Sunday, May 31, 2015

Prickly Rose - Rosa acicularis - Rosier aciculaire

Though most people see roses all the time, the roses that you do see will tend to be one of the wide array of species and varieties that have been bred as ornamental flowers.

These are a bit different. Rosa acicularis (prickly rose, prickly wild rose, arctic rose) is a holarctically (arctic regions around the globe) distributed species [1] that hasn't been particularly altered or bred by humans.

Rosa acicularis
One of the most immediately striking differences between this species and most commercial roses is of course the number of petals. This species, like most Rosaceae (rose family), has five petals. A number of ornamental roses have been developed (from this species and others), and one of the methods of increasing the ornamental appeal of roses (and a number of other ornamentals including peonies) involves causing a transformation of the stamens into petal-like structures or into petals [2]. In a very general sense, an ornamental flower in one of these lines with many petals is more likely to be one which has been bred or selected to replace stamens with petals.

In a North American context, this plant's range is fairly broad but mostly northern. US range map here, Canadian range map here. Although it is often abundant where it actually does occur, it is actually an endangered species in Illinois, Iowa, Massachusetts, New Hampshire, and Vermont [3]. It is listed as secure in most of its Canadian range, except in Nunavut where it is sensitive and New Brunswick where it may be at risk [4]. With that in mind, please treat the species with reasonable care if you encounter it in those places where it has legal status, and with the regular respect that is due any undisturbed population elsewhere.

Solitary bee (I believe this is Hoplitis fulgida) collecting pollen from Rosa acicularis
This species reproduces vegetatively through its roots, and sexually through the production of seeds [5]. Seed production is reasonably abundant [5,6], but germination conditions have to be suitable (especially with respect to temperature) for the seeds to actually sprout [5]. R. acicularis blooms much less frequently when it grows in the forest understory (in shady areas) than in forest edge areas [5].

R. acicularis is a source of food for a number of species including the snowshoe hare, grouse, some rodents, and deer [5]. It is also a shelter plant for many birds and small mammals [5].

If you encounter this species, one of the first things you will notice if you get close is the wonderful smell. This smell is advertising to pollinators; the plant is announcing that there is nectar available, and in this case, unlike Cypripedium acaule, the advertising is accurate. R. acicularis produces plenty of nectar, which attracts bees and other pollinators [5,7]. I observed several pollinators on R. acicularis, notably those pictured in this post.

Unidentified Syrphid (bee imitator) fly on R. acicularis
Many parts of this plant are edible; the hips (bulbous fruit) are of course the most popular, primarily for use in teas, jams, or jellies because of their high vitamin A and C content. The fresh shoots and petals are also used for teas.

Saturday, May 30, 2015

Lepidopteran Pollinators & the Proboscis

So I've talked about various types of bee pollinator, fly pollinators, and even wind. But I haven't talked much about Lepidopterans (butterflies).

Today, while out enjoying the weather in the wooded portion of the Notre-Dame-des-Neiges cemetery, I encountered a couple of common butterflies that, unusually, held still long enough for me to photograph them, so I'm going to take my opportunity to talk a little bit about this group of pollinators.

First up, we have the very common Glaucopsyche lygdamus couperi ('Silvery Blue' butterfly), a native of North America with a fairly broad range [1] which you have probably seen before:

Glaucopsyche lygdamus couperi - this individual very obligingly held still for me so I could get a few photos
 Lepidopterans tend to be nectar-feeders, so plants that have co-evolutionary relationships with them will generally produce it in reasonable quantity. They are not as efficient at pollen transfer as bees, as their bodies tend to be lifted up on long legs that prevent the extensive physical contact that we often observe between bee and stamen. Nevertheless, they are valuable and effective pollinators.

Glaucopsyche lygdamus couperi on Vicia cracca (cow vetch) - this is what the underside of the wings looks like
Lepidopterans have one piece of handy equipment that other pollinators do not: a proboscis. The proboscis is a tubular mouthpart that serves essentially as a straw. It varies in length depending on species and, in the case of the longer ones, can be extended or coiled as needed.

