My Unforgettable Encounter with a Fevertree

When someone asks you if you would like to see a wild fever tree, you have to say yes. As a denizen of cold climates defined by months of freezing temperatures, I will never miss an opportunity to encounter any species in its native habitat that cannot survive frosts. This was the scenario I found myself in last week as friend and habitat restoration specialist for the Atlanta Botanical Garden, Jeff Talbert, was showing us around a wonderful chunk of Florida scrubland he has been managing over the last few years.

He drove our small group over to an area that, up until a year or two ago, was completely choked with swamp titi (Cyrilla racemiflora). Like many habitats throughout southeastern North America, this patch of Florida scrub is dependent on regular fires to maintain ecological function. Without it, aggressive shrubs like titi completely take over, choking out much of the amazing biodiversity that makes this region unique. Jeff and his team have been very busy restoring fire to this ecosystem and the results have been impressive to say the least.

We walked off the two-track, down into a wet depression and were greeted by an impressive population of spoon-leaf sundews (Drosera intermedia), which is a good sign that water quality on the site is improving. After a few minutes of sundew admiration, Jeff motioned for us to look upward towards the surrounding tree line. That’s when we saw it. Growing up out of the small seep that was feeding this wet depression was a spindly tree with bright pink splotches decorating its canopy. This was to be my first encounter with a fevertree (Pinckneya bracteata).

A few of us were willing to get our feet wet and were rewarded with a close look at the growth habit of this incredible tree. Clustered at the end of its spindly branches are dark green, ovate leaves that give the tree a tropical appearance. Erupting from the middle of some of those leafy branches were the inflorescences. These are what produce the pink splotches I could see in the canopy of larger individuals. They remind me a lot of a poinsettia and at first, I thought this tree might be a member of the genus Euphorbia. Indeed, the pink coloration comes from a handful of rather large, leaf-like sepals attached to the base of each inflorescence.

Upon seeing the flowers, I instantly knew this was not a member of Euphorbiaceae. Each flower was long and tubular ending in five reflexed lobes. They are colorful structures in and of themselves, adorned with splashes of pink and yellow. After a bit of scrutiny, our group was finally able to place this within its true taxonomic lineage, the coffee family (Rubiaceae).

Within the coffee family, fevertree is closely related to the genus Cinchona. Like Cinchona, the fevertree produces quinine and other alkaloids that are effective in treating malaria. Fevertree has been used for millennia to do just that, hence the common name. It also seems fitting that fevertrees tend to grow in wetland habitats where mosquitos can be abundant. However, this is by no means an obligate wetland species. Those who have grown fevertree frequently succeed in establishing plants in dry, upland habitats as well. Perhaps highly disturbed wetlands are some of the few places where this spindly tree can avoid intense competition from other forms of vegetation.

Fevertrees do need regular disturbance to persist. They are not a large, robust tree by any means and can easily get outcompeted by more aggressive vegetation. However, this species does have a trick that enables individuals to persist when disturbances don’t come frequent enough. Fevertree is highly clonal. Instead of producing a single trunk, it sends out numerous stems in all directions in search of a gap in the canopy. This clonal habit allows it to eek out an existence in the gaps between its more robust neighbors until disturbances return and clear things out.

This clonal habit is also very important when it comes to reproduction. Fevertree requires a decent amount of sunlight to successfully flower and set seed. By using its clonal stems to find light gaps, it can at least guarantee some level of reproduction until fires, floods, or some other form of canopy clearing disturbance frees up enough space for it to prosper and its seeds to germinate. However, its clonal habit can also hurt its reproductive capacity over the long term if recruitment of new individuals does not occur.

Fevertree is considered self-incompatible. In other words, its flowers cannot be pollinated via pollen from a genetically identical individual. As more and more clonal shoots are produced, the tree effectively increases the chances that its own pollen will end up on its own flowers. This is yet another important reason why regular disturbance favors fevertree reproduction. Fevertree seeds need light and bare ground to germinate, which is usually provided as fires and other disturbances clear the canopy and open up bare ground. Only then can enough unrelated individuals establish to ensure plenty of successful pollination opportunities.

With its long, tubular flowers and bright pink sepals, fevertrees don’t seem to have any trouble attracting pollinators, which mainly consist of ruby-throated hummingbirds and bumblebees. Only these organisms have what it takes to successfully access the pollen and nectar rewards of this plant and travel the distances necessary to ensure pollen ends up on unrelated individuals. The seeds that result from pollination are winged and can travel a decent distance with a decent wind. With any luck, a few seeds will end up in another disturbance-cleared wet area and usher in the next generation of fevertrees.

I am so happy that restoration activities at this site are making more suitable habitat for this unique tree. Looking around, we saw many more small individuals starting to emerge where there was once a dense canopy of titi. Hopefully with ongoing management, this population will continue to grow and spread, securing the a future for this species in a region with an ever-growing human presence. If you ever find the opportunity to see one of these trees in person, do yourself a favor and take it!

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

Dendrologist Squirrels

Gary Cobb licensed under CC BY-ND 2.0

I find it fun to watch squirrels frantically scurrying about during the months of fall. Their usually playful demeanor seems to have been replaced with more serious and directed undertones. If you watch squirrels close enough you may quickly realize that, when it comes to oaks, squirrels seem to have a knack for taxonomy. They quickly bury red oak acorns while immediately set to work on eating white oak acorns. Why is this?

If you have ever tried to eat a raw acorn then you may know the reason. They are packed full of bitter tannins that quickly dry up your mouth and leave an awful after taste. Tannins are secondary chemicals that plants manufacture for protection. Tannins bind to proteins and keep them from being easily digested. This is how leather is made. When you tan a hide you are literally dousing it with tannins that bind to the proteins and keep them from rotting.

Back to the squirrels. The reason they seem to be choosy about how they deal with acorns all comes down to tannins. They bury red oak acorns because acorns in the red oak group have the highest levels of tannins. This is because red oak acorns do not germinate until spring. They have high levels of tannins to fight off fungi and other pathogens over the long, dreary winter. Thus, red oak acorns store better. White oaks germinate in the fall, using a long taproot to pull them into the soil. Because of this, white oaks don't have to dump as much tannin into their acorns. The squirrels seem to know this and simply bite out the white oak embryo before it can germinate. White oak acorns get eaten much sooner than reds because they simply do not keep as long.

There is also evidence that oaks and squirrels have struck a balance. Oaks do rely on squirrels as well as birds like jays to disperse their seeds. These critters can't remember where they cached all of their seeds so some are bound to germinate. What some researchers have found is that oaks place more tannins near the embryos in the acorn than they do at the tips. Why is this? As it turns out, acorns that have had their tips bit off can still germinate as long as their embryo remains unharmed. It is believed that this satisfies squirrels and jays enough to keep them from downing the entire acorn every time. Knowledge such as this puts a whole new spin on backyard ecology.

Photo Credit: Gary Cobb licensed under CC BY-ND 2.0.

Further Reading: [1]

Burrowing Birds, Biocrust, and Biodiversity: A Microclimate Story

Nolana humifusa (Solanaceae) Photo by Michael Wolf licensed by GNU Free Documentation License

Peru’s coastal deserts are some of the driest places on Earth. Most of the water they receive comes not from rain but rather fog rolling in off the ocean. These fog-fed habitats are known as Lomas and they support a surprising diversity of plant species. Still, life in the Lomas is no treat so plants growing there need a bit more than a tough disposition to get by. Many components of the Lomas flora rely on favorable microclimates to survive long enough to reproduce. Recently it has been found that a few species of burrowing birds are responsible for creating some of these favorable microclimates.

