Mauritius Island, where the Roussea simplex is found.
Photo: Chuckas_McFly (Flickr)

Not everyone imagines plants to be much fun. But for Spanish horticulturist Carlos Magdalena, also known as the Plant Messiah, the secret lives of plants are fascinating. After reading his new book The Plant Messiah, you might be inclined to agree.

In the book, Magdalena takes readers along on his quest to save some of the world’s rarest flora, through the trial and error of seed collecting, propagation, and replanting. His subjects include the café marron (Ramosmania rodrisguesi), the Rodrigues hurricane palm (Dictyosperma album var. aureum), and the Roussea simplex, a gecko-pollinated shrub that doesn’t care for a common name. All are island plants, and endangered. Due to their endemic nature, these species can be easily lost if their habitat is destroyed.

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I’m not much for plants, but Magdalena’s poetic prose and attention to detail drew me in. He reminded me that we not only have birds and lizards to lose. We can also lose food sources, culture, and beauty.

Below is an excerpt from The Plant Messiah, in which Magdalena shares the story of the Roussea simplex, a plant that blooms pure white flowers and needs some saving—from global warming and “human-introduced eco-bombs,” as the author puts it.

The latest edition of the book was published April 10, 2018, and can be purchased here.

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From Chapter 4: The Messiah in Mauritius

Imagine a plant that is part liana and part shrub, with mangrove-like roots—how strange would that be? Let me introduce you to the critically endangered Roussea simplex, from the wet, high-altitude forest on Mauritius. At the moment it is in its own family, so if we lose it, the genus, species, and family will instantly become extinct.

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In 1937, Reginald Edward Vaughan, a British botanist who lived in Mauritius, and scientist Paul Octave Wiehe wrote in the Journal of Ecology that this species was widespread. “In other places an extremely thick canopy of woody lianes (Roussea simplex) develops about 4–6 meters above ground level, causing such dense shade that both terrestrial and epiphytic plants are practically excluded,” they said.

Picture that. Nowadays it has almost vanished.

After an exhaustive search of the island in 2003 and 2004, fewer than ninety were found. One group in the north of the island, at Le Pouce and other small localities, contained about eighty-five plants; the other, a long distance away in the south, in Pétrin, an area of heathland in the Black River Gorges National Park, had only three. In 2007 I visited these three plants. On my second trip to the island, though, just two were left—while one was very healthy, the other was being overgrown by a massive screw pine (Pandanus), threatening its survival.

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This dramatic decline is attributed to deforestation; the introduction of animals like rats, pigs, and monkeys, which grub up or eat the seedlings; and invasive plants competing for space—not to mention one other, odd factor, which I will come to later.

One of the healthy plants I saw was just teeming with life. You could spend a whole afternoon looking at this plant; it was loaded with flowers and fruits both times I visited. The flowers are complex, the fruits unusual, and the ecology incredible. Nearly every branch was loaded with orchids, lichens, and mosses, giving me an idea of just how much it was relied on by surrounding species. One of the orchids making itself at home on the Roussea was a lovely blooming specimen of the Mascarene endemic orchid Cryptopus elatus—a real stunner. It has a pure-white flower, which looks like one of those intricate paper snowflakes that children cut out with scissors at school.

Roussea simplex is a unique plant in many ways. Besides being the sole member of the subfamily (Rousseoideae), it is the only plant in the world that relies on the same animal for both pollination and seed dispersal—the rare Mauritian blue-tailed day gecko (Phelsuma cepediana), which lives mostly in the prickly-leaved screw pines, drinking the water that pools at the base of the leaves and eating the many insects that also live there, while protected from predators. I imagine it has a pretty good life.

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But as the same animal is relied upon to pollinate and disperse the seeds, this makes the plant extremely vulnerable: if the pollinator and seed-disperser goes, the plant goes too. In fact, no other plant does this, for just this reason. A single extinction of the helper, and all of a sudden there are two problems to solve.

Blue-tailed day gecko
Photo: George Sayer (Flickr)

The plant itself has long stems but can be bushy too, and bears bright orange hanging flowers with thick, waxy petals that produce lots of yellow nectar for the gecko to drink in return for pollination. When the fruit develops, it is like the teat on a baby’s bottle, and secretes a jamlike substance from its tip, full of seeds. The gecko licks the sweet gel, then disperses the seeds in its poo. The gecko never ventures farther than 160 feet from home, so for the plant to be pollinated and disperse its seeds it has to be close to a screw pine—a kind of lavatorial symbiosis. This intricate ecological association seems to be necessary for Roussea simplex to have a fulfilled and happy life.

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The first time I saw the plant, I took cuttings, including one piece of stem where a root had appeared naturally due to the damp conditions. “This is going to be easy,” I thought. But my optimism rapidly disappeared. Some of the cuttings stayed alive for about a year but never produced roots, so eventually died. The piece of stem with a root (known in horticulture as a naturally layered plant) was little better. Although it had a single large root, it did nothing, then died. It was very strange.

I tried again in 2010—this time from seed that I had brought back with me from my second trip, seed that the staff from the National Parks and Conservation Service told me would be difficult to germinate. I had also emailed my friend Dr. Viswambharan Sarasan in the Micropropagation Unit at Kew while I was in Mauritius, and he suggested something other than the traditional method of sowing seed when ripe: “Do exactly what you do with the orchids—collect unripe fruits, take them to the flow bench, sterilize them, and put them in flasks.” I did this, and the unripe fruits arrived back at Kew with me, less than thirty-six hours after collection.

