Note: Let’s start off by agreeing that no matter how this post turns out, this is clearly the best post-title I’ve come up with yet.
OK, time to stop dinking around. I’ve been blogging on and on about Costa Rica, the desert, and whatever else while pretty much totally ignoring the Wasatch. And so here we are, half-way through April, Spring-type things are happening right & left, and I haven’t blogged beans about it. So let’s get busy!
When I came home from Costa Rica, the Globe Willows (pic left, a block from my office) were already leafing out (blogged about them last year, you can come up to speed here.) And in the foothills, a little yellow “micro-flower” is blooming all over the place that I’ll blog about tomorrow. There are also all kinds of interesting things going on with the birds in my yard, in the foothills, and in my office parking lot.
But first, let’s back up for a moment. Last year, when I kicked off this blog, one of the first things I did was profile a flower. The flower was a Glacier Lily (pic right), which any day now should start popping up alongside the foothill trails. Doing that post was a good way for me to learn about the basic parts of a flower, and how “traditional” flowers work. A Lily was a good choice because it’s pretty simple, all the parts are clearly visible, and it’s nice to look at. It’s a hermaphroditic flower, so it’s got male and female parts, both of which are real easy to see.
Side Note: That said, Lilies have a couple “non-standard” features to make them interesting. First, 3 of the “petals” are actually sepals, which becomes obvious as you look at the base of the “petals”, and how they’re attached to the stem. And second, because Lilies are monocots, so that the leaf and petal growth occurs at the vase of the leaf/petal/sepal, rather than at the tip, as in a dicot.
So let’s kick off the season with another flower, one that is blooming like crazy right now, all across the Salt Lake Valley. Ready? Here it is:
What?? That’s not a flower! That’s just some random doohickey hanging off a tree. Actually, it is a flower, specifically the male flower of a Fremont Cottonwood, Populus fremontii, growing about 50 feet from my office.
Tangent: I hemmed and hawed a bit before selecting this tree/flower. Although Fremont Cottonwoods are native to Utah, I’m pretty sure they’re not native to the Salt Lake Valley. (Our native cottonwood is the Narrowleaf Cottonwood, Populus angustifolia.) But Fremonts have long been naturalized along many watercourses in the valley, and I walk by this tree ~1/2 dozen times/week, so it’s one I tend to keep an eye on.
When we think of wildflowers, we think of things that look like, well flowers, like the ones we buy in a floral shop (or wish our lazy, good-for-nothing, take-us-for-granted husband/boyfriend would get off his ass and go buy for us.) Flowers that are colorful and eye-catching. The reason of course that so many flowers are eye-catching is to attract pollinators- bees, flies, birds, bats, etc.- to disperse their pollen and/or bring them pollen from other flowers. But many, many angiosperms are wind-pollinated, and the flowers of these plants are structured not to look good, but to efficiently catch a breeze.
This type of dangly, cylindrical flower is called a catkin, and it’s actually a cluster of many, many separate flowers, analogous to the composite agent-pollinated flowers we looked at last year such as Dandelions, Mules Ears and Balsamroots. This one is male, but many plants (including Cottonwoods) have female catkins as well. Cottonwoods are dioecious, so each tree has only male or female flowers, unlike Oaks, which are also wind-pollinated, but are monoecious, bearing both separate male catkins and female flowers on the same tree. (Female Oak flowers are not catkins, but rather single flowers.)
The architecture of a catkin differs not only in form, but also in the sheer quantity of pollen it’s structured to deliver. A Glacier Lily has 6 stamens, each topped by one, pollen-filled anther.
A Cottonwood catkin bears… well, each one of those red nodules is an unopened anther. I can’t count that high, but we’re clearly into 4 figures (I’d guess 3,000+) anthers are on that catkin. Why the huge difference?
Glacier Lilies are pollinated by Bumblebees. They need to produce enough pollen to make sure that when a Bumblebee crawls inside to collect some nectar, it can’t help but rub up against some pollen, which it will then carry to the successive flowers it visits, one or more of which may also be Glacier Lilies.
But no Bumblebees are visiting Cottonwood catkins, which like pretty much all wind-pollinated flowers don’t even bother to produce nectar (or flashy petals.) The Cottonwood is simply blasting out into the wind as much pollen as it possibly can, on the “bet” that if it blasts out enough pollen grains, some tiny fraction of the them will eventually get blown/carried onto a female Cottonwood catkin. That’s why catkins are built the way they are; they’re pollen-machines on overdrive. The photo above is of a catkin I picked and left on my desk for a day; about a third of the anthers have opened, showing the yellow pollen within.