The beneficial effects of burrowing or “fossorial” animals on plant diversity has many examples in nature. This is especially true in harsh climates. The act of burrowing disturbs the surrounding soil and can expose nutrient-rich soils as well as increase hydrology. However, more than just mammals burrow. As such, researchers wanted to investigate the role of burrowing birds on Lomas plant diversity.

A pair of burrowing owls (Athene cunicularia) Photo by Ron Knight licensed by CC BY 2.0

The birds in this study consist of one owl - the burrowing owl (Athene cunicularia), and two species of miner birds (Geositta peruviana & G. maritima). Instead of nesting in trees, which are few and far between in such arid habitats, these birds nest in the ground. To do so, they excavate burrows. As they excavate, these birds break up the thin biocrust of cyanobacteria that carpets undisturbed stretches of sand. This biocrust is an immensely important component of the local ecology. It stabilizes sandy soils and increases their fertility. It also has a considerable impact on water infiltration, runoff, albedo, and temperature of the soil.

The greyish miner (Geositta maritima)

The coastal miner (Geositta peruviana) Photo by Berichard licensed by CC BY-SA 2.0

Taken together, it is easy to see how large patches of biocrust can either promote or inhibit plant germination and growth. Some species perform well under such conditions while others do not. This is why researchers were so interested in burrowing birds. By breaking up the biocrust and constructing mounds outside of their burrows, these birds are changing the microclimates of the surrounding area. This creates a heterogeneous patchwork of soil types that in turn influence the plant species that can grow and survive.

It turns out, burrowing birds on the Peruvian coast are having considerable effects on local plant diversity. By studying the soil properties around burrows and comparing it to undisturbed soil patches nearby, researchers were able to show that the plant communities living in these areas are in fact different. For starters, despite undisturbed soils having far more seeds in the soil seed bank than burrow mound soils, far more plants germinated and grew on the mounds than in the biocrusts. Also, though the seed bank of the mounds was largely comprised of similar species to that of the undisturbed soils, the seeds of species that produce bird-dispersed berries such as Solanum montanum were more abundant in the mound soil.

Fuertesimalva peruviana (Malvaceae) Photo by Jose Roque licensed by CC BY-SA 3.0

In terms of seedlings, mound soils not only exhibited higher seedling emergence, they also exhibited a higher species richness than the undisturbed biocrust soils nearby. The benefits of growing in the mound soils were most apparent for three plant species in particular: Cistanthe paniculata (Montiaceae), S. montanum (Solanaceae), and Fuertesimalva peruviana (Malvaceae). It appears that these species are much more likely to germinate and survive in and around the burrows than they are in the surrounding landscape. Such a boost to growth and survival, however marginal, means a lot in such a harsh, uninviting landscape.

Even more incredible is how specific burrow microclimates can be. Plants growing on the mounds didn’t do so in a uniform way. Instead, tiny variations in the soil of the burrow mound appeared to make a huge difference for plants. Soils near the entrance of an active burrow are disturbed far more often than soils on the backside of the mound. As such, more plants were found growing on the backside of the mound, demonstrating yet again how slight improvements in favorable microclimates can have astounding impacts on plant survival and diversity.

A. Soil profiles of the studied treatments. B. Landscape of the study area. The lower site of the hills is covered in biocrust except where it is disturbed by birds' burrows (Bioperturbation labeled in the picture). C. Dark cyanobacterial biological soil crust that covers the study site. D. Burrowing owl Athene cunicularia standing on its bioperturbation. [SOURCE}

The reason some plants do much better in disturbed soils over those covered in cyanobacteria biocrust are still not entirely clear. It is likely that some plants simply can’t break through the biocrust as they germinate. It is also possible that the seeds of some of these species simply can’t break through the biocrust to even make it into the soil seedbank. Not only would this cause them to blow around, it also means that they aren’t contacting the soil enough to imbibe water and germinate. Despite containing fewer seeds, the act of digging a burrow may loosen up the soil enough so that seeds are properly buried and thus can maintain good soil to seed contact for long enough to promote germination and growth.

All in all it appears that these three bird species are important ecosystem engineers across the Lomas of the Peruvian coast. By creating a patchwork of different soil properties, these birds are essentially creating a patchwork of different habitats that support different plant species. Take the birds away and it is reasonable to assume that plant diversity would decline. This is yet another important reminder of how interconnected the natural world truly is. It is also an important reminder of why habitat, rather than species-specific conservation efforts should be a much higher priority than it is today. Please, support a land conservation agency today!

Photo Credits: [1] [2] [3] [4] [5] [6]

Further Reading: [1]

Emus + Ants = One Heck of a Seed Dispersal Strategy

A guest post by Dr. Scott Zona

The emu is a large, flightless bird, a cousin of kiwis and cassowaries. They range throughout much of Australia, favoring savannah woodlands and sclerophyll forests, where they are generalist feeders, consuming a variety of plants and arthropods. A favorite food of the emu is Petalostigma pubescens, a tree variously known as quinine tree, bitter bark or quinine berry. Petalostigma is in the Picrodendraceae, a family formerly included in the Euphorbiaceae. Quinine trees grow in the same open woodlands favored by emus.

The quinine tree bears yellow fruits, 2.0-2.5 cm in diameter, with a thin layer of flesh. The fruits are divided into six to eight segmented, like a tangerine, and each segment contains a hard endocarp or stone (technically, a pyrene). Each endocarp contains a single seed, 6-8 mm long. Left on the tree, the fruits will eventually dry up and open to release their seeds, but if ripe fruits are discovered by a hungry emu, the feasting begins.

A quinine tree (Petalostigma pubescens) in bloom. Photo by Ethel Aardvark licensed by CC BY 3.0

An emu may eat dozens of fruits in one meal. It swallows fruits whole, digesting the soft, fleshy part and defecating the hard, indigestible endocarps. On an average day, an emu can range over a large territory, spreading endocarps as it goes. In one of science's least glamorous moments, Australian biologists counted by hand as many as 142 endocarps in one emu dropping. If the story ended with Quinine Tree seeds in a pile of emu dung, we would say that the emu provided excellent seed dispersal services for the quinine tree, but the dispersal story is not over.

Quinine tree (Petalostigma pubescens) fruits. Photo by Robert Whyte licensed by CC BY-NC-ND 2.0

The emu dung and endocarps begin to bake in the hot, outback sun. As the endocarps dry, they explode. Just like the pod of a legume, the endocarp has fibers in its tissues oriented in opposing directions.  As the fibers dry, they contract and pull the endocarp apart. The dehiscence is sudden and explosive, sending seeds up to 2.5 m from the point of origin. Launching seeds away from the dung pile is beneficial to seeds: the special separation means that seedlings well be less likely to compete with one another.

But that is not the final disposition of Quinine Tree seeds. Each Petalostigma seed bears a small, oily food body, called an elaiosome, that is attractive to ants. Ants pick up the seed with its attached elaisome and carry it back to their nest. Once at the nest, the ants will remove and consume the elaisome and deposit the inedible seed in midden outside the nest. It is the ants that disperse the seeds to their ultimate site.

