The Future of New Zealand's Shrubby Tororaro Lies in Cultivation

May 2, 2021

Photo by Jon Sullivan licensed under CC BY-NC 2.0

I was watching a gardening show hosted by one of my favorite gardeners, Carol Klein, when she introduced viewers to a beautiful, divaricating shrub whose branching structure looked like a dense tracery of orange twigs. She referred to the shrub as a wiggy wig and remarked on its beauty and form before moving on to another wonderful plant. I was taken aback by the structure of the shrub and had to learn more. Certainly its form had to be the result of delicate pruning and selective breeding. Imagine my surprise when I found its growth habit was inherent to this wonderful and rare species.

The wiggy wig or shrubby tororaro is known to science as Muehlenbeckia astonii. It is a member of the buckwheat family (Polygonaceae) endemic to grey scrub habitats of eastern New Zealand. Though this species is widely cultivated for its unique appearance, the shrubby tororaro is not faring well in the wild. For reasons I will cover in a bit, this unique shrub is considered endangered. To understand some of these threats as well as what it will take to bring it back from the brink, we must first take a closer look at its ecology.

Photo by WJV&DB licensed under CC BY-SA 3.0

As mentioned, the shrubby tororaro is endemic to grey scrub habitats of eastern New Zealand. It is a long lived species, with individuals living upwards of 80 years inder the right conditions. Because its habitat is rather dry, the shrubby tororaro grows a deep taproot that allows it to access water deep within the soil. That is not to say that it doesn’t have to worry about drought. Indeed, the shrubby tororaro also has a deciduous habit, dropping most if not all of its tiny, heart-shaped leaves when conditions become too dry. During the wetter winter months, its divaricating twigs become bathed in tiny, cream colored flowers that are very reminiscent of the buckwheat family. From a reproductive standpoint, its flowers are quite interesting.

The shrubby tororaro is gynodioecious, which means individual shrubs produce either only female flowers or what is referred to as ‘inconstant male flowers.’ Essentially what this means is that certain individuals will produce some perfect flowers that have functional male and female parts. This reproductive strategy is thought to increase the chances of cross pollination among unrelated individuals when populations are large enough. Following successful pollination, the remaining tepals begin to swell and surround the hard nut at the center, forming a lovely translucent fruit-like structure that entices dispersal by birds. As interesting and effective as this reproductive strategy can be in healthy populations, the shrubby tororaro’s gynodioecious habit starts to break down as its numbers decrease in the wild.

As New Zealand was colonized, lowland habitats like the grey scrub were among the first to be converted to agriculture and that trend has not stopped. What grey scrub habitat remains today is highly degraded by intense grazing and invasive species. Habitat loss has been disastrous for the shrubby tororaro and its neighbors. Though this shrub was likely never common, today only a few widely scattered populations remain and most of these are located on private property, which make regular monitoring and protection difficult.

Observations made within remnant populations indicate that very little reproduction occurs anymore. Either populations are comprised of entirely female individuals or the few inconstant males that are produced are too widely spaced for pollination to occur. Even when a crop of viable seeds are produced, seedlings rarely find the proper conditions needed to germinate and grow. Invasive grasses and other plants shade them out and invasive insects and rodents consume the few that manage to make it to the seedling stage. Without intervention, this species will likely go extinct in the wild in the coming decades.

Photo by John Pons licensed under CC BY-SA 4.0

Luckily, conservation measures are well underway and they involve cultivation by scientists and gardeners alike. There is a reason this shrub has become very popular among gardeners - it is relatively easy to grow and propagate. From hardwood cuttings taken in winter, the shrubby tororaro will readily root and grow into a clone of the parent plant. Not only has this aided in spreading the plant among gardeners, it has also allowed conservationists to preserve and bolster much of the genetic diversity within remaining wild populations. By cloning, growing, and distributing individuals among various living collections, conservationists have at least safeguarded many of the remaining individuals.

Moreover, cultivation on this scale means dwindling wild populations can be supplemented with unrelated individuals that produce both kinds of flowers. By increasing the numbers within each population, conservationists are also decreasing the distances between female and inconstant male individuals, which means more chances for pollination and seed production. Though by no means out of the proverbial woods yet, the shrubby tororaro’s future in the wild is looking a bit brighter.

