Tuesday, September 19, 2017

Impatiens capensis pollination (Bonus: even bees can be clumsy)

I know I haven't blogged in quite a while. Life got very hectic for a while. In the months my last post, I have finished my M.Sc., gotten published, and moved to the University of Toronto to start my Ph.D.!

Over the weekend I got a chance to take a long walk with my patient and long-suffering husband, who indulged my snagging his new blackberry to take a ton of footage of bees visiting the tens of thousands (at least!) of Impatiens capensis (common name jewel-weed) in the ravine park near our new home. I made all sorts of exciting videos, but today I'm going to share just a few simple ones, as the others will take quite a bit of research and time to write up. I will post these throughout the fall because they're very exciting.

NOTE: I have been informed that my videos don't work on mobile. I'm working on it, but in the meantime they do run on desktop.
UPDATE: try clicking the title of the video instead (treat as link) on mobile. Opens in youtube app. If you don't have youtube app, please report back telling me what it does when you click the video link!

To start, here's a picture of the plant itself:

Impatiens capensis whole plant view

Let's take a quick look at some general reproductive biology of I. capensis. The plant is monoecious, meaning that each plant reproduces through both male and female function; however, each individual flower is unisexual (i.e., any given flower is either male or female but not both). In the photo below, I show three flowers on the same individual. If you look at the top of the "mouth" of each of the lower two flowers in the picture, you will see that each has a different structure; the middle flower has a large, bulbous, whitish structure, while the rightmost flower has a slender green structure.

Impatiens capensis male (middle) and female (right) flower
The middle flower is a male flower; the whitish deposit on it is pollen, ready to be deposited on the back of a pollinator that climbs into the flower looking for nectar (the nectar is in the nectar spur, the little narrow tube curling off the back of the flower, visible on the middle flower). The rightmost flower is a female flower, with a stigma ready to pick up pollen from the back of a visiting insect.

The flower has some rather complex floral anatomy I won't get into right now. There's a pretty good explanation of which parts are sepals and which parts are petals here for those interested. The important thing to note is the lower lip, made of two structures wrapping around the front of the flower, one on each side, that form a sort of landing area of pollinators. They also restrict the width of the flower opening (see photos below).

Impatiens capensis male flower front view. Note that the two sides of the "landing" petals on the front are not fused, just overlapping, and that their shape, because they come down from above around the opening of the cone, reduces the size of the entrance into the flower

Impatiens capensis male flower side view. Notice that the lower "landing" petals are not attached to the conical structure behind.

So I'm going to skip over all sorts of exciting stuff about this plant (why does it have unisexual flowers? Why place pollen on a visitor's back? What's up with that super-complex floral shape?) in order to move straight to some awesome video of assorted Hymenopterans (bees, wasps, ants) visiting this awesome flower!

So I noted above that the '"landing" petals form not just a place for a pollinator to land on the flower, but also a constriction around the opening of the conical part; remember that the nectar is all the way at the back of that cone, in the little nectar spur curling down under the flower. There are several strategies to get past the opening to access this nectar (and then leave again after): one is to simply be small enough to fit through the constriction made by the landing petals; that's how Apis mellifera (honeybee) is doing it (note at 10:00 that you can really see the pollen on this honey bee's back!):

Backing out of the flower can be quite tricky. I managed to get some footage of a visiting wasp finding an alternate method of exiting, which capitalises on the fact that the landing platform and the conical structure behind are not attached to each other:

The Bombus sp. (bumblebee) workers I saw visiting the plants, however, were too big to fit through the opening. But, have no fear! They worked it out anyway. Here's one worker diligently visiting lots of flowers. She's making more room for herself by using her strong back legs (2 pairs) to push the landing petals apart a bit, so that she can shove her head and thorax into the flower and get at the nectar. You'll notice that she doesn't have much difficulty leaving, either, since she's well placed with four legs outside the flower. As far as I can tell, she's just dropping right out of the flower and then flying away.

Here's a longer video of the same bee, diligently visiting a lot of flowers in a row. There's also a little bonus at the end of this video. If you've been clumsy and felt ridiculous for it recently, I have something to comfort you: even bees can be clumsy. If you watch closely at the end, you'll see her climb into a flower, and then she and the flower both fall off the plant to the ground!

