Monday, 21 March 2016

Skunk Cabbage: The sweet stench of spring

One of the earliest flowering spring wildflowers is also the stinkiest - Skunk Cabbage (Symplocarpus foetidus). My family and I make an annual trip in early spring to one of a couple of specific spots in the Credit Valley of Mississauga (write a comment below if you would like the specific location) to behold the beauty and the stench of this plant from the Arum family. We just made our trip this past Saturday (March 19) and many plants were in various stages of bloom. More on the smell shortly, but let me first describe this unusual plant a little more so you can recognize it when you come across it.
The spathe of the Skunk Cabbage
Skunk Cabbage is not your typical spring wildflower. Like all plants in the Arum family the most visible part of the "flower" is not actually the flower, but instead a hood-like structure called a spathe (the mottled dark red structure shown above) covering a cluster of flowers on a thick, fleshy structure called a spadix.
Part of the spathe removed to show the spadix (cluster of flowers)
These plants prefer wet seepy soils where the flowers emerge even when there is snow on the ground. They flower for 2-3 weeks and before the flowers senesce the leaves start to emerge as green pillars up out of the mud. By late spring the leaves unfurl to form large shield-shaped green umbrellas that last through the summer, typically in the shade of larger trees above.

Young Skunk Cabbage leaves in mid-spring ( (cc) 
These plants have many fantastically unusual features. The most stunning is the smell. It isn't so strong to cause you to want to run from the forest for want of fresh air. In my case I really need to get my nose right in the flower to smell it. To me the flower smells slightly foul, like a dead squirrel left to rot for 1-2 weeks; incidentally, there was a dead squirrel near these plants, which didn't improve the aroma. My 7-year-old son described the flower's smell as vinegar; I'm not sure where he got that from. My 10 year-old daughter described it as being like lemon juice, whereas my wife said "skunky", which might be closest to the mark. 

Regardless, there is no question there is a stench, which leaves us with the question - What is with that smell? That smell is a complex blend of chemicals (ref 1, ref 2) believed to be the sweet perfume that attracts pollinators of the carrion-eating kind. That is right, flesh flies (Sarcophagidae) and carrion beetles (Silphidae) are attracted to the flowers. They are likely fooled by both the scent and the colour, thinking that they've found a dead animal ripe enough to provide the meal for their maggot babies. "Gross" you say? Well, that's nature and some of the most amazing biology of a wildflower that exists anywhere, although there are some other fantastical wildflower stories that I might tell another time if I come across them on the trail.

Before I finish this post I would be remiss if I didn't share with you one more amazing thing about this plant. The flowers generate heat - they are endothermic - a condition they share with mammals and birds. The spathe and spadix can be us much as 25C above ambient temperatures, making it possible for this plant to develop its flowers, facilitate pollination, and develop seeds and fruits even at sub-0C temperatures.

So next time you are outside, breath deeply and you might be lucky enough to smell the sweet stench of the Skunk Cabbage.  

Sunday, 20 March 2016

Woodland wildflowers: The ephemeral lifestyle of spring beauty

Some might despair that cool temperatures have returned this weekend, but let there be no doubt - SPRING IS HERE! I am not simply stating the obvious that today is the first day of official spring. Spring has been underway for at least two weeks. But if I needed further evidence, I found it under the layer of leaves on the forest floor where woodland ephemeral wildflowers are already making their first appearance if you rake away a few leaves and look closely.
Many spring wildflower species are common in the woodlands of the Credit Valley. The most abundant is the trout lily, which is just starting to emerge through the soil right now, growing from shallow bulbs below or even at the soil surface.
Yellow trout lily that just emerged (2 cm tall) from the ground under last fall's leaves (March 19, 2016)

In another week the characteristically blotched leaves will be clearly visible.

And then the following week a select few plants will produce their six petaled blooms. There are two species of these trout lilies, a common species that is yellow (Erythronium rostratum) and an uncommon one that is white (E. albidum). 

White trout lily (E. albidum), which is uncommon in Ontario but fairly common in the Credit Valley
There are other plants that have just emerged and will flower in the next two weeks. On a south facing slope I found a patch of Virginia Spring Beauty (Claytonia virginica), with its narrow leaves and flower buds that will open next week.

Virginia Spring Beauty (C. virginica), with a cluster of developing flowers (March 19, 2016)

Nearby a rue anemone (Thalictrum thalictroides) plant has just emerged from the soil.

A wee little Rue Anemone (Thalictrum thalictroides) emerging from the soil, just 2 cm tall
I realize it doesn't look like much just yet, but give it another week or two and these beautiful flowers will be out.