This is good news for biodiversity of the region as well. After all, the shrubby tororaro does not exist in a vacuum. Numerous other organisms rely on this shrub for their survival. Birds feed heavily on its fruits and disperse its seeds while the larvae of at least a handful of moths feed on its foliage. In fact, the larvae of a few moths utilize the shrubby tororaro as their sole food source. Without it, these moths would perish as well. Of course, those larvae also serve as food for birds and lizards. Needless to say, saving the shrubby tororaro benefits far more than just the plant itself. Certainly more work is needed to restore shrubby tororaro habitat but in the meantime, cultivation is ensuring this species will persist into the future.

Further Reading: [1] [2] [3]

The Creeping Fuchsia

February 19, 2019

Photo by James Gaither licensed under CC BY-NC-ND 2.0

Meet Fuchsia procumbens aka the creeping Fuchsia. This lovely plant is endemic to New Zealand where, sadly, it is threatened. In its native habitat, it is strictly a coastal species, prefering to grow in sandy soils. The flowers are quite unlike most other members of the genus Fuchshia and they exhibit an interesting flowering strategy.

Fuchsia procumbens produces 3 distinct flower forms, flowers with only working male parts, flowers with only working female parts, and hermaphroditic flowers. One reason for this is to avoid self-pollination. The other reason may have something to do with energy costs. When growing conditions are less than stellar, the plant saves energy by producing male flowers.

Photo by Martin Reith licensed under CC BY-SA 4.0

Pollen is relatively cheap after all. When conditions improve, the plant may allocate more resources to female and hermaphroditic flowers. This strategy worries some botanists because it seems like some populations of F. procumbens only ever produce single sex flowers. After pollination, the flowers give way to bright red berries that are larger than the flowers themselves!

The most interesting thing about this species is, despite its apparent specificity in habitat preferences in the wild, it competes well with aggressive grasses, which has made it a very popular ground cover. As it turns out, its growing popularity in the garden trade may save this species from being placed on the endangered species list.

Photo Credits: [1] [2]

Meet the Pygmy Clubmoss

November 14, 2018

Photo by Leon Perrie licensed under CC BY 4.0

No, these are not some sort of grass or rush. What you are looking at here is actually a member of the clubmoss family (Lycopodiaceae). Colloquially known as the pygmy clubmoss, this odd little plant is the only species in its genus - Phylloglossum drummondii. Despite its peculiar nature, very little is known about it.

The pygmy clubmoss is native to parts of Australia, Tasmania, and New Zealand but common it is not. From what I can gather, it grows in scattered coastal and lowland sites where regular fires clear the ground of competing vegetation. It is a perennial plant that makes its appearance around July and reaches reproductive size around August through to October.

Reproduction for the pygmy clubmoss is what you would expect from this family. In dividual plants will produce a reproductive stem that is tipped with a cone-like structure. This cone houses the spores, which are dispersed by wind. If a spore lands in a suitable spot, it germinates into a tiny gametophyte. As you can probably imagine, the gametophyte is small and hard to locate. Indeed, little is known about this part of its life cycle. Nonetheless, like all gametophytes, the end goal of this stage is sexual reproduction. Sperm are released and with any luck will find a female gametophyte and fertilize the ovules within. From the fertilized ovule emerges the sporophytes we see pictured above.

As dormancy approaches, this strange clubmoss retreats underground where it persists as a tiny tuber-like stem. Though it is rather obscure no matter who you ask, there has been some scientific attention paid to this odd little plant, especially as it relates to its position on the tree of life. Since it was first described, its taxonomic affinity has moved around a bit. Early debates seemed to center around whether it belonged in Lycopodiaceae or its own family, Phylloglossaceae.

Recent molecular work put this to rest showing that genetically the pygmy clubmoss is most closely related to another genus of clubmoss - Huperzia. This was bolstered by the fact that it shares a lot of features with this group such as spore morphology, phytochemistry, and chromosome number. The biggest difference between these two genera is the development of the pygmy clubmoss tuber, which is unique to this species. However, even this seems to have its roots in Lycopodiaceae.

If you look closely at the development of some lycopods, it becomes apparent that the pygmy clubmoss most closely resembles an early stage of development called the “protocorm.” Protocorms are a tuberous mass of cells that is the embryonic form of clubmosses (as well as orchids). Essentially, the pygmy clubmoss is so similar to the protocorm of some lycopods that some experts actually think of it as a permanent protocorm capable of sexual reproduction. Quite amazing if you ask me.

