Life With Endophytic Fungi

 Endophytic fungi living in the cells of a grass leaf.

Endophytic fungi living in the cells of a grass leaf.

Talk about plants long enough and fungi eventually make their way into the conversation. These two walks of life are inextricably linked and probably have been since the earliest days. At this point we are well aware of beneficial fungal partners like mycorrhizae or pathogens like the cedar apple rust. Another type of relationship we are only starting to fully appreciate is that of plants and endophytic fungi living in their above ground tissues. 

Endophytic fungi have been discovered in many different types of plants, however, it is best studied in grasses. The closer we look at these symbiotic relationships, the more complex the picture becomes. There are many ways in which plants can benefit from the presence of these fungi in their tissues and it appears that some plants even stock their seeds with fungi, which appears to give their offspring a better chance at establishment. 

To start, the benefits to the fungi are rather straight forward. They get a relatively safe place to live within the tissues of a plant. They also gain access to all of the carbohydrates the plants produce via photosynthesis. This is not unlike what we see with mycorrhizae. But what about the plants? What could they gain from letting fungi live in and around their cells?

One amazing benefit endophytic fungi offer plants is protection. Fungi are famous for the chemical cocktails they produce and many of these can harm animals. Such benefits vary from plant to plant and fungi to fungi, however, the overall effect is largely the same. Herbivores feeding on plants like grasses that have been infected with endophytic fungi are deterred from doing so either because the fungi make the plant distasteful or downright toxic. It isn't just big herbivores that are deterred either. Evidence has shown that insects are also affected.

There is even some evidence to suggest that these anti-herbivore compounds might have influences farther up the food chain. It usually takes a lot of toxins to bring down a large herbivore, however, some of these toxins have the potential to build up in the tissues of some herbivores and therefore may influence their appeal to predators. Some have hypothesized that the endophytic fungal toxins may make herbivores more susceptible to predators. Perhaps the toxins make the herbivores less cautious or slow them down, making them more likely targets. Certainly more work is needed before anyone can say for sure.

 Italian ryegrass ( Lolium multiflorum ) is one of the most studied grasses that host endophytic fungi.

Italian ryegrass (Lolium multiflorum) is one of the most studied grasses that host endophytic fungi.

Another amazing example deals with parasitoids like wasps that lay their eggs in other insects. Researchers found that female parasitoid wasps can discriminate between aphids that have been feeding on plants with endophytic fungi and those without endophytic fungi. Wasp larvae developed more slowly and had a shorter lifespan when raised in aphids that have fed on endophytic fungi plants. As such, the distribution of plants with endophytic symbionts may have serious ramifications for parasitoid abundance in any given habitat.

Another benefit these endophytic fungi offer plants is increased photosynthesis. Amazingly, some grasses appear to photosynthesize better with endophytic fungi living in their tissues than plants without fungi. There are many mechanisms by which this may work but to simplify the matter, it appears that by producing defense compounds, endophytic fungi allow the plant to redistribute their metabolic processes towards photosynthesis and growth. In return, the plants produce more carbohydrates that then feed the fungi living in their tissues. 

One of the most remarkable aspects about the relationship between endophytic fungi and plants is that the plants can pass these fungi on to their offspring. Fungi are able to infect the tissues of the host plants' seeds and therefore can be carried with the seeds wherever they go. As the seedlings grow, so do the fungi. Some evidence suggests this gives infected seedlings a leg up on the competition. Other studies have not found such pronounced effects.

Still other studies have shown that it may not be fungi in the seeds that make a big difference but rather the fungi present in the decaying tissues of plants growing around them. Endophytic fungi have been shown to produce allelopathic compounds that poison neighboring plants. Areas receiving lots of plant litter containing endophytic fungi produced fewer plants but these plants grew larger than areas without endophytic fungi litter. Perhaps this reduces competition in favor of plant species than can host said endophytes. Again, this has potentially huge ramifications for the diversity and abundance of plant species living in a given area.

We are only beginning to understand the role of endophytic fungi in the lives of plants and the communities they make up. To date, it would appear that endophytic fungi are potentially having huge impacts on ecosystems around the globe. It goes without saying that more research is needed.

Photo Credits: [1] [2]

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

                                                        

Growing Camouflage

 A garden on the back of a weevil living a humid Chilean rainforest.

A garden on the back of a weevil living a humid Chilean rainforest.

Lots of us will be familiar with organisms like decorator crabs that utilize bits and pieces of their environment, especially living sea anemones, as a form of camouflage and protection. Examples of terrestrial insects attaching bits and pieces of lichens to their body are not unheard of either. However, there are at least two groups of arthropods that take their camouflage to a whole new level by actively growing miniature gardens on their bodies.

Little is known about these garden-growing arthropods. To date, these miniature gardens have only been reported on a few species of weevil in the genus Gymnopholus as well as a species of millipede called Psammodesmus bryophorus. Coined epizoic symbiosis, it is thought that these gardens serve as a form of protection by camouflaging the gardeners against the backdrop of their environment.

 Bryophytes on a  Psammodesmus bryophorus  male.

Bryophytes on a Psammodesmus bryophorus male.

Indeed, both groups of arthropods frequent exposed areas. What is most remarkable about this relationship is that these plants were not placed on the carapace from elsewhere in the environment. Instead, they have been actively growing there from the beginning. Closer inspection of the cuticle of these arthropods reveals unique structural adaptations like pits and hairs that provide favorable microclimates for spores to germinate and grow.

The plant communities largely consist of mosses and liverworts. At least 5 different liverwort families are represented and at least one family of moss. Even more remarkable is the fact that even these small botanical communities are enough to support a miniature ecosystem of their own. Researchers have found numerous algae such as diatoms, lichens, and a variety of fungi growing amidst the mosses and liverworts. These in turn support small communities of mites. It appears that an entire unknown ecosystem lives on the backs of these mysterious arthropods.

 FIGURE 39. Elytral base of Gymnopholus (Niphetoscapha) nitidus with exudates. FIGURES 40a–b. Gymnopholus (Niphetoscapha) inexspectatus sp. n., live specimen with incrustrations of algae and lichens; photographs M. Wild, Mokndoma.  [SOURCE]

FIGURE 39. Elytral base of Gymnopholus (Niphetoscapha) nitidus with exudates. FIGURES 40a–b. Gymnopholus (Niphetoscapha) inexspectatus sp. n., live specimen with incrustrations of algae and lichens; photographs M. Wild, Mokndoma. [SOURCE]

There is still much to be learned about this symbiotic relationship. Although camouflage is the leading hypothesis, no work has been done to actually investigate the benefits these arthropods receive from actively growing these miniature gardens on their backs. Mysteries still abound. For instance, in the case of the millipede, gardens are found more frequently on the backs of males than on the backs of females. Could it be that males spend more time searching their environment and thus benefit from the added camouflage? Only further research will tell.

