A Fern With Flower Genes - An Odd Case of Horizontal Gene Transfer

Photo by Aaron Carlson licensed under CC BY-SA 2.0

When researchers at Harvard decided to take a look at the genome of the rattlesnake fern (Botrypus virginianum) they found something completely unexpected. Whereas one set of genes they looked at placed this species firmly in the family to which it belongs, Ophioglossaceae, two other genes placed it in the Loranthaceae, a completely unrelated family of flowering plants. What are flowering plant genes doing in a fern?

The rattlesnake fern is a ubiquitous species found throughout the northern hemisphere. It is believed to have evolved in Asia and then radiated outward using ancient land bridges that once connected the continents. At some point before this radiation occurred, the rattlesnake fern picked up some genes that were entirely foreign.

Horizontal gene transfer, the transfer of genes from one organism to another without reproduction, is nothing new in nature. Bacteria do it all the time. Even plants dabble in it every now and then. The surprising thing about this recently documented case is that it is the first discovery of horizontal gene transfer between an angiosperm and a fern. Up until this point, examples within the plant realm have been seen between ferns and hornworts as well as some parasitic plants and their hosts.

This is why the rattlesnake fern genome is so interesting. How did this occur? Though there is no way of telling for sure, researchers believe that one of two things could have happened. The first involves root parasitism. The family Loranthaceae is home to the mistletoes, a group of plants most famous for their parasitic nature. Although the majority of mistletoe species are stem parasites, at least three genera utilize root parasitism. It could be that an ancient species of mistletoe transferred some genes while parasitizing a rattlesnake fern.

This scenario seems to be the least likely of the two as no representatives of the root parasitic mistletoes currently exist in Asia, though it is entirely possible that some did at one time. The other possibility doesn't involve parasitism at all but rather fungi. Rattlesnake ferns are obligate mycotrophs and thus cannot live without certain species of mycorrhizal fungi. Perhaps the transfer of genes was achieved indirectly via a shared mycorrhizal network. This hypothesis is especially tantalizing because if it is found to be true, it would help explain many other examples of horizontal gene transfer that currently lack a mechanism. Only time and more research will tell.

Photo Credit: Aaron Carlson (http://bit.ly/1OAVhNZ)

Further Reading:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1560187/

Conifer Leaf Drop

It's that time of year when evergreen trees become apparent. The most obvious are the conifers. These trees hold steady while everything else seems to be in a mad rush for winter. Despite the term "evergreen" the conifers are nonetheless preparing for winter as well, though on a much more subtle level. Anyone paying close attention will see some color changes happening to them too. Despite the designation as "evergreen" conifers do shed leaves.

Timescales are everything for us humans. We tend to notice things that happen relatively fast, like an entire forest turning color in only a few weeks. The conifers have adopted a strategy that isn't as in tune with our perception. Conifers, for the most part, specialize in harsh habitats. Excelling in poor soils and extreme cold, they tend to invest in the long term. Needles are one such adaptation. Their minimal surface area and structural integrity make up for their costly production in nutrient poor conditions. When a conifer produces needles, they need to last for a while.

And that is exactly what they do. The average conifer needle has a lifetime of roughly 2 years (with some exceptions of course). It doesn't make sense for them to bank on a whole new set leaves every year. Because of the way they grow, conifers usually shed their leaves from the inside out. New leaves are produced at the tips of branches and, as older leaves get shaded out, conifers cut their losses and drop them. If you take a close look at conifers during the fall, this pattern becomes readily apparent.

Leaf drop doesn't always happen quickly either. They are often spaced out over time. One of the reasons I like plants so much is that they operate on vastly different timescales than we do. As you become more and more familiar with different species, plants can teach you to start looking at things a bit different than you are used to. Get outside and find some needle dropping conifers of your own.

Further Reading: [1]

The Darth Vader Begonia

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Cue the Imperial March, it is time to talk about the Darth Vader Begonia. This atramentous plant had only been known to the world since 2014. The discovery of this species (as well as two other new Begonia species) occured in Sarawak, on the island of Borneo. This region is a hot spot for plant diversity and this is especially true for begonias. A combination of diverse terrain and varied microclimates have led to an explosion of speciation events resulting in endemic species found nowhere else in the world.

With its leaves so deeply green that they almost appear black and deep red flowers it's not a stretch to imagine why this begonia has been named Begonia darthvaderiana. Until 2014, no one had ever laid eyes on this species, not even the locals. It was found growing in the deep shade of a forested cliff mixed in among other shade-loving vegetation. It is likely that the dark coloration of its leaves enables it to take advantage of what little sunlight makes it down to the forest floor.

Not long after its discovery was reported, something alarming happened. The so-called Darth Vader begonia began appearing for sale online. With a price tag of $80+, this is one expensive little plant. Apparently a plant poacher from Taiwan managed to smuggle some plants out of the country. This is especially upsetting because of its extreme rarity. Despite its namesake, the force is not strong enough to protect this species from greedy collectors. If you have somehow managed to obtain one of these plants, please do everything in your power to propagate it. Plants produced in captivity take pressure off of wild populations.