Sadly, because of its obscurity, many feel this plant may be approaching endangered status. There have been notable declines in population size throughout its range thanks to things like conversion of its habitat to farmland, over-collection for both novelty and scientific purposes, and sequestration of life-giving fires. As mentioned, the pygmy clubmoss needs fire. Without it, natural vegetative succession quickly crowds out these delicate little plants. Hopefully more attention coupled with better land management can save this odd clubmoss from going the way of its Carboniferous relatives.

Further Reading: [1] [2] [3] [4] [5] [6]

How a Conifer May Hold the Key to Kākāpō Recovery

November 4, 2018

Photo by Department of Conservation licensed under CC BY 2.0

The plight of the kākāpō is a tragedy. Once the third most common bird in New Zealand, this large, flightless parrot has seen its numbers reduced to less than 150. In fact, for a time, it was even thought to be extinct. Today, serious effort has been put forth to try and recover this species from the brink of extinction. It has long been recognized that kākāpō breeding efforts are conspicuously tied to the phenology of certain trees but recent research suggests one in particular may hold the key to survival of the species.

The kākāpō shares its island homes (saving the kākāpō involved moving birds to rat-free islands) with a handful of conifers from the families Podocarpaceae and Araucariaceae. Of these conifers, one species is of particular interest to those concerned with kākāpō breeding - the rimu. Known to science as Dacrydium cupressinum, this evergreen tree represents one of the most important food sources for breeding kākāpō. Before we get to that, however, it is worth getting to know the rimu a bit better.

Rimu are remarkable, albeit slow-growing trees. They are endemic to New Zealand where they make up a considerable portion of the forest canopy. Like many slow-growing species, rimu can live for quite a long time. Before commercial logging moved in, trees of 800 to 900 years of age were not unheard of. Also, they can reach immense sizes. Historical accounts speak of trees that reached 200 ft. (61 m) in height. Today you are more likely to encounter trees in the 60 to 100 ft. (20 to 35 m) range.

The rimu is a dioecious tree, meaning individuals are either male or female. Rimu rely on wind for pollination and female cones can take upwards of 15 months to fully mature following pollination. The rimu is yet another one of those conifers that has converged on fruit-like structures for seed dispersal. As the female cones mature, the scales gradually begin to swell and turn red. Once fully ripened, the fleshy red “fruit” displays one or two black seeds at the tip. Its these “fruits” that have kākāpō researchers so excited.

As mentioned, it is a common observation that kākāpō only tend to breed when trees like the rimu experience reproductive booms. The “fruits” and seeds they produce are an important component of the diets of not only female kākāpō but their developing chicks as well. Because kākāpō are critically endangered, captive breeding is one of the main ways in which conservationists are supplementing numbers in the wild. The problem with breeding kakapo in captivity is that supplemental food doesn’t seem to bring them into proper breeding condition. This is where the rimu “fruits” come in.

Breeding birds desperately need calcium and vitamin D for proper egg production and they seek out diets high in these nutrients. When researchers took a closer look at the “fruits” of the rimu, the kākāpō’s reliance on these trees made a whole lot more sense. It turns out, those fleshy scales surrounding rimu seeds are exceptionally high in not only calcium, but various forms of vitamin D once thought to be produced by animals alone. The nutritional quality of these “fruits” provides a wonderful explanation for why kākāpō reproduction seems to be tied to rimu reproduction. Females can gorge themselves on the “fruits,” which brings them into breeding condition. They also go on to feed these “fruits” to their developing chicks. For a slow growing, flightless parrot, it seems that it only makes sense to breed when this food source is abundant.

Though far from a smoking gun, researchers believe that the rimu is the missing piece of the puzzle in captive kākāpō breeding. If these “fruits” really are the trigger needed to bring female kākāpō into good shape for breeding and raising chicks, this may make breeding kākāpō in captivity that much easier. Captive breeding is the key to the long term survival of these odd yet charismatic, flightless parrots. By ensuring the production and survival of future generations of kākāpō, conservationists may be able to turn this tragedy into a real success story. What’s more, this research underscores the importance of understanding the ecology of the organisms we are desperately trying to save.