The association between emus, exploding endocarps, ants and Petalostigma pubescens probably represents one of the most complicated dispersal scenarios in the Plant Kingdom.

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

Further Reading: [1]

NOTE: Guest posts are invite only

Path Rush

Photo by Matt Lavin licensed by CC BY-SA 2.0

Path rush (Juncus tenuis) is one of those plants that has really benefited from human expansion. Originally native to North America, it can now be found in numerous countries around the globe. It owes much of its success to both its ability to tolerate lots of disturbance as well as an ingenious seed dispersal mechanism. If you like to hike, there is a good chance you have encountered path rush somewhere along the way. There is also a strong chance that you have dispersed its seeds.

Path rush is a relatively small species, topping out around 60 cm in height. Because it frequently grows where foot traffic is heavy, plants don’t always reach such stature. Like most rushes, it has round stems and surprisingly attractive flowers, though one would need a hand lens to fully appreciate their beauty. Flowering for path rush occurs during the summer and it is thought that wind is the main pollination mechanism for this species.

The darker vegetation running along the path is all path rush! Photo by Tom Potterfield licensed by CC BY-NC-SA 2.0

Following pollination, each flower is replaced by a tiny capsule filled with tiny seeds. Each seed is covered in a substance that turns into a sticky mucilage when wet. This mucilage is how path rush manages to move around the landscape so easily. The sticky seeds glom onto pretty much everything from fur to feathers, boots to car tires. This is why you most often find path rush on, well, paths! Its sticky seeds are carried far and wide by foot traffic. It is also why you can now find path rush growing well outside of North America.

Path rush enjoying a crack in the sidewalk.

Path rush frequents more habitats than simply paths too. The key to its success is soil disturbance. Anywhere the soil has been compacted and disturbed, path rush can find its niche. With little competition from surrounding vegetation, this tiny rush can grow into impressive colonies. Even cracks in asphalt can harbor a plant or two. Aside from its ability to tolerate soil disturbance, its tough, stringy foliage is not fed on by a lot of herbivores, which gives it yet another leg up on potential competitors. All in all, this is one tough little plant.

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

Further Reading: [1] [2]

Let's Talk About Recruitment

Photo by --Tico-- licensed by CC BY-NC-ND 2.0

For any species to be considered successful, it must replace itself generation after generation. We call this process recruitment and it is very important. After all, reproduction is arguably the most fundamental aspect of life in a Darwinian sense. For plants, this can be done either vegetatively or sexually via seeds and spores. Though vegetative reproduction is a fundamental process for many plants around the globe, seed or spore germination is arguably the most important. To truly understand what a plant needs, we have to understand its germination requirements.

Recruitment is a considerable limiting factor for plant populations. In fact, it is the first major bottleneck plants must pass through. It is estimated that a majority of plant mortality occurs during the germination and seedling stages. However, not all plants are equal in this way. Some plants are considered seed or propagule limited whereas others are habitat limited.

If a plant is seed limited, it means that its ability to expand its population or colonize new habitats its limited by the ability of seeds (or spores) to make it to a new location. Once there, nature takes its course and germination occurs with little impediment. If a plant is habitat limited, however, things get a bit more tricky. For habitat limited plants, simply getting seeds to a new location is not enough. Some other aspect of the environment (soil moisture, texture, temperature, disturbance, etc.) limit successful germination. Only when the right conditions are present can habitat limited plants germinate and begin to grow.

Habitat limitation is probably the most common limit to plant establishment. Simply put, not all plants will be successful everywhere. Even the successful growth and persistence of adult plants can be poor predictors of seedling success. Many plants can live for decades or even centuries and the conditions that were present when they germinated may have long since changed. Even the presence of the adults themselves can make a site unsuitable for germination. Think of all of those fire adapted species out there that require the entire community to burn before their seeds will ever germinate.

In reality, it is likely that most plants are habitat limited to some degree. These are not binary categories after all, rather they are aligned along a spectrum of possibilities. The fact that most plants don’t completely take over an area once seeds or spores arrive is proof of the myriad limits to plant establishment. As such, recruitment limitation is extremely important to study. It can make a huge difference in the context of conservation and restoration. Even the successful establishment of adult plants is no guarantee that seedlings stand a chance. Without successful recruitment, all you have left is a nice garden that is doomed to run its course. By understanding the limits to plant recruitment, we can do much more than just improve on our ability to protect and bolster plant populations, we can also gain insights into why so many plants remain rare on the landscape and so few ever rise to dominance.

Photo Credits: [1]

Further Reading: [1] [2]

The Cypress-Knee Sedge

Sedges (Carex spp.) simply do not get the attention they deserve. I am part of this problem because like so many others, I have breezed over them in vegetation surveys as “just another graminoid.” This is truly a shame because not only are sedges absolutely fascinating organisms, they are immensely important ecologically as well. I am working hard to get to know sedges better so that I too can fully appreciate their place in our ecosystems. One of the coolest specialist sedges I just recently learned about is the so-called cypress-knee sedge (Carex decomposita). For all intents and purposes, this sedge is considered something of an epiphyte!

The cypress-knee sedge has a fondness for growing on wood. Most often you will find it rooted to the buttresses and knees of bald cypress (Taxodium distichum) or the swollen trunk of a swamp tupelo (Nyssa aquatica). It can also be found growing out of rotting logs that float on the surface of the water. It is a long lived species, with individuals having records stretching back through decades of wetland plant surveys. When supplied with the conditions it likes, populations can thrive. That is not to say that it does well everywhere. In fact, it has declined quite a bit throughout its range.

Juvenile cypress-knee sedges establishing in moss along the water line of a bald cypress.

One of the key wetland features that the cypress-knee sedge needs to survive and prosper is a stable water level. If water levels change too much, entire populations can be wiped out either by drowning or desiccation. Even before the sedge gets established, its seeds require stable water levels to even get to suitable germination sites. Each achene (fruit) comes complete with a tiny, corky area at its tip that allows the seeds to float. Floating seeds are how this species gets around. With any luck, some seeds will end up at the base of a tree or on a floating log where they can germinate and grow. If water levels fluctuate too much, the seeds simply can’t reach such locations.

Its dependence on high quality wetlands is one of the major reasons why the cypress-knee sedge has declined so much in recent decades. Aside from outright destruction of wetlands, changes in wetland hydrology can have dire consequences for its survival. One of the major issues for the cypress-knee sedge is boat traffic. Boat wakes create a lot of disturbance in the water that can literally scour away entire populations from the base of trees and logs. Another major threat are changes to upstream habitats. Any alteration to the watersheds of wetland habitats can spell disaster for the cypress-knee sedge. Alterations to creeks, streams, and rivers, as well as changes in ground water infiltration rates can severely alter the water levels in the swamps that this sedge depends on for survival.

Closeups of the infructescence showing details of the perigynia (fruit).

Less obvious threats also include changes in plant cover. If the wetlands in which it grows become too dense, the cypress-knee sedge quickly gets out-competed. To thrive, the cypress-knee sedge needs slightly more sunlight than a densely forested wetland can provide. In fact, some have even noted that cypress-knee sedge populations can explode after selective logging of such wetlands. Such explosions have been attributed to not only extra sunlight but also the addition of woody debris, which provides much needed germination sites. That being said, such explosions can only be maintained if woody debris is left in place and further wetland disturbances do not continue.

