Our promiscuous Pseudopanax plants

New Zealand’s plants have a bit of a reputation for pronounced promiscuity. There is supposedly a high rate of hybridisation, or individuals of one species breeding with individuals of a different species.

I’m not entirely sure that this reputation is nationally deserved. Nevertheless, a striking example of hybridisation occurs in Pseudopanax, which is one of the groups I am researching; indeed, their hybridisation is what attracted me to them!

Two of the species – Pseudopanax crassifolius, horoeka, lancewood, and Pseudopanax lessonii, houpara, coastal five-finger – hybridise wherever they occur together, be this in the wild or in cultivation.

The leaf on the left is of coastal five-finger, that on the right is from a juvenile lancewood, and the three in between are from different hybrid individuals. Photos by Leon Perrie. Montage (c) Museum of New Zealand Te Papa Tongarewa.

The leaf on the left is of coastal five-finger, that on the right is from a juvenile lancewood, and the three in between are from different hybrid individuals. Photos by Leon Perrie. Montage (c) Museum of New Zealand Te Papa Tongarewa.

There are several other five-finger and lancewood Pseudopanax species in New Zealand. However, despite their very different appearance, most of the hybridisation I have seen appears to be between lancewood and coastal five-finger, and we are using genetic analyses to determine just how much gene-flow occurs between them.

 

Juvenile lancewood, horoeka, Pseudopanax crassifolius. Photo by Leon Perrie. (c) Leon Perrie, Wellington.

Juvenile lancewood, horoeka, Pseudopanax crassifolius. Photo by Leon Perrie. (c) Leon Perrie, Wellington.

Adult lancewood, horoeka, Pseudopanax crassifolius. Photo by Leon Perrie, Curator. (c) Museum of New Zealand Te Papa Tongarewa.

Adult lancewood, horoeka, Pseudopanax crassifolius. Photo by Leon Perrie, Curator. (c) Museum of New Zealand Te Papa Tongarewa.

 

Coastal five-finger, houpara, Pseudopanax lessonii. Photo by Leon Perrie. (c) Leon Perrie, Wellington.

Coastal five-finger, houpara, Pseudopanax lessonii. Photo by Leon Perrie. (c) Leon Perrie, Wellington.

Some of the hybrids are easy to identify, but others closely resemble one or other of the parental species. Any individual with leaves that look like those of lancewood but with two or more leaflets is actually a hybrid. Coastal five-finger always has broad leaflets.

Wellington’s Otari-Wilton’s Bush has a garden display of lancewood, coastal five-finger, and their hybrids, for 2009.

Lancewood occurs naturally throughout New Zealand. Coastal five-finger and the hybrids are native only to the coasts of the northern North Island (about Raglan and Gisborne northwards), but are frequently cultivated elsewhere. Coastal five-finger and the hybrids have escaped from cultivation, effectively becoming weeds, in many places outside their native distribution.  They can be very invasive.

Distribution maps for (A) lancewood, (B) coastal five-finger, and (C) their hybrids. Circles indicate natural distributions, and were compiled using data from the AK (Auckland Museum), CHR (Landcare Research), NZFRI (Scion), and WELT (Te Papa) herbaria. Squares for coastal five-finger and the hybrids indicate their ‘weedy’ distribution, this being a preliminary assessment based on my observations.

Distribution maps for (A) lancewood, (B) coastal five-finger, and (C) their hybrids. Circles indicate natural distributions, and were compiled using data from the AK (Auckland Museum), CHR (Landcare Research), and WELT (Te Papa) herbaria. Squares for coastal five-finger and the hybrids indicate their ‘weedy’ distribution, this being a preliminary assessment based on my observations.

8 Responses

  1. Pete Ozich

    Great article. I’m involved in reforestation projects in diamond harbour banks peninsular. We have a lot of these hybrids around. Do you know if the hybrids are fertile? I assume there must be some selection pressure that has kept them from completely blending up north. If hybrids are sterile or otherwise disadvantaged, I will concentrate on removing p lessonii rather than all hybrids.

    Reply
    • Leon Perrie

      Hi Pete,
      I’m fairly sure that the hybrids are fertile, based on the morphological and genetic patterns I have seen. There has also been anecdotal reports of successful propagation of seeds from hybrids.
      I don’t know what keeps the species from blending in their native zone of overlap!
      But I suspect it is primarily ecological. Lessonii does well/best on the coast; crassifolius in inland forest; and hybrids in between. But it seems that hybrids can also do well in disturbed areas, at least in some cases. There are places where the hybrids occur in big numbers with only one of the parents; this suggests to me that a ‘hybrid population’ can persist for some time, with hybrids breeding successfully with other hybrids.
      You might, then, be better to target both lessonii and the hybrids. Sorry I can’t give you more convenient news.
      Leon

  2. Renee

    I need some help identifying Pseudopanax plants please

    can you give me your email so I can email you the photos?

    Reply
  3. Florence Liger

    Just wanted to say thanks, Leon :)
    Your blog posts are always so so helpful for identifying all the plants in my photos!

    Reply
  4. Leon

    My email is leonp@tepapa.govt.nz
    Birds do disperse the seed around, but evidently the seeds never made it to Wellington, or if they did, the seeds never grew into plants, at the time of human settlement. Why that was, I don’t know. Perhaps there was an ecological region, or maybe it was just chance (other species were here first, and they couldn’t invade).
    From the earliest observations it is known that a whole suite of plants that now occur in Wellington formerly occurred only elsewhere in NZ. The inference is that they have got here only via humans. In some cases the transfer is actually recorded.
    Examples beside coastal five-finger include pohutukawa, karo (Pittosporum crassifolium and P. ralphii), and lacebark (Hoheria populnea). None were present in Wellington at human settlement, but all now part of Wellington’s ‘wild’ landscape.
    Most native NZ plants don’t occur naturally throughout the county; many are/were naturally restricted to one region or another. But, humans have moved them round a lot, and a few of them have become weedy in places they previously didn’t occur.

    Reply
  5. Tom Robinson

    I’m following most of the argument, and that hybrids are considered native in the far north.
    I don’t understand why Coastal 5-Finger is only present in Wellington (and other areas) now NZ’s been settled—wouldn’t birds have distributed the seeds around NZ in prior times?
    And yes, would like to e-mail some photos for confirmation but can only find a generic Te Papa address…

    Reply
  6. Leon

    Good question Tom.
    Coastal five-finger and its hybrids with lancewood may be propagating without human assistance in Wellington, but they are not indigenous to Wellington. That is, they were not part of Wellington’s flora at initial human contact.
    I would argue that their occurrence outside the northern North Island is not natural.
    I regard it as an analogous situation to gorse, pines, boneseed, pampas, barberry etc. etc. None native to Wellington, but all now naturalised in Wellington, and all regarded as most of us as weeds.
    But, to step back, you say that your plants have “small stalks their fingers”. The leaflet stalks of coastal five-finger (P. lessonii) and the hybrids are so small that they’re pretty much absent. If your plants have definite stalked leaflets, they might be five-finger (P. arboreus), which is native to Wellington. Feel free to email me photos if you’d like me to check.

    Reply
  7. Tom Robinson

    Thanks for the interesting article Leon. I’ve been converting our suburban property in Wellington to natives (plus edibles) and have been told what I thought were 5-fingers are actually a hybrid (they have small stalks on their fingers and irregular number of leaves). Given the hybrids occur naturally what’s the reasoning/advantage of removing them and trying to keep the strain pure? Thanks

    Reply

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