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

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

The Bladderwort Microbiome Revealed

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The bladderworts (Utricularia spp.) are among the most cosmopolitan groups of carnivorous plants on this planet. Despite their popularity, their carnivorous habits have been subject to some debate. Close observation reveals that prey capture rates are surprisingly low for most species. This has led some to suggest that the bladderworts may be benefiting from more passive forms of nutrient acquisition. To better understand how these plants utilize their traps, a team of researchers decided to take a closer look at the microbiome living within. 

The team analyzed the trap fluid of a handful of floating aquatic bladderwort species - U. vulgaris, U. australis, and U reflexa. In doing so, they uncovered a bewildering variety of microorganisms perfectly at home within the bladderwort traps. Thanks to sophisticated genetic tools, they were able to classify these microbes in order to investigate what exactly they might be doing inside the traps. 

Their findings were quite astonishing to say the least. The traps of these plants harbor extremely rich microbial communities, far richer than the microbial diversity of other carnivorous plant traps. In fact, the richness of these microbial communities were more akin to the richness seen in the rooting zone of terrestrial plants or the gut of a cow. In terms of the species present, the microbial communities of bladderwort traps most closely resembled that of the pitchers of Sarracenia species as well as the guts of herbivorous iguanas.

The similarities with herbivore guts is quite remarkable. Its not just coincidental either. The types of microbes they found weren't new to science but their function was a bit of a surprise. A large percentage of the bacteria living within the fluid are famously known for producing enzymes that digest complex plant tissues. Similarly, the team found related microbe groups that specialize on anaerobic fermentation. These types of microbes in particular are largely responsible for the breakdown of plant materials in the rumen of cattle.

As it turns out, the microbes living within the traps of these bladderworts are serving a very important purpose for the plant - they are breaking down plant and algae cells that find their way into the traps each time they open and close. In doing so, they give off valuable nutrients that the bladderworts can then absorb and utilize. Let me say that again, the bacteria living in bladderwort traps are digesting algae and other plant materials that these carnivorous plants can then absorb.

Now these bacteria are also responsible for producing a lot of methane in the process. Interestingly enough, the team was not able to detect measurable levels of methane leaving the traps. This would be odd if it wasn't for the community of methane-feeding microbes also discovered living within the traps. The team believes that these organisms metabolize all of the methane being produced before it can escape the traps. 

As remarkable as these findings are, I don't want to give the impression that these carnivorous plants have taken up a strict vegetarian lifestyle. The team also found myriad other microorganisms within the bladder traps, many of them being carnivores themselves. The team also found a rich protist community. A majority of these were euglenids and ciliates. 

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These sorts of protists are important microbial predators and the numbers recorded within the traps suggest that they are a rather significant component of these trap communities. As they chase down and consume bacteria and other protists, they release valuable nutrients that the plants can absorb and utilize. Numbers of these predatory protists were much higher in older traps, which have had much more time to accumulate a diverse microbiome. Astonishingly, it is estimated that the protist communities can cycle the entire contents of the bladderwort traps upwards of 4 or 5 times in a 24 hour period. That is some serious turnover of nutrients!

The protists weren't the only predators found within the traps either. There are also a considerable amount of bacterial predators living there as well. These not only cycle nutrients in similar ways to the protist community, it is likely they also exhibit strong controls on the biodiversity within this miniature ecosystem. In other words, they are considered keystone predators of these microcosms.

Also present within the traps were large amounts of fungal DNA. None of the species they found are thought to actually live within the traps. Rather, it is thought that they are taken up as spores blown in from the surrounding environment. Exactly how these organisms find themselves living inside bladderwort traps is something worth considering. The plants themselves are known for being covered in biomfilms. It is likely that many of the organisms living within the traps were those found living on the plants originally. 

Taken together, the remarkable discovery of such complex microbial communities living on and within these carnivorous plants shows just how complex the ecology of such systems really are. Far from the active predators we like to think of them as, the bladderworts nonetheless rely on a mixture of symbiotic orgnaisms to provide them with the nutrients that they need. The fact that these plants are in large part digesting plant and algae materials is what I find most astonishing.

Essentially, one can almost think of bladderworts as plants adorned with tiny, complex cow stomachs, each utilizing their microbial community to gain as much nutrients as they can from their living environment. The bladderworts gain access to nutrients and the microbes get a place to live. The bladderworts really do seem to be cultivating a favorable habitat for these organisms as well. Analysis of the bladder fluid demonstrated that the plants actively regulate the pH of the fluid to maintain their living community of digestive assistants. In doing so, they are able to offset the relative rarity of prey capture. Keep in mind that this research was performed on only three species of bladderwort originating from similar habitats. Imagine what we will find in the traps of the multitude of other Utricularia species.

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

Further Reading: [1]

 

Resin Midges, Basal Angiosperms, and a Strange Pollination Syndrome

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When we try to talk about clades that are "basal" or "sister" to large taxonomic groups, your average listener either consciously or unconsciously thinks "primitive." Primitive has connotations of something that under-developed or unfinished. This is simply not the case. Take, for instance, a family of basal angiosperms called Schisandraceae.

This family is nestled within the order Austrobaileyales, which, along with a small handful of other families, represent the earliest branches of the angiosperm family tree still alive today.  To call them primitive, however, would be a serious misnomer. Because they diverged so early on, these lineages represent serious success stories in flowering plant evolution, having survived for hundreds of millions of years. Instead, we must think of them as fruitful early experiments in angiosperm evolution.

Floral morphology of and interaction between midge and their larvae (white arrows) in Illicium dunnianum

Still, the proverbial proof is in the pudding and if there was any sort of physical evidence one could put forth to remove our hierarchical prejudices about the taxonomic position of these plants, it would have to be their bizarrely specific pollination syndromes.  Members of the family Schisandraceae have entered into intense relationships with a group of flies known as midges and their interactions are anything but primitive. 

We will start with two species of plant native throughout parts of Asia. Meet as Illicium dunnianum and Illicium tsangii. More will be familiar with this genus than they may realize as Illicium gives us the dreaded star anise flavor our grandparents liked to sneak into our cookies as kids (but I digress). These particular species, however, have more to offer the world than flavoring. They are also very important plants for a group of gall midges in the genus Clinodiplosis.