The plight of the cypress-knee sedge stands as a reminder of just how poorly we treat wetlands around the globe. Aside from providing valuable ecosystem services for the human environment (flood control, water filtration, etc.), wetlands are home to countless unique species. Only by treating wetlands betters and attempting to restore some of what has been lost will we ever do better by wetland species like the cypress-knee sedge. Hopefully by showcasing species like this, people will begin to feel a little more compassion towards the ecosystems on which they depend. Please consider supporting a wetland conservation and restoration initiative in your region!

Photo Credits : LDWF Natural Heritage Program [1] & Paul Marcum (Midwest Graminoides) [2] [3] [4]

Further Reading: [1] [2]

Fluorescent Bananas

Photo by endolith licensed under CC BY-SA 2.0

Bananas are one of the most popular fruits in the world. Love them or hate them, most of us know what they look like. Despite their global presence, few stop to think about where these fruits come from. That is a shame because bananas are fascinating plants for many reasons but now we can add blue fluorescence to that list.

Before we dive into the intriguing phenomenon of fluorescence in bananas, I think it is worth talking about the plants that produce them in a little more detail. Bananas belong to the genus Musa, which is located in its own family - Musaceae. Take a step back and look at a banana plant and it won't take long to realize they are distant relatives of the gingers. There are at least 68 recognized species of banana in the world and many more cultivated varieties. Despite their pan-tropical distribution, the genus Musa is native only to parts of the Indo-Malesian, Asian, and Australian tropics.

Photo by Forest & Kim Starr licensed under CC BY 3.0

Banana plants vary in height from species to species. At the smaller end of the spectrum you have species like the diminutive Musa velutina, which maxes out at about 2 meters (6 ft.) in height. On the taller side of things, there are species such as the monstrous Musa ingens, which can reach heights of 20 meters (66ft.)! Despite their arborescent appearance, bananas are not trees at all. They do not produce any wood. Instead, what looks like a tree trunk is actually the fused petioles of their leaves. Bananas are essentially giant herbs with the aforementioned M. ingens holding the world record for largest herb in the world.

When it comes time to flower, a long spike emerges from the main growing tip. This spike gradually elongates, revealing long, beautiful, tubular flowers arranged in whorls. For many banana species, bats are the main pollinators, however, a variety of insects will visit as well. In the wild, fruits appear following pollination, a trait that has been bred out of their cultivated relatives, which produce fruits without needing pollination. The fruits of a banana are actually a type a berry that dehisce like a capsule upon ripening, revealing delicious pulp chock full of hard seeds. Not all bananas turn yellow upon ripening. In fact, some are pink!

CC0 Public Domain

For many fruits, the act of ripening often coincides with a change in color. This is a way for the plant to signal to seed dispersers that the fruits, and the seeds inside, are ready. As many of us know, many bananas start off green and gradually ripen to a bright yellow. This process involves a gradual breakdown of the chlorophyll within the banana skin. As the chlorophyll within the skin of a banana breaks down, it leaves behind a handful of byproducts. It turns out, some of these byproducts fluoresce blue under UV light. 

Amazingly, the fluorescent properties of bananas was only recently discovered. Researchers studying chlorophyll breakdown in the skins of various fruits identified some intriguing compounds in the skins of ripe Cavendish bananas. When viewed under UV light, these compounds gave off a luminescent blue hue. Further investigation revealed that as bananas ripen, their fluorescent properties grow more and more intense.

There could be a couple reasons why this happens. First, it could simply be happenstance. Perhaps these fluorescent compounds are simply a curious byproduct of chlorophyll breakdown and serve no function for the plant whatsoever. However, bananas seem to be a special case. The way in which chlorophyll in the skin of a banana breaks down is quite different than the process of chlorophyll breakdown in other plants. What's more, the abundance of these compounds in the banana skin seems to suggest that the fluorescence does indeed have a function - seed dispersal.

Researchers now believe that the fluorescent properties of some ripe bananas serves as an additional signal to potential seed dispersers that the time is right for harvest. Many animals including birds and some mammals can see well into the UV spectrum and it is likely that the blue fluorescence of these bananas is a means of attracting such animals. Additionally, researchers also found that banana leaves fluoresce in a similar way, perhaps to sweeten the attractive display of the ripening fruits.

To date, little follow up has been done on fluorescence in bananas. It is likely that far more banana species exhibit this trait. Certainly more work is needed before we can say for sure what role, if any, these compounds play in the lives of wild bananas. Until then, this could be a fun trait to investigate in the comfort of your own home. Grab a black light and see if your bananas glow blue!

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

Further Reading: [1] [2]

The Rose of Jericho

To survive in a desert, plants must eek out an existence in specific microclimates that provide conditions that are only slightly better than the surrounding landscape. Such is the case for the Rose of Jericho (Anastatica hierochuntica). This tenacious little mustard is found throughout arid regions of the Middle East and the Saharan Desert and it has been made famous the world over for its "resurrection" abilities. It is also the subject of much speculation so today we are going to separate fact from fiction and reveal what years of research has taught about this desert survivor. 

Natural selection has shaped this species into an organism fully ready to take advantage of those fleeting moments when favorable growing conditions present themselves. A. hierochuntica makes its living in dry channels called runnels or wadis, which concentrate water during periods of rain. It is a desert annual meaning the growth period of any individual is relatively short. Once all the water in the sandy soil has evaporated, this plant shrivels up and dies. This is not the end of its story though. With a little luck, the plants were pollinated and multiple spoon-shaped fruits have formed on its stems.

Photo by Phil41 licensed under CC BY 1.0

As the dead husk of the plant starts to dry out, its branches curl up into a ball-like mass with most of the fruits tucked away in the interior. There the plant will sit, often for many years, until rain returns. When rain does finally arrive, things happen fast. After all, who knows how long it will be before it rains again. Thanks to a quirk of physiology, the dried tissues of A. hierochuntica are extremely elastic and can return to their normal shape and position once hydrated. As the soil soaks up water, the dried up stems and roots just under the surface also begin taking up water and the stems unfurl.

To call this resurrection is being a bit too generous. The plant is not returning to life. Instead, its dead tissues simply expand as they imbibe liquid. Water usually does not come to the desert without rain and rain is exactly what A. hierochuntica needs to complete its life cycle. Unfurling of its stems exposes its spoon-shaped fruits to the elements. Their convex shape is actually an adaptation for seed dispersal by rain, a mechanism termed ombrohydrochory. When a raindrop hits the fruit, it catapults the seed outward from the dead parent.

Photo by Roland Unger licensed under CC BY-SA 3.0

If rains are light, seeds do not get very far. They tend to cluster around the immediate area of their parent. If rains are heavy, however, seeds can travel quite a distance. This is why one will only ever find this species growing in channels. During the rare occasions when those channels fill with water, seeds quickly float away on the current. In fact, experts believe that the buoyancy of A. hierochuntica seed is an adaptation that evolved in response to flooding events. It is quite ironic that water dispersal is such an important factor for a plant growing in some of the driest habitats on Earth.

To aid in germination, the seeds themselves are coated in a material that becomes mucilaginous upon wetting. When the seeds eventually come into contact with the soil, the mucilage sticks to the ground and causes the seeds to adhere to the surface upon drying. This way, they are able to effectively germinate instead of blowing around in the wind.

