The Wild World of Rattan Palms

Calamus_gibbsianus.jpg

There are a lot of big organisms out there. A small handful of these are truly massive. When someone mentions big plants, minds will quickly drift to giant sequoias or coastal redwoods. These species are indeed massive. The tallest tree on record is a coastal redwood measuring 369 feet tall. That's a whole lot of tree! What some may not realize is that there are other plants out there that can grow much "taller" than even the tallest redwood. For instance, there is a group of palms that hail from Africa, Asia, and Australasia that grow to staggering lengths albeit without the mass of a redwood.

You are probably quite familiar with some of these palm species, though not as living specimens. If you have ever owned or sat upon a piece of wicker furniture then you were sitting on pieces of a rattan palm. Rattan palms do not grow in typical palm tree fashion. Rattans are climbers, more like vines. All palms grow from a central part of the plant called the heart. They grow as bromeliads do, from meristem tissue in the center of a rosette of leaves. As a rattan grows, its stem lengthens and grabs hold of the surrounding vegetation using some seriously sharp, hooked spikes. For much of their early life they generally sprawl across the forest floor but the real goal of the rattan is to reach up into the canopy where they can access the best sunlight.

3070456167_a06111dd01_o.jpg

Rattans are not a single taxonomic unit. Though they are all palms, at least 13 genera contain palms that exhibit this climbing habit. With over 600 species included in these groups, it goes without saying that there is a lot of variation on the theme. The largest rattan palms hail from the genus Calamus and all but one are native to Asia.

Many species of rattan have whip-like stems that would be easy to miss in a lush jungle. Be aware of your surroundings though, because these spikes are quite capable of ripping clothes and flesh to pieces. The rattans are like any other vine, sacrificing bulk for an easy ride into the light at the expense of whatever it climbs on. Indeed some get so big that they break their host tree. It is this searching, sprawling nature of the rattans that allow them to reach some impressive lengths. Some species of rattan have been reported with stems measuring over 500 feet!

10368246_1018184728208392_2661304592123048565_n.jpg

Getting back to what I mentioned earlier about wicker furniture, rattans are a very important resource for the people of the jungles in which they grow. They offer food, building materials, shelter materials, an artistic medium, and a source of economic gain. In many areas, rattans are being heavily exploited as a result. This is bad for both the ecology of the forest and the locals who depend upon these species.

The global rattan trade is estimated at around $4 billion dollars. Because of this, rattans are harvested quite heavily and many are cut at too young of an age to re-sprout meaning little to no recruitment occurs in these areas. There is a lot of work being done by a few organizations to try to set up sustainable rattan markets in the regions that have been hit the hardest. More information can be found at sites like the World Wildlife Fund.

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

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

Ancient Saw Palmettos in the Heart of Florida

When we think about long lived plants, our minds tend to fixate on bristlecone pines (Pinus longaeva), coastal redwoods (Sequoia sempervirens), or that clonal patch of quaking aspen (Populus tremuloides) in Utah. What would you say if I told you that we can add a palm tree to that list? Indeed, recent evidence suggests that the saw palmetto (Serenoa repens) can reach a ripe old age measured in thousands (yes, thousands) of years.

Now, at this point some of you are probably thinking "how can you measure the age of a palm when there are no annual growth rings?!" This is a legitimate hurdle that had to be overcome before such a claim was made. Using a lot of attention to detail and some crafty mathematics, a team of researchers was able to age saw palmettos in Florida's most ancient habitats.

This work was performed on a peculiar geological formation. Aptly named the "Mid-Florida Ridge," this 150 mile sand ridge bisects the middle of the state. Throughout much of the Pliocene and early Pleistocene, sea levels were as much as 50 meters higher than they were today. Nearly all of Florida was underwater during this time. All that stuck out above the water were a series of small islands. These islands served as refugia for flora and fauna pushed south by repeated glaciations. Once the ocean receded to its current level, these islands were left high and dry, thus forming the ridge in question. Because of its history as a refugium, the Mid-Florida Ridge is home to a staggering array of plant species, some of which are endemic to this relatively small area of Florida.

Because of its relative stability through time, the Mid-Florida Ridge is a haven for long lived plant species. Thus, it was a prime location for trying to understand the longevity of the charismatic and ecologically important saw palmetto. By tagging individual palms and observing them year after year, researchers were able to get an idea of exactly how fast this species can grow. Depending on soil conditions, saw palmettos grow at a rate of somewhere between 0.88 and 2.2 cm per year. They certainly aren't winning any speed races at that rate. Regardless, you can begin to see that an estimate of yearly growth rate can shine a light on how long these palms have been around. Measurements of tagged palmettos growing on the sand ridge show that individuals aged at a staggering 500 years are not uncommon!

