On the Flora of Antarctica

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Antarctica - the frozen continent. It is hard to think of a place on Earth that is less hospitable to life. Yet life does exist here and some of it is botanical. Though few in number, Anarctica’s diminutive flora is able to eke out an existence wherever the right conditions present themselves. It goes without saying that these plants are some of the hardiest around.

It is strange to think of Antarctica as having any flora at all. How many descriptions of plant families and genera say something to the effect of “found on nearly every continent except for Antarctica.” It didn’t always used to be this way though. Antarctica was once home to a diverse floral assemblage that rivaled anything we see in the tropics today. Millions upon millions of years of continental drift has seen this once lush landmass positioned squarely at Earth’s southern pole.

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Situated that far south, Antarctica has long since become a frozen wasteland of sorts. The landscape is essentially a desert. Instead of no precipitation, however, most water in this neck of the woods is completely locked up in ice for most of the year. This is one reason why plants have had such a hard time making a living here. That is not to say that some plants haven’t made it. In fact, a handful of species thrive under these conditions.

When anyone goes looking for plants in Antarctica, they must do so wherever conditions ease up enough for part of the year to allow terrestrial life to exist. In the case of this frozen continent, this means hanging out along the coast or one of handful of islands situated just off of the mainland. Here, enough land thaws during the brief summer months to allow a few plant species to take root and grow.

 Antarctic hair grass ( Deschamsia antarctica )

Antarctic hair grass (Deschamsia antarctica)

The flora of Antarctica proper consists of 2 flowering plant species, about 100 species of mosses, and roughly 30 species of liverwort. The largest of these are the flowering plants - a grass known as Antarctic hair grass (Deschamsia antarctica), and member of the pink family with a cushion-like growth habit called Antarctic pearlwort (Colobanthus quitensis). Whereas the hair grass benefits from being wind pollinated, the Antarctic pearlwort has had to get creative with its reproductive needs. Instead of relying on pollinators, which simply aren’t present in any abundance on Antarctica, it appears that the pearlwort has shifted over to being entirely self-pollinated. This seems to work for it because if the mother plant is capable of living on Antarctica, so too will its clonal offspring.

By far the dominant plant life on the continent are the mosses. With 100 species known to live on Antarctica, it is hard to make generalizations about their habits other than to say they are pretty tough plants. Most live out their lives among the saturated rocks of the intertidal zones. What we can say about these mosses is that they support a bewildering array of microbial life, from fungi and lichens to protists and tardigrades. Even in this frozen corner of the world, plants form the foundation for all other forms of life.

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 Antarctic pearlwort ( Colobanthus quitensis )

Antarctic pearlwort (Colobanthus quitensis)

The coastal plant communities of Antarctica represent hotbeds of biodiversity for this depauperate continent. They reach their highest densities on the Antarctic Peninsula as well as on coastal islands such as south Orkney Islands and the South Shetland Islands. Here, conditions are just mild enough among the various rocky crevices for germination and growth to occur. Still, life on Antarctica is no cake walk. A short growing season, punishing waves, blistering winds, and trampling by penguins and seals present quite a challenge to Antarctica’s botanical denizens. They are able to live here despite these challenges.

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Still, humans take their toll. The Antarctic Peninsula is experiencing some of the most rapid warming on the planet over the last century. As this region grows warmer and drier each year, plants are responding accordingly. Antarctic mosses along the peninsula are increasingly showing signs of stress. They are starting to prioritize the production of protective pigments in their tissues over growth and reproduction. Moreover, new species of moss are starting to take over. Rapid warming and drying of the Antarctic Peninsula appears to be favoring species that are more desiccation tolerant at the expense of the continents endemic moss species.

Changes in the structure and composition of Antarctica’s moss beds is far from being a scientific curiosity for only bryologists to ponder. It is a symptom of greater changes to come.

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

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

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]

Yeast in Lichens

Quite possibly one of the oldest symbiotic relationships on Earth has been hiding in plain sight all this time. Lichens have long been regarded as the poster child for symbiotic relationships. Certain species of fungi team up with specific algae and/or cyanobacteria in a sort of "you scratch my back and I'll scratch yours" type of relationship. In return for room and board the photosynthetic partner feeds the fungus. There are many variations on this theme which translates into the myriad shapes and colors of lichen species around the globe. For 150 years we have been operating under the assumption that there is only ever one species of fungus (in the phylum Ascomycota) for any given lichen. We were wrong. 

Originally thought to be contamination, researchers at the University of Montana and Perdue found gene expression belonging to the other major fungal phyla, Basidiomycota. The research team soon realized that they had uncovered something quite monumental. Lichens were harboring a partner we never knew existed. These newly discovered fungi are an entirely new lineage of yeast. What's more, this relationship has been documented in upwards of 52 other lichen genera worldwide! 

This discovery has led to another major breakthrough in lichen biology, their bizarre variety. The exact same species of fungus and alga can produce completely different lichens with wildly different attributes. Take the example of Bryoria torturosa and B. fremontii. They were thought to share the same partners and yet one is yellow and toxic whereas the other is brown and innocuous. Knowing what to look for, however, has revealed that their yeast partners are entirely different. The yeast is thought to be a sort of shield for the lichen, producing noxious acids that deter infections and predation. 

Almost overnight a new light has been shown on our lichen neighbors. These newly discovered partners aren't a recent evolutionary development. This trifecta likely stems back to the early days when little else lived on land. It just goes to show you how much we still do not know about our planet. It's nice to be reminded of this. 

Further Reading:

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