So if you're a plant that would benefit from attracting butterflies and excluding other pollinators (perhaps in order to devote your resources to a single, more loyal species rather than take your chances with more fickle visitors), what kind of structure is most suitable? A deep nectar spur (pocket where nectar is produced and stored) that can only be accessed with an insecty straw, of course! So the more exclusively Lepidopteran-pollinated a species, the more likely it is to have a long nectar spur which can only be accessed via proboscis.

I got a fantastic shot of the very common Poanes hobomok ('hobomok skipper' butterfly) using its proboscis to suck up some nectar from Vicia cracca (cow vetch):

Poanes hobomok collecting nectar from Vicia cracca
Poanes hobomok, like G. lygdamus couperi, is native to this region and also very common [2], so it's very likely you've seen one of these before.

Of course, Lepidopterans can and do get nectar from a variety of flowers, many of which aren't specialized exclusively to them, such as Vicia cracca (cow vetch). This introduced species is originally native to Europe which is now broadly distributed in North America (range map here). It is listed as invasive but with low current threat status in Minnesota [3]. Apparently the spread of this species is also leading to a range expansion for the native Lepidopteran G. lygdamus couperi [1].

Vicia cracca
The peas produced by this plant are edible [4] though in my experience not that tasty (starchy, bland).

Vicia cracca
The USDA forest service has a little blurb page about butterfly pollination for those interested. And, a bonus picture:

Poanes hobomok on Vicia cracca

Wednesday, May 27, 2015

Kill it With Fire, and Other Methods of Invasive Species Management : Garlic Mustard - Alliaria petiolata - Herbe à ail

Though you may not have thought much about it, I can guarantee that you've encountered this extremely invasive species. Alliaria petiolata (garlic mustard) is native to Europe and was introduced in North America as a flavouring herb [1]. Since its introduction, this plant has spread broadly, and, because of some of its growth and reproductive characteristics, poses a serious threat to the biodiversity of forest understory habitats [2].

Alliaria petiolata in a park in Montreal
A North American range map for the introduced species can be found here. The plant is listed as invasive, prohibited, prohibited invasive, prohibited noxious, banned, and Class A or B invasive in various parts of the US [3]. The plant is prohibited in Alberta and Saskatchewan [4]. It is a member of the Brassicaceae (mustard family) and is biennial; the first year, it produces a basal rosette of leaves, and the second, a flowering stalk [2].

So what's the big deal with this plant?

Well, it's a collection of things. This introduced plant has none of the natural predators here that are present in its native range [5], so unlike in its native range it spreads here essentially unchecked. It is known to damage native plant and tree populations [5,6]. There is some evidence that it inhibits the growth of other plants around it, as well [5,6]. This plant is also very difficult to control, as it produces large amounts of seed, is a perennial, and prospers in disturbed areas [5].

Dense population of Alliaria petiolata
What do we do about these kinds of plants? Well, it depends a lot on the particular environments in which we are trying to control the species, and on the species and its life cycles and reproductive ecology. In the case of A. petiolata, for example, pulling is a poor method of control which can actually make the situation worse, as the plant thrives in disturbed habitats and pulling creates lots of disturbed soil [5]. With other plants, pulling might be a better solution.

Flowers and seed pods of Alliaria petiolata
Burning has been attempted as well, but unfortunately not very successfully; when the fire doesn't get every last seed, the burning produces a habitat that is very favourable to the spread and reestablishment of the population [6]. Chemical control is similarly patchily effective at best.

Simply clipping the plant back also isn't enough; if it's clipped back before it has produced flowers, it'll just keep on coming back [5]. But, cutting after the flowers have started but before the seeds have set is an effective strategy if repeated over time, especially if the plants are cut as low as possible (ground level) [5,6] -- but note that the clipped parts must be removed and properly disposed of or they can still set the seed - the Nature Conservancy of Canada recommends cutting the plant repeatedly from top to bottom [5]. A the population level, it is recommended to clip the smaller spreading populations first and then work on controlling the source populations [5].

Basically if you're in North America and you've got this plant somewhere, be ruthless. Wait until it flowers, then cut it up from top to bottom. Then do it again in the next years until the thing stops coming back up.