Again, things happen fast for A. hierochuntica. Most of its seeds will germinate within 12 hours of rainfall. Though they are relatively drought tolerant, the resulting seedlings nonetheless cannot survive without water. As such, their quick germination allows them to make the most out of fleeting wet conditions.

Photo by Nikswieweg at German Wikipedia licensed under CC BY-SA 2.0 DE

Occasionally, the balled up husks of these plants will become dislodged from the sand and begin to blow around the landscape like little tumbleweeds. This has led some to suggest that A. hierochuntica utilizes this as a form a seed dispersal, scattering seeds about the landscape as it bounces around in the wind. Though this seems like an appealing hypothesis, experts believe that this is not the best means of disseminating propagules. Seeds dispersed in this way are much less likely to end up in favorable spots for germination. Though it certainly occurs, it is likely that this is just something that happens from time to time rather than something the plant has evolved to do.

In total, the Rose of Jericho is one tough cookie. Thanks to quick germination and growth, it is able to take advantage of those rare times when its desert environment become hospitable.

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

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

Rein In Those Seeds

Photo by Stan Shebs licensed under CC BY-SA 3.0

Plants living on islands face a bit of a conundrum. In order to get to said islands, the ancestors of those plants had to exhibit extreme seed or spore dispersal strategies. However, if plants are to persist after arriving to an island, long-distance dispersal becomes rather risky. In the case of oceanic islands, seeds or spores that travel too far end up in the water. As such, we often observe an evolutionary reduction in dispersal ability for island residents. 

Islands, however, are not always surrounded by water. You can have "islands" on land as well. The easiest example for most to picture would be the alpine zone of a mountain. Species adapted to these high-elevation habitats find it hard to compete with species native to low-elevation habitats and are therefore stuck on these "islands in the sky." Less obvious are islands created by a specific soil type. 

Take, for instance, gypseous soils. Such soils are the result of large amounts of gypsum deposits at or near the soil surface. Gypseous soils are found in large quantities throughout parts of western North America, North and South Africa, western Asia, Australia, and eastern Spain. They are largely the result of a massive climatic shift that occurred during the Eocene, some 50 million years ago. 

Licensed under public domain

Massive mountain building events during that time were causing large reductions in atmospheric CO2 concentrations. The removal of this greenhouse gas via chemical weathering caused a gradual decline in average temperatures around the world. Earth was also becoming a much drier place and throughout the areas mentioned above, hyper-saline lakes began to dry up. As they did, copious amount of minerals, including gypsum, were left behind. 

These mineral-rich soils differ from the surrounding soils in that they contain a lot of salts. Salt makes life incredibly difficult for most terrestrial plants. Life finds a way, however, and a handful of plant species inevitably adapted to these mineral-rich soils, becoming specialists in the process. They are so specialized on these types of soils that they simply cannot compete with other plant species when growing in more "normal" soils. 

Essentially, these gypseous soils function like soil or edaphic islands. Plants specialized in growing there really don't have the option to disperse far and wide. They have to rein it in or risk extirpation. For a group of plants growing in gypseous soils in western North America, this equates to changes in seed morphology. 

Mentzelia is a genus of flowering plants in the family Loasaceae. There are somewhere around 60 to 70 different species, ranging from annuals to perennials, and forbs to shrubs (they are often referred to as blazing stars but since that would lead to too much confusion with Liatris, I will continue to refer to them as Mentzelia).

For most species in this genus, seed dispersal is accomplished by wind. Plants growing on "normal" soils produce seeds with a distinct wing surrounding the seed. A decent breeze will dislodge them from their capsule, causing them blow around. With any luck some of those seeds will land in a suitable spot for germination, far from their parents. Such is not the case for all Mentzelia though. When researchers took a closer look at species that have specialized on gypseous soils, they found something intriguing. 

Mentzelia phylogeny showing reduction in seed wings. [source]

The wings surrounding the seeds of gypseous Mentzelia were either extremely reduced in size or had disappeared altogether. Just as it makes no sense for a plant living on an oceanic island to disperse its seeds far out into the ocean, it too makes no sense for gypseous Mentzelia to disperse their seeds into soils in which they cannot compete. It is thought that limited dispersal may help reinforce the types of habitat specialization that we see in species like these Mentzelia. The next question that must be answered is whether or not such specialization and limited dispersal comes at the cost of genetic diversity. More work will be needed to understand such dynamics. 

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

Further Reading: [1] [2]

Cockroaches & Unexpected Partnerships

Photo by Alpsdake licensed under CC BY-SA 4.0

Say "cockroach" and most people will start to squirm. These indefatigable insects are maligned the world over because of a handful of species that have settled in quite nicely among human habitats. The world of cockroaches is far more diverse than most even care to realize, and where they occur naturally, these insects provide important ecological services. For instance, over the last decade or so, researchers have added pollination and seed dispersal to the list of cockroach activities. 

That's right, pollination and seed dispersal. It may seem odd to think of roaches partaking in such interactions but a study published in 2008 provides some of the first evidence that roaches are doing more with plants than eating their decaying tissues. After describing a new species of Clusia in French Guiana, researchers set out to investigate what, if anything, was pollinating it. The plant was named Clusia sellowiana and its flowers emitted a strange scent. 

Cockroach pollinating C. sellowiana. [SOURCE]

The source of this scent was the chemical acetoin. It seemed to be a rather attractive scent as a small variety of insects were observed visiting the flowers. However, only one insect seemed to be performing the bulk of pollination services for this new species - a small cockroach called Amazonia platystylata. It turns out that the roaches are particularly sensitive to acetoin and although they don't have any specific anatomical features for transferring pollen, their rough exoskeleton nonetheless picks up and deposits ample amounts of the stuff. 

It would appear that C. sellowiana has entered into a rather specific relationship with this species of cockroach. Although this is only the second documentation of roach pollination, it certainly suggests that more attention is needed. This Clusia isn't alone in its interactions with cockroaches either. As I hinted above, roaches can now be added to the list of seed dispersers of a small parasitic plant native to Japan. 

View fullsize

 (A) M. humile fruit showing many minute seeds embedded in the less juicy pulp. (B) Fallen fruits. (C) Blattella nipponica feeding on the fruit. (D) Cockroach poop with seeds. (E) Stained cockroach-ingested seeds. [SOURCE]

Monotropastrum humile looks a lot like Monotropa found growing in North America. Indeed, these plants are close cousins, united under the family Ericaceae. Interestingly enough, it was only recently found that camel crickets are playing an important role in the seed dispersal of this species. However, it looks like they aren't the only game in town. Researchers have also found that a forest dwelling cockroach called Blattella nipponica serves as a seed disperser as well. 

The roaches were observed feeding on the fruits of this parasitic plant, consuming pulp and seed alike. What's more, careful observation of their poop revealed that seeds of M. humile passed through the digestive tract unharmed. Cockroaches can travel great distances and therefore may provide an important service in distributing the seeds of a rather obscure parasitic plant. To think that this is an isolated case seems a bit naive. It seems to me like we should pay a little more attention to what cockroaches are doing in forests around the world. 

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

Further Reading: [1] [2]

Are Crickets Dispersing Seeds of Parasitic Plants?

