An Endemic Spurge in Florida

A pistillate cyathium of a Telephus spurge.

Endemism fascinates me. Why some organisms occur in certain restrict areas geographically and nowhere else is such a fun topic to ponder. On a recent trip to the Florida Panhandle, I was lucky enough to encounter a wonderful little plant endemic to pine flatwoods located at the very tip of the Apalachicola region. It is a type of spurge known as Telephus spurge (Euphorbia telephioides) whose natural history is captivating to say the least.

The Telephus spurge is a denizen of dry, sandy soils. Its fleshy leaves and deep, tuberous taproot not only allow it to handle drought via the storage of water and nutrients, its root system also allows it to live a long time. Though it is hard to say how long individuals can actually live, lifetimes measured in decades are well within the realm of possibility. Like many members of the spurge family (Euphorbiaceae), the Telephus spurge is also well defended by toxic, milky sap.

A staminate cyathium of a Telephus spurge.

The inflorescence of the Telephus spurge is defined as a cyathium. Plants can produce multiple cyathia per plant, and for the Telephus spurge, these can contain only male, only female, or both reproductive structures. Sex of individual Telephus spurge is an interesting topic unto itself and very important when it comes to conservation (more on that in a bit). Individual Telephus spurge can be fluid in their sexual expression from one year to the next. Individuals that produced only male cyathia one year can go on to produce only female or bisexual cyathia in subsequent years. No one can say for sure what triggers these changes among individuals, but disturbance and energy reserves likely play a considerable role.

One of the most important aspects of Telephus spurge ecology is fire. Without regular fires, the entire habitat of the Telephus spurge would gradually close in with woody shrubs and trees and disappear. Even though most of the top parts of these plants are killed by fires, their large tuberous root system allows them to readily regrow what was lost. That is not to say that individuals regularly regrow after fires. In fact, plants have been known to disappear for years at a time following top killing events, only to resprout at some point in the future when favorable conditions return.

Telephus spurge fruits are quite pretty!

At this point, it should be obvious that for this species to persist, its habitat needs to be maintain via fire. Management for this species is very important given its narrow distribution and sporadic occurrence on the landscape. However, there are still many hurdles in the way of effective Telephus spurge conservation. For starters, though it once likely enjoyed a more contiguous distribution throughout the Apalachicola region, habitat destruction from logging, ditching, and development have highly fragmented its populations into tiny clusters. The smaller these clusters become, the more vulnerable they are to extirpation.

Another factor complicating the conservation of this species is its aforementioned sexual fluidity. Because we still don’t know what triggers a change in sexual expression among individuals from one year to the next, populations can fluctuate greatly in terms of their reproductive capacity. For instance, if a population comprised of many individuals with bisexual cyathia one year suddenly switches to producing mostly male cyathia the following year, seed production can decrease greatly. Until we know more about the reproductive ecology of this species, maintaining populations with regular fire while limiting the amount of logging and development is the best chance we have at ensuring this extremely rare spurge has a future on this planet.

The one upside to this story is that, where properly managed, Telephus spurge can reach high abundances. With a little bit of effort, these populations are relatively easy to map and seed can be collected and maintained to preserve valuable genetic material. Still, without proper management and land conservation/restoration efforts, the future of this tiny spurge and many of its botanical neighbors hangs in the balance. Support your local land conservancy today, because stories like this are far more common than you think!

Further Reading: [1] [2]

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

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.

Photo by Jon Sullivan licensed under CC BY-NC 2.0

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]

Can Cultivation Save the Canary Island Lotuses?

Photo by VoDeTan2 Dericks-Tan licensed under the GNU Free Documentation License

Growing and propagating plants is, in my opinion, one of the most important skills humanity has ever developed. That is one of the reasons why I love gardening so much. Growing a plant allows you to strike up a close relationship with that species, which provides valuable insights into its biology. In today’s human-dominated world, it can also be an important step in preventing the extinction of some plants. Such may be the case for four unique legumes native to the Canary Islands provided it is done properly.

The Canary Islands are home to an impressive collection of plants in the genus Lotus, many of which are endemic. Four of those endemic Lotus species are at serious risk of extinction. Lotus berthelotii, L. eremiticus, L. maculatus, and L. pyranthus are endemic to only a few sites on this archipelago. Based on old records, it would appear that these four were never very common components of the island flora. Despite their rarity in the wild, at least one species, L. berthelotii, has been known to science since it was first described in 1881. The other three were described within the last 40 years after noting differences among plants being grown locally as ornamentals.

Photo by John Rusk licensed under CC BY 2.0

All four species look superficially similar to one another with their thin, silvery leaves and bright red to yellow flowers that do a great impression of a birds beak. The beak analogy seems apt for these flowers as evidence suggests that they are pollinated by birds. In the wild, they exhibit a creeping habit, growing over rocks and down overhangs. It is difficult to assess whether their current distributions truly reflect their ecological needs or if they are populations that are simply hanging on in sites that provide refugia from the myriad threats plaguing their survival.

None of these four Lotus species are doing well in the wild. Habitat destruction, the introduction of large herbivores like goats and cattle, as well as a change in the fire regime have seen alarming declines in their already small populations. Today, L. eremiticus and L. pyranthus are restricted to a handful of sites on the island of La Palma and L. berthelotii and L. maculatus are restricted to the island of Tenerife. In fact, L. berthelotii numbers have declined so dramatically that today it is considered nearly extinct in the wild.

Contrast this with their numbers in captivity. Whereas cultivation of L. eremiticus and L. pyranthus is largely restricted to island residents, L. berthelotii and L. maculatus and their hybrids can be found in nurseries all over the world. Far more plants exist in captivity than in their natural habitat. This fact has not been lost on conservationists working hard to ensure these plants have a future in the wild. However, simply having plants in captivity does not mean that the Canary Island Lotus are by any means safe.

One of the biggest issues facing any organism whose numbers have declined is that of reduced genetic diversity. Before plants from captivity can be used to augment wild populations, we need to know a thing or two about their genetic makeup. Because these Lotus can readily be rooted from cuttings, it is feared that most of the plants available in the nursery trade are simply clones of only a handful of individuals. Also, because hybrids are common and cross-pollination is always a possibility, conservationists fear that the individual genomes of each species may run the risk of being diluted by other species’ DNA.

Photo by VoDeTan2 Dericks-Tan licensed under the GNU Free Documentation License

Luckily for the Canary Island Lotus species, a fair amount of work is being done to not only protect the remaining wild plants, but also augment existing as well as establish new populations. To date, many of the remaining plants are found within the borders of protected areas of the island. Also, new areas are being identified as potential places where small populations or individuals may be hanging on, protected all this time by their inaccessibility. At the same time, each species has been seed banked and entered into cultivation programs in a handful of botanical gardens.

Still, one of the best means of ensuring these species can enjoy a continued existence in the wild is by encouraging their cultivation. Though hybrids have historically been popular with the locals, there are enough true species in cultivation that there is still reason for hope. Their ease of cultivation and propagation means that plants growing in peoples’ gardens can escape at least some of the pressures that they face in the wild. If done correctly, ex situ cultivation could offer a safe haven for these unique species until the Canary Islands can deal with the issues facing the remaining wild populations.

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

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