Tuesday, May 26, 2015

Sometimes Flowers are Jerks Part 2: Jack-in-the-Pulpit - Arisaema triphyllum - Petit prêcheur

Another plant currently in bloom is Arisaema triphyllum (jack-in-the-pulpit), a rather intriguing-looking plant with large three-lobed leaves and unusually shaped flowers.

Arisaema triphyllum
This species is native to eastern North America (range maps: North America, Canada). This plant has no protected status listings in the US [1] and is listed as secure in its Canadian range, except in Manitoba where it may be at risk [2].

Arisaema triphyllum

The flower of this plant tends to attract a lot of interest and attention because of its unusual shape. These two structures are called the spathe (the striped, green-purple hood section) and the spadix (the cylinder in the centre). The spadix is actually the inflorescence (structure to which the flowers are attached); the flowers are hidden inside the spathe.

Arisaema triphyllum spathe & spadix
Why would a plant be shaped this way, carefully shielding and reducing access to its flowers? Wouldn't that reduce pollination?

Well, certainly that would be the case if the plant were wind-pollinated. Or if it were pollinated by larger animals eg bats.

But A. triphyllum is pollinated by fungus gnats [3]*. And this plant is a giant jerk about it.

The plant is visited by fungus gnats, which crawl on in to get access to the flowers. But then once they're inside, the size and shape of the hood make it seem totally closed [4]; the flies have a hard time getting out. The male flowers, which have some interest in the pollinator escaping, have a small hole at the bottom of the spathe through which pollinators can escape (after brushing past all the male flowers on the way down) [4]. The females have no such hole, so pollinators are more likely to die in there [4]. But while they're stuck in there they fly around and thrash and generally get themselves coated in pollen, or in the case of the female flowers, coat the pistils with the pollen they've already collected.

So this flower traps its pollinators to increase its odds of successful pollen transfer, and with the female flowers has a high chance of killing the pollinator outright. Harsh.

Other plants do this, of course, with varying degrees of harm. For example, in yesterday's post I talked about Cypripedium acaule, which also traps its pollinators (but it always lets them out!). C. acaule has a one-way hole in the front of the flower through which pollinators enter, and then a sort of pollination-tunnel through which they can exit up around the top of the flower [5]. First, the pollinator is forced to rub past the pistil, which ensures that if they're carrying pollen it's transferred over [5]. Next, they get brushed with a ton of little pollen-covered hairs, ensuring that the pollinator leaves with plenty of pollen for the next flower [5].

Cypripedium parviflorum and Cypripedium arietinum are both also pollinator trappers (sometimes referred to as kidnapping).

Trapping helps to increase the odds of successful pollination when a pollinator does come by, by increasing the odds that pollen will be deposited on the pistil.

A. triphyllum is often considered dioecious [6]; bisexual flowers have been noted but whether these flowers reproduce bisexually is debated [7]. An interesting aspect of this species' gender segregation is that it is not fixed by generation; a given individual can vary its sex from year to year; this sex variation is generally thought to be linked to the size/age (available stored resources in the roots) of the plant [3,4,6,8]. The general idea is that female function (production of fruit and seeds) takes more energy than male function (production of pollen), so a plant with more available resources in its roots, eg one which is larger or one which was able to store more energy the previous year (which would be more possible if it was male the previous year), is more likely to be female for the season.

I did manage to get a photo of a unisexual female, showing the flowers at the bottom of the spathe. I apologize for the poor image quality, I was in a hurry.

Female flowers of Arisaema triphyllum
As you can see, this flower has very plain flowers, just a little fruiting bulb (an ovary) with a pistil on the tip (the white part). Given that their visual characteristics are not related to attracting pollinators, it is no surprise that the flowers are unremarkable to look at; resources are redirected to more valuable functions such as producing fruit.

*there is debate and disagreement about this [4]

Monday, May 25, 2015

Sometimes Flowers are Jerks Part 1: Pink Ladyslipper - Cypripedium acaule - Sabot de la vierge

The Orchidaceae (orchid family) have started to bloom now. My father and brother have reported that the Cypripedium arietinum (ram's head orchid) and the Cypripedium parviflorum (yellow ladyslipper) are both blooming now on my parents' property in the upper Gatineau. I wrote a blog post about those species last year. This year, my father and brother also reported something special.