[SOURCE]

Parasitic plants lead unique lifestyles. Many have foregone photosynthesis entirely by living off fungi or their photosynthetic neighbors. Indeed, there are many anatomical and physiological adaptations that are associated with making a living parasitically. Whether they are full parasites or only partial, one thing that many parasitic plants have in common are tiny, dust-like seeds. Their reduced size and thin seed coats are generally associated with wind dispersal, however, there are always exceptions to the rule. Recent evidence has demonstrated that a handful of parasitic plants have evolved in response to a unique seed dispersal agent - camel crickets.

A research team based out of Japan recently published a paper describing a rather intriguing seed dispersal situation involving three species of parasitic plants (Yoania amagiensis - Orchidaceae, Monotropastrum humile - Ericaceae, and Phacellanthus tubiflorus - Orobanchaceae). These are all small, achlorophyllous herbs that either parasitize trees directly through their roots or they parasitize the mycorrhizal fungi associated with said trees. What's more, each of these species are largely inhabitants of the dense, shaded understory of rich forests.

These sorts of habitats don't lend well to wind dispersal. The closed forest canopy and dense understory really limits wind flow. It would appear that these three plant species have found away around this issue. Each of these plants invest in surprisingly fleshy fruits for their parasitic lifestyle. Also, their seeds aren't as dust-like as many of their relatives. They are actually very fleshy. This is odd considering the thin margins many parasitic plants live on. Any sort of investment in costly tissues must have considerable benefits for the plants if they are to successfully get their genes into the next generation.

Fleshy fruits like this are usually associated with a form of animal dispersal called endozoochory. Anyone that has ever found seed-laden bird poop understands how this process works. Still, simply getting an animal to eat your seeds isn't necessarily enough for successful dispersal. Seeds must survive their trip through the gut and come out the other end relatively in tact for the process to work. That is where a bit of close observation came into play.

View fullsize

[SOURCE]

After hours of observation, the team found that the usual frugivorous suspects such as birds and small mammals showed little to no interest in the fruits of these parasites. Beetles were observed munching on the fruits a bit but the real attention was given by a group of stumpy-looking nocturnal insects collectively referred to as camel crickets. Again, eating the fruits is but one step in the process of successful seed dispersal. The real question was whether or not the seeds of these parasites survived their time inside either of these insect groups. To answer this question, the team employed feeding trials.

They compared seed viability by offering up fruits to beetles and crickets both in the field and back in the lab. Whereas both groups of insects readily consumed the fruits and seeds, only the crickets appeared to offer the greatest chances of a seed surviving the process. Beetles never pooped out viable seeds. The strong mandibles of the beetles fatally damaged the seeds. This was not the case for the camel crickets. Instead, these nocturnal insects frequently pooped out tens to hundreds of healthy, viable seeds. Considering the distances the crickets can travel as well as their propensity for enjoying similar habitats as the plants, this stacks up to potentially be a beneficial interaction. 

The authors are sure to note that these results do not suggest that camel crickets are the sole seed dispersal agents for these plants. Still, the fact that they are effective at moving large amounts of seeds is tantalizing to say the least. Taken together with other evidence such as the fact that the fruits of these plants often give off a fermented odor, which is known to attract camel crickets, the fleshy nature of their fruits and seeds, and the fact that these plants present ripe seed capsules at or near the soil surface suggests that crickets (and potentially other insects) may very well be important factors in the reproductive ecology of these plants.

Coupled with previous evidence of cricket seed dispersal, it would appear that this sort of relationship between plants and crickets is more widespread than we ever imagined. It is interesting to note that relatives of both the plants in this study and the camel crickets occur in both temperate and tropical habitats around the globe. We very well could be overlooking a considerable component of seed dispersal ecology via crickets. Certainly more work is needed.

Photo Credits: [1]

Further Reading: [1] [2]

Caliochory - A Freshly Coined Form of Seed Dispersal

Photo by Ude licensed under CC BY-SA 3.0

A new form of seed dispersal has been described. It involves birds but not in the sense we traditionally think. Everyone understands how effectively birds disperse seeds contained in small fruits such as berries, or as barbs attached to their feathers. It took finding an out-of-place patch of Japanese stiltgrass (Microstegium vimineum) for lead author Dr. Robert Warren to start looking at bird dispersal in a different light. 

While working in his yard, he noticed a patch of Japanese stiltgrass growing out of a window planter some 6 feet off the ground. Japanese stiltgrass can be highly invasive but its seeds aren't adapted for vertical dispersal. However, it does employ a mixed mating system composed of outcrossing flowers at the tips of the spikes along with cleistogamous flowers whose seeds remain on the stem. Taking out a ladder, Warren discovered that the grass was growing out of a bird nest. It would appear that stiltgrass stems containing seeds were incorporated into the nest as building material and then germinated the following year. Thus began a deeper investigation into the realm of nest seeds.

Teaming up with researchers at Yale and the United States Forest Service, they set out to determine how often seeds are contained within bird nests. They collected nests from 23 different bird species and spread them over seed trays. After ruling out seeds from potential contamination sources (feces, wind, etc.), they irrigated the nests to see what would germinate. The results are quite remarkable to say the least.

Over 2,000 plants, hailing from 37 plant families successfully germinated. In total, 144 different plant species grew from these germination trials. The seeds appeared to be coming in from the various plant materials as well as the mud used to build these nests. What's more, nearly half of the seeds they found came from cleistogamous sources. Birds whose nests contained the highest amounts of seeds were the American robbin (Turdus migratorius) and the eastern bluebird (Sialia sialis). These results have led the authors to coin the term "caliochory," 'calio' being Greek for nest and 'chory' being Greek for spread.

It has long been assumed that cleistogamous reproduction kept seeds in the immediate area of the parent plant. This evidence suggests that it might actually be farther reaching than we presumed. What's more, these numbers certainly hint that this otherwise unreported method of seed dispersal may be far more common than we ever realized. Whether or not plants have evolved in response to such dispersal methods remains to be tested. Still, considering the diversity of birds, their nesting habits, and the availability of various plant materials, these findings are quite remarkable!

Photo Credits: [1]

Further Reading: [1]

Birds Work a Double Shift For Osmoxylon

Photo by Forest & Kim Starr licensed under CC BY 3.0

Plants go to great lengths to achieve pollination. Some can be tricky, luring in pollinators with a promise of food where there is none. Others, however, really sweeten the deal with ample food reserves. At least one genus of plants has taken this to the extreme, using the same techniques for pollination as it does for seed dispersal. I present to you the genus Osmoxylon.

Comprised of roughly 60 species spread around parts of southeast Asia and the western Pacific, the genus Osmoxylon hail from a variety of habitats. Some live in the deep shade of the forest understory whereas others prefer more open conditions. They range in size from medium sized shrubs to small trees and, upon flowering, their place within the family Araliaceae becomes more apparent.

Photo by Mokkie licensed under CC BY-SA 3.0

Look closely at the flowers, however, and you might notice a strange pattern. It would appear that as soon as flowers develop, the plant has already produced berries. How could this be? Are there cleistogamous flowers we aren't aware of? Not quite. The truth, in fact, is quite peculiar. Of the various characteristics of the genus, one that repeatedly stands out is the production of pseudo-fruits. As the fertile flowers begin to produce pollen, these fake fruits begin to ripen. There aren't any seed inside. In truth, I don't think they can technically be called fruits at all. So, why are they there?

Although actual observations will be required to say for sure, the running hypothesis is that these pseudo-fruits have evolved in response to the presence of birds. They are pretty fleshy and would make a decent meal. It is thought that as birds land on the umbel to eat these pseudo-fruits, they invariably pick up pollen in the process. The bird the exchanges pollen with every subsequent plant it visits. Thus, pollination is achieved.