Monday, May 29, 2017

It takes a special kind of obsession to do fieldwork

I wrote a few weeks ago about the start of the field season. I have been back up to the field site a couple of times since then mostly for basic surveying and laying out the plots that will stay in place for the next few years.

This week things got serious, though. Our orchids of interest, Cypripedium arietinum (ram's head orchid, fr: Cypripède tête-de-bélier), are finally blooming! This year they're blooming rather later than usual, as I have informal records going back several years showing the orchid flowering by May 17th -- they didn't start this year until May 22nd.

Here's what these little beauties look like:

C. arietinum
These little guys are gorgeous up close, but actually not very showy (at least to the human eye) -- they are very small, generally somewhere between 10 and 25cm tall at the flower (around a handspan off the ground) and the labellum (white and purple-veined petal-looking portion of the flower) is only about 1-1.5cm tall from lip to point, around 1cm wide, and only 1-1.5cm from front to back -- similar in size to the tip of an index finger. Moreover, their sepals (the brownish-red petal-like things sticking up, or out to the sides) are brownish and earlier in flowering development they lean down over the labellum, disguising it from view from above. This position of the sepal over the labellum can be seen in a photo in one of my previous blog posts, here. These factors come together to make C. arietinum a subtle, hard-to-spot little orchid.

C. arietinum flower
One rather interesting aspect of orchid pollination biology is the production of pollinia. Basically, instead of presenting pollen in loose grains that are removed and delivered in small numbers by pollinators, orchids (and a few other plants, e.g. milkweeds) produce their pollen in two big sticky masses called pollinia (singular pollinium) -- a pollinator either leaves with a big blob of sticky pollen, or without any pollen at all. Similarly, a flower receives pollen in big sticky masses. There are a couple of advantages to this kind of system: paternal success per pollinator visit is improved, because if a flower gets an opportunity to sire seed (i.e. its pollinium is transported to another flower), it gets to sire a lot of seed all at once because there are enough pollen grains in the pollinium to fertilize most/all of the available ovules; maternal success per pollinator visit is also improved, for similar reasons to the above. Of course, there's a loss of genetic diversity in offspring, as under these conditions all seeds from the same flower are full-siblings (same paternal and maternal parent), whereas if pollen grains were carried individually or in small numbers many of the resulting seeds would be half-siblings (same maternal parent, but different male parents).

I actually took some photos that show the pollinia of C. arietinum, so let's take a look:

C. arietinum pollinium -- look at the top of the labellum, where we have a fleshy structure below the dorsal (top) sepal -- if you look closely, under that structure (which is composed of filaments and pistil, fused), we see a round yellow blob -- that's the pollinum!
So why would it be better to increase reproductive success per pollinator visit at the expense of genetic diversity of the offspring? Current thought is that it's related to the plant being deceptive (or rather, to the plant receiving very few floral visitors because it's deceptive). I've talked about floral deception before, but in a nutshell the flower lures pollinators in by signalling that it offers a reward (nectar), but once the pollinator arrives it discovers that it's been had, that there's no nectar reward at all. Being food deceptive allows a flower to reduce its investment of energy in pollinator attraction (it doesn't have to make nectar, which is costly), but being food deceptive also means that the flower gets a lot fewer visits, because the pollinators learn that this flower is a liar and not worth visiting.

It's a pretty liar, though, eh? C. arietinum looking into the labellum

Regardless of the delay in their flowering time this year, now that the orchids are blooming the intensive fieldwork starts. We set out several days this week to tag all of the flowering individuals (we're already up over 200 individual orchids), measure a suite of their characteristics, measure soil pH and moisture for each of them, take down canopy closure and other plot characteristics, and note the size of the flowering community around each individual. This is an enormous amount of work, as you might have guessed. And there are still at least 100 orchids left to go!