Rue Anemone, by Derek Ramsey (cc)
On a nearby slope in the Credit Valley is Bloodroot (Sanguinaria canadensis) starting to poke through the soil; its large white blooms will appear within a week.

Bloodroot (S. canadensis) on the forest floor of the Credit Valley (April 2015)
I haven't spotted any evidence of the trilliums, solomon's seal, mayapple or wood lily, but they will make their first appearance in early-April.

For many of these wildflower species their existence is a short one, hence the name "ephemerals". Let me correct myself, their visible existence is ephemeral, but they can in fact live for many many years below the soil as bulbs and tubers, emerging each year for just a few weeks. They emerge from the soil after the snow melts, produce leaves, flowers and fruits, and then as the trees leaf out, they vanish with almost no trace. These plants have evolved a specialized lifestyle that takes advantage of those few weeks that are warm enough for growth and the first emerging pollinators. 

Why don't the wildflowers stick around longer on the forest floor? It all comes down to the balance between the benefit of leaves and flowers and the costs of maintaining them. The function of leaves is to produce energy from sunlight through the process of photosynthesis. There is a lot of sunlight hitting the forest floor right now, enough to produce leaves, flowers, fruits and even a little extra to save away in underground storage structures for next year. When the tree's leaves come out, the light hitting the forest floor drops dramatically. Maintaining a leaf is costly because it requires the maintenance of cellular processes (e.g., ATP synthesis), the production of defences, the replacement of old or lost tissue, and the list goes on. In the simplest of terms, the calculation of BENEFITS-COSTS goes from positive in the early spring before the trees leaf out, to negative once the canopy closes. It is this simple equation, not to mention the underlying complex cellular processes, physiology, evolution and ecology, that have driven the beauty of spring wildflowers's to an ephemeral lifestyle.

Enjoy these plants while while they last this spring. The best viewing will start late March until mid-April this year.

Saturday, 19 March 2016

This mighty river used to be mightier

I love the varying moods of the Credit River in Mississauga, one of Lake Ontario's healthier rivers. A quick snow-melt and several days of rain have left the river high and the current swift, with possibly as much as 3x the volume as usual.

In some years the river is even higher. For example, the long and cold winter of 2014/2015 produced heavy ice that created an ice dam in Erindale Park during the spring, which flooded large parts of the river valley.

River break-up during the spring of 2015
Flooding in the Credit River valley in the spring of 2015
When the summer gets hot and dry the river is low, lazy and warm.
The Credit River in the summer of 2014, with Oscar and Mae Johnson hunting for aquatic invertebrates
As mighty and moody as this Credit River is today, there was a time not long ago when this river was even mightier - MUCH mightier! If you look at the first photo in this post, you can see the banks on the horizon from a time when this river was higher (30-40m higher) and wider - about 400m across at the spot where I took that picture!

When and how did this happen? If we roll back the clock 14-16 thousand years, this river valley didn't exist. There were no grasses, trees, deer or coyotes roaming the valley. Their ancestors were were further south beyond the glacier's reach, south of what is now Pennsylvania and Ohio. The would-be Credit Valley sat under 1-2km of the Wisconsin ice sheet. As the Earth warmed the glaciers began to melt and retreat further north. The melting glaciers gave way to large roaring rivers that that drained into Lake Iroquois, which would later become what is now Lake Ontario.  That is how our Credit Valley and all of the valleys along the north shore of Lake Ontario came to be; they were carved by these fierce rivers.

You can see the signs of this mightier river beyond the high banks in that first photo. As I walk up the valley to University of Toronto Mississauga, I see very young conglomerate rock made of gravel and sand cemented together right at the top of the valley, far beyond the reaches of today's river. These materials were the outwash of the large braided river that once ran here, just a few thousand years ago.
Conglomerate rock at the top of the Credit Valley, deposited by the river several thousand years ago. 
When I stand at the top of the valley, I sometimes like to close my eyes and imagine the river as it was in its glory, a mighty river with its banks lapping against the foundation of my house. When I open my eyes I see the river below as it is now, just a whisper of its former self. I wish I had a time machine.

Thursday, 17 March 2016

Nothing sweet about this honeysuckle

Tatarian honeysuckle (Lonicera tatarica) is the scourge of many grasslands in my area. An invader from Asia,  it is quick to invade grasslands where it forms dense thickets where little can grow underneath their canopy. But how can they invade these fields so quickly and successfully?

Tatarian honeysuckle invading a field at University of Toronto Mississuaga (left). Little vegetation can grow underneath the canopy of tatarian honeysuckle (right). The dead stocks in the foreground is crown vetch, which grows just outside of the honeysuckle's crown.
One solution to this conundrum is playing out right now in the very early spring. I was surprised to see on my walk this week that honeysuckles have wasted no time in producing their leaves, which is weeks ahead of other plants. By producing leaves so early they are getting a head-start on the growing season, and shading out any late comers to the light capture game. 

