwood/porokaiwhiri (Hedycarya arborea). Photo by Lara Shepherd

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Left: Toropapa, Wellsford. Photo by Leon Perrie. Te Papa. Right: Lowland horopito (Pseudowintera axillaris). Photo by Pat Enright. CC BY-NC 4.0

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Left: Toropapa, Taipa. Photo by Leon Perrie. Te Papa. Right: Ramarama (Lophomyrtus bullata). Photo by Lara Shepherd. Te Papa

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Left: Toropapa, Kerikeri. Photo by Leon Perrie. Te Papa. Right: Pittosporum pimeleoides subsp. pimeleoides. Photo by Bill Campbell. CC BY-NC 4.0

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.

15 Responses

  1. Barbara Hammonds

    Wow! Thanks Lara, Leon, Andrew and the rest of the team. I knew they could be variable but had no idea it went to this extreme level. Look forward to the next instalment.

    Reply
  2. Bruce Calvert

    Hi, I am sure you know of the toropapa that looks like Pseudowintera colorata, and grows near Mt Ruapehu.

    Reply
    • Lara Shepherd

      Thanks Bruce. Yes, that species is Alseuosmia pusilla and I have been fooled many times into thinking it is Pseudowintera colorata. The trick is to turn the leaves over – P. colorata is white underneath while A. pusilla is not.

  3. Graeme Atkins

    Fascinating. Ive noticed similar variation and mimicry amongst the toropapa where I live at East Cape and its only the flowers or fruits that give it away as an Alseuosmia . Runaway deer numbers are eliminating this and other sub canopy species before they can be studied .

    Reply
    • Lara Shepherd

      Thanks Graeme. Its neat there is variation in toropapa at East Cape too but terrible about the deer browse!

  4. Al Fraser

    Fascinating! I thought I had a handle on ID-ing ramarama but it seems I may not have been as sure as I thought. Thanks Te Papa!

    Reply
  5. Reuben Booth

    Wow this is so interesting! The ALS mac and ALS que that we saw with the Te Papa team in Waima were the forms I often see on my travels through the Northland bush. I could never have imagined the variety that I’ve seen in photos (above). Great work team Te Papa, it was very cool to be part of this, and I look forward to the results of the genetics work.

    Reply
    • Lara Shepherd

      Thanks for your help Reuben! We found most morphological diversity in eastern and northern Northland rather than your part of the country. However, the long skinny form seemed to be centred in western Northland, around Warawara and Omahuta.

  6. John Grehan

    Since this is a public venue I would like to suggest an amendment regarding the phrase “… in this case toropapa, mimic unpalatable plants to avoid being eaten by browsing animals.” That makes it read as if toropapa consciously do something to avoid a future outcome. This might work with ‘Intelligent Design’ theory but there is no empirical evidence, as yet, that evolution works through teleological (purposeful) mechanisms. Best to avoid teleological language unless one is really making such an assertion.

    Reply
    • Lara Shepherd

      Thanks for your comment John. I’m certainly not suggesting toropapa is making a decision to mimic something else. To me it seems more likely that some of the morphological variation in toropapa, by chance, resembles other species and this provided a selective advantage over other toropapa forms.

  7. John Grehan

    Very nice pictures. Fascinating variety of vegetative growth and hope you can sort them out. The genus is certainly significant for its endemism. As Heads (2017) pointed out, it is an example of a New Zealand genus that does not nest within an Australian group as may be expected if it were the result of chance dispersal from Australia. One systematic study suggests that Alseuosmia is the sister group of Wittsteinia (one species in Victoria and one in New Guinea). Another classic case of Mesozoic vicariance.

    Reply
  8. Olwen Mason

    Good luck with your project.

    Reply
  9. Lynn Cadenhead

    It will be interesting to see the outcome of this project

    Reply
    • Lara Shepherd

      Hi Lynn, I’ll be blogging about the results sometime in the future.

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