One of the best things about fieldwork, which I touched on briefly in my last post, is that making close observations out in the field can lead to new questions and new discoveries. For example, yesterday during my fieldwork I noticed something very odd and cool. It won't come as a complete surprise to my blog readers, as I have talked about mutations twice before. This time, no fasciation, but instead I found five two-flowered individuals in this species that generally only has one flower per stalk. Individuals producing more than one flower on the same stalk naturally have been documented in quite a few orchids, especially Cypripedium spp.; however, there are a number of possible reasons for the multiple flowers: stress-related growth malfunction? soil contamination growth malfunction? natural genetic mutation? natural morphological variation? When it comes right down to it, we don't currently know the cause.

Of these two-flowered individuals, there seemed to be two broad 'types'. The first is a two-flowered individual wherein the upper flower is right-side-up and the lower flower is upside-down. There were three of this type in one of our study plots. Here are some pictures:

C. arietinum two-flowered individual. The upper flower is on the right, and the lower on the left.
One visible consequence of the orientation of the second (lower) flower is that the bottoms of the labellums of the two flowers press together and result in some distortion of the shape of the labellum -- for all three of this type of two-flowered individual in the plot, the lower flower's labellum was compressed such that the point at the bottom (oriented upward in this flower) was folded back instead of deployed (flower on the left in the above photo), while the upper flower's labellum had its point deployed (flower on the left in the photo below).

C. arietinum two-flowered individual, from the other side -- the upper flower is on the left and the lower on the right
 As you may have guessed, the second type of two-flowered individual I saw yesterday during my fieldwork was on in which both the first and second flowers were oriented correctly.

C. arietinum 2-flowered individual with both flowers correctly oriented
Though there's no interference between the two flowers in their growth like with the two-flowered individual above, I did notice that this individual also had some weird sepals on the upper flower -- notably, the dorsal sepal is oddly tilted off to the side (you can't really see it in the photo below, for example), and on that side where the dorsal sepal is the lateral sepals are actually entirely missing, so it's short a pair of lateral sepals and the dorsal sepal is positioned oddly. Because of my low sample size (only two flowers), I have no idea if this weird sepal situation is related at all to the double flowers. The lower flower, though smaller than the upper, appears well-formed.

C. arietinum two-flowered individual showing the flowers up close
I am still mulling over what kind of work we might be able to do with these unusual individuals. We will be limited by our very low sample size, but I live in hope -- maybe there will be more that we haven't spotted yet, as there are quite a few plots left to go! In the meantime, they're a curiosity worth documenting. Maybe this natural history find will turn into an ecological one in future!

I suppose I've had a good ramble through the orchid patch now and will get back to the title of this post, which is ostensibly the main point here. These lovely pictures don't convey one aspect of the season: blackflies! It is peak blackfly season, so it's absolutely brutal out there. We are all wearing bug hats and tucking our pants into our socks, our shirts into our pants, binding our cuffs with rubber bands, wearing gloves, and just about bathing in DEET because the blackflies are ravenous and exceptionally numerous. It takes a special sort of obsession to put up with them for ten hours a day!

I shared this video last year, but it's particularly apropos at the moment. Here's some delightful Canadiana about blackflies, sung by Wade Hemsworth and the McGarrigle Sisters and with animation by the national film board:

Wednesday, May 24, 2017

Natural history and ecology go together like flowers and pollinators

I've only very recently returned from Victoria, where I attended CSEE2017 and gave a talk. CSEE2017 was fantastic, but I will save my commentary thereupon for another post. I'm only mentioning my visit to Victoria now because I went to the Butchart Gardens while there. To be perfectly honest, these days as a plant ecologist I often get grumpy visiting ornamental gardens, as they generally have few or no native plants, usually have virtually no pollinators to watch, and just lack ecological interest. Certainly I found the gardens beautiful, and if I were a horticulture aficionado I might have found more to interest my curiosity while there, but what actually caught my attention was this:

Tulip showing stem fasciation and an abnormal number of flowers.
Fasciation: an abnormal condition of growth tissues, wherein in the meristem (area of actively dividing, growing, and differentiating cells), rather than having its normal domed/round shape, is elongated in one dimension, resulting in thick, wide organs and distorted growth. For a more detailed discussion of fasciation, I invite you to read my previous blog post on the topic (linked below).