While wandering around, they found another orchid, this one quite unusual for the area: the pink ladyslipper (pink lady's slipper, moccasin flower). The species is relatively abundant in Canada but occurs more in pine forests rather than deciduous (or mixed deciduous like is found on my parents' property). They were kind enough to send me photographs so that I could write a blog post about them, so today's photos were taken by guest photographers!

Cypripedium acaule with leaves - note the paired basal leaves and the lack of leaves on the stalk
This lovely flower is native to eastern North America (NA range map here; Canadian range map here). Unfortunately this plant is endangered in Tennessee (also commercially exploited in this state) and Illinois, exploitably vulnerable in New York, and unusual in Georgia [1]. In Canada it is doing better, listed as secure for the country as a whole and in most of its range; it is sensitive in Alberta, and has an undetermined status in the Northwest Territories [2].

Cypripedium acaule front view
So why do I call this pretty flower a jerk? Well, this is a 'deceptive' flower. Specifically, this is a food-deceptive flower. This species (along with both C. parviflorum [3] and C. arietinum [4]) has a strong fragrance which it uses to attract pollinators who associate the fragrance with nectar rewards -- but the plant doesn't produce any nectar at all, so the pollinator gains no benefit for its visit [5]. One might wonder why a plant would evolve such a system, of course; these plants are pollinated much less frequently than reward-offering plants [6,7,8], and not producing nectar would not necessarily constitute a particularly large energy savings [8]. The question of why deception is such a common strategy in orchids is an interesting one for researchers as a consequence. A number of theories have been proposed, some of which are discussed here for those interested.

Cypripedium acaule side view
One of the natural consequences of the plant's deception is that it depends on naive bees (bees that haven't visited it much before) for pollination, because they learn after a few tries that the flower doesn't have any reward and stop visiting [5,6]. So, there are few fruit produced each year (few successfully pollinated flowers) [5].

Cypripedium acaule front view - close - note the fine hairs (trichomes) on the petals and sepals
There is another interesting aspect of this (and other orchids') reproductive ecology that I will discuss in conjunction with some other flowers later this week, so those who are aware of the interesting thing I am skipping over -- I know, I'm just saving it for another post.

Cypripedium acaule bottom view
Many of these orchids are rare, and tend to do very poorly when transplanted in gardens. One of the major reasons for this is that many orchids are reliant on a particular type of fungus in order to germinate seeds [5,6], so they can't reproduce outside of areas where the fungus is present; so, when gardeners dig the flowers up and bring them to their gardens, the plants will not survive or reproduce effectively [6]. Thus, if you find these species in the wild please do not give in to the temptation to take the flowers. They won't survive and you will damage the population's genetic diversity. In fact, it is illegal to remove the pink ladyslipper in Georgia (poaching) [6], as this is becoming a serious threat to a variety of orchid populations. This caution applies to most wild orchids including the yellow ladyslipper and the ram's head orchid.

Many thanks to my guest photographers for the gorgeous shots!

Sunday, May 24, 2015

Violets 2 - Viola spp. - Violettes 2

When I went off to visit with my parents in the upper Gatineau region, I encountered a couple of species of violet that I haven't already talked about in my previous post about violets. So today I'm going to add those species to the list of currently-blooming violets.

Viola labradorica
First up, we have Viola labradorica (aka Viola conspersa, alpine violet), which actually I've been seeing in lawns in Montreal, too. This little pale purple violet is native to eastern North America (US range map here, Canadian range map here), and is threatened in Illinois [1]. It is secure across Canada but sensitive in Prince Edward Island, may be at risk in Saskatchewan, and its status is unknown in Newfoundland and Labrador [2].

Viola labradorica flower
The leaves and flowers of V. labradorica are edible [3]. It is sometimes used in gardens as a ground cover in shaded areas [4].

Viola macloskeyi
Next up we have Viola macloskeyi (northern white violet). This little violet is native to North America and has a very broad range (range map here). It does not have any listed protected status in the US [5]. The species is sensitive in the Northwest Territories, Nunavut, and Alberta, and it may be at risk in Saskatchewan [6]. Its status has not been assessed in Newfoundland and Labrador, and it is secure in the rest of its Canadian range [6].