The midges cannot reproduce without I. dunnianum or I. tsangii. You see, these midges lay their eggs within the flowers of these plants and, in doing so, end up pollinating them in the process. At first glance it may seem like a very one-sided relationship. Female midges deposit their eggs all along the carpels packed away inside large, fleshy whorl of tepals. As the midges crawl all over the reproductive organs looking for a suitable place to lay, they inevitably pick up and deposit pollen. 

Floral morphology and interaction between midge larvae (white arrows) in  Illicium tsangii

This is not the end of this relationship though. After eggs have been deposited, something strange happens to the Illicium flowers. For starters, they develop nursery chambers around the midge larvae. Additionally, their tepals begin producing heat. Enough heat is produced to keep the nursery chamber temperature significantly warmer than the ambient air temperature. What's more flower heating intensifies throughout the duration of fruit development. It was originally hypothesized that this heating had something to do with floral odor volatilization and seed incubation, however, experiments have shown that at least seed development in these two shrubs is not influenced by floral heat in any major way. The same cannot be said for the midge larvae. 

As the flowers mature and give way to developing seeds, the midge larvae are hard at work feeding on tiny bits of the flowers themselves. When researchers looked at midge larvae development on these Illicium species, they found that they were completely dependent upon the floral heat for survival. Any significant drop in temperature caused them to die. Essentially, the plants appear to be producing heat more for the midges than for themselves. It may seem odd that these two plants would invest so much energy to heat their flowers so that midge larvae feeding on their tissues can survive but such face-value opinions rarely stand in ecology.

One must not forget that those larvae grow up to be adult midges that will go on to pollinate the Illicium flowers the following season. Although the plants are taking a bit of a hit by allowing the larvae to develop within their tissues, they are nonetheless ensuring that enough pollinators will be around to repeat the process again. If that wasn't cool enough, the relationship between each of these plants and their pollinators are rather specific and the authors of at least one paper believe that the midges that pollinate each species are new to science. 

Now, if I haven't managed to convince you that this angiosperm sister lineage is anything but primitive, then let's take a look at another genus within the family Schisandraceae that have taken this midge pollination syndrome to the next level. This story also takes place in Asia but instead involves a genus of woody vines known as Kadsura

Like the Illicium we mentioned earlier, a handful of Kadsura species rely on midges for pollination. The way in which they go about maintaining this relationship is a bit more involved. The midges that are attracted by Kadsura flowers are known as resin midges and their larvae live off of plant resins. The flowers of Kadsura are another story entirely. They are as odd as they are beautiful. 

 Flowers, pollinators ,and their larvae (white arrows) in  Kadsura heteroclita .

Flowers, pollinators ,and their larvae (white arrows) in Kadsura heteroclita.

In male flowers, stamens are arranged in dense, cone-like structures called androecia whereas the female flowers contain a compact shield-like structure with the uppermost part of the stigma barely emerging. This is called a gynoecium. Even weirder, the male flowers of one particularly strange species, Kadsura coccinea, produce large, swollen inner tepals. 

Once Kadsura flowers begin to open, visiting midges are not far behind. Male flowers seem to attract more midges than female flowers and it is thought that this has to do with varying amounts of special attractant chemicals produced by the flowers themselves. Regardless, midges set to work exploring the blooms with males looking for mates and females looking for a place to lay their eggs. 

When a suitable spot has been found, females will deposit their eggs into the floral tissues with their ovipositor. The wounded plant tissues immediately begin producing resin, not unlike a wounded pine tree. In the case of K. coccinea, it would appear that the oddly swollen tepals are specifically targeted by female midges for egg laying. They too produce resin upon having eggs laid within. 

The oddball flowers of Kadsura coccinea showing swollen tepals.

The function of plant resins in many cases are to fight off pathogens. From beetles to fungi, resin helps plug up and seal off wounds. This does not seem to be the case in the Kadsura-midge relationship though. The so-called "brood chambers" within the floral tissues go on producing resin for upwards of 6 days after the midge eggs were laid. Eventually the floral parts whither and drop off but the midge larvae seem to be quite happy in their resin-filled homes. 

As it turns out, the resin midge larvae feed on the viscous resin as their sole food source. Instead of trying to ward off these pesky little insects, the plants seem to be encouraging them to raise their offspring within! Just as we saw in the Asian Illicium, these Kadsura vines seem to be providing brood sites for their pollinators. Also, just as the Illicium-midge relationship thought to be species specific, each species of Kadsura appears to have its own specific species of resin midge pollinator! K. coccinea even goes as far as to produce tepals specifically geared towards raising midge larvae, thus keeping them away from their more valuable reproductive organs. In return for the nursery service, Kadsura have their pollinators all to themselves.

Pollination mutualisms in which plants trade raising larvae for pollen transfer are extremely derived and some of the most specialize plant/animal interactions on the planet. To find such relationships in these basal or sister lineages is living proof that these plants are anything but primitive. In the energy-reproductive investment trade-off, it appears that ensuring ample pollinator opportunities far outweighs the cost of providing them with nursery chambers. It is remarkable to think just how intertwined the relationships between these plants and there pollinators truly are. Take that, plant taxonomic prejudices! 

Photo Credits: [1] [2]

Further Reading: [1] [2] 

 

Devil's Gardens

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Imagine, if you will, walking through the dense understory somewhere in the Amazon basin. Diversity reigns supreme here and it would seem that every few steps reveals myriad new plant species. As you walk along, something in the vegetation changes. You stumble into a clearing in the middle of the forest dominated entirely by a single species of tree. Why the sudden change? How did this monoculture develop? You, my friend, have just found yourself on the edge of a Devil's garden. 

Devil's gardens are said to be the resting place of an evil spirit known to local tribes as Chullachaki. Anyone unlucky enough to stumble into his garden is said at risk of attack or curse. In reality, these gardens have a biological origin. The real gardeners are a handful of ant species which seem to have rather specific gardening preferences. Careful inspection would reveal that the gardens largely consist of trees in one of three genera - Duroia, Tococa, or Clidemia

  Tococa  sp. (Melastomataceae)

Tococa sp. (Melastomataceae)

The reason that ants are so fond of these genera has to do with housing. These plant groups contain species which produce swellings along their stems and petioles known as domatia. These domatia are hollow and are the favorite nesting spots of various ant species. Ant colonies set up shop within. As anyone who has ever blundered into an ant colony can attest, ants are quite voracious at defending their home. 