This was not the only new begonia species to be named after a Star Wars character. A larger species with green and silver leaves was given the scientific name of Begonia amidalae after Queen Amidala. It too is endemic to the region. The future of these plants as well as many others hangs in the balance. A growing human population is putting pressure on the rainforests of Borneo. As more and more forest is lost to development, countless endemic species are disappearing with it. This is yet another example of why land conservation is a must. Please consider lending your support to organizations such as the Rainforest Trust. Together, we can ensure that there are wild spaces left.

CLICK HERE TO HELP LAND CONSERVATION EFFORTS IN BORNEO

Photo Credit: Che-Wei Lin, Shih-Wen Chung, & Ching-I Peng

Further Reading: [1] [2]

 

Sticky Friend

Photo by David A. Hofmann licensed under CC BY-NC-ND 2.0

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

Is it a pine? Is it an apple? It's neither!

Photo by Fractalux Public Domain

Pineapples - the fruit that is neither a pine nor an apple. In reality, pineapples are a type of bromeliad. The genus to which they belong, Ananas, is comprised of something like 7 different species, all of which are native to Central and South America. Considering we rarely encounter these plants outside of a grocery store, it is no wonder then that many are surprised to realize how pineapples grow.

Photo by H. Zell licensed under CC BY-SA 3.0

The fruit itself is not the entire plant. It is made up of many fruits that fuse together after flowering. The flowers themselves are quite lovely and originate from the center of the hexagonal units that make up the tough rind. The whole inflorescence arises from the center of a large rosette of leaves. Only when you see the entire plant does the bromeliad affinity become apparent. Like all other bromeliads, pineapples undergo vegetative reproduction as well. Small offshoots called "pups" arise from the base of the plant and the axils of the leaves. These can take root and grow into clones of the parent plant.

In the wild, pineapples require pollination to set seed. This is undesirable in cultivation because pollination means lots of seeds that consumers don't want to contend with. Because of this, pineapples are gassed with ethylene, the simplest of plant hormones. Ethylene causes the fruits to artificially ripen without being pollinated. In this way, no ovules mature into seeds.

Photo by hiroo yamagata licensed under CC BY-SA 2.0

The dirty little secret about pineapple farming is that it is done at great environmental cost. The dominant producer of pineapples is Costa Rica. Because of the humid, tropical climate, insects and fungi flourish. In order to ensure that production is maximized, pineapple farmers dump thousands of gallons of pesticides and herbicides onto their crops. These farms are largely void of all other lifeforms save for endless hectares of pineapples. This, however, is not a story unique to pineapple farming. The same could be said for all other forms of monoculture farming.

Photo Credits: Fractalux, H. Zell, and hiyori13 - Wikimedia Commons

Further Reading:

http://www.kew.org/science-conservation/plants-fungi/ananas-comosus-pineapple

http://www.theguardian.com/business/2010/oct/02/truth-about-pineapple-production

Insect Eating Bats Eat More Insects Than Birds in Tropical Forests

If the early bird gets the worm, it is only because we haven't been observing bats the right way, at least not in the rainforests of Central America. It has long been thought that insects such as katydids and caterpillars exhibit night feeding in order to escape day-active birds. This theory has influenced the way in which researchers investigate insect herbivory in tropical forests. However, recent studies have shown that bats, not birds, are doing the bulk of the insect eating in both natural and man-made habitats. 

In order to accurately investigate the role of insectivorous bats play in limiting herbivory in tropical forests, researchers decided to look at the common big-eared bat (Micronycteris microtis). They wanted to find out exactly how much insect predation could be attributed to these nocturnal hunters. As it turns out, 70% of the bats diet consists of plant eating insects, which is quite significant. Extrapolating upwards, it was apparent that we have been overlooking quite a bit.

Photo by Christian Ziegler via Santana SE, Geipel I, Dumont ER, Kalka MB, Kalko EKV (2011) All You Can Eat: High Performance Capacity and Plasticity in the Common Big-Eared Bat, Micronycteris microtis (Chiroptera: Phyllostomidae). PLoS ONE 6(12): e28584. doi:10.1371/journal.pone.0028584 licensed under CC BY 2.5

Using special exclosures, researchers set out to try to quantify herbivory rates when bats and birds were excluded. What they found was staggering. When birds were excluded from hunting on trees, insect presence went up 65%. When bats were excluded, insect presence skyrocketed by 153%! What this amounts to is roughly three times as much damage to trees when bats are removed - a significant cost to forests. 

To prove that it wasn't only natural forests that were benefitting from the presence of bats, the researchers then replicated their experiments in an organic cacao farm. Again, bats proved to be the top insect predators, eating three times as many insects than birds. This amounts to massive economic benefits to farmers. Bats have long been viewed as the enemies of both the farm as well as the farmers. Research like this is starting to change such perspectives. 

This certainly doesn't diminish the role of birds in such systems. Instead, it serves to elevate bats to a more prominent stature in the healthy functioning of forest ecosystems. Findings such as these are changing the way we look at these furry fliers and hopefully improving our relationship as well. 