The relationship with birds doesn't end here. Like other members of this family, pollination results in the formation of actual fruits full of seeds. Birds are known for their seed dispersal abilities and the Osmoxylon capitalize on that as well. As such, the reproductive input of their avian neighbors is thought to be two-fold. Not only are birds potentially great pollinators, they are also great seed dispersers, taking fruits far and wide and depositing them in nutrient-rich packets wherever they poop.

Photo Credits: [1] [2]

Further Reading: [1]

Large Parrots And Their Influence On Amazonian Ecosystems

Photo by I, Luc Viatour licensed under CC BY 2.0

Parrots, especially the larger species, have long been thought to be a bane to plant reproduction. Anyone that has watched a parrot feed may understand why this has been the case. With their incredible beaks, parrots make short work of even the toughest seeds. However, this assumption is much too broad. In fact, recent research suggests that entire Amazonian ecosystems may have parrots to thank.

Bolivia's Amazonian savannas are remarkable and dynamic ecosystems. These seasonally flooded grasslands are dotted with forest islands dominated by the motacú palm (Attalea princeps). These forest patches are an integral part of the local ecology and have thus received a lot of attention both culturally and scientifically. The dominance of motacú palm poses an intriguing question - what maintains them on the landscape?

The fruits of this palm are quite large and fleshy. Some have hypothesized that this represents an anachronism of sorts, with the large fruit having once been dispersed by now extinct Pleistocene megafauna. Despite this assumption, these forest islands persist. What's more, motacú palms still manage to germinate. Obviously there was more to this story than meets the theoretical eye. As it turns out, macaws seem to be the missing piece of this ecological puzzle. 

Researchers found that three species of macaw (Ara ararauna, A. glaucogularis, and A. severus) comprised the main seed dispersers of this dominant palm species. What's more, they manage to do so over great distances. You see, the palms offer up vast quantities of fleshy fruits but not much in the way of a good perch on which to eat them. Parrots such as macaws cannot take an entire seed down in one gulp. They must manipulate it with their beak and feet in order to consume the flesh. To do this they need to find a perch.

Suitable perches aren't always in the immediate area so the macaws take to the wing along with their seedy meals. Researchers found that these three macaw species will fly upwards of 1,200 meters to perch and eat. Far from being the seed predators they were assumed to be, the birds are actually quite good for the seeds. The fleshy outer covering is consumed and the seed itself is discarded intact. This suggests that preferred perching trees become centers of palm propagation and they have the parrots to thank. 

Indeed, seedling motacú palms are frequently found within 1 - 5 meters of the nearest perching tree. No other seed disperser even came close to the macaws. What's more, introduced cattle (thought to mimic the seed dispersing capabilities of some extinct megafauna) had a markedly negative effect on palm seed germination thanks to issues such as soil compaction, trampling, and herbivory. Taken together, this paints a radically different picture of the forces structuring this unique Amazonian community.

Photo Credits: Wikimedia Commons

Further Reading: [1]

A Beautiful and Bizarre Gentian

There is something about gentians that I am drawn to. I can't quite put my finger on it but it definitely has something to do with their interesting pollination strategies. One of the coolest gentian species I have ever met grows in the mountainous regions of western North America.

Meet Frasera speciosa a.k.a. the monument plant (a.k.a. elkweed). It is only one of 14 species in the genus. This fascinating species (as well as its relatives) lives out most of its life as a rosette of large, floppy leaves. The monument plant is what is known as a "monocarpic perennial", meaning it lives for many years as a rosette before flowering once and dying. It has been recorded that some individuals can be upwards of 30 years old by the time they flower!

This reproductive strategy brings with it a specific set of challenges but yet, if balanced correctly, offers many advantages. For starters, if you only flower once in a life time, you best make it count. The good news is, if flowering events are rare and widely spaced, this is a good strategy for avoiding herbivores. Such an irregular reproductive lifestyle means that the likelihood of a flowering population getting munched on is greatly reduced.

The same goes for seeds. If setting seed is a rare and widely spaced event, the likelihood of seed predation is also reduced. This is what is known as predator avoidance behavior. While it is not quite understood how plants synchronize flowering (though environmental conditions do play a role), it has been found that, for at least some populations, it alternates in intervals of 3 and 7 years. In essence, each flowering event can be seen as mast event. This keeps the overall impact of any potential herbivores and seed predators to a minimum.

This synchronous flowering strategy can also be beneficial for insuring cross pollination. The flowers are large and seemingly quite attractive to many different species of pollinators. By flowering all at once, a population is offering a tempting bonanza for pollinators that ensures many visits to each flower, thus increasing the chances of reproductive success. Since each individual plant invests all of its collective energy into a single flowering event, more energy is allocated to producing flowers and seed than if it flowered year after year.

The interesting habits of this plant's lifestyle don't end there. Each plant is essentially a pretty awesome parent! It has been found that seeds that are buried under the decomposing remains of a parent plant not only germinate better but the resulting seedlings also have a much higher rate of survival. This is good news for two big reasons.

For one, the decomposing remains enrich the surrounding soil while also creating a humid micro climate that is very conducive to growth. Second, the fact that they all germinate and grow relatively close to the parent plant, means that the density of young plants closely mimics that of the parental population. If the seeds were to be dispersed great distances from each other, it would be much more difficult to synchronize a flowering event and to ensure sufficient pollination. This way, entire populations grow up together in this nursery made from the remains of their parents. This is such a cool genus and I hope you get the chance to meet one for yourself.

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

The Fetid Adderstongue

Photo by Ken-ichi Ueda licensed under CC BY-NC 2.0

"Fetid adderstongue" seems like a pretty ominous name for such a small and beautiful plant. Hailing from coastal North America, the genus Scoliopus is most at home in the deep shaded forests of California and Oregon. Spring is the best time to see these little lilies and once you know a little bit about their ecology, such encounters are made all the more interesting.

There are two species nestled within this genus - S. bigelovii and S. hallii. Both are similar in that they are plants of deep shaded environments, however, you are more likely to find S. hallii growing along the banks of wooded streams. As is typical of many members of the lily family, their flowers are quite beautiful in appearance. The trick is finding them. Though showy, they are rather small and their dark coloration causes them to blend in well in their shaded environments. That is all fine and dandy for a species that relies more on smell rather than looks to attract pollinators.

As the common name suggests, the flowers of the fetid adderstongues give off a bit of an odor. I have heard it best described as "musty." The flowers of these two species attract a lot of fungus gnats. Although these tiny flies are generally viewed as sub par pollinators for most flowering plants, the fetid adderstongues seem to do well with them. What they lack in robust pollination behavior, they make up for in sheer numbers. There are a lot of fungus gnats hanging around wet, shaded forests.

Photo by Eric in SF licensed under CC BY-SA 3.0

The flowers themselves are borne on tall stalks. Though they look separate, they are actually an extension of a large, underground umbel. Once pollination has been achieved, the flower stalks begin to bend over, putting the developing ovaries much closer to the ground. Each seed comes equip with a fleshy little attachment called an eliasome. These are essentially ant bait. Once mature, the seeds are released near the base of the parent. Hungry ants that are out foraging find the fleshy attachment much to their liking.