Viola macloskeyi flower
This species is distinguished from Viola blanda, another white violet, by its scent [7].

One of the things that may jump out at you when looking at my viola photos is that most of them are "bearded" - meaning that they have fine hairs along the inner portions of the petals. So what's that all about?

Well, those fine hairs are there to increase the odds of pollination. While the pollinator is pushing its way up the throat of the flower to get at the nectar in the spur (which extends behind the flower), its body is rubbing over the hairs and the pistil of the flower. Pollen that has already been deposited on the belly of the pollinator will be transferred to the pistil, while pollen from the flower will be spread over its sides and belly to be carried to the next flower.

So those hairs aren't just decoration; they help the flower increase its chances of spreading its genes.

Friday, May 22, 2015

Heartleaf Foamflower - Tiarella cordifolia

Another plant that was blooming at the lake over the weekend was Tiarella cordifolia (heartleaf foamflower), a rather unassuming little plant which is a used as a groundcover in gardens for its shade tolerance and vegetative propagation [1,2,3].

Tiarella cordifolia inflorescence
This plant's native range is in eastern North America (range map here). The plant is listed as endangered in New Jersey and Wisconsin [4] (no listing for the rest of its US range), and secure in its Canadian range except in Nova Scotia, where it is sensitive [5].

Tiarella cordifolia inflorescence (close view)
T. cordifolia is a member of the Saxigragaceae (saxifrage family) and exhibits the floral characteristics of the family (radially symmetric, hermaphroditic flowers with 4 or 5 petals and sepals, 5 or 10 stamens).

One source claims that this perennial species has winter-green leaves [6], a trait that would increase its ability to bloom quickly in the spring.

Thursday, May 21, 2015

Gynodioecy and the Wild Strawberry - Fragaria virginiana - Fraisier sauvage

So, why will I talk about gynodioecy today? Well, I noticed that Fragaria virginiana (wild strawberry) is blooming! F. virginiana is a gynodioecious species, so I thought I might try my hand at explaining why this plant is of so much interest to scientists. Gynodioecious species like this one help us to investigate questions about the evolution of separate sexes (among other things). Definitions, explanations, and much more below, after my usual more basic commentary about this lovely species.

Fragaria virginiana in bloom
This species is very widely distributed, native to all parts of North America (range map here). It is not at risk anywhere in its US range [1] (and, in fact, is considered a weed in some parts of its US range for its ability to spread prodigiously [1]), and is secure in all parts of its Canadian range except Nunavut, where it is sensitive [2].

This plant produces a fruit which is edible (and delicious!), and is one of the two species which was used to breed Fragaria x ananassa (commercial strawberries) -- the other species being the Fragaria chiloensis (coastal strawberry) [3,4,5].

Fragaria virginiana flower
F. virginiana grows primarily in meadows and open spaces [3,5,6] and will also reproduce via vegetative propagation (not just sexual reproduction!) [3,5,7,8].

Now hold onto your hats, ladies and gentlemen, we're going to talk about the evolution of separate sexes!

In animals, dioecy (separate male and female individuals for sexual reproduction) is the norm. In plants, however, dioecy is relatively uncommon, with only roughly 6% of known species of angiosperm (flowering plants) having separate sexes [9]. The primordial state for angiosperms (flowering plants) is monoecy, where both male and female gametes are produced by any given individual (hermaphroditism). So this raises the question of what evolutionary path has led from hermaphroditism to dioecy.

There are a number of proposed avenues for the evolution of dioecy. I'm only going to talk about one of them today: gynodioecy. This pathway is the most commonly studied [9], likely because gynodioecy is relatively common in plants, with about 7% of known species being gynodioecious [9].