By providing ant colonies with a home base, these plants have essentially hired body guards. It is a wonderful form of symbiosis in which the ants aggressively defend against anything that might want to take a bite out of their host tree. Any herbivore trying to take up residence or lay eggs within the Devil's garden is viciously attacked. In doing so, the ants are protecting their host trees at the cost of all other plants unlucky enough to germinate within the garden. Still, this anti-herbivore behavior doesn't totally explain the monoculture status these host trees achieve within the garden itself. Why are these gardens so ominously devoid of other plant species?

To answer this, one would have to watch how the ants behave as they forage. While scouting, if ants encounter a seedling of their host tree, nothing really happens. They go about their business and let the seedling grow into a future home. When they encounter a non-host tree, however, their behavior completely changes. 

 Behold - A Devil's Garden

Behold - A Devil's Garden

The ants begin biting the stem of the plant, exposing its vascular tissue. As they bite, the ants also sting the foreign seedling, injecting minute amounts of formic acid into the wound. One or two ants isn't enough to bring down a seedling but one thing ants have on their side are numbers. Soon an entire platoon of ants descend upon the hapless seedling, stinging it repeatedly. In no time at all, the seedling succumbs to the formic acid injections and dies. By repeating this process any time a foreign plant is found growing within the vicinity of the garden, the resident ants ensure that only trees that will produce domatia are allowed to grow in their garden. Thus, a Devil's garden has been formed. 

Although this relationship seems incredibly beneficial for each party, it does come at some cost to the plants themselves. Certainly forming the domatia is a costly endeavor on the part of the plant, but research has also shown that growing in such high, monoculture-like densities in the jungle has its downsides. It has been found that individual host trees can actually experience more herbivore pressures when growing within a Devil's garden than if it was growing alone, elsewhere in the forest. 

Despite their aggression towards herbivores, the ants simply cannot be everywhere at once. As such, the high densities of host tree species within a Devil's garden act like a dinner bell for any insect that enjoys feeding on that particular type of plant. Essentially, the ants are concentrating a potential food source. Experts believe that this might explain why Devil's gardens never completely take over entire swaths of forest. Essentially, there are diminishing returns to living in such high densities. Still, benefits must outweigh costs if such mutualisms are to be maintained and it is quite obvious that both plant and ant benefit from this interaction to a great degree. 

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

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

The Early Days Of A Symbiosis?

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Despite the ubiquitous nature of symbioses across the globe, evidence of their origins is scant to say the least. Mostly we look for clues of their origin hidden within the fossil record. Excitingly, a series of fossils discovered in Scotland reveal what very well be the early days of plant-cyanobacterial interactions. Thanks to these exquisitely preserved fossils, we now have the earliest record of an association between these two groups of organisms.

The fossils themselves date back to the early Devonian, some 400 million years ago. They hail from a hot spring community which allowed wonderfully detailed preservation of everything down to the cellular level. Needless to say, this was a drastically different time for life on this planet. Plants were really starting to dominate the landscape. In the case of the fossil discoveries in question, one plant in particular is the star of this show. 

Meet Aglaophyton major. This odd looking plant would have been a common site in these sorts of habitats. It largely consisted of a small, leafless stem that branched as it ambled over the ground. These stems bore the stomata, which allowed gas exchange to occur. Every once in a while, a stem would throw up a reproductive structure called a sporangium, which housed the spores. At the ground level, the stems would occasionally produce root-like rhizoids that have been found in association with fossilized mycorrhizal fungi in the soil.

In total, A. major only stood about 18 cm in height. Though abundant, it was relatively small compared to some of the other vegetation coming online at this point in time. It is likely that A. major could tolerate occasional flooding. In fact, some have speculated that flooding may have been necessary for the germination of its spores. It's this periodic inundation with water that likely led to an interesting and tantalizing relationship with cyanobacteria. 

 1. Transverse section through two typical axes showing the simple internal organization; slide P1828; bar = 1 mm. 2. Anatomy of the prostrate mycorrhizal axis (E = epidermis; OC = outer cortex; MAZ = mycorrhizal arbuscule-zone; IC = inner cortex; PIT = phloem-like tissue; CT = conducting tissue); slide P1612; bar = 150 μm. 3. Dense aggregate of cyanobacterial filaments in an area where the axis is injured and has exuded some type of wound secretion (opaque mass); slide P1289; bar = 100 μm. 4. Detail of Plate I, 3, showing part of the cyanobacterial aggregate; bar = 100 μm. 5. Intercellular cyanobacterial filaments near the mycorrhizal arbuscule-zone of the cortex (darker tissue in lower third of image); slide P3652; bar = 50 μm. 6. Group of filaments passing through the intercellular system of the outer cortex; slide P3652; bar = 20 μm.

1. Transverse section through two typical axes showing the simple internal organization; slide P1828; bar = 1 mm. 2. Anatomy of the prostrate mycorrhizal axis (E = epidermis; OC = outer cortex; MAZ = mycorrhizal arbuscule-zone; IC = inner cortex; PIT = phloem-like tissue; CT = conducting tissue); slide P1612; bar = 150 μm. 3. Dense aggregate of cyanobacterial filaments in an area where the axis is injured and has exuded some type of wound secretion (opaque mass); slide P1289; bar = 100 μm. 4. Detail of Plate I, 3, showing part of the cyanobacterial aggregate; bar = 100 μm. 5. Intercellular cyanobacterial filaments near the mycorrhizal arbuscule-zone of the cortex (darker tissue in lower third of image); slide P3652; bar = 50 μm. 6. Group of filaments passing through the intercellular system of the outer cortex; slide P3652; bar = 20 μm.

Cyanobacteria are probably best known for their contribution of oxygen to Earth's early atmosphere. What's more, many also fix nitrogen. That is why the fossil discovery of A. major with cyanobacteria in and around its cells is so exciting. These 400 million year old fossils provide the first evidence of a plant and cyanobacteria in an intimate association.

As mentioned above, the fossilization process was so thorough that it preserved subcellular structures. After thin sectioning some A. major stems, a team of researchers found filaments of cyanobacteria in the process of invading the plant and taking up residence. The cyanobacteria appears to be entering the plant through the stomatal openings along the stem. Once inside, the cyanobacteria show signs of colonazation of substomatal chambers as well as intercellular spaces within the plants tissues.

Although the authors cannot say whether this association was mutualistic or not, it nonetheless represents a model situation detailing how such a symbiotic relationship could have evolved in the first place. Because the cyanobacteria in question here is thought to be aquatic, the only way for it to move into the plant would have been during periodic flooding events. The idea that this could be simply an infection following the death of the plant was considered. However, the non-random distribution of cyanobacteria within A. major cells suggests that this relationship was no accident.