I have talked about fasciation before, in context of a rather awesome monster thistle that displayed multiple levels of fasciation plus homeosis (substitution of one organ for another), so that was an individual with a lot of issues. But this fasciated  tulip is rather intriguing to me because it exhibits only stem fasciation, with no other visible abnormalities. The photo below shows the fasciated stem clearly.

Fasciated tulip stem
Now, the fasciation of just the stem is interesting to me because it is specifically accompanied by a subsequent splitting of the fasciated stem and the production of multiple otherwise normal flowers, as seen in the first photo and even the one below, where there are two tulips rather too close to one another, but they are not fused (i.e. they grew on separate meristems) and they seem to be anatomically normal. You may have noticed that the photo below is a different plant -- at the gardens I saw three cases of this kind of stem fasciation in tulips with an abnormally large number of otherwise anatomically normal flowers.

Fasciated tulip again
Since I saw it three times, it may well have been more common than that at the garden. Possibly this is a heritable fasciation (i.e. fasciation resulting from a genetic mutation); the probability of this option depends a bit on how the garden acquires and maintains their tulip population -- if they breed their own tulips, then it is possible that these fasciated individuals are actually related to each other, which increases the probability of this being a heritable genetic mutation.

Fasciated tulip!

However, as with the thistle, there are other reasonable possibilities, among them the possibility that the fasciation has an environmental cause (e.g. a pesticide or fertilizer applied to all the tulips), or that it results from a bacterial or fungal pathogen transmitted through the garden by gardening activities like watering and weeding.

My friend and travelling companion, Kayleigh, also found a case of fasciation in Bellis perennis (english daisy) in Victoria. First, here's a normal one:

Bellis perennis normal specimen -- photo taken by K.G. Nielson and used with permission
And our weird mutant showing floral fasciation (this is what is not seen in the tulips above; with them, the stem is fasciated but the flowers normal; with this one, the stem is normal but the flower is fasciated):

Bellis perennis fasciated individual -- photo taken by K.G. Nielson and used with permission
So you might be wondering when I'm going to get to the point. The point is this: an ecologist should also be a natural historian! There was an interesting opinion piece recently published about the importance ecologists place on natural history (the largely observational study of organisms, particularly their traits, their interactions with their environment, and their history), and how ill-equipped many young ecologists feel to teach natural history.

This story resonates with me, because I adore natural history but make no pretensions to having great skill or knowledge in the area; I am largely self-taught on this subject. I run this blog partly to share the beauty and wonder and amazing scientific appeal of nature, and partly to remind myself to root my ideas firmly in the reality (read: natural history) of the organisms and communities I study.

I believe that natural history is where it all begins: a couple of ecologists on a walk notice a bunch of fasciated plants, and this spurs all sorts of wonderful lines of inquiry about how the fasciation comes about, how the condition might spread in a population, the particular mechanisms of function, the possible associations between assorted fasciation types, etc etc etc.

Darwin is a particularly notable example of beginning ecology with natural history: his work starts with incisive observation and proceeds from there into testable hypotheses and experiments.

When it comes down to it, everything we do as ecologists starts in with natural history.

I don't have enough experience or expertise to weigh in on whether natural history training is lacking in many universities as suggested in the article I linked. I can't even say whether my own lack of extensive natural history training is due to my own neglect of my options, or due to an absence of options available to me. But at the personal heart of it, I'm an ecologist because it allows me to blend my deep and abiding love of natural history with the elegance, logic, and rigour of the scientific approach. I'm sure I'm not alone.

The best ecological questions and hypotheses happen because ecologists are also natural historians.

Besides, it's better for our health to get outside and wander around once in a while with our eyes wide open.

Monday, April 24, 2017

A new field season begins!

I have been working away at my stats, analysis, and writing in the lab since my last post in September about the transition between fieldwork and data analysis. With the melting of the snow, I'm now heading back out into the summer portion of the ecology research cycle: field research!

I will be collaborating with my labmate Cory and his old supervisor on long-term research with the population of Cypripedium arietinum (ram's head orchid) at the lake; I've written about this plant before -- there's a nice photo of the flower over on that post as well so go check it out!