In a gynodioecious species, there are two types of flower: female flowers, and hermaphroditic ("perfect") flowers. The categorization of the flowers as female or hermaphroditic is based more on function than appearance. This is because the occurrence of this type of sex distribution begins with a deactivation of male fertility in some individuals [9,10] -- in other words, some of the individuals stop producing pollen or stop producing viable pollen but may still, at first, have the physical structures associated with pollen production (there are a number of possible ways that this can occur, but for today's post just the fact that it happens should suffice). At this point, we have two types of flowers: those which are functionally female (minimal or no male reproduction -- nobody's getting pollen from them), and those which are functionally hermaphroditic (their pollen fertilizes others, and they receive pollen from others).

So it's fairly intuitively obvious that the hermaphroditic individuals have a reproductive advantage in this kind of scenario: they get more chances to pass on their genes. To make this easier to understand, I've created a little table which should help to illustrate the situation. Let's take the theoretical reproductive opportunities for any given individual. That individual, if it produces fruit, has guaranteed that it gets to be the female parent of those seeds; and if it produces pollen, has the chance of also being the male parent of other seeds. The columns represent the two parents of any given fruit (female parent and male parent).

Table 1. Reproductive opportunities (parentage) for hermaphroditic plants
Table 2. Reproductive opportunities (parentage) for female plants
Basically, out of 4 reproductive opportunities, the hermaphrodite takes 2. 2/4 certainly isn't bad! Flowers that don't produce pollen, however, lose their chance to be the male parent of other fruit, as illustrated in Table 2. So these flowers only take 1/4 opportunities to pass on their genes.

So wait, you might say. Wouldn't that mean that plants that are female will be outpaced by hermaphrodites, and their genes will just eventually disappear?

That's would certainly be the case if it weren't for female compensation. Those plants which aren't producing pollen anymore see a rise in seed viability [9,10]. Basically, their female fertility is increased when their male fertility ends. This is probably because the energy that was originally being devoted to producing pollen can be redirected toward improving seed viability [9]. So the female individual actually is also coming out better in this system; she gets a better return on her investment for the fruit and seeds she produces, producing more viable offspring from her fruit than a hermaphrodite.

From this point on we get to theory, but the principle is that because there is less competition for male parentage (more chances to fertilize a female flower), and because it takes a lot of energy to produce fruit and seed, it will be more and more advantageous for the remaining hermaphrodite flowers to shift toward investing more energy in pollen and less energy in fruit [9,10]. This process would eventually lead to dioecy (separate sexes).

Wednesday, May 20, 2015

A note about Trillium grandiflorum (white trillium)

Trillium grandiflorum (white trillium) is putting on a great show this spring. This flower is native to eastern North America (range map here). It is listed as secure in most of its range, but is endangered in Maine and exploitably vulnerable in New York [1], and its status is undetermined in New Brunswick [2]. The species is a member of the family Melanthiaceae.

Trillium grandiflorum
T. grandiflorum is a very distinctive flower, easy to identify. I have already commented quite extensively on this flower in a post I made last summer, including a discussion of its pollinators and its interesting seed dispersal mechanism (myrmechory - ant dispersal).

Trillium grandiflorum population
Where it is not vulnerable to deer predation, T. grandiflorum can form very large, dramatic colonies, like the one pictured above which is in the park portion of the Notre-Dame-des-Neiges cemetery in Montreal (on the west side of the mountain).

Trillium grandiflorum - yes, T. grandiflorum, not T. grandiflorum f. roseum
Sometimes, when people see a trillium like the above, they assume that they are seeing a different variety; there does exist a variety of trillium (T. grandiflorum f. roseum) which is pink. However, this variety is extremely rare, and has a sharper, wavier appearance. This is actually just a regular T. grandiflorum.

Trillium grandiflorum
So if this is a regular T. grandiflorum, why is it pink?

T. grandiflorum is a flower which changes colour as it ages. A pink flower like the above is just an older one, approaching its time of senescence. So when you see a pink individual (or a few pink individuals) among your T. grandiflorum population, just remember that it is more than likely just another T. grandiflorum that happens to be a bit older than the others.

Tuesday, May 19, 2015

Keys - Samaras - Samares

Less than three weeks ago, I started posting about the maple trees in bloom. Well, they've wasted no time! I've been watching the samaras (samara: winged fruit) developing since about May 4.