For now, the relationship between A. major and cyanobacteria was likely an "on-again–off-again incidental association" centered around flood events. The fact that A. major was already associated with mycorrhizal fungi at this point in Earth's history certainly suggests that the genetic adaptations necessary for symbiotic relationships were already in place. Though it isn't a smoking gun, these fossils provide the earliest evidence of plants' relationship with cyanobacteria.

Photo Credits: [1]

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

The Nitrogen-Fixing Abilities of Cycads

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Long before the first legumes came onto the scene, the early ancestors of Cycads were hard at work fixing atmospheric nitrogen. However, they don't do this on their own. Despite being plentiful in Earth's atmosphere, gaseous nitrogen is not readily available to most forms of life. Only a special subset of organisms are capable of turning gaseous nitrogen into forms usable for life. Some of the first organisms to do this were the cyanobacteria, which has led them down the path towards symbioses with various plants on many occasions. 

Cycads are but one branch of the gymnosperm tree. Their lineage arose at some point between the Carboniferous and Permian eras. Throughout their history it would seem that Cycads have done quite well in poor soils. They owe this success to a partnership they struck up with cyanobacteria. Although it is impossible to say when exactly this happened, all extant cycads we know of today maintain this symbiotic relationship with these tiny prokaryotic organisms. 

 Cross section of a coralloid cycad root showing the green cyanobacteria inside.

Cross section of a coralloid cycad root showing the green cyanobacteria inside.

The relationship takes place in Cycad roots. Cycads don't germinate with cyanobacteria in tow. They must acquire them from their immediate environment. To do so, they begin forming specialized structures called precoralloid roots. Unlike other roots that generally grow downwards, these roots grow upwards. They must situate themselves in the upper layer of soil where enough light penetrates for cyanobacteria to photosynthesize.

The cyanobacteria enter into the precoralloid roots through tiny cracks and take up residence. This causes a change in root development. The Cycad then initiates their development into true coralloid roots, which will house the cyanobacteria from that point on. Cycads appear to be in full control of the relationship, dolling out carbohydrates in return for nitrogen depending on the demands of their environment. Coralloid roots can shed and reform throughout the lifetime of the plant. It is quite remarkable to think about how nitrogen-fixing symbiotic relationships between plants and microbes have evolved independently throughout the history of life on this planet.

Photo Credits: [1] [2]

Further Reading: [1] [2]

 

The World's Only (Known) Photosynthetic Vertebrate

You may be asking yourself right now why I have posted a picture of a salamander this morning. This is a plant blog after all! Well, what I am about to tell you may seem a bit crazy, but I assure you this discovery has opened up some doors that science never really considered a possibility before. The yellow spotted salamander (Ambystoma maculatum) is the first and only (known) photosynthetic vertebrate ever discovered!

That's right. You heard me. A photosynthetic animal. More accurately speaking, it is the embryos of this species that undergo photosynthesis. To understand why this happens we must back up a little bit. Yellow spotted salamanders are a species of mole salamander that can be found in wet areas of eastern North America. They spend most of their adult lives underground, hiding beneath logs and rocks in the forest, feeding on any manner of invertebrates. Once a year (around this time) adult yellow spotted salamanders undertake a massive migration down to the pools where they mate. On the first few warm, rainy nights, thousands of salamanders can be seen trucking their way to vernal pools and ponds to breed. It is an amazing sight to behold.

The thing about yellow spotted salamanders is they will only breed in fishless ponds. Their larvae would be an easy meal for many predatory fish species. The problem that arises out of this breeding strategy is that fishless ponds tend to be very low in oxygen. It has long been known that the eggs of this species form a symbiotic relationship with an algae. The algae produce oxygen for the developing embryo and the embryo feeds the algae via its nitrogen rich waste and CO2. This relationship was always thought to be external, that is until Ryan Kerney of Dalhousie University in Halifax, Nova Scotia discovered that embryos of a certain age actually had algae living within their cells.

They algae don't seem to start off inside the cells though. This may be why this relationship wasn't discovered earlier. Roger Hangarter at Indiana University found that it isn't until parts of the salamander's nervous system begin to develop that the algae move into the embryo and set up shop. The algae then reside near the salamander's mitochondria, which are the powerhouses of the cell. So where are the algae coming from? While more research needs to be done, Karney also discovered the presence of algae in the oviducts of adult female spotted salamanders. It is looking like mother salamanders are actually passing the algae on to their offspring. 

Though this is the first and only instance we know of this sort of photosynthetic relationship in vertebrate animals, this discovery has opened the door for exploring the possibility of other photosynthetic symbionts. It has also allowed scientists a different avenue to explore just how cells recognize and deal with foreign bodies. We live in such an amazing world!

Further Reading: [1] [2] [3]

 

Orchid Dormancy Mediated by Fungi

North America's terrestrial orchids seem to have mastered the disappearing act. When stressed, these plants can enter into a vegetative dormancy, existing entirely underground for years until the right conditions return for them to grow and bloom. Cryptic dormancy periods like this can make assessing populations quite difficult. Orchids that were happy and flowering one year can be gone the next... and the next... and the next...

How and why this dormancy is triggered has confused ecologists and botanists alike. Certainly stress is a factor but what else triggers the plant into going dormant? According to a recent paper published in the American Journal of Botany, the answer is fungal.

Orchids are the poster children for mycorrhizal symbioses. Every aspect of an orchid's life is dependent on these fungal interactions. Despite our knowledge of the importance of mycorrhizal presence in orchid biology, no one had looked at how the abundance of mycorrhizal fungi influenced the life history of these charismatic plants until now.

By observing the presence and abundance of a family of orchid associated fungi known as Russulaceae, researchers found that the abundance of mycorrhizal fungi in the environment is directly related to whether or not an orchid will emerge. The team focused on a species of orchid known commonly as the small whorled pogonia (Isotria medeoloides). Populations of this federally threatened orchid are quite variable and assessing their numbers is difficult.

The team found that the abundance of mycorrhizal fungi is not only related to prior emergence of these plants but could also be used as a predictor of future emergence. This has major implications for orchid conservation overall. It's not enough to simply protect orchids, we must also protect the fungal communities they associate with.

Research like this highlights the need for a holistic habitat approach to conservation issues. So many species are partners in symbiotic relationships and we simply can't value one partner over the other. If conditions change to the point that they no longer favor the mycorrhizal partner, it stands to reason that it would only be a matter of years before the orchids disappeared for good.

