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It's happening right before our eyes!

11/29/2013

By JON HAUXWELL

Special to the HDN

When Charles Darwin observed the deep-throated star orchids of Madagascar, he predicted that a pollinator with a very long tongue must exist. He took a lot of ribbing over this leap of -- well, not faith, but careful extrapolation of prior observations.

After Darwin's death, hawk moths were discovered on Madagascar with tongues that perfectly matched the star orchids' nectar spurs.

Hawk moths, or sphinx moths, co-evolved with orchids, which Darwin had studied extensively. Some species can unfurl a tongue up to 14 inches long.

Co-evolution is a well-recognized phenomenon. When variations spontaneously arise in one species, another species that interacts with it is presented with a new "selective pressure." If the variation in a flower produces a deeper nectar well, only those moths with longer tongues can access that food source. They're more likely to survive to reproduce, and eventually this type will dominate the moth population.

Co-evolution produces biological arms races too. The "old" version of rabbit isn't any more likely to become coyote food than it ever was; but the "new," faster rabbit is less likely to get caught. The coyotes that are fast enough to catch the new rabbit will, in turn, come to dominate the coyote population in time, and the race continues.

Jaws and teeth versus armor. Speed versus speed. And long tongues, deep flowers. The race isn't always adversarial -- both moth and flower profit from their arrangement.

While we usually think of evolution as a process that spans millennia, sometimes it emerges in a generation, right before our eyes. This is