Tangent: As if on cue last week, I awoke Tuesday with a tell-tale itch in my eyes. It’s always the exact same place- the inside corner of each eye. The more I rub it, the worse it gets. Depending on the year, the weather, that may be it, or it may affect my sinuses, even my lungs. And when you think about how much pollen there is in the air, from so many trees, it’s a miracle we don’t all choke to death.
Later that day I picked the catkin in the photo, and left it on my desk at work. (I have a habit of plucking interesting seeds, flowers, cones, etc., and leaving them around for a couple of days, checking them out while on phone calls, etc.) By Wednesday afternoon my symptoms had expanded to include a runny nose and watery eyes. Then- and only then- did it occur to me that sitting all day 3 feet away from a pollen-bomb in a closed office was probably not my brightest idea.
This, right here, is why I could never get a job handling hazardous materials- because I am a Complete Idiot.
The Part About Testicles
There’s a fascinating analogy here that may hit a lot closer to home for you: testicles. Different species of primates have wildly varying-sized testicles, or more specifically, varying testicle weight to body weight ratios. Chimpanzees for example weigh ~60 kg and ~119 gram* testicles. Male gorillas on the other hand weigh ~170 kg and yet have only ~30 gram* testicles. Why the huge difference?
When a female Chimpanzee comes into estrus, she mates with multiple males in her troop, often with all of them. The greater the quantity of sperm that a male Chimpanzee is able to deliver when mating, the greater likelihood that it will be one of his sperm cells that impregnates the female. In this environment, it’s not hard to see how natural selection would favor males who produce more sperm, and that means larger testicles.
But gorillas have a different mating system. A male Gorilla guards a “harem”, typically of 3 or 4 females, whom he vigorously “defends” from other male Gorillas. As a result, a female Gorilla in estrus practically always mates with exactly 1 male Gorilla, and so that male needs only to produce enough sperm cells to have a decent chance that one will do the job.
Side Note: This is a greatly simplified version of the mechanics of primate mating, as it completely glosses over sperm competition or “warfare” as it is sometimes characterized, but a full description would certainly merit a post of its own. I should also mention that although the evidence for real sperm “warfare” in primates is mixed, the sperm competition/warfare mechanisms of many insects are both well-documented and way more sophisticated and fascinating than anything suggested in primates, but I picked primates because most of us can relate to them better.
…And speaking of relating, where do we humans* fall on the testicle-to-body-weight scale? About mid-way; our testicles are roughly 4X larger than they need to be to get the job done, suggesting a significant level of sperm competition in our recent evolutionary past, though not at the level of Chimpanzees.
*This stuff is somewhat top of mind for me right now, as I was recently toying with doing a post on male human genitalia and bicycling. I bounced it off Cory and Colin last weekend and they sort of talked me out of it, on the basis that it might exceed the generally PG rating of this blog…
Just as certainly as selection pressures drive the size of our own sexual organs, selection also drives those of a flower.
Clarification: I recognize of course that this analogy is imperfect; wind-pollinated and agent-pollinated flowers deliver their pollen via radically different mechanisms, while Chimpanzees, Gorillas (and people) use pretty much the same “delivery mechanism.” But I maintain that the analogy is valid; in each case, different environmental selection pressures are have radically affected the size of the organ in question.
Back To Wind
On the surface, it seems strange that any angiosperm is wind-pollinated. Agent-pollination is the crowning achievement of angiosperms. While they didn’t invent it (Cycads probably did) they’ve clearly taken it to levels of complexity and sophistication unmatched by the gymnosperms. But strangely, in temperate forests around the world, it’s wind-pollinated trees that dominate. Here in the Wasatch, Cottonwoods, Maples, Oaks, Aspens and of course all the conifers are wind-pollinated. What does that leave us?
It leaves us Willows and Mountain Mahogany. Willows are a special case that we’ll come back to in a moment. Mountain Mahogany seems to be pollinated by insects (bees and flies) as well as wind.
Tangent: Oddly, many (most?) common native shrubs around here tend to be agent-pollinated, examples being Rabbitbrush, Snakeweed, Bitterbrush, Serviceberry and Chokecherry. (Although Sagebrush is wind-pollinated.) I have no idea why the trees of the Wasatch should tend toward wind-pollination, while shrubs tend to employ agents. I wondered if height could make wind a more effective agent, but that seems a stretch. In any case, it’s worth noting that the three most common angiosperm trees in the Wasatch- Aspen, Gambel Oak and Bigtooth Maple- all are able to reproduce asexually as well, and for the first 2, the vast majority of reproduction in the Wasatch (virtually all for Aspen) is asexual.
