Monday, October 11, 2010

The Vagaries of Houston Weather, and Angiosperm Evolution

Sigh... that spell of cool, dry autumn days that descended upon Houston and lingered for a couple weeks seems to have gone. My ankles ache with the familiar old rheumatic pain, an ominous portent of coming rain. Ever since I was a kid, my ankles have ached right before a rainstorm. Sometimes if it was a snowstorm, the pain would go all the way up to my knees. Mom used to rub it with that stuff they rub on athletes' joints. I remember the bottle - it had red bullseyes at the ankles and knees. The pain isn't bad, more of a dull ache. I remember acutely one time it was particularly bad: right before a brutal snowstorm in the dead of winter. But otherwise, it was never more than a minor nuisance. Anyway, the rheumatic rain pain has been subdued, but not entirely disappeared, ever since I moved down to the South. Perhaps being in a general state of constant humid conditions suppressed it. It does, however, come back if there's a spell of dry weather preceding rain. And of course I get it when I go back home and it snows or rains. So, I think it might rain this week. At the very least, the humidity increased today.

On a completely different note, I've been trying to do a bit of "leisure" reading, mostly before bed. Although sometimes it totally backfires and I stay up way too late because I get too into a book. I have been reading To A God Unknown by John Steinbeck, which, so far, is excellent. I've also been (re) reading parts of The Evolution and Classification of Flowering Plants, by Arthur Cronquist. I've actually had this book checked out from the library for over two years now. (I remember I checked it out pretty much as soon as I got to Rice because I had wanted to read it since I took botany, which was right before coming to Rice). Apparently, no one's wanted to check out this incredible book in all my time here, which I find kind of amazing (unless they require botany students to buy it or something). Although it is a textbook, it's actually a good read. For those of you who do not know who Arthur Cronquist was, he is credited with dividing the flowering plants into the two classes Magnoliopsida (the dicots) and the Liliopsida (the monocots), which is probably familiar to anyone who took intro biology. Cronquist wasn't the first to make the distinction, but followed in the footsteps of the "phylogenists" before him (Bessey, Engler), and ultimately from Bentham, de Jussieu, and of course Linnaeus (the "taxonomists"). But after Cronquist, there were no more classical taxonomists of his sort. Botany entered the "modern era" of cladistic methods and molecular DNA data. So, all in all, Cronquist's book distills centuries of botanical thought into an integrated taxonomy scheme for plants.

I haven't read the whole thing yet, but I do particularly enjoy reading the chapter on the Origin of the Angiosperms. When you think about it, angiosperm evolution is quite incredible, particularly if we believe that angiosperms evolved from cumbersome things like cycads. (Compare that to some of the incredible things flowers get animals to do in the quest for pollination, like bees and orchids). Cycads, ginkgo, and other primitive gymnosperms, as Cronquist put it, were "locked into a slow, perilous, and wasteful reproductive process." This is particularly evident in Ginkgo, wherein the entire seed, minus the embryo, is formed prior to it even being fertilized. Then it falls to the ground and hopes that some Ginkgo pollen will fly by and fertilize it. This is why male and female Ginkgos need to be near each other or else they have no hope of reproducing successfully. I also thought the theory that pollination by beetles is an ancient, primitive feature was quite interesting (think of the strobiloid flowers of Magnolia). Isn't it fascinating to think of giant magnolia-like flowers during the Cretaceous, being chewed upon and crawled over by giant black rhinocerous beetles?

Anyway, just reminiscing back on botany lab and drawing flowers of Liriodendron tulipfera (one of my favorite plants). Lots of new plants to learn, and old ones to remember.

5 comments:

CTA Lee said...

hmmm... your ankles swell and the weather changes. interesting piece on the angiosperms. thanks for sharing. so angiosperms started appearing 200 My ago or something like that... why did they begin to diversify like crazy only in the Cretaceous? and no, this has nothing to do with my cretaceous love affair...or does it?

Emily J. Chin said...

Because it was so warm in the Cretaceous! You probably had proliferation of much more than just flowering plants. Beetles, insects, dinosaurs, small mammals... Magnolia has these garishly red seeds when the "cones" ripen and fall to the ground. I remember Darwin (my botany prof was named Darwin... no relation though.) said that was a signal for dinosaurs to eat them. (who knows) But anyway, I believe that the rise of the angiosperms might be intimately linked with the evolutionary diversification of animals, from dinos to bugs... not just more species, but perhaps species evolving into rather specialized niches (caused by the diversification of angiosperms thermselves). This prompted flowers to exploit new tactics, and you get things like nectaries, extremely complicated pollination rituals involving one species of bee, etc. I wonder if there are any giant beetles from the Cretaceous.

Emily J. Chin said...

BTW... my ankles don't actually swell. They just ache with a dulling pain. Like a bone bruise. No swollenness though.

CTA Lee said...

why were the beetles there? the beetles need the angiosperms? the birds began then too, perhaps because they ate the insects? warmer climate the cause? i suppose... higher pCO2? gymnosperms and angiosperms probably behave quite differently to variations in pCO2.

Emily J. Chin said...

Perhaps some beetles and angiosperms coevolved. Or, maybe beetles just explored a new niche with the advent of angiosperms... they probably saw the strobiloid flowers as easy food targets, but they probably didn't use flowers as their main food source. Check out this Science paper:

http://www.sciencemag.org/cgi/content/full/281/5376/555