Acer saccharinum samaras
Acer platanoides samaras
Acer negundo samaras
Samaras are a useful adaptation. Because of the thin, papery 'sail' portion, this seed will travel further from the tree than other types of nuts, allowing better dispersal of seeds and therefore a better territorial expansion for the population. Note that all maple keys are samaras, but not all samaras are maple keys; many other genera of trees produce samara, including the elms and ashes.

The photo below shows a close look on an A. saccharinum samara which was not successfully fertilized and so is not developing (note the small, shrivelled samara on the right-hand side). The tree does not invest energy in developing samaras which are not fertilized, as it would be wasted energy; an unfertilized samara that flies away from the tree won't result in a new tree, so there's no point in investing the energy.

A. saccharnum samaras
In some cases the samaras are developing before the leaves. This tree looks very green and filled out, but all of that green is from samaras, not leaves. Depending on the species, these samaras will take to the air throughout the spring and summer.

Acer saccharinum crown

Monday, May 18, 2015

Watch Where You Stick Your Nose

I am visiting with my parents at the moment, enjoying my time in the upper Gatineau. I went outside to photograph the flowers of a Brassica sp (mustard), which came out rather well:

Brassica sp. with an insect visitor
The genus Brassica (mustard) is member of an economically important family, the Brassicaceae (crucifers or cabbage family). This family is the source of quite a lot of our food, including some familiar ones such as mustard & mustard greens of course, as well as broccoli, cabbage, cauliflower, turnip, Chinese cabbage, radish, horseradish, stock, and even rapeseed (source of canola oil).

Brassica sp.
Pieris rapae, the cabbage white butterfly, which I mentioned having seen in Montreal recently, is one of the major predators of this particular family and is often considered a pest on farms where Brassicaceae are being grown.

So did you notice anything odd about that last photo?

If you didn't (and you probably didn't, be honest with yourself), then you are excellent proof of the effectiveness of the camouflage of Misumena vatia (goldenrod crab spider). If you look closely, you can see the legs of this spider, one extending beyond the stamens of the top left flower, and two more below that flower. Here's a better shot of M. vatia:

Misumena vatia on Brassica sp.
Even in this one, you might miss the spider if you're not looking too closely. But she's hanging off the underside of the flower on the left.

I say she, and I know she, because individuals with yellow legs and of this size must be the females; the males are much smaller with brown legs.

Misumena vatia on Brassica sp.
Apparently the female of this species is able to change colour (though it takes a matter of weeks, not moments) between yellow and white, so they can be found on white flowers as well as yellow ones.

This effective camouflage confers two major benefits for the species: the first is that the female doesn't have to displace herself or to construct webs in order to capture prey. She simply sits on the flower and waits for pollinators to visit, and then eats them. This tough spider can and will take down even a wasp.

The second major advantage of the camouflage is that she doesn't have to do much to avoid predation. Predators will usually not even notice her (as you likely didn't notice her in that second photo, up above).

These two facts allow the female to devote a great deal of energy toward growing and producing her eggs, increasing her reproductive success.

This female also exhibited another very interesting behaviour. What happens if the spider isn't on a yellow or white flower? Well, I got to find out, as she got tired of my pursuit with my camera and jumped ship into the grass, treating me to this fascinating pose:

Misumena vatia imitating a flower
If I hadn't actually watched her assume this pose, I might well have glanced over this spider thinking she was an orchid or similar flower.

Animal adaptations to predation are quite fascinating, indeed!

Misumena vatia imitating a flower
My takeaway from this particular experience is: the next time somebody suggests you stop to smell the flowers, check that you're not sticking your nose into a spider's hunting ground first!

Sunday, May 17, 2015

Early Meadow-Rue - Thalictrum dioicum - Pigamon dioique

Thalictrum dioicum (early meadow-rue) is native to North America (range map here), with a listed global conservation status of secure [1], unlisted in the US [2], and secure in Canada [3] except in Manitoba where its conservation status is unknown [3]. Note that, as with many of the USDA maps, the Canadian range is listed as more limited than the corresponding Plants of Canada database map.