Photo Credit: Christian Ziegler - Wikimedia Commons

Further Reading: [1] [2]
 

Germinating a Seed After 32,000 Years

[SOURCE]

What you are looking at are plants that were grown from seeds buried in permafrost for nearly 32,000 years. The seeds were discovered on the banks of the Kolyma River in Siberia. The river is constantly eroding into the permafrost and uncovering frozen Pleistocene relics. Upon their discovery, researchers took the seeds and did the unthinkable - they grew them into adult plants. To date, this is the oldest resurrected plant material. 

The key to their extreme longevity lies in the permafrost. They were found inside the frozen burrow of an Arctic ground squirrel. The state of the burrow suggests that everything froze quite rapidly. As such, the seeds remained in a state of suspended animation for 32,000 years. This is not the first time viable plant materials have been recovered from Pleistocene permafrost. Spores, mosses, as well as seeds of other flowering plants have been rejuvenated to some degree in the past but none of these were grown to maturity. 

Using micropropagation techniques coupled with tissue cultures, researchers were able to grow and flower the 32,000 year old seeds. What they discovered was that these seeds belonged to a plant that can still be found in the Arctic today. It is a small species in the family Caryophyllaceae called Silene stenophylla. However, there were some interesting differences. 

As it turns out, the seeds taken from the burrow proved to be a phenotype quite distinct from extant S. stenophylla populations. For instance, their flowers were thinner and less dissected than extant populations. Also, whereas the flowers of extant populations are all bisexual, individuals grown from the ancient seeds first produced only female flowers followed by fewer bisexual flowers towards the end of their blooming period.Though there are many possible reasons for this, it certainly hints at the different environmental parameters faced by this species through time. What's more, such findings allow us a unique window into the world of seed dormancy. Researchers are now looking at such cases to better inform how we can preserve seeds for longer periods of time. 

Photo Credit: Svetlana Yashinaa, Stanislav Gubin, Stanislav Maksimovich, Alexandra Yashina, Edith Gakhova, and David Gilichinsky

Further Reading: [1]

The Strangest Spiderworts

What if I told you that what you are looking at right now is a member of the spiderwort family (Commelinaceae)? At first, I didn't believe it either. Even after seeing those magnificent blooms, it took a bit of convincing. Regardless, the genus Cochliostema represents some of the strangest members of the family.

Cochliostema can be found growing in Central and South America. There are only two species in the genus, C. odoratissimum and C. jacobianum. My introduction to this group was Cochliostema odoratissimum. It is one of those plants that you smell before you see. The fragrance of the flowers is something worth experiencing. Because I lack the descriptive vocabulary needed to convey the proper respect, I'm going to ask you to trust me when I say that its lovely. The fragrance emanates from some seriously awesome flowers. It has been suggested that they are quite possibly the most complex flowers in the entire family. They are born on a type of spike called a "thyrse." Each flower consists of 3 sepals, 3 fringed petals, 3 stamens, which are fused in the upper half of the flower, and 3 carpels fused into a single pistil. The end result, as you can clearly see, is stunning.

The plants themselves are epiphytes, though they will grow terrestrially if they happen to fall from their host tree. As evidenced by their radial growth habit, they are akin to bromeliads in their ecology with at least one species considered a tank epiphyte. As such, they provide ample habitat in the canopy for a variety of flora and fauna.

Further Reading:

http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8339.2000.tb02348.x/abstract

Orchid Ant Farms

Photo by Scott Zona licensed under CC BY-NC 2.0

I am beginning to think that there is no strategy for survival that is off-limits to the orchid family. Yes, as you may have figured out by now, I am a bit obsessed with these plants. Can you really blame me though? Take for instance Schomburgkia tibicinis (though you may also see it listed under the genera Laelia or more accurately, Myrmecophila). These North, Central, and South American orchids are more commonly referred to as cow-horn orchids because they possess hollow pseudobulbs that have been said to been used by children as toy horns. What is the point of these hollow pseudobulbs?

A paper published back in 1989 in the American Journal of Botany found the answer to that question. As it turns out, ants are quite closely associated with orchids in this genus. They crawl all over the flowers, feeding on nectar. The relationship goes much deeper though. If you were to cut open one of these hollow pseudobulbs, you would find ant colonies living within them. The ants nest inside and often pile up great stores of food and eventually waste within these chambers. The walls of the chambers are lined with a dark tissue that was suspect to researchers.

Using radioactively labeled ants, the researchers found that the orchids were actually taking up nutrients from the ant middens! What's more, nutrients weren't found solely in adjacent tissues but also far away, in the actively growing parts of the roots. These orchids are not only absorbing nutrients from the ants but also translocating it to growing tissues.

While orchids without a resident ant colony seem to do okay, it is believed that orchids with a resident ant colony do ever so slightly better. This makes sense. These orchids grow as epiphytes on trees, a niche that is not high in nutrients. Any additional sources of nutrients these plants can get will undoubtedly aid in their long-term survival. Also, because the ants use the orchids as a food source and a nest site, they are likely defending them from herbivores.

Photo Credit: Scott.Zona (http://bit.ly/1hvWiGX)

Further Reading:
http://www.jstor.org/stable/2444355

Feed Me, Seymour!