The light sandy looking area in the middle is the Mid-Florida Ridge

This estimate gets a bit complicated when we consider another aspect of saw palmetto biology - they are clonal. For a variety of reasons, as saw palmettos grow, their sprawling stem will often branch out, creating clones of themselves. Over time, the trunk portions that connect these clones rot away, giving the impression that they are unique individuals. Genetic analyses showed that many of the palmettos in the study area were actually clones. Using some pretty sophisticated models coupled with DNA evidence, the research team was able to reconstruct the growth history of many of these clones, thus allowing them to more accurately age these clonal colonies.

Their results are staggering to say the least. Based on the rate of growth and spread, the estimated age of these clonal patches of saw palmetto range anywhere between 1227–5215 years! At this point you should be asking yourself "how accurate are these data?" The truth is that the researchers were actually being quite conservative in their estimates. For instance, there were likely many clones well outside their study area. If so, they were likely underestimating the growth time of these clonal colonies. Additionally, they were only using the growth rates of adult saw palmettos in calculating average growth rates.

Seedling saw palmettos have been shown to have a reduced growth rate compared to adults, only 0.3 cm per year. Thus, they did not take into account the time it takes for seedlings to reach maturity. The team feel that accounting for such variables could increase the age estimates for such clonal patches to well over 8,000 years! I don't think we should be looking into buying that many birthday candles just yet, however, even their reported estimates are shocking to say the least.

Saw-Palmetto_(5614235753).gif

What we can say is that for as long as Florida has been above water, saw palmettos have played an integral role in the ecology of the region. Long before humans began developing the state, the saw palmetto was functioning as a major player, shaping these sand ridge communities into the ecosystems they are today. It is without a doubt, a species worthy of our admiration and respect.

Photo Credits: [1] [2]

Further Reading: [1]

Walking Palms

I don't know about you but Socratea exorrhiza has to be the strangest species of palm that I have ever laid eyes on. Native to Central and South America, its peculiarly stilted appearance has earned it the common name of "the walking palm." Whereas most palms invest in heavy trunks, the walking palm sends out a lanky set of stilt-roots upon which the palm grows like some otherworldly tripod.

There has been a lot of debate over the last few decades as to the purpose of these stilt-roots. In 1961 it was suggested that they were an adaptation for living in swampy areas. To date, no evidence of this has been found. Others have suggested that these roots are relatively cheap to produce compared to a solid trunk, thus allowing more investment in growing taller in a shorter amount of time while still maintaining structural integrity. This sounds attractive and is probably part of the puzzle. However, I feel that a particular study published in 1980 offers the best explanation.

Tropical forests are full of decomposition. The omnipresent threat of rot means there is a constant rain of limbs and snags from the canopy above. Trees regularly topple as well. For most plants, getting flattened by such debris is usually fatal. This is not necessarily so for the walking palm.

It has been observed that walking palms flattened by a fallen limb or tree can actually "walk" themselves out from underneath. Since most of the trunk is capable of producing stilt-roots, it doesn't take long for a new anchor to become established. Once this occurs, the palm is free to continue its journey into the canopy.

Getting squashed isn't the only worry either. Light is a premium in the deep shade of a rainforest understory. It is also short lived. A hole in the canopy that provided ample light one week may quickly close in the next, removing the life-giving rays of the sun. If a plant were able to "move around" it could potentially relocate to a sunnier spot. In a sense, this is what the walking palm does.

Walking palms are positively phototropic, meaning they lean towards a light source. Leaning can put stress on a trunk to the point that the tree topples over. The walking palm gets around this by sending down those stilt-roots, which provide support as it chases light through the canopy. In a sense, this palm "walks" itself around the forest in search of the best light. Whereas most trees are stuck where they germinate, the walking palm has, in a sense, freed itself from such restrictions. As such, older trees are often found far from their original germination point.

Once in a favorable location, the walking palm will right itself and continue upwards. At this point, the old trunk and roots are superfluous and will often rot away. For a young tree, this process can happen in as fast as two or three years. This is an incredible feat considering the time scale most trees operate on. Personally I would love to be able to observe a forest with walking palms over a few decades. Seeing how their positions change with time would be fascinating. At the very least, their bark is often covered in epiphytes, which offers a lot to comb over on our timescale.

Photo Credits: Hans Hillewaert (Wikimedia Commons) and John H. Bodley and Foley C. Benson (infographic)

Further Reading:

http://www.revistas.ucr.ac.cr/index.php/rbt/article/view/5955

http://www.jstor.org/stable/2387775?seq=1#page_scan_tab_contents

The Largest Seed in the World

For Lodoicea maldivica, better known as coco de mer, producing the largest seeds in the world may seem like a cool fact for the record books but it certainly has its drawbacks. However, as with anything in nature, selection would not allow for wasteful traits to be passed on. Costs must be offset by a reproductive advantage on some level. A recent study looked at what these tradeoffs might be and what they found is pretty incredible.