Photo Credits: [1] [2] [3] [4] [5]

The Colorful Megaherbs of Sub-Antarctic New Zealand

September 28, 2016

Photo by twiddleblat licensed under CC BY-SA 2.0

There is a common morphological thread among herbaceous plants growing in the colder regions of the world. Most grow small and take on a cushion-like habit. For these species, it is all about getting sensitive tissues out of the chilling winds and into an insulated microclimate. This convergent morphology seems to have been entirely lost on a cohort of plants native to the sub-Antarctic islands of New Zealand. The aptly named "megaherbs" are characterized by their large size an the often gaudy dark coloration of their blooms. Why would an entire guild of plants growing in such cold, dreary, harsh conditions converge on a strategy that, for most plants of their size, spell certain death?

The answer to this mystery is heat. In such a harsh environment any advantage, no matter how slight, can make a huge difference. What's more, whereas smaller neighboring species largely reproduce asexually, these bizarre behemoths seem to have sexual reproduction all to themselves. The key lies in their large size and extravagant coloration. A team of researchers looking at six different species of megaherb found that the thick, hairy leaves and dark colored flowers were able to take advantage of the rare occasions when the sun poked through the thick, grey, sub-Antarctic clouds.

On average, leaf and inflorescence temperatures of these megaherbs were significantly higher than the ambient conditions. For instance, in the Campbell Island daisy (Pleurophyllum speciosum), leaf and flower temperatures were consistently 9 and 11 degrees Celsius warmer than their surroundings during periods of sunshine. Because of their large size (think surface area to volume ratio), they were able to hold on to this heat much longer than smaller plant species in the same habitat. In essence, they are creating a glasshouse effect.

This means more than just a warm microclimate for these plants. Insects in this environment seek out these plants for warmth and shelter. In a region with such a sparse insect community, concentrating pollinators in and around your leaves means a higher chance of pollination, a win-win for both sides. As if this wasn't enough, higher temperatures can also facilitate seed production, adding yet another layer of benefit to growing large and darkly colored.

Photo Credits: [1] [2]

On the Wood Rose and its Bats

August 28, 2016

New Zealand has some weird nature. It is amazing to see what an island free of any major terrestrial predators can produce. Unfortunately, ever since humans found their way to this unique island, the ecology has suffered. One of the most unique plant and animal interactions in the world can be found on this archipelago but for how much longer is the question.

The story starts with a species of bat. In fact, this bat is New Zealand's only native terrestrial mammal. That's right, I said terrestrial. The New Zealand lesser short-tailed bat spends roughly 40% of its time foraging for insects on the ground. It has lots of specialized adaptations that I won't go into here but the cool part is they forage in packs, stirring up insects from the leaf litter until they reach a level of feeding frenzy that I thought was only reserved for sharks or piranhas. Along with using echo location, they also have a highly developed sense of smell. This is important for our second player in this forest floor drama.

Enter Dactylanthus taylorii, the wood rose. This plant is not a rose at all but rather a member of the tropical family Balanophoraceae. More importantly, it is parasitic. It produces no chlorophyll and lives most of its life wrapped around the roots of its host tree underground. Every once in a while a small patch of flowers break through the dirt and just barely peak above the leaf litter. This give this species it's Māori name of "pua o te reinga" or "pua reinga", which translates to "flower of the underworld." The flowers emit a musky, sweet smell that attracts these ground foraging bats. The bats are one of the only pollinators left on the island. They sniff out the flowers and dine on the nectar, all the while being dusted with pollen. Recently, it has been found that New Zealand's giant ground parrot, the kakapo, is also believed to have been a pollinator of this plant. Sadly, today the kakapo exists solely on one small island of the New Zealand archipelago.

Both the wood rose and the New Zealand lesser short-tailed bat are considered at risk for extinction. When modern man came to these islands they brought with them the general suite of mammalian invasives like rats, mongoose, cats, and pigs, which are exacting a major toll on the local ecology. The plants and animals native to New Zealand have not shared an evolutionary history with such aggressive mammalian invaders and thus have no adaptations for coping with their sudden presence. The future of the wood rose, the New Zealand lesser short-tailed bat, and the kakapo, along with many other uniquely New Zealand species are for now uncertain.

Photo Credits: Joseph Dalton Hooker (1859) and Nga Manu Nature Reserve (http://www.ngamanu.co.nz/)