Orchids are interesting for lots of reasons. Here are just a few:

(1) Many orchids are unrewarding, which means that they don't offer nectar to pollinators in exchange for pollen transport. With unrewarding orchids we can investigate questions about the evolutionary consequences and/or adaptive mechanisms for deceiving pollinators into moving pollen from plant to plant

(2) Many orchids are spring ephemerals. This means that they flower in the brief window in the spring after the snow melts and before the trees put out their leaves. Synchronizing with their pollinators, which are just waking up from their winter hibernation, is particularly important for them to successfully reproduce. With these plants, then, we have opportunities to investigate how small- and large-scale variation in climatic conditions (e.g. timing of first snow melt, date of tree leaf bud bursting, quantity of canopy that's open throughout the blooming period, variation in temperatures, etc) can affect the emergence synchronization of flowers and their pollinator.

(3) Orchids rely on fungi in the soil in order to germinate and grow, so we can ask questions about how such a system might evolve and how the orchids and fungi can affect each other over time and space.

Cory and I went out yesterday to get some basic information about the areas where the plants are found, so that we can get a sense of what kind of designs are going to work best.

At the start of the season we're often just exploring a bit, to get a sense of what we have to work with with respect to terrain and space. This kind of knowledge is invaluable for designing studies and making decisions about what kinds of tools and techniques we want to use.

We were delighted to notice that we could pinpoint a few clumps of the plants because we found some old fruiting stalks (seed pods on old stalks) that survived over the winter. They aren't easy to spot because they're small and about the same colour as dead leaves and twigs on the ground, but with a bit of crawling around and some prior knowledge, they can be found.

These old seed pods are great not just to help us locate plants, but also because they allow us to glean a bit of information about last year, too; a rough count of how many old seed pods there were this spring gives us a minimum number of seed pods that were produced last year (we can't know what proportion were lost over the winter, so we can't say how many more than this count were produced).

Old seed pod of C. arietinum
Because these orchids are perennials, finding these old stalks allowed us to locate at least some of the clumps of C. arietinum at our sites. What's more, we even found some very young shoots already coming up!

In the centre of this photo (look closely) there are several little C. arietinum shoots just starting to come up; the white thing is a tag that we put in to mark the location of this clump

Cory and I put in some temporary tags and some flags to mark off the general areas where we know there are plants; this will make our work easier next week when we go back next weekend to install permanent tags for the clumps of C. arietinum, since we're going to want to be able to track them across years.

Cory, next to a pole that he placed to mark one of the areas of the property where we found some C. arietinum clumps
At that point, we'll also start making a GPS map of the coordinates of our populations and clumps for good long-term data maintenance, and as insurance against long-term markers being lost or displaced accidentally.

My husband was recruited as an unpaid but dearly appreciated field assistant; here we are counting old stalks, fruit, and new shoots in a clump of C. arietinum that he found.
We'll be going back throughout the season to track these plants as they grow, bloom, and fruit. I will post some more updates as the season progresses.

Purely out of curiosity, we spent a bit of time fiddling with the old seed pods; we noticed that most of them had opened and dispersed all their seeds, already, but that some still contained seeds and were in varying stages of openness. Those that were partially open were interesting because when shaken or nudged, they sent out clouds of thousands of miniscule seeds! We took a video that is unfortunately out of focus, but you can see the seeds as little blurry pale things in the video clip below:


We also collected a couple of old seed pods from last year that hadn't opened and released all their seeds and spent a few minutes today looking at the seeds under the microscope out of curiosity. We weren't using the fancy Zeiss research scope in the lab upstairs, so there's no camera mount on this microscope and it's not the most amazing scope ever, but I can at least give an idea of what the seeds look like:

C. arietinum seeds; the dark spot in the centre is the seed itself. The old cell walls are visible in this image as dark lines that seem to be outlining somewhat rectangular shapes. This image is at taken at 100X magnification, so the entire structure including coat is maybe 1mm long or a bit less, while the seed is less than that. Tiny!
I am absolutely delighted that the field season has started up again. This is just one of a few projects I'm hoping to work on this year. I will make sure to post a bit more this year than last about what I'm up to and why over the field season.