Of ants and seeds
I finally got around to reading the September issue of Natural History – possibly my favorite magazine – which features a marvelous article on how ants disperse seeds: “Jaws of Life,” by Robert R. Dunn. I knew this was an important topic for Appalachian forest ecology, because many of our spring wildflowers, such as bloodroot, Dutchman’s breeches and stinking Benjamin, depend on ants as the sole or primary agent of seed dispersal. This means, among other things, that once such wildflowers are eliminated from an area by several decades of overbrowsing by deer, or through large-scale clearcutting or other landscape alterations, they may take centuries to return on their own. As Dunn puts it, “Getting dispersed by ants… is like trying to get out of town on the local city bus. As often as not, you circle back to where you started. Seeds carried by ants are rarely taken more than a few feet from where they fall.”
So this obviously raises the question of why plants rely on ant dispersal in the first place: what advantage does it confer? Suggestions include protection from predators or from fire, or taking advantage of the rich nutrients available for the seeds’ growth in an ant nest’s midden. This last suggestion seems especially likely for the thin, acid soils of the Appalachians.
The plants go to the trouble of manufacturing a special ant lure, “a small, fatty appendage known as an elaiosome, from the Greek elaios, ‘oil,’ and soma, ‘body.'” The ants seem to find it more economical to carry the entire seed back to their nests so their larvae can eat the elaiosome, following which the seed gets chucked into their compost heap. “Elaiosomes… have evolved at least eighty-six and perhaps several hundred times around the globe…. In the Liliales (the group that includes the lilies) alone, ant dispersal may have evolved independently at least eight times.”
So it’s obvious that ants are highly valued partners for plants, even if we can’t determine the exact reasons yet. Nor is this rather extreme example of convergent evolution restricted to the plant kingdom, as a sidebar explains. This is worth quoting in full, I think. It accompanies an arresting photo of green and yellow, seed-like things with brown knobs on their ends.
The eggs of some stick insects, like the seeds of many plants, have nourishing appendages that encourage ants to pick them up and carry them away. The appendage of an insect egg is called a capitulum, and ants can remove it without damaging the egg. In the photograph above, for instance, eggs from the Central American stick-insect genus Bacteria are shown, magnified roughly fifteen diameters; the brown, knobby protuberances are the capitula.
The parallels between the elaiosomes of plant seeds and the capitula of insect eggs were first highlighted in 1992 by Mark Westoby and Lesley Hughes, both ecologists at MacQuarie University in Sydney, Australia. They gave seeds with elaiosomes and stick-insect eggs with capitula, along with several control items, to various ant species in southeastern Australia. The ants removed the seeds and eggs at a similar rate, treated them similarly, and threw them together into their garbage piles. The apparent advantage for the eggs is that, buried in the debris, they are less likely to be parasitized by wasps.
Perhaps it is appropriate that stick insects, which as adults mimic sticks, start out by living the lives of seeds.
Words on the street
Seven things that make me happy right now
1) Republican “leaders” in the House of “Representatives” giving up, at least temporarily, on their latest attempt to deface and destroy the Arctic wilderness.
2) The good people of Dover, Pennsylvania voting in a new slate of school board candidates who have promised to restore natural causation to the science curriculum – and incidentally restore religion to its rightful position as an outside counter-weight to scientific hubris. (If only Kansas voters were less credulous about arguments that denature and attempt to second-guess Creation!)
3) The impossibility of discerning what is most likely to be true apart from considerations of what appears to be the most beautiful (or, as scientists like to say, elegant). As the New Yorker’s exposé on “intelligent design” points out, “to scientists, a good theory is one that inspires new experiments and provides unexpected insights into familiar phenomena.” Over the past century or more since the general acceptance of Darwin and Wallace’s theory of evolution by natural selection, some of those insights have included the astonishingly beautiful ideas of coevolution, convergent evolution, and cladistics. I.D., by contrast, “has inspired no nontrivial experiments and has provided no surprising insights into biology. As the years pass, intelligent design looks less and less like the science it claimed to be and more and more like an extended exercise in polemics.” And what could be uglier than that?
4) The fact that, thanks to evolution, one can think compassionately and synergistically, comprehending the world as numinous Creation – or givenness, as a philosopher might say. One corollary of this is that one can appreciate – and, with luck, communicate – the beauty of scientific theories without fully understanding the complex math, chemistry or physics upon which they are based, thus keeping one’s head from hurting too much.
5) The presence of readers who are co-creators, and writers who co-evolve and sometimes converge – in the blogosphere and beyond.