With seeds clocking in at upwards of 30 kg (66 lbs.) one has to wonder what L. maldivica is up to. It was long thought that, like the coconut, seeds of this palm must be dispersed by sea. However, they are simply too dense to float. Indeed, seed dispersal for this peculiar species of palm is quite limited. They simply fall from the tree and germinate below the canopy. This may explain why L. maldivica is endemic to the islands of Praslin and Curieuse in the Seychelles. It's not just the seeds that are huge either. The female flowers, which are borne on separate trees than the males, are the largest female flowers of any species of palm. At 10 m (32 ft.) in diameter, the leaves too are quite massive, fanning outwards on petioles that can reach 2 m to 4 m (6.5 - 13 ft) in length!

Counterintuitively, the habitats in which they grow are notoriously low in nutrients. Why then would this palm invest so much energy into growing these gigantic structures? Because they tend to germinate and grow beneath their parents, the offspring of L. maldivica would appear to be at a disadvantage from the start. A recent study suggests that the answer lies in those massive leaves.

Researchers found that the areas directly beneath the adult trees were wetter and had elevated soil nutrients compared to the surroundings. As it turns out, L. maldivica modifies its own habitat. Those massive leaves do more than just collect sun, they also act as giant funnels. In fact, most of the water that rains down onto the canopy is collected by the leaves. In this way, everything from water, debris, and even excess pollen is funneled down to the base of each tree. Not only is this good for the parent tree, it is also a boon for the dispersal-limited offspring. Coupled with the considerable endosperm in those massive seeds, all of this additional water and fertilizer means that seedling L. maldivica enter into the world at a distinct advantage over many other plants on the islands.

Sadly, over-harvesting of the seeds has crippled natural reproduction for L. maldivica. This coupled with habitat desctruction paints a bleak picture for this record-holding palm. It has already been lost from three other Seychelles islands. Luckily there are many conservation efforts underway that are aimed at saving L. maldivica. The Seychelles are now considered a World Heritage Site and many of the wild populations of this palm lie within national parks.

Photo Credits: Wendy Cutler (http://bit.ly/1bcKefb) and John Mauremootoo (http://bit.ly/1BriXdS)

Further Reading:
http://onlinelibrary.wiley.com/d…/10.1111/nph.13272/abstract

http://www.arkive.org/coco-de-mer/lodoicea-maldivica/

Common Yet Endangered Palms

Raise you hand if you have ever had a parlor palm (Chamaedorea elegans). I see most of you have raised your hands. Palms in the genus Chamaedorea are the most commonly kept palms on the market. They are small, very shade tolerant, and nearly indestructible. The clear winner in this regard is the parlor palm. We have all given these little palms a shot at one time or another. They are so common that we rarely give a second thought as to where they come from. Surely they did not evolve in a nursery. It may surprise you that for as ubiquitous as these palms are, they are actually quite threatened in the wild.

The genus Chamaedorea is endemic to sub-tropical forests of the Americas and is comprised of roughly 80 species. They are understory palms that are most at home under the deep shade of the canopy. Most species are generally pretty small, rarely growing over 10 feet. All of these factors add up to some resilient and fun houseplants. It doesn't take much to keep them happy. Every once in a while they will produce flowers. Though small, they are often brightly colored. The preferred method for mass cultivation is via seed. However, seed production outside of their native range is notoriously difficult and often requires human intervention. For this reason, a vast majority of nursery grown palms are grown from wild collected seeds.

This may not seem like a bad deal until you look at the numbers. I have seen reports of over 500 million seeds exported from Mexico annually. Couple this with the fact that many species of Chamaedorea are known to grow in very restricted ranges and suddenly the picture becomes very bleak. Over collecting of seeds has decimated wild populations. Without seeds there is no recruitment, no seedlings to take the place of adult plants.

Another considerable threat to these palms comes from the cut flower industry. Palm fronds are notoriously gorgeous and many people like to include them in their displays. Most of the leaves cut come from wild plants. Normally palm fronds are harvested in a manner that doesn't kill the plant, however, in Mexico children are often employed to collect them and their lack of experience can severely damage wild populations.

On top of all of this, the forests in which these palms grow are now being converted to agriculture. If actions are not taken to limit the abuse of wild populations, it is likely that some of the most commonly encountered house plants are going to be extinct in the wild. This is a hard pill to swallow. If you have any of these species growing in your home, take care of them. Perhaps knowing how uncertain the future is for many of these palms will earn them a little more respect.

10394534_1069406709752860_2870126728832887767_n.jpg

Here is a list of some of the most threatened species in this genus:

Chamaedorea amabilis
Chamaedorea klotzschiana
Chamaedorea metalica
Chamaedorea pumila
Chamaedorea sullivaniorum
Chamaedorea tuerckheimii

Photo Credits: Michael Wolf (http://bit.ly/16suMsf), scott.zona (http://bit.ly/1zHdUII),

Further Reading:
http://bit.ly/1ADC3mw