It’s particularly weird because we know that wind-pollinated (and water-pollinated) plants existed for millions of years before agent-pollination came about. And we’re pretty sure that all angiosperms evolved from a common ancestor, and that that ancestor was agent-pollinated.
Side Note: Why do we “know” this? Botanists believe angiosperms evolved from a common ancestor because the hallmark mechanism of angiosperm reproduction- double fertilization- is so complex and weird that it’s thought to have only occurred once. (For a simple, clear and excellent description* of double fertilization, see here.) And all flowers share enough basic common structure that it appears almost certain that wind-pollinated flowers evolved from agent-pollinated flowers.
*OK I’m a little biased.
So it seems puzzling that some angiosperms should then evolve the other way back toward wind-pollination, which seems more “primitive”, but when we step back and think about it, it’s only puzzling when we think of evolution as “going somewhere”. But evolution isn’t going anywhere (as I explained in the Darwin-Aeneid-Days-Of-Our-Lives post. Man, I loved doing that post.) It’s just always adapting to whatever selection pressures organisms find themselves facing at any particular place and time. And when we see it that way, the re-evolution of wind-pollination makes perfect sense, particular in windy areas with a dearth of effective pollinator-agents. Furthermore, we shouldn’t be surprised if some of these wind-pollinated plants re-re-evolved agent-pollination if conditions warranted, and in fact this appears to be exactly what happened in Willows (whose pollination-strategy-evolution I described in this post.)
So fine. The re-evolution of wind-pollination by angiosperms makes sense, at least at a cerebral level. But at an intuitive level, no matter how hard I try, I can’t quite get my head around wind pollination overall. Think about it: That Cottonwood is just going to spray pollen out into the air, and “hope” that one of those little grains of glorified dust is going to land in- of all places- a tree. And that the tree it lands on will be- of all possible trees- a Fremont Cottonwood (specifically a female Fremont Cottonwood.) And that of all the possible parts of that tree to land on, it’s going to land on the catkin of that female Fremont Cottonwood.
Seriously, what are the chances of that happening? Surely the likelihood that any one wind-blown pollen grain will make it to a female flower of the same species is fantastically less than the chances of any one of us winning the lottery. It just seems so impossible.
The Part About Cold-Calling
When I think of wind-pollination, I sometimes think of cold-calling. As longtime readers know, I’ve worked in sales for many years. For a period of roughly a decade, I made many, many cold-calls*. And though my personal work-duties today no longer involve making cold-calls, I still manage a team of people who regularly make them. And cold-calls, no matter what you think of them, work. Every year my company- and thousands of other companies- sells services to many new clients, clients who would never have heard of us if they hadn’t received a cold-call (or cold-email) from one of our salespeople. So it’s somewhat comforting sometimes for me to think of wind-pollination as a form of natural cold-calling, whose success is ensured through sheer power of numbers.
*I once calculated that I have made roughly 18,000 cold calls. If you worked in IT application development in New England in the late 1980’s or Northern California in the early-to-mid 1990’s, there’s a good chance I cold-called you.
But when I think it through, even the cold-calling analogy falters. Though I describe our prospecting calls and emails as “cold”, that’s somewhat of an overstatement. Like every sales organization, we direct our prospecting calls to particular organizations (Fortune 1000 companies, universities, govt agencies) that we know use services like ours (technology research services) and to specific individuals within those organizations (CIOs, CISOs, technology architects, etc.) who we know are actively trying to solve many of the problems our services address. Furthermore, we use various resources and tools (Hoovers, RainKing, Jigsaw) to help us identify those organizations and prospective contacts within them.
But imagine that one day I came into the office and threw out all of those tools, our Internet access, and even our paper telephone directories, and told our salespeople to cold-call by picking up the phone and dialing random numbers, in the hope that some portion of random numbers they dialed would be valid phone numbers, that some portion of those valid phone numbers would be extensions at F1000 companies, and that some portion of those numbers would be F1000 CIOs. How many cold-calls would they have to make before they got an F1000 CIO on the line?
That’s more like the scale of wind-pollination. It seems just utterly and completely impossible. And yet it so obviously works; the world is filled with wind-pollinated plants. (pic left = Fremont Cottonwood leaves, last May, Twin Corral Box Canyon) That’s what blows me away about wind-pollination: that something so wildly scattershot and improbable can work so reliably well. If that doesn’t convince you that the world we live in is just unbelievably incredible, amazing and outright astounding, I don’t know what will.
Post-script: Know what else is like that? The fact that bicycles stay upright. Yes, I ride a bicycle every day, and yes, I know all about the physics behind it and the angular momentum of the wheels and all that. But when I really, really think about it, I just can’t quite get that it stays upright. I try not to think about that too long while track-standing at traffic lights.