Tatarian honeysuckle with a fresh flush of leaves on March 15, 2016 in Mississauga ON
However, this early leafing strategy is just one of a trifecta of traits that make for a super weed strategy. These plants also hold their leaves long into the fall, typically weeks longer than native species, which allows them to capture more carbon than their native competitors. This strategy of holding leaves late into the fall is a common feature shared by many invasive shrubs successfully invading eastern North American forests and fields, as shown by Dr. Jason Fridley's research at the University of Syracuse. The final strategy these plants employ is perhaps the most exciting and cunning - they poison their competitors. Invasive honeysuckles secrete toxic phenolic compounds into the soil which inhibits the germination and growth of native competitors (see work by Dr. Don Cipollini here and also here). 

Why should we care about this invader from the far east? The spread of this invader in my local field (and in many fields throughout North America) is pushing out populations of native plant species like hairy beard's tongue (Penstemon hirsutus), Canada tick-trefoi (Desmodium canadense), early goldendrod (Solidago juncea), heart-leaved aster (Aster cordifolius), prairie anemone (Anemone cyldindrica), common milkweed (Asclepias syriaca), and common evening primrose (Oenothera biennis), to name just a few that are on their way out in the same field as this honeysuckle. These plants in turn support a wide diversity of pollinating bees, butterflies, beetles, flies and moths, plus a wide diversity of insects that only feed on these specific plant species. If honeysuckle prevails than this native biodiversity will blink out and the ecosystem will be fundamentally altered.

In other words, this honeysuckle isn't as sweet as its name suggests. 

Wednesday, 16 March 2016

Salamanders: Endangered love in the vernal pool

The frost is barely out of the ground but salamanders are not wasting any time in finding love pool side. It is at this time of year that three related salamander species, the Spotted Salamander (Ambystoma maculatum), the Blue-spotted Salamander (Ambystoma laterale) and Jefferson Salamander (Ambystoma jeffersonianum), crawl from their hibernation deep in the forest soil in search of fishless temporary pools of water (called "vernal pools") within forests, which will dry up by early-summer. In these pools the salamanders go in search of love in the night, and if they find a suitable mate the females deposit their egg masses on stems submerged in the water, males then fertilize these eggs externally with their sperm.

Today I went in search of these salamanders with an undergraduate student in my Evolutionary Biology class. The University of Toronto Mississauga is fortunate to be surrounded by forest, and in some of the forests closest to the escarpment overlooking the Credit River one can find vernal pools that attract salamanders. 

As you can see from the photo below, the vernal pool was perfect today - it had lots of water. 
Vernal pool , a temporary body of water, at University of Toronto Mississauga on on March 15, 2016
A quick survey of the waters from the shore (we didn't enter the water so as not to damage this sensitive ecosystem or the species living within it) revealed no eggs. Were we too early? The conditions seemed just right. The student and I went in search of adults under logs near the vernal pool. One log, two logs, three, four .... six ... still nothing (Note: please return logs as you find them if you go in search of salamanders yourself-it is a unique habitat that takes years to make just right). Finally, we worked together to turn a large fallen log at least 4m long and VOILA - a salamander! And this was no ordinary salamander, this was a Jefferson Salamander - an endangered species in Canada since 2011 - see assessment report.
Jefferson Salamander, an endangered species, on its way to mate at the vernal pool
It appears we were not too early after all, we arrived at the very beginning of their mating season.

The individual we found was a dark brown colour with tiny blue flecks along its sides, and 10-15cm long from snout to the tip of its tail - a beautiful animal! Although we would have loved to admire this animal longer, this species is exceedingly rare and we didn't want to bother it any longer than was necessary. We quickly returned the log to the way we found it and released the salamander underneath leaves beside the log.

Let me explain the reason for our caution a little more. Spotted Salamanders and Blue Spotted Salamanders are fairly common, albeit rarely seen because of their subterranean habits. Visiting their breeding habitat is your best chance to see them. The Jefferson Salamander has similar behaviours and habitats to the other two species, but it is both extremely rare and in rapid decline. Although its range extends further south into the U.S.A., in Canada it is only found at a small number of localities in southern Ontario. Of the 87 historical breeding sites of this species (mostly along the Niagara escarpment), only a third remained as of 2011, with this population on our campus being one of those last remaining ones. Is the population healthy? How many animals are there? What is the age distribution? I have no idea, but the population is persisting, possibly due to the reported longevity of these animals (up to 30 years some say!)