Photo Credit: NC Orchid

Further Reading: [1]

The Ant-Farming Tillandsias

Tillandsias are all the rage. Their relative ease of care has found them included in seemingly every terrarium sold these days; often in very inappropriate circumstances that result in their death. There is no denying that these epiphytic relatives of the pineapple are unique and beautiful plants but I would argue that their ecology is probably the coolest aspect about them. I am particularly fond of the bulbous species because of their relationship with ants.

That's right, there are upwards of 13 species of bulbous Tillandsia that offer up housing for ants. If you look closely at the leaves of these species, you will notice that they roll up to form tubes that lead down into the bulb at the base. The space between the leaves forms a hollow chamber, functioning as a perfect microclimate for ants to nest. In many habitats, these Tillandsia offer better housing than the surrounding environment. One would be surprised at how many ants can fit in there too. Colonies containing anywhere between 100 - 300 ants are not unheard of.

The rewards for the plant are obvious. Ants provide nutrients as well as protection. In return the ants get a relatively safe and dry place to live. Ant domatia have been recorded in roughly 13 different species, many of which are some of the most commonly sold Tillandsias on the market such as T. baileyi, T. balbisiana, T. bulbosa, and T. caput-medusae. If this doesn't make your hanging glass Tillandsia orb even cooler then I don't know what will.

Photo Credits: scott.zona (http://bit.ly/16kZ1RR) and Alex Popovkin (http://bit.ly/1BXMEUH)

Further Reading: [1] [2]

A Poop-Eating Pitcher Plant

The aerial pitchers of Nepenthes hemsleyana (http://bit.ly/2hC94fO) are quite unique in that they are not intended to catch insects. Instead, they have evolved as specialized roosts for Hardwicke's woolly bats (Kerivoula hardwickii). This incredible mutualism is quite unique among these tropical carnivores. The bats get a safe place to roost and in return, they deposit nitrogen-rich feces. 

This mutualism is quite remarkable in that the upper pitchers of N. hemsleyana have pretty much forgone insect capture altogether. Despite the obvious benefits of this evolutionary relationship, no one had bothered to quantify the benefits gained by turning insect catching pitchers into bat roosts. That is, until now. 

A team of researchers based out of University of Greifswald in Germany utilized some cunning methods to demonstrate exactly how much N. hemsleyana relies on bat droppings. What they found what quite remarkable. Plants offered only insects not only had fewer leaves, they also exhibited slower growth, reduced photosynthetic capacity, and reduced survival. It would seem that this mutualism has evolved to the point of being obligate. 

It is estimated that around 95% of the nitrogen needs of this plant are met by bat feces alone. As it turns out, nitrogen bound up in insect tissues were mostly unavailable to the plant. This is not the case for nitrogen in bat poop. Nitrogen deposited by bats comes mostly in the form of urea, which degrades into ammonium and is readily absorbed by the pitchers. 

Essentially Nepenthes hemsleyana now relies on bats to capture prey for them. This "ecological outsourcing," as it has been termed, frees the plant from the rigors of having to capture and digest insects on its own, thus saving valuable energy reserves that can be allocated to structures such as leaves, stems, and flowers. Why this species has evolved this strategy is anyone's guess. Perhaps it has to do with the deep shaded forest understory in which it grows. 

Photo Credit: Merlin Tuttle (www.merlintuttle.smugmug.com)

Further Reading: [1]

Bacteria Help the Cobra Lily Subdue Prey

The aptly named cobra lily (Darlingtonia californica) is one of North America's most stunning pitcher plants. Native to a small region between northern California and southwestern Oregon, this bizarrely beautiful carnivore lives out its life in nutrient poor, cold water bogs and seeps. Although it resides in the same family as our other North American pitcher plants, Sarraceniaceae, the cobra lily has a unique taxonomic position as the only member of its genus.

It doesn't take much familiarity with this plant to guess that it is carnivorous. Its highly modified leaves function has superb insect traps. Lured in by the brightly colored, tongue-like protrusions near the front tip of the hood, insects find a sweet surprise. These tongue-like structures secrete nectar. As insects gradually make their way up the tongue, they inevitably find themselves within the downward pointing mouth of the pitcher. This is where those translucent spots on the top of the hood come in.

These translucent spots trick the insects into flying upwards into the light. Instead of a clean getaway, insects crash into the inside of the hood and fall down within the trap. The slippery walls of the pitchers interior make escape nearly impossible but that isn't the only thing keeping insects inside. Research has shown that the cobra lily gets a helping hand from bacteria living within the pitcher fluid.

Unlike other pitcher plants, the cobra lily does not fill its traps with rain water. The downward pointing mouth prevents that from happening. Instead, the pitchers secrete their own fluid by pumping water up from the roots. Although there is evidence that the cobra lily does produce at least some of its own digestive enzymes, it is largely believed that this species relies heavily on a robust microbial community living within its pitchers to do most of the digesting for it. This mutualistic community of microbes save the plant a lot of energy while also providing it with essential nutrients like nitrogen in return for a safe place to live.

That isn't all the bacteria are doing for this pitcher plant either. As it turns out, the pitchers' microbial community may also be helping the plant capture and subdue its prey. A recent study based out of UC Berkeley demonstrated that the presence of these microbes helps lower the surface tension of the water, effectively drowning any insect almost immediately.

The microbes release certain compounds called biosurfactants. Through an interesting chemical/physical process that I won't go into here, this keeps insects from using the surface tension of the water's surface to keep them afloat, not unlike a water strider on a pond. Instead, as soon as insects hit the bacteria infested waters, they break the surface tension and sink down to the bottom of the pitcher where they quickly drown. There is little chance of escape for a hapless insect unlucky enough to fall into a cobra lily trap.

Although plant-microbe interactions are nothing new to science, this example is the first of its kind. Although this prey capture role is very likely a secondary benefit of the microbial community within the pitchers, it very likely makes a big difference for these carnivores living in such nutrient poor conditions.

Photo Credit: Wikimedia Commons

Further Reading: [1]

Live-In Mites

Hearing the word "mite" as a gardener instantly makes me think of pests such as spider mites. This is not fair. The family to which mites belong (Acari) is highly varied and contains many beneficial species. Many mites are important predators at the micro scale. Some are fungivorous, eating potentially harmful species of fungi. Whereas this may be lost on the majority of us humans, it is certainly not lost on many species of plants. In fact, the relationship between some plants and mites is so strong that these plants go as far as to provide them with a sort of home.

Domatia are specialized structures that are produced by plants to house arthropods. A lot of different plant species produce domatia but not all of them are readily apparent to us. For instance, many trees and vines such as red oak (Quercus rubra), sugar maples (Acer saccharum), black cherries (Prunus serotina), and many species of grape (Vitis spp.) produce tiny domatia specifically for mites. The domatia are often small, hairy, and function as shelter for both the mites and their eggs.