I decided to try to sow the seeds from ripe fruit in conventional ways, since there were plenty of them. The challenge, though, was how best to clean them. The sticky jelly had to be removed to prevent the seeds from rotting. In the wild, this jelly would be digested by the blue-tailed day gecko’s gut. What I needed was a bit of lizard mimicry.

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I tried spreading them out on paper to dry, but that didn’t work very well, as the jelly formed a thick crust rather than evaporating, so I went for a cup of coffee and thought again. The second time I squeezed a massive ball of jelly out of the fruit so I could get plenty of seeds, and put them in water. By adding water, then decanting, over and over again, a bit like panning for gold, I managed to wash away the jelly successfully and was then able to sow my “gold dust” seeds.

Only one germinated, but with this washing technique I became the first person in the world to germinate a seed from this plant in cultivation.

A year later it was not doing much—just like the cuttings, it was going yellow and chlorotic. I decided it was probably lack of nutrients and fertilized it a tiny little bit. As a result it died. That’s a drastic way of showing your disapproval. At least I learned something from its demise, though.

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The plants that Sarasan had managed to grow in the Micropropagation Unit were now doing well, though. No one knew if the plant I had collected the unripe fruits from had been cross-pollinated by another, so there was a chance that most of the seeds would be sterile. Germination was poor, but we still managed to keep alive those growing in sterile conditions, and multiplied them by division too. I also contacted botanist Claudia Baider, who works at the Mauritius herbarium, to ask if she would collect me some seeds from the other end of the island, where there was a larger population. Together we could gather a much greater volume of seed and get some genetic diversity in the offspring.

With the original plants from Micropropagation and those that survived from a second batch I germinated, we were at last gaining some momentum, though it had taken four or five years. But then this second batch died during a hot summer and the number in cultivation crashed once again.

Maybe the species was sensitive to high temperatures, I wondered. After all, the small population in the south was in a cooler part of the island. But then they are from Mauritius, and the article said that they used to be all over the island—they should be able to take the heat.

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It was only then that I had the thought: “Perhaps it is because the seed was taken from the population of three, at a high point on the island. That population may be more sensitive to heat.”

I needed to find out about the conditions at Le Pouce, where most of the rest of the plants were growing, and Claudia Baider again came to the rescue. She said this population was found in a southeast-facing position—the equivalent of northwest- facing in the northern hemisphere—and that Le Pouce was rather cool, so high temperatures, even in an English summer, could indeed be too much for the plants.

I experimented. The following summer of 2013 I put some tiny plants inside an air-conditioned cabinet and they all survived. Far from liking it hot, as expected, they just like to be cool.

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Perhaps this plant has been alerting us to the fact that global warming has been happening for much longer than we thought; the plant and its ecosystem have been nearly wiped out by a warming world. Claudia also reckoned it germinates only at the base of tree ferns in its native habitat because it is moist there and free of competing weeds, and the plant has adventurous roots that end up growing all over the place. Even then it would still need the gecko to deposit the seeds.

There is a further twist. Not all the damage on Mauritius has been done by large grazing animals like sheep and goats. Settlers accidentally introduced a tiny ant, first described in Indonesia in 1861—Technomyrmex albipes, found in the Indo-Australian region, from India to eastern Australia and throughout the Pacific—which forages on nectar and fruit pulp. The ant has discovered that the hollow flowers of Roussea simplex last for a few days, so it puts mealybugs inside the flowers, seals them in with clay, then farms them for “honeydew” in captivity. When the gecko comes to pollinate the flowers, the ants attack the lizard to drive it away and the critically endangered Roussea simplex isn’t pollinated. If, after a constant ant attack, the gecko stops visiting a plant, it will stop reproducing through lack of seed.

When you think of threats to endangered plants on Mauritius, you would never think of an ant. Human-introduced eco-bombs strike in the most unexpected places.

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Luckily, the plants are finally doing well in cultivation, surviving with careful monitoring inside the protected fenced reserves of Mauritius and the glass nurseries of Kew. Hopefully one day they will break free.

One final thought: Roussea simplex was named after the intellectual Jean-Jacques Rousseau, an eighteenth-century Francophone-Genevan philosopher, writer, and composer. I am an admirer of his political philosophy, and he was a fan of natural science too. While reading Rousseau, I came across this quote:

The first man who, having fenced in a piece of land, said “This is mine,” and found people naïve enough to believe him, that man was the true founder of civil society. From how many crimes, wars, and murders, from how many horrors and misfortunes might not any one have saved mankind, by pulling up the stakes, or filling up the ditch, and crying to his fellows: Beware of listening to this impostor; you are undone if you once forget that the fruits of the earth belong to us all, and the earth itself to nobody.

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Fences were once used to protect private property and livestock from wild nature, but nowadays fences protect wildlife from us. Funny, that. I wonder what Rousseau would have thought about the plight of his plant.

From the book THE PLANT MESSIAH by Carlos Magdalena. Copyright © 2018 by Carlos Magdalena. Published by arrangement with Doubleday, an imprint of The Knopf Doubleday Publishing Group, a division of Penguin Random House LLC.