6) The fact that the beauty- and symmetry-obsessed Navajos, well in advance of J. B. S. Haldane, gave primacy in their creation story to the Air-Spirit People – insects. Long before anything else stirred,
Yellow beetles lived there. Hard beetles lived there. Stone-carrier beetles lived there. Black beetles lived there. Coyote-dung beetles lived there. … Whitefaced beetles made their homes there…
7) The pear tree behind my house, which this year turned a wondrous shade of orange instead of its usual dingy yellow.
With beauty before me, I walk.
With beauty behind me, I walk.
With beauty above me, I walk.
With beauty below me, I walk.
With beauty all around me, I walk.
It is finished in beauty.
It is finished in beauty.
(Navajo chantway refrain)
Words on the street
String theories
I’m reading Paul Zweig. This is the thirteenth poem in the third (“Eternity’s Woods”) section of his Selected and Last Poems, followed by my response. See here for details on this experiment in responsive reading.
Anything Long and Thin
by Paul Zweig
All traffickings upward out of the earth
Or sideways across it: longitudes,
Desperations; the glue of sentences . . .
[Remainder of poem removed 11-18-05]
* * * *
Living On
Consider what one might learn
by meditating on a corpse:
how the flesh can crawl, the bones
of a beautiful face break
the crust of fantasy like little moons
out of the ground, vacant snail-shells
still glistening with an off-white rheum.
Or consider swallowing two squares
of LSD & looking in the mirror:
what perfectly disintegrating visions
might be yours, & with what slight effort.
It’s exhilarating, really, to find this
blind matter – that it somehow coheres
despite its utter insensitivity to longing
or loneliness. It gives itself
only half-grudgingly to the chance
mouths of the shark or the brown bear.
True horror comes disguised
as cold necessity: learning about cells
in the fourth grade, our bodies began
to dissolve into prisons
or office towers populated by soft-
walled cubicles. Then atoms:
solar systems with pin-prick suns,
barely enclosed eternities
of inner space. The schoolroom clock
made a mockery of turning.
To know that emptiness, they suggested,
was to know ourselves. They could have said
that matter is incredibly rare,
a temporary resting state for energy.
They could have told us
about fictons, their mad spinning
that somehow keeps the lover’s caress
from encountering a null set,
bodies collapsing into a shrug
of cold fusion. What a comfort
it would’ve been, maybe,
to learn about the stubborn corpse
rippling outward for millions of years,
if only in bone shards or a line
of footprints in some fossilized beach
that come to a sudden end: indelible
record of buoyancy, & the killer wave.
__________
For more on fictons, see here. Please note, however, that I mean something different from Robert Heinlein, whose fictons inhabited a thoroughly Newtonian, narrative space. My fictons are massless and carry a negative charge.
Words on the street
Gleaning
Yesterday afternoon, I picked and ate a ripe cherry tomato from my garden. For those who shuddered at my report of an early snowstorm two weeks ago, the real news here is the unprecedented lateness of a frost. Those white shooting-stars that were bent down by the snow? They’ve put out new blossoms.
It’s hard what to know what to make of it all, but this much I can tell you: the tomato was delicious.
Deep in the weeds,
the wrong shade of red for autumn:
last ripe tomato.
Words on the street
Ash fruits
An impressionistic review of the article “Night of the Growing Dead: A Cult of Virabhadra in Coastal Andhra,” by David M. Kline, in Criminal Gods and Demon Devotees: Essays on the Guardians of Popular Hinduism, edited by Alf Hiltebeitel and published by State University of New York Press in Albany, 1989.
A cobra moves into the termite mound, which has grown tall & full of turrets, like a Disneyland of dirt. The villagers build a shrine around it as a home for orphaned spirits, who inhabit large, gray, egg-shaped fruits that the potters fashion out of tree semen & the ash from burnt cow dung. Those who could not be burned are jealous of ashes.
And the ash fruits grow, year after year. They swell with offerings – the rounded towers of rice – having no way to take a shit. Every dead thing resembles a fruit, the sum of long-ripening actions. But these ones, with all chance of future action cut off, ripen only in their rage.
They are the pills too bitter to swallow, the gray implacable grief that drives every cycle of violence. The deaths of innocents violate the law of the universe, so the world must burn. The spine of Sati crumbles in the funeral pyre & God smears her ashes all over His skin, as sealed off now as a stone in these avatars of ash.
One night a year when they travel in procession to the river to be dipped & blessed, they can seize anyone by the throat – an onlooker, or their own former mother – & make him or her throw up the indigestible pits of their words. Which, however disjointed, always add up to a single, non-negotiable demand: more life.