I should also note that there is some long-standing taxonomic confusion in this species, with some sexual Jefferson Salamanders and some that form all-female triploid populations (i.e., they have three sets of chromosomes instead of the usual 2 - weird I know, but nature is wonderfully bizarre). It is difficult if not impossible to distinguish these forms without genetics (see work by Dr. Jim Bogart from U. Guelph). Nevertheless, seeing this beauty was a great treat and I hope they have a great year of mating in the vernal pools.

Tuesday, 15 March 2016

Racoons: Sleeping it off after a night of cavorting

Raccoons are much maligned in major cities like Toronto and Mississauga, where they spend their nights prowling the local neighbourhoods in search of garbage left unsecured before nightfall. But what happens to those masked raiders during the day? Where do they all go? 

The answer to that question is up in the trees. Most racoons try to find a spot to catch a few Zzzzs, where they'll be safe from predators and humans alike. They often sleep in the crook of large branches, or better yet, in a hollowed out trunk that will keep them warmer and drier. That is where I found this individual on my walk through the Credit Valley of Mississauga today. Can you see the raccoon peaking from the inside of the tree? 

Raccoon peaking through a large tree cavity, viewed through my binoculars
Most days I can see a furry head, back or bottom of a raccoon sneaking out of one of the many large tree cavities that are common in the valley. This daytime rest is only temporary as they will be out and at it again as soon as the sun sets.

For all who are interested, we'll leave on a walk today (Tuesday, March 15) at noon from my office (Davis Bldg 3040, University of Toronto Mississauga)

Monday, 14 March 2016

Oh deer, even a mild winter is tough

By all accounts the winter of 2016 was very mild, but even the mildest winters in northern climates pose a significant challenge for animals. Some animals migrate, others hibernate, while a select few tough it out. White-tailed deer are a prime example of this last strategy.
Young white-tailed deer walking through the forest at University of Toronto Mississauga
In spring, summer and fall, times are good for deer. As herbivores, they feed on plants where favourite food include the tasty green leaves and stems of evening primrose (Oenothera spp.), the fruits of Trillium or the berries of poison ivy - yes, they eat the berries of this toxic plant!

In winter, life is a different story. Getting enough food makes the difference between life and death. Fresh leaves are gone and fruits are in dwindling supply. What is a deer to eat? Twigs from shrubs and trees are always an option, but a toothpick-like diet leads to the desire for a little diversity.

On my walk today I couldn't help but notice the signs of a deer's winter diet in abundant evidence. The first obvious winter food I saw was that of staghorn sumac (Rhus typhina),
Fruits of staghorn sumac. A favourite food of American Robins in early spring
or more specifically the bark and inner cambium (the living part of the trunk that move water and sugars throughout the plant) of this plant. The deer had used their lower incisors (they don't have upper incisors) to dig deep (~0.5cm) into the trunk on a number of sumacs.
Sumac bark and cambium stripped away by deer in winter
There are sumac relatives (Toxicodendron spp., like poison ivy and mango) that are highly toxic (and deer eat some of these species' fruits!), so I was naturally interested in how the bark tasted. Now I've tried bark and cambium before and typically it is a tough, tasteless and somewhat bitter affair. To my surprise the bark of R. typhina isn't that bad. It is soft, chewable, filled with a fair amount of water and it doesn't taste like much of anything. That is a lot better than being poisonous - a check on the edible index.

As I walked down into the valley (the Credit Valley of Mississauga, ON, Canada) a second major winter diet item of deer was evident - white cedar (Thuja occidentalis). 
Heavy deer browse on white cedar. The height of the browse is set by the upper reach of the larger deer
The deer in our area are so abundant that their effects on these cedars could be confused for a talented landscaper. All of the white cedars' leaves are stripped bare below a certain level, the height that is exactly as high as they can reach - hence the beautiful straight line trimming in the photo above. This diet option is a lot harder for me to understand. 

Have you ever tried to eat cedar leaves? Well, I did today - imagine the strong bouquet of a beautifully rich Christmas tree exploding in your mouth. That beautiful smell is bitter in the mouth and my lips were ever so slightly numb on the walk home - needless to say, don't try this at home. This taste (and the Xmas tree smell) is due to the rich diversity of terpenoids that cedars and other conifers produce. Actually many plants produce terpenoids, some are defences against herbivores, others are attractants for pollinators, but in this case cedar terpenoids are almost certainly defensive against herbivores. Those defences are evidently not good enough to protect cedars against deer in winter. 

I don't think the cedar leaves, the sumac bark or the twigs are the desired choice for deer at any time of year - indeed, deer will rapidly eat dried and partially rotten apples when offered them in winter. But, when options are few and life is hard, you eat what you can when you can, so long as it doesn't kill you.