Photo by Ebony Black Public Domain

In the spirit of spooky-ness, today I would like to introduce you to some of the most bizarre looking plants on our planet. I am of course talking about the genus Hydnora. Known locally as jakkalskos (jackal food) or bobbejaankos (baboon food), these odd parasites certainly look creepy. However, their ecology is downright fascinating and well worth a closer look.

Hydnora comprises roughly seven species and currently resides in its own family, Hydnoraceae. More recent taxonomic work suggests that this may actually be a subgroup within the family Aristolochiaceae, but as far as I know, the jury is still out on this. All species are native to southern Africa and as you can probably tell from the picture, they produce no leaves and no chlorophyll. Instead of wasting energy on producing its own food, Hydnora has resorted to parasitism. They are root parasites on members of the family Euphorbiaceae. They tap into the roots of their host plants using specialized structures called "haustoria." In this way they are able to gather all their nutritional needs from their host. Once a Hydnora has obtained enough energy it will produce a flower.

The flower is all you will ever see of this plant. The strange, scaly structure emerges from the ground underneath its host. Three slits begin to form, each lined with white, hair-like structures. At first these structures remain intact. The spaces between are just big enough to allow entry of pollinators, which in this case are dung beetles. Once the flower opens these slits it begins to produce some heat, not unlike what we see in many aroids. The heat helps to spread the scent and the smell is what you would expect from a plant trying to attract dung beetles - it smells like feces.

Photo by Charles Stirton licensed under CC BY-NC-ND 2.0

When a dung beetle arrives looking for some fresh poop, it enters the flower through those slits and falls down into the trap. The rest of the flower consists of a tube-like structure underground. To keep the beetles from escaping, Hydnora employs a trick used by many carnivorous pitcher plants. Lining the walls are downward pointing hairs that prevent the beetles from crawling out before their job is done. Once inside, the beetles are drawn to the center where the smell is emitted. Here they are dusted with generous amounts of pollen. If the beetles have arrived after a previous Hydnora visit then they will also deposit pollen and thus reproduction is achieved. Once the plant releases pollen onto the beetles, the hairs lining the wall relax and the slits open completely, allowing the beetles to escape.

I hope some day to see one of these in person. To the best of my knowledge, only a single species (Hydnora africana) has ever been grown in cultivation and that was a single event. Seeds were sown in a pot containing a known host species of Euphorbia. It took a very long time for germination and even longer to mature and produce a flower. Either way this creepy species is actually quite fascinating.

Photo Credit: [1] [2]

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

Pumpkins!

Ah, the pumpkin. Nothing signifies fall to me more than this lovely orange gourd. Who doesn't love the eerie glow of a jack-o-lantern or the pleasing taste of roasted pumpkin seeds? Don't even get me started on my love for pumpkin pie! This gourd has certainly ingrained itself in our culture but, from a botanical standpoint, pumpkins, or at least the species from which they hail, are quite interesting.

Cucurbita pepo is native to North America and is a member of the gourd family. Though it should come as no surprised, this group is characterized by the large fruits that they produce. The gourds themselves are actually a type of berry. C. pepo is one of the oldest species of plants ever domesticated. Records from Mexico show humans cultivating this species as far back as 8750 BC. The origins of this domesticated species are still a bit fuzzy but experts believe that C. pepo is a hybrid of Cucurbita texana and Cucurbita fraterna, though the former may just be a feral form of C. pepo.

As it turns out, pumpkins are only one domesticated variety of Cucurbita pepo. Many of the gourds we enjoy are also varieties of this species. These include crops like acorn squash, delicata squash, gem squash, several types of ornamental squash (often called "gourds"), pattypan squash, spaghetti squash, yellow crookneck squash, yellow summer squash, and zucchini. Pretty impressive, no?

Many of these varieties are believed to have originated in the southern portions of Mexico but that is still being resolved. So, if you find yourself carving pumpkins and eating some other form of gourd, like spaghetti squash, realize that you are spending your evening celebrating the many uses of a single species!

Photo Credit: Thom Pirson & Wikimedia Commons

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

 

Devil's Claws

Proboscidea louisianica

I would like to introduce you to the genus Proboscidea. These lovely, albeit sticky plants are collectively referred to as the Devil's claw plants. The common name comes from the nasty looking seed pods which likely evolved in response to large mammals that once roamed this continent. The genus Proboscidea has traditionally been placed into the sesame family (Pedaliaceae) due to superficial similarities in flower and seed morphology, but more recent work has moved it into the unicorn plant family, Martyniaceae. That's right... unicorn plants.

The entire family is found in the New World, with two species (P. lousianica & P. althaeifolia) hailing from arid parts of the southern portions of North America. At least two other species are readily naturalizing in this region as well. There are some aspects of these species that make them quite interesting to botanists. For starters, the apt name of Devil's claw was bestowed upon this genus because of the bizarre seed pods they produce. Similar to burs, they can become entangled in fur quite readily. The odd thing about this seed dispersal mechanism for some Devil's claws is how big those seed pods are. Until cattle were introduced to this continent, animals large enough to effectively disperse these massive seed pods seemed to be missing, having gone extinct at the end of the last ice age. It is believed that these plants may be an anachronism of this era.

