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World’s rarest tree gets some help

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The last wild Pennantia baylisiana treeThe tree species known only as Pennantia baylisiana could be the rarest plant on Earth. In fact, the Guinness Book of World Records once called it that. Just a single tree exists in the wild, on one of the Three Kings Islands off the coast of New Zealand, where it has sat, alone, since 1945. It didn’t used to be so solitary, but humans introduced goats to the island, which ate every other member of its species.

Over the last few decades, scientists have tried to create more P. baylisiana trees, but aside from getting cuttings to grow, simple biology got in the way: The tree was thought to be female, and it appeared to need a male to properly generate fruit and seeds.

While preparing a recovery plan for the species in the early 1990s, Peter de Lange, a scientist with the New Zealand Department of Conservation (DoC), found several intriguing pieces of information. First, gardeners on the New Zealand mainland had several P. baylisiana seedlings (all cloned from cuttings of the original plant), which proved to be pure examples of the species, not hybrids of other Pennantia species as had originally been thought. Second, one of the seedlings had actually produced fruit following manual pollination. This led de Lange to conclude that the wild tree might not truly be female after all. Additionally, similar research published around the same time suggested that the tree was female but appeared to also bear a low level of male-like qualities that would allow it to pollinate itself.

Since then, hundreds of P. baylisiana seedlings have been sold by mainland nurseries, but scientists delayed taking trees or seeds back to Three Kings Islands for fear of introducing diseases or fungal pathogens that could harm the healthy wild tree.

But this year, de Lange and his team have returned to Three Kings Islands with the intention of planting 1,600 P. baylisiana seeds. The seeds, says de Lange, have been carefully prepared to eliminate any possibility of disease. "We removed the flesh, air-dried the seeds and then washed them in 10 percent hypochlorite and then 70 percent ethanol in a lamina flow hood. We found the seeds germinated fine with this treatment, and preliminary screening showed no evidence of virus or other diseases."

And so P. baylisiana seeds are returning to their native land, and it is hoped that new trees will soon follow. The seeds are expected to take six to 10 years to grow large enough to themselves start flowering. The project will continue until they have 500 viable adult trees.

De Lange says this stage is exciting, but there is still risk. "Of course this action does not address the fact that all seedlings are derived from one tree," he says, "so the species is severely bottlenecked," meaning it lacks the genetic diversity that could protect it in the long run from diseases and other factors. "But we have the knowledge that the species is a polyploid [has extra chromosomes], so hopefully it has plenty of resilience."

Meanwhile, de Lange reports that his colleagues have not been idle on the island. Janeen Collings, a botanist with the DoC, has planted several cuttings near the original tree, several of which have grown and, with her help, produced fruit. "While birds probably took most mature fruit, some she managed to get and sow in the field," de Lange says. Although the seedlings grew, they unfortunately died within a year. "Although this sounds unpromising, when you consider the islands are virtually inaccessible and it’s expensive to get there, and to do this type of work you need to visit three to four times a year, her work is spectacular to say the least," de Lange says.

Photo: The last wild Pennantia baylisiana tree. Photo by Tony Silbery. Used with permission.

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  1. 1. way2ec 10:24 pm 04/20/2010

    All involved should be given medals! Are the goats under control and or have the seedlings been fenced in? How many trees are there in the world, arboretums, private collections, etc.? From the story it sounds like there is only this one individual which luckily self-seeded. Are there other similar programs for the second and third rarest trees, if in fact they have been identified?

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  2. 2. candide 8:47 am 04/21/2010

    @way2ec -

    " Are there other similar programs for the second and third rarest trees, if in fact they have been identified"

    I would doubt that there are similar programs. If there were – at what "level" would it stop? Should we also have programs for rare animals?

    I fear that we (humans) are simply having far reaching effects on many, many plants and animals. We are, no doubt, making many species extinct – well beyond the ‘normal’ rate.

    What we don’t understand about the interconnectedness of other plants and animals can, indeed, harm us, and most certainly will. Until we collectively learn to live sustainably and cooperatively with the rest of nature the future doesn’t look good.

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  3. 3. dbtinc 9:18 am 04/21/2010

    doesn’t this imply that humans are an instrument of evolution?

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  4. 4. candide 9:48 am 04/21/2010

    @dbtinc -

    "doesn’t this imply that humans are an instrument of evolution?"

    - In what way?

    Yes, we are part of nature and we evolve. We also affect other species, more so than any species (so far).

    But, like bacteria in a petrie dish will grow and exhaust its food supply then collapse, we humans live in a closed system with finite supplies. Whether or not we exhaust our resources and collapse has yet to be determined.

    Just because we do anything doesn’t mean its right, sustainable and part of natural evolution. If we had a full-scale nuclear/biochemical war and extinguished ourselves and much of the rest of the planets life forms – would that just be natural evolution?

    Suppose, just for an example, we used fertilizers and insecticides in an ill-advised manner and extinguished ALL bees (along with a bunch of other insect species). Would that be just natural evolution? It certainly would have far reaching consequences.

    The main point is that we (humans) should collectively learn to live sustainably and cooperatively with the rest of nature, to be a working part of the whole, rather than a force that extinguishes other species through its dominant, irreversible, unsustainable actions.

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  5. 5. dbtinc 9:58 am 04/21/2010

    "…in what way" – in just about every human endeavor; these apply an evolutionary pressure. Maybe this is a natural part of evolution?

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  6. 6. SensiJoe 10:25 am 04/21/2010

    i hope i can be involved int eh bringing back of so many species that we as humans have had a hand in destroying.

    dbtinc – i think you are right. i remember watching a documentary about cork trees. and how they are harvested ever so cautiously to get the precious cork from them. and not all are harvested in the same year. – however, my point, these peoples (i think it they were Italian or Greek) knew that once they intervened with the life of the tree they must continue to do so the rest of the trees life. continuing to groom it, cut it back, not cut it back, ect and so forth. inevitably we (they) must have an effect on the evolution of that species of tree; perhaps the cork bark will be easier to remove in the future, perhaps more difficult.

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  7. 7. candide 10:49 am 04/21/2010

    @dbtinc -

    " Maybe this is a natural part of evolution?"

    - In a way one could say that ANYTHING that happens is part of natural evolution. Extinction is part of natural evolution.

    So why should we bother to even try to live sustainably, it’s all just part of natural history and evolution of earth.

    If we humans disappear, so what? Just another chapter…

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  8. 8. dbtinc 10:52 am 04/21/2010

    as will most likely happen…

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  9. 9. way2ec 1:14 am 04/22/2010

    Agreed! Sometimes the only way I can maintain a positive outlook on the future is take the LONG view, 10,000, 100,000, a million years down the road. As far as the comments as to humans being part of the evolutionary processes of this planet, ecology teaches that everything interacts with everything else. Can’t imagine NOT being part of the process, like what would that look like?

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