This has happened a few times now with range maps I've looked at recently, so I'm going to take a moment to talk about my stance on disagreements between USDA listings and Plants of Canada database listings. For Canadian range information I will put my faith in the Canadian government source. So if you're in Manitoba with T. dioicum in front of you, scratching your head wondering if you're looking at evidence of the introduction or spread of T. dioicum based on that USDA map-- I doubt it, since the Canadian listing includes Manitoba in the native range of the plant. Ideally I would only draw the data from one source, but the Plants of Canada database maps don't show any information about US distribution at all. Since plants don't care about human borders, it is still informative to determine the rest of the range of the plant. So, two sources it is. In all cases where the two sources disagree about the Canadian range of a plant, I will assume that the data from the Canadian government is more accurate. I won't mention this again in my blog posts.

Thalictrum dioicum in bloom (male)
This plant is a perennial and a spring ephemeral. I noticed that it had started to emerge on May 2. Here is a picture of what the young, emerging plant looks like:

Thalictrum dioicum sprouting - note the furled leaves and the emerging flower stalk, with tightly closed buds
This species is wind-pollinated [4], a fact which shows very clearly in the structure of the flowers. Like most other anemophilous (wind-pollinated) plants in the angiosperm lineages, the display parts of the flower (petals, sepals) are either absent or much reduced; T. dioicum has 4 small sepals but no petals [4]. There is no scent, and no nectar [4].

Thalictrum dioicum male inflorescence - notice the sepals, which are spread up and almost flat above the dangling anthers - there are four on each flower, but they are small and unassuming ; note the absence of petals
T. dioicum is a dioecious species [4], meaning that each individual is either male or female but never both. It is easy to distinguish between the two when they are blooming, as the male flowers are staminate (contain stamens), and the female flowers are pistillate (contain pistils).

The two sexes are easy to distinguish. The males have visibly pendulous anthers which are quite numerous. This configuration makes it easy for pollen to become airborne whenever there is a wind gust.

Thalictrum dioicum - staminate (male) flowers - note the dangling stamens
The pistillate (female) flowers, meanwhile, look quite different. They are composed of pistils, and because reproductive success relies on the pistils sifting pollen from the air, they fan out a bit relative each other and are visibly thick and fuzzy - these characteristics increase the flowers' capacity to sift pollen from passing air currents and therefore improves the odds of fertilization.

Thalictrum dioicum - pistillate (female) flowers - note the fanning pistils
In my meanderings, I noticed what appeared to be two quite distinctive colourings for T. dioicum's staminate (male) inflorescences. The above-pictured individual had a yellowy-green-brown cast, while the individual below has a distinctively red-brown colour:

Red-tinted Thalictrum dioicum staminate inflorescence
The red tint also is visible, in these photographs, on all parts of the flower: the darker sepals, the red-tinted filament (thin part on which the anther sits) and the anther (pollen-producing portion, thicker part).

Close-up of the red-brown individual shows that the colour difference is present in the sepals (green but with purplish veins), filaments (visibly red-brown), and anthers (red-brown tint as well as yellowish portions)
In my various readings, I haven't found any indication that there is any documented polymorphism (polymorphism: distinctive groupings for shape or colouring) in this species, not even in the more extensive reports, like this one produced by the US Forest Service. So, I hazarded the guess that the difference in colouring between these two individuals is related to other factors, eg the soil composition or age of the flower. I set out to test the age of the flower hypothesis by going to re-photograph the two individuals pictured here (fortunately I remembered where I photographed them!). 

However, when I returned I found that neither individual showed any colour change over time, and both were arriving at senescence.

So there was no change in colour even as they senesced. Curiouser and curiouser. Therefore the difference is likely not related to the age of the flower. Is this polymorphism? If it is, I would have to wonder why; polymorphism is usually believed to be pollinator-mediated, and for obvious reasons pollinator perception doesn't really come into play for a wind-pollinated plant. 

There is also the possibility that individual b is a different species of Thalictrum, of which there are several, eg Thalictrum occidentaleThalictrum fendleri, Thalictrum venulosum; however, these species have quite distinctive-looking females and I only saw Thalicturm dioicum females on the mountain. An interesting conundrum. If you have a positive ID or an explanation, I would be very glad to hear from you.