Photo by T.K. Naliaka licensed under CC BY-SA 4.0

Photo by Roger Culos licensed under CC BY-SA 3.0

The flora we are familiar with today spent millennia co-evolving with ice age megafauna like mammoths and giant ground sloths. There is a growing school of thought that many close relationships probably developed over this time and have not yet been lost due to the relatively limited amount of time since the extinction of these large mammals. There are some people who will tell you that the seed pods are "designed" to ensnare small mammals like mice, causing them to die, which then provides the seeds a nutrient-rich, rotting corpses on which to germinate. I have never been able to find any evidence in support of these claims.

Another intriguing anatomical feature of this species are the countless sticky glands that cover the entire plant. These readily ensnare insects that land on or try to climb up the plant. Analysis of the fluids secreted by these glands show evidence of digestive enzymes but the jury still seems to be out on whether or not Devil's claws are undergoing any active carnivorous behavior.

Proboscidea althaeifolia. Public Domain

It is more likely that these glands are a form of defense against insect herbivores and indeed they work quite well. Even a brief run-in with this plant leaves you quite sticky and slimy. It is possible that by ensnaring herbivorous insects, the plant can attract carnivorous insects that will eat the herbivores and then "repay" the devil's claw with nutrient-rich feces. Another possibility is that the glands cause the plant to become covered in sand grains over time. Such sandy armor would get in the way of hungry herbivores. To ad insult to injury, the plant kind of smells. It has been likened to old gym clothes.

These are neat plants. I have had fun growing them in the past. They are an annual but may reseed if care is not taken to removing the seed pods before they pop open. Because of their lively appearance and the unique look of their seed pods, these plants are often grown as horticultural oddities. Be careful though, as they have escaped cultivation outside of their native range and can be considered a noxious weed!

Photo Credit: [1] [2] [3]

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

American Witch Hazel

With October nearly over, temperatures are starting to dip. The asters and goldenrods have traded their floral displays for their wind-dispersed seeds that take advantage of the fall breeze. Alas, floral displays in the northern hemisphere are nearly over. There is one major show left for those living in eastern North America. From October through November (and even into December in some regions) one species of understory shrub puts forth a display reminiscent of a firework extravaganza if the fireworks only came in yellow.

I am, of course, talking about American witch hazel (Hamamelis virginiana). This wonderful shade-loving shrub goes largely unnoticed throughout the summer. Come fall, however, it makes up for its subtle appearance by offering up some of the last flowers of the season. Seemingly overnight their branches become adorned with unique little flowers whose petals shoot out like four little party streamers. They somehow manage to look both modest and showy all at once.

It may seem strange for any plant to be flowering so late. What possible advantage could this entail? Some experts believe that late flowering evolved as a way for American witch hazel to avoid competition with other flowering plants. Indeed, it certainly attracts its fair share of pollinators in desperate search of a late season meal. Flies and bees make up a majority of pollinator visits. It could also be possible that American witch hazel flowers so late to avoid hybridizing with its spring-flowering cousin, the Ozark witch hazel (Hamamelis vernalis). Regardless of its "intentions," this fall flowering strategy comes at a cost.

Despite garnishing a fair amount of pollinator attention, American witch hazel doesn't have enough time following pollination to produce fruit before winter hits. As such, fertilization of the ovaries is delayed until May the following year. The fruits, which are contained in woody capsules, spend the entire growing season maturing into viable propagules. Once mature, the seed capsules begin to dry until they become so taught that the capsule bursts. If you are lucky and attentive enough, you may be able to hear a small snap as the seeds are forcibly ejected from the capsule.

What's more, fruit set in this species is rather low. Analyses of over 40,000 witch hazel flowers showed that less than 1% produced viable seeds. Despite all of this, American witch hazel is nonetheless a successful species in eastern North American forests. It is proof that evolution need not be all or nothing. Any slight advantage is still an advantage. This hardy shrub is, at the end of the day, a survivor.

Further Reading:
http://www.amjbot.org/content/89/1/67.abstract

Aquatic Angiosperm: A Cretaceous Origin?

Via Bernard Gomeza, Véronique Daviero-Gomeza, Clément Coiffardb, Carles Martín-Closasc, David L. Dilcherd, and O. Sanisidro [SOURCE]

It would seem that yet another piece of the evolutionary puzzle that are flowering plants has been found. I have discussed the paleontological debate centered around the angiosperm lineage in the past (http://bit.ly/1S6WLkf), and I don't think the recent news will put any of it to rest. However, I do think it serves to expand our limited view into the history of flowering plant evolution.

Meet Montsechia vidalii, an extinct species that offers tantalizing evidence that flowering plants were kicking around some 130–125 million years ago, during the early days of the Cretaceous. It is by no means showy and I myself would have a hard time distinguishing its reproductive structures as flowers yet that is indeed what they are thought to be. Detailed (and I mean detailed) analyses of over 1,000 fossilized specimens reveals that the seeds are enclosed in tissue, a true hallmark of the angiosperm lineage.

On top of this feature, the fossils also offer clues to the kind of habitat Montsechia would have been found in. As it turns out, this was an aquatic species. The flowers, instead of poking above the water, would have remained submerged. An opening at the top of each flower would have allowed pollen to float inside for fertilization. Another interesting feature of Montsechia is that it had no roots. Instead, it likely floated around in shallow water.