By housing certain species of mites, these plants are ensuring that they have a steady supply of hunters and cleaners living on their leaves. Predatory mites are voracious hunters, keeping valuable leaves free of microscopic herbivores while frugivorous mites clean the leaves of detrimental fungi that are known to cause infections such as powdery mildew. The exchange is pretty straight forward. Mites get a home and a place to breed and the plants get some protection. Still, some plants seem to want to sweeten the relationship in a literal sense.

Some plants, specifically grape vines in the genus Vitis, also produce extrafloral nectaries on their leaves. These tiny glands secrete sugary nectar. In a paper recently published in the Annals of Botany, it was found that extrafloral nectaries enhances the efficacy of these mite domatia by enticing more mites to stick around. By adding nectar to domatia-producing leaves that did not secrete it, the researchers found that nectar increases beneficial mite densities on these leaves by 60 - 80%. This translates to an increase in fitness for these plants in the long run.

I love research like this. I had no idea that so many of my favorite and most familiar tree and vine species had entered into an evolutionary relationship with beneficial mites. This adds a whole new layer of complexity to the interactions within any given environment. It just goes to show you how much is left to be discovered in our own back yards.

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

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

A Carnivorous Plant and its Bug

Carnivory and symbiosis are two topics within the field of botany that are endlessly fascinating. Because they are static entities, plant evolution has gone through some very interesting pathways for survival. Recently, a group of plants found only on the southern tip of Africa have shone a light on yet another interesting plant/insect relationship that is unlike any other yet known to science.

The genus Roridula contains two species that, for all intents and purposes, look like carnivorous plants. They closely resemble sundews in having leaves packed full of sticky hairs that ensnare hapless insects. However, they are neither closely related to sundews nor do they have any sort of digestive enzyme for breaking down their insect victims. Why then would these plants go through the trouble of producing glandular traps? There must be some adaptive benefit to make up for the cost of production. A closer look at these plants revealed that indeed there is.

Living on Roridula plants are tiny capsid bugs that are covered in a special waxy substance that keeps them from getting stuck in the sticky traps. The bugs move about the sticky leaves, looking for trapped insects. When the insects are found, the capsid bugs impale them with their proboscis and suck them dry. As the capsid bugs feed, their droppings end up littering the Roridula leaves. This is how Roridula gets the added nutrients it needs to survive. Although the plants are not capable of actively digesting the full insects, they are capable of absorbing the components of the capsid bug feces. They are literally getting a little bit of fertilizer every time a capsid bug goes to the bathroom. By offering the capsid bugs a place to live and plenty of free, immobilized prey, the plant is able to get nitrogen-rich meals in return!

Photo Credit: Alex Lomas, CARNIVORASLAND, and Darwiniana

Further Reading:
http://aob.oxfordjournals.org/content/95/5/757

The Whorled Pogonia

I live for moments like this. The only downside to that is I can never really predict when they are going to happen. There I was driving up a mountain road in search of a handful of other plant species related to my research. The road was narrow and there was a steep bank on the drivers side. The Southern Appalachian Mountains are brimming with botanical diversity. As such, it can be hard to tease out individual plants, especially while driving. This is why having a refined search image comes in handy. 

I was rounding a bend in the road when something out my window caught my eye. My mind went racing and it wasn't long before a suspicion crept into my head. If I was right, this was an opportunity I was not going to miss. I found the nearest pull off, parked the truck, and ran back down the road. I am so happy that I decided to trust my instincts. There in front of me was a small population of whorled pogonia orchids (Isotria verticillata). 

It was like being in the presence of a celebrity that I had been stalking for years. This was an orchid I have been dying to see. The harder I looked the more I saw. I had to sit down. Here in front of me was a species of orchid that isn't seen by many. In fact, entire populations of these species can go unseen for decades until they have enough energy to flower. 

Flowering in this species is said to be quite erratic. Because they live in shaded environments, building up the energy needed to reproduce can be difficult. Like all orchids, the whorled pogonia relies on an obligate relationship with mycorrhizal fungi to supply the nutrients it needs. In return, the orchids provide fungi with carbohydrates. The problem with erratic flowering, however, is that it makes reproduction difficult. Rarely are two populations flowering at the same time and in close enough proximity for successful cross pollination. More often, these orchids will self fertilize, which can lead to high rates of inbreeding. 

Large bees are the main pollinators of the whorled pogonia. The flowers themselves are reported to produce a feint odor reminiscent of Vanilla. This is interesting to note because in the greater scheme of orchid phylogenetics, this species is placed in the Vanilla subfamily, although such distinctions can get muddled quickly. Regardless, simply being in the presence of this orchid was enough to give me goosebumps. It is a shame that such a species is being lost throughout much of its range. 

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

http://bit.ly/1WEmZzm

On Peonies and Ants

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It is just about that time when peony buds burst forth and put on their late spring display. My mother loves her peonies and she gets very excited every year when they bloom. It's adorable. However, she has always been disgusted by the amount of ants the peonies attract. Indeed, many people all over the internet seem to feel the same way. Growing up, I always wondered why the ants seemed to swarm all over peony buds, so I decided to look into it a little deeper.

There are many sources out there that claim that peonies need ants in order to bloom. To me, this seems very maladaptive on the part of the peony. The genus Paeonia is represented in Asia, Southern Europe and parts of western North America. I am going to assume that the ant/peony relationship didn't start in the garden so it's roots have to be somewhere in the evolutionary history of the plant. What sense does it make for a plant to produce flower buds that excrete sticky sugars that keep them from opening until something cleans the sugars off? In fact, despite anecdotal reports, peony buds will open without ants. So then why does the plant bother to produce sugars that attract ants?

Interestingly enough, despite a good amount of searching, there is not a lot of research done on this subject but the answer to this question can come from looking at how ants interact with other plants and animals. Many plant species have special glands on their stems that produce sugary secretions which attract ants. It's not just plants either. Insects such as aphids and leafhoppers famously excrete honeydew that ants can't resist. In each of these cases, organisms are using the ants' natural tendency to guard a food source. The ants will viciously attack anything that threatens this easy meal.

It would seem to me that the peonies are doing just that with their flower buds. By secreting a sugary substance during their development, the plant are likely recruiting ants to protect the flowers, which in the plant kingdom, are the most precious part of the plant. It takes a lot out of a plant to flower and the threat of herbivory is ever present. If an insect tries to take a bite out of a bud, the ants quickly swarm and drive it off. It's a win win situation. The ants get an easy, high-energy food source and the plant suffers less damage to its reproductive organs.

The scary part to me in researching all of this is plethora of information out there on how to get rid of the ants. People go through chemical after chemical to rid their peonies of ants when, in reality, the ants are some of the best friends a peony could have! So leave those ants alone and enjoy the free pest removal services they provide every spring!

Photo Credit: [1]

Further Reading:

http://www.youtube.com/watch?v=Gnm2nV_nwOk

Of Gunnera and Cyanobacteria

Nitrogen is a limiting resource for plants. It is essential for life functions and yet they do not produce it on their own. Instead, plants need to get it from their environment. They cannot uptake gaseous nitrogen, which is a shame because it makes up 78.09% of our atmosphere. As such, some plants have developed very interesting ways of obtaining nitrogen from their environment. Some, like the legumes, produce special nodules on their roots, which house bacteria that fix atmospheric nitrogen. Other plants utilize certain species of mycorrhizal fungi. One family of plants, however, has evolved a symbiotic relationship that is unlike any other in the angiosperm world.

Meet the Gunneras. This genus has a family all to itself - Gunneraceae. They can be found in many tropical regions from South America to Africa and New Zealand. Some species of Gunnera are small while others, like Gunnera manicata, have leaves that can be upwards of 6 feet in diameter. Their leaves are well armed with spikes and spines. All in all they are rather prehistoric looking. The real interesting thing about the Gunneras though, is in the symbiotic relationship they have formed with cyanobacteria in the genus Nostoc.

Gunnera produce specialized glands that house these cyanobacteria. The glands are filled with a special mucilage that not only attracts the cyanobacteria, but also stimulates it to grow. Once inside the glands, the cyanobacteria begins to grow into the plant, eventually fusing with the Gunnera cells. From there the cyanobacteria earn their keep by producing copious amounts of usable nitrogen and in return, the Gunnera supplies carbohydrates. This relationship is amazing and quite complex. It also offers researchers an insight into how such symbiotic relationships evolve.

Photo Credit: Fluffymuppet (http://bit.ly/1QARvXm) and Lotus Johnson (http://bit.ly/1QEBegP)

Further Reading:
http://www.sfbotanicalgarden.org/garden/bloom_07_09.shtml

http://bit.ly/1U8SUHr

http://bit.ly/1q2cNDt

http://bit.ly/1UkBvvF

http://bit.ly/1MCgnsE

Sticky Friend

We have all had encounters with sticky plants. Outside of being an interesting sensory experience, the sticky nature of these floral entities would appear to have some evolutionary significance. Considering the cost of producing the glandular trichomes responsible for their stickiness, function is a reasonable question to ask about. For anyone who has taken the time to observe such plants, you will have undoubtedly noticed that insects tend to get stuck to them.

For carnivorous plants, the utility of these glands is readily obvious - trapped insects become food. Even non-carnivores like Roridula gain a nutrient benefit in the form of nutrient-rich feces deposited around the plant by specialized carnivorous bugs that consume trapped insects. However, there are many species of plants out there that fall under the category of "sticky" and a new paper explores this in a more general way.

The serpentine columbine (Aquilegia eximia) is endemic to the Coastal Range of California and it is indeed quite sticky. Its surfaces are covered in glandular hairs. Any given plant can be covered in insects unfortunate enough to come into contact with it. However, it is not a carnivore. As such, researchers wanted to see what benefits, if any, the columbine gained from producing these glands.

By manipulating the amount of insects that were stuck to each plant, researchers found that plants without "victims" actually received more insect damage. The key to this mystery were predators. Plants with lots of trapped victims had more predatory bugs hanging around. These predators, when present, reduced herbivory by deterring other insects that were too large to get stuck. What's more, most of the benefits were observed in the flower buds, which means predators increased the overall reproductive fitness of the serpentine columbine. If the columbine did not trap small insects, these predators would have no reason to hang around.

These predatory bugs were by no means specific to the columbine. In fact, observation of the surrounding plant community found that these predatory insects were present on other sticky genera such as Arctostaphylos, Hemizoni, Holocarpha, Calycidenia, Cordelanthus, Castilleja, Mimulus, Trichostema, and Grindelia. This suggests that the relationship between sticky plants and these generalist predators is more widespread than previously thought. It may also offer a unique window into one possible driver behind the evolution of carnivory in plants.

Photo Credit: David A. Hofmann (http://bit.ly/1l9OtwC)

Further Reading:
http://www.esajournals.org/doi/abs/10.1890/15-0342.1

Echoes of a Glacial Past

Climate change is often talked about in the context of direct effects on species. However, as John Muir so eloquently put it, "When we try to pick out anything by itself, we find it hitched to everything else in the Universe." In essence, nothing is ever black and white and a recent publication by Dr. Robert Warren and Dr. Mark Bradford illustrates this fact quite well.

Ants and plants have some very intricate interactions. A multitude of plant species rely on ants as their seed dispersers. Many of these plant species are spring ephemerals that take advantage of the fact that there is little else for ants to eat in the early spring by attaching fatty capsules to their seeds that are very attractive to foraging ant species. There are two big players in the foraging ant communities of eastern North America, the warm adapted Aphaenogaster rudis and the cold adapted Aphaenogaster picea. The cold adapted A. picea emerges from winter dormancy early in the spring while the warm adapted species emerges from dormancy much later in the spring. In the southern portions of their range, A. rudis outcompetes A. picea.

What is the big deal? Well, the researchers looked at two plant species that rely on these ants for seed dispersal, Hepatica nobilis and Hexastylis arifolia. Hepatica nobilis sets seed early in the spring, relying on ant species like A. picea to disperse its seed whereas Hexastylis arifolia sets seed late in spring, which is prime time for A. rudis. They noticed that, in the southern portions of their range where A. picea had been displaced, Hepatica has a very clumped and patchy growth habit where farther north it did not. Hexastylis on the other hand seemed to have a more normal growth pattern in the south.

By performing some transplanting and examining foraging and seed dispersal, they found that the absence of A. picea in the south spelled ecological disaster for Hepatica. It continues to set seed but because A. rudis emerges long after seed set, it is not filling the gap left by the missing A. picea. Hexastylis, which only grows in the south and sets seed much later, does just fine with the warm adapted A. rudis. Farther north where A. picea still rules, Hepatica has no trouble with seed dispersal but Hexastylis drops out of the ecosystem entirely. In essence, because of warming climate trends since the end of the Pleistocene, Hepatica is falling out of sync with its mutualistic ant partner in the southern portions of its range and, in time, may become extirpated.

Further Reading:
http://bit.ly/1J4VnN7