They bring the seeds back to the nest, remove the eliasomes, and discard the seed into a trash midden. Inside the ant nest, seeds are well protected, surrounded by nutrient-rich compost, and as some evidence is starting to suggest, guarded against damaging fungal invaders. In other words, the plants have tricked ants into planting their seeds for them. This is a very successful strategy that is adopted by many different plant species the world over.

Though small, the fetid adderstongues are two plants with a lot of character. They are definitely a group that you want to keep an eye out for the next time you find yourself in the forests of western North America. If you do end up finding some, just take some time to think of all the interesting ecological interactions these small lilies maintain.

Photo Credits: [1] [2]

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

Thanks, Ducks!

Photo by loren chipman licensed under CC BY-NC 2.0

Recent research suggests that certain duck species are crucial for maintaining wetland plant diversity in highly fragmented landscapes. Functioning wetlands are becoming more and more isolated each year. As more land is gobbled up for farming and development, the ability for plants to get their seeds into new habitats is made even more difficult. Luckily, many plants utilize animals for this job. Seeds can become stuck in fur or feathers, and some can even pass through the gut unharmed. What's more, animals can move great distances in a short amount of time. For wetland plants, the daily movements of ducks seems to be paramount. 

By tracking the daily movements of mallards, a team of researchers from Utretch University were able to quantify how crucial these water fowl are for moving seeds around. What they found was quite remarkable. In autumn and winter, the diet of mallards switches over to seeds. Not all seeds that a mallard eats get digested. Many pass through the gut unharmed. Additionally, mallards are strong flyers. On any given day they can travel great distances in search of winter foraging grounds. In the evenings, they return to roosting sites with a high degree of fidelity. 

[SOURCE]

The research team was able to demonstrate that their movements cover even greater distances in highly fragmented landscapes. It's these daily migrations that are playing a major role in maintaining plant diversity between distant wetlands. This is especially important for wetlands that function as roost sites. Whereas mallards distribute around 7% of the surviving seeds they eat among foraging sites, that number jumps to 34% for surviving seeds at roost sites. Given the sheer number of mallards on the landscape, these estimates can really add up. 

It is likely that without mallards, North American wetlands would be much less diverse given their increasingly isolated nature. However, not all seeds are dispersed equally. Small seeds are far more likely to pass through the gut of a duck unharmed, meaning only a portion of the plant species that grow in these habitats are getting a helping hand (wing?). Still, the importance of these birds cannot be overlooked. The next time you see a mallard, thank it for maintaining wetland plant diversity. 

Photo Credits: [1] [2]

Further Reading: [1]

Lizard Helpers

Photo by Tatters ✾ licensed under CC BY-NC-ND 2.0

The beauty of Tasmania's honeybush, Richea scoparia, is equally matched by its hardiness. At home across alpine areas of this island, this stout Ericaceous shrub has to contend with cold temperatures and turbulent winds. The honeybush is superbly adapted to these conditions with its compact growth, and tough, pointy leaves. Even its flowers are primed for its environment. They emerge in dense spikes and are covered by a protective casing comprised of fused petals called a "calyptra." Such adaptations are great for protecting the plant and its valuable flowers from such brutal conditions but how does this plant manage pollination if its flowers are closed off to the rest of the world? The answer lies in a wonderful little lizard known as the snow skink (Niveoscincus microlepidotus).

The snow skink is not a pollinator. Far from it. All the snow skink wants is access to the energy rich nectar contained within the calyptra. In reality, the snow skink is a facilitator. You see, the calyptra may be very good at shielding the developing flower parts from harsh conditions, but it tends to get in the way of pollination. That is where the snow skink comes in. Attracted by the bright coloration and the nectar inside, the snow skink climbs up to the flower spike and starts eating the calyptra. In doing so, the plants reproductive structures are liberated from their protective sheath. 

Photo by Tindo2 - Tim Rudman licensed under CC BY-NC 2.0

Once removed, the flowers are visited by a wide array of insect pollinators. In fact, research shows that this is the only mechanism by which these plants can successfully outcross with their neighbors. Not only does the removal of the calyptra increase pollination for the honeybush, it also aids in seed dispersal. Experiments have shown that leaving the calyptra on resulted in no seed dispersal. The dried covering kept the seed capsules from opening. When calyptras are removed, upwards of 87% of seeds were released successfully. 

Although several lizard species have been identified as pollinators and seed dispersers, this is some of the first evidence of a reptilian pollination syndrome that doesn't actually involve a lizard in the act of pollination. It is kind of bizarre when you think about it. As if pollination wasn't strange enough in requiring a third party for sexual reproduction to occur, here is evidence of a fourth party required to facilitate the action in the first place. It may not be just snow skinks that are involved either. Evidence of birds removing the calyptra have also been documented. Whether its bird or lizard, this is nonetheless a fascinating coevolutionary relationship in response to cold alpine conditions. 

Photo Credits: [1] [2]

Further Reading: [1]

On Crickets and Seed Dispersal

Photo by Vojtěch Zavadil licensed under CC BY-SA 4.0

The world of seed dispersal strategies is fascinating. Since the survival of any plant species requires that its seed find a suitable place to germinate, it is no wonder then that there are myriad ways in which plants disseminate their propagules. Probably my favorite strategies to ponder are those involving diplochory. Diplochory is a fancy way of saying that seed dispersal involves two or more dispersal agents. Probably the most obvious to us are those that utilize fruit. For example, any time a bird eats a fruit and poops out the seeds elsewhere, diplochory has happened.

Less familiar but equally as cool forms of diplochory involve insect vectors. We have discussed myrmecochory (ant dispersal) in the past as well as a unique form of dispersal in which seeds mimic animal dung and are dispersed by dung beetles. But what about other insects? Are there more forms of insect seed dispersal out there? Yes there are. In fact, a 2016 paper offers evidence of a completely overlooked form of insect seed dispersal in the rainforests of Brazil. The seed dispersers in this case are crickets.

Yes, you read that correctly - crickets. Crickets have been largely ignored as potential seed dispersers. Most are omnivores that eat everything from leaves to seeds and even other insects. One report from New Zealand showed that a large species of cricket known as the King weta can disperse viable seeds in its poop after consuming fruits. However, this is largely thought to be incidental. Despite this, few plant folk have ever considered looking at this melodic group of insects... until now. 

The team who published the paper noticed some interesting behavior between crickets and seeds of plants in the family Marantaceae. Plants in this group attach a fleshy structure to their seeds called an aril. The function of this aril is to attract potential seed dispersers. By offering up seeds from various members of the family, the research team were able to demonstrate that seed dispersal by crickets in this region is quite common. Even more astounding, they found that at least six different species of cricket were involved in removing seeds from the study area. What's more, these crickets only ate the aril, leaving the seed behind.

[SOURCE]

The question of whether this constitutes effective seed dispersal remains to be seen. Still, this research suggests some very interesting things regarding crickets as seed dispersal agents. Not only did the crickets in this study remove the same amount of seeds as ants, they also removed larger seeds and took them farther than any ant species. Since only the aril is consumed, such behavior can seriously benefit large-seeded plants. Also, whereas ant seed dispersal occurs largely during daylight hours, cricket dispersal occurs mostly at night, thus adding more resolution to the story of seed dispersal in these habitats. I am very interested to see if this sort of cricket/seed interaction happens elsewhere in the world.

Photo Credits: [1] [2]

Further Reading: [1]