Via Bernard Gomeza, Véronique Daviero-Gomeza, Clément Coiffardb, Carles Martín-Closasc, David L. Dilcherd, and O. Sanisidro [SOURCE]

This is all very similar to another group of extant aquatic flowering plants in the genus Ceratophyllum (often called hornworts or coon's tail). Based on such morphological evidence, it has been agreed that these two groups represent early stem lineages of the angiosperm tree. Coupled with what we now know about the habitat of Archaefructus (http://bit.ly/1S6WLkf), it is becoming evident that the evolution of flowers may have happened in and around water. This in turn brings up many more questions regarding the selective pressures that led to flowers.

What is even more amazing is that these fossils are by no means recent discoveries. They were part of a collection that was excavated in Spain over 100 years ago. Discoveries like this happen all the time. Someone finds a interesting set of fossils that are then stored away on a dark shelf in the bowels of a museum only to be rediscovered decades or even centuries later.

All in all I think this discovery lends credence to the idea that flowering plants are a bit older than we like to think. Also, one should be wary of anyone claiming to have found "the first flower." The idea that there could be a fossil out there that depicts the first anything is flawed a leads to a lot of confusion. Instead, fossils like these represent snapshots in the continuum that is evolution. Each new discovery reveals a little bit more about the evolution of that lineage. We will never find the first flower but we will continue to refine our understanding of life on this planet.

Photo Credits: Bernard Gomeza, Véronique Daviero-Gomeza, Clément Coiffardb, Carles Martín-Closasc, David L. Dilcherd, and O. Sanisidro,

Further Reading:
http://www.pnas.org/content/112/35/10985.abstract

When a Mutualism Becomes Obligate

Photo by Tony Rodd licensed under CC BY-NC-SA 2.0

Mutualism. The word invokes this warm and fuzzy "you scratch my back and I'll scratch yours" feeling. It is easy to grasp how a mutualism would develop and be maintained. But, in any system, there are bound to be cheaters. Cheaters reduce the fitness of one of the partners so to avoid such things, some species up the ante by resorting to some interestingly "sinister" methods.

Acacias and ants have quite the relationship. Acacias protect themselves by offering ants hollow spines and branches where their colonies can live. They even sweeten the deal via extrafloral nectaries. These are glands on the stems that secrete nectar that the ants eat. In some ant species, this is their only source of food. Needless to say, the ants become highly protective of their acacia trees. They readily attack herbivores and even go as far as to prune away vegetation that may interfere with their host. This seems like a pretty straight forward mutualistic relationship, right?

Ah, but it goes deeper. To make sure that the ants will solely rely on the acacia and are thus completely tied up in the well being of their host, the acacia alters the ants phenotype at birth. Normally these ants have no issues digesting sucrose. Researchers found that the nectar in the extrafloral nectaries contains a protein called "chitinase." Chitinase inhibits the ability of the ants to digest sucrose. When ant eggs hatch into larvae, their first meal is nectar from the extra floral nectaries. Once the larvae ingest this protein they are no longer able to feed on anything other than their hosts nectar. Thus their very survival is completely tied to the Acacia.

I am positive that more examples of such obligate mutualisms abound in nature. We only have to ask the right questions to discover them. It is also interesting considering what we are finding out about our own behavior and how it relates to the microbiome living on and within us. What about human behavior could be described in the context of a relationship similar to ants and acacias?

Photo Credit: Tony Rodd

Further Reading:
http://www.ncbi.nlm.nih.gov/pubmed/24188323

Ruta-Muraria

In my opinion, the smaller a plant is, the more character it has. Wall rue (Asplenium ruta-muraria) is a wonderful demonstration of this. The genus of ferns to which it belongs, Asplenium, is rather large, containing somewhere along the lines of 700 species worldwide. 

Wall rue can be found growing both in North America and Europe. Its distribution is a reminder of the great land bridges that once connected the continents back when ocean levels were much lower than they are today. The specific epithet "ruta-muraria" roughly translates to "bitter herb of walls." Along with its common name, these seem to hint at where this tiny fern likes to grow. Indeed, at least in Europe, this is a fern of stone walls, growing among the myriad cracks and crevices where microclimates are favorable for its spores to germinate. 

In North America, however, wall rue seems to be a bit more picky. Wall rue is a calciphile meaning it can really only be found in abundance on natural limestone outcroppings. As a result, it is considered a threatened or endangered species throughout most of the continent. The aspect of its habitat I find most interesting is that the limestone it relies upon is the result of an ancient sea that covered parts of North America during the Silurian Period some 443.8–419.2 million years ago. If it were not for the solidified remains of ancient marine organisms, wall rue and many other plant lineages would not be here, at least not in the way in which we know them. 

Another interesting aspect of wall rue biology is that this little fern is helping paleontologists in Europe discover potential glacial refugia - ice free areas where plants and animals were able to survive during the height of glaciation. Refugia were likely epicenters of biodiversity, which expanded to recolonize the continents once the ice sheets receded. 

Wall rue, as well as other rock ferns in the genus Asplenium occur in two forms in nature - a diploid form with two sets of chromosomes and a polyploid form containing multiple sets of chromosomes. Polyploids arise from mutated diploids and can be found growing over a wider range than their more restricted diploid parents. By studying the relatedness of different diploid populations, researchers are able to deduce where some glacial refugia may have been located. In this way, these tiny little ferns are offering a rare but clear window into the Earth's long gone past. 

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

American Persimmon

Photo by Doug McAbee licensed under CC BY-NC 2.0

I will never forget the time I went to the grocery store and bought what I thought were strange tomato varieties. I got home and dug into them only to discover they were not tomatoes at all. I quickly realized the error in my judgment. Instead of the unmistakable flavor of a tomato, what I experienced was something slightly sweet and kind of astringent. I had inadvertently purchased a couple persimmon fruits. I was young and naive so I will cut myself some slack, however, like any good mistake, I was rewarded by the inadvertent introduction to a fascinating fruit I had never experienced before. 

Thinking this to be some strange tropical species, I was surprised to learn that North America does indeed have its own species of persimmon. Known scientifically as Diospyros virginiana, the American persimmon is native to much of the eastern U.S. but is absent north of Pennsylvania. We are lucky, biogeographically speaking, to have this species as the family to which it belongs, Ebenaceae, is predominantly tropical. It is an early successional tree species, often growing on recently abandoned farmland. In the spring this shrubby tree produces small yet attractive white and yellow flowers. American persimmon are dioecious meaning individual trees are either male or female. Their main pollinators are bees.  

As is often seen with many fruiting tree species,  there is a lot of variety between the fruits of different persimmons. They can range in size from small crabapples to the tomato-like fruits we find in the grocery store. There are those who suspect the fruits of the American persimmon to be a throwback to a time when animals like woolly mammoths and ground sloths roamed this continent, dispersing persimmon seeds as they roamed across the terrain. Indeed, fossils of American persimmon have been found in Miocene deposits in areas of Greenland and Alaska which suggests that this species has undergone range contraction, potentially due to the loss of these large seed dispersers. However, modern day evidence would seem to suggest otherwise. Today, much smaller animals like raccoons and opossum seem to do just as good of a job as a larger animal would. It is likely that the constricted range of the American persimmon has more to do with climate than seed dispersal. 

If you have never tried a persimmon before then seek one out and give it a go. If you find them in a grocery store, there is a good chance the fruit belongs to the Asian species (Diospyros kaki). The key to enjoying an American persimmon is making sure its ripe. If you are too early you are going experience some of the worst tannin dry mouth (I honestly don't think I will ever convince my mother to eat another strange fruit again). Either way, this neat species often goes overlooked until it is in fruit. Keep your eye out for fruiting persimmon in your area and report back if you decide to sample some. 

Photo Credit: Doug McAbee (http://bit.ly/1xznvPx)

Further Reading:
http://www.na.fs.fed.us/pubs/silvics_manual/volume_2/diospyros/virginiana.htm

Is it a Fungus? Is it a Forb? No, it's a Tree!

Botanical gardens are winter sanctuaries for a northerner like myself. Winter tree ID can only do so much for me during these times. As such, I try my best to make regular trips to tropical houses wherever and whenever I can. On a recent excursion to the Missouri Botanical Garden, I came across something completely unexpected.

I was perusing their tropical house aptly named "The Climatron." As I rounded a corner I happened to look down and saw what looked like something only a member of the birthwort family (Aristolochiaceae) could produce. There, lying near the ground were a cluster of some of the coolest flowers I have personally laid eyes on.

Photo by Cymothoa exigua licensed under CC BY-SA 3.0

I began searching for the plant that produced them. Up until this point, I have only encountered members of this family in the form of low-lying understory herbs and scrambling vines dangling from the canopy. There were no apparent leaves associated with these flowers and the part of my brain responsible for search images became confused. I traced the flower stems to their place of origin and realized they were attached to the nearest trunk. I followed the trunk upwards and realized that what I had found was in fact a small tree!

The species I was looking at was none other than Aristolochia arborea, a small tree native to the tropical forests of Central America. Needless to say I was floored. There is something to be said about any plant family than can vary this much in size and habit. The coolest aspect about this tree is that, similar to the more herbaceous members of this family, the flowers are produced close to or directly on the forest floor.

A closer inspection of these strange blooms reveals an interesting morphology. It would appear that they are mimicking fungi in the genus Marasimus. Now this could simply be a manifestation of apophenia. Was I seeing patterns where there are none? Of course, this was a job for scientific literature.

It seems I may have been on to something. Botanists agree that in the wild this plant is pollinated by fungus gnats and flies. However, no direct observations of this have ever been made. That being said, the flowers do emit a rather musty smell that could very well be described as "fungal." Regardless, this is an excellent choice of tree to showcase in a botanical garden because stumbling into it like I did led me down an curious path of discovery.

Tree photo credit: Cymothoa exigua (Wikimedia Commons)

Further Reading: [1] [2]

Bird's Foot Violet

As a life long denizen of deciduous forests, prairies and savannas present an entirely new set of stimuli. A recent excursion into an expansive oak savanna found me overwhelmed by the beauty of such places. Being mid October, the color pallet of the landscape ranged from myriad shades of reds, browns, yellows, and oranges. I was walking through a particularly sandy patch of soil when something caught my eye. A little flash of lavender shone through the amber grasses. To my astonishment I had found a plant that has managed to elude me for many years. 

What I had found was a bird's-foot violet (Viola pedata). Its deeply divided leaves, which faintly resemble a bird's foot, are unmistakable. What was even more fantastic was that this particular plant was in full bloom. I looked around and found only a small handful of other plants. This one was the only one in bloom. Though not unheard of for this time of year, I couldn't help but revel in the serendipity of the moment. 

Like all members of the genus Viola, bird's-foot violet is a photoperiodic plant. By this I mean that all aspects of its growth are sensitive to the relative amount of sunlight in any given day. Violets are generally spring time plants, however, the shortening days and cooler temperatures of fall aren't that different from spring. As such, this lovely little plant was perhaps a bit confused by the cool October weather. I didn't see any pollinators out and about but that doesn't mean that a hardy bumblebee wouldn't be lucky to stumble into its blooms. 

Back in my home state of New York, this particular species of violet is truly a rare find. The kind of habitats which it frequents have been largely destroyed. It is a xeric species that doesn't appreciate water hanging around for very long. Finding it growing in mostly sand was not surprising to say the least. Like most other violets, its seeds come complete with their own fleshy protuberance called an elaiosome. The purpose of these fatty attachments are to attract foraging ants in the genus Aphenogaster. The ants find the elaiosomes to their liking and take them back to their nest. Once the elaiosome is eaten, the seed is discarded into a refuse chamber inside the nest. There it finds a favorable microsite for germination full of nutrient-rich ant compost.

Further Reading:
http://www.jstor.org/stable/3668940?seq=1#page_scan_tab_contents

http://www.illinoiswildflowers.info/prairie/plantx/bird_violet.htm

Osage Orange

As a kid I used to get a kick out of a couple trees without ever giving any thought towards what it was. My friend's neighbor had a some Osage orange trees (Maclura pomifera) growing at the end of his driveway. Their houses were situated atop a large hill and the road was pretty much a straight drop down into a small river valley. After school on fall afternoons, we would hang out in my friends front yard and watch as the large "hedge apples" would fall from the tree, bounce off the hood of his neighbor's car (why he insisted on parking there is beyond me) and go rolling down the hill. I never would have guessed that almost two decades later the Osage orange would bring intrigue into my life yet again. This time, however, it would be because of the evolutionary conundrum it presents to those interested in a paleontological mystery...

The fruit of this tree are strange. They are about the size of a softball, they are green and wrinkly, and their insides are filled with small seeds encased in a rather fibrous pulp that oozes with slightly toxic white sap. No wild animal alive today regularly nibbles on these fruits besides the occasional squirrel and certainly none can swallow one whole. Why then would the tree go through so much energy to produce them when all they do anymore is fall off and rot on the ground? The answer lies in the recently extinct Pleistocene megafauna. 

The tree is named after the Osage tribe who used to travel great distances to the only known natural range of this tree in order to gather wood from it for making arrows. It only grew in a small range within the Red River region of Texas. When settlers made it to this continent, they too utilized this tree for things like hedgerows and natural fences. 

What is even stranger is that recent fossil evidence shows that Maclura once had a much greater distribution. Fossils have been found all the way up into Ontario, Canada. In fact, it is believed that there were once 7 different species of Maclura. It was quickly realized that this tree did quite well far outside of its current natural range. Why then was it so limited in distribution? Without the Pleistocene megafauna to distribute seeds, the tree had to rely on flood events to carry the large fruit any great distance. With a little luck, a few seeds would be able to germinate out of the rotting pulp. Botanists agree that the Red River region was a the last stronghold for this once wide ranging species until modern man came on the scene. 

Another clue comes from the toxicity of the fruits. Small animals cannot eat much of it without being poisoned. This makes sense if you are a Maclura relying on large animals as dispersers. You would want to arm your fruit just enough to discourage little, inefficient fruit thieves from making a wasteful meal out of your reproductive effort. However, by limiting the amount of toxins produced in the fruit, Maclura was still able to rely on large bodied animals that can eat a lot more fruit without getting poisoned. Today, with the introduction of domesticated megafauna such as horses and cows, we can once again observe how well these fruits perform in the presence of large mammals. 

Finally, for anyone familiar with Maclura, you will notice that the tree is armed with large spines. Why the heck does a large tree need to arm itself so extravagantly all the way to the top? Again, if you need things like mammoths or giant ground sloths to disperse your seeds, you may want to take some extra precautions to make sure they aren't snacking on you as well. It takes energy to produce spines so it is reasonable to assume that the tree would not go through so much trouble to protect even its crown if there once wasn't animals large enough to reach that high. The Pleistocene megafauna went extinct in what is evolutionarily speaking only the blink of an eye. Trees like the Osage orange have not had time to adapt accordingly. As such, without the helping hand of humans, this tree would still be hanging on to a mere fraction of its former range down in the Red River region of Texas.

Further Reading:
http://plants.usda.gov/core/profile?symbol=MAPO

http://www.americanforests.org/magazine/article/trees-that-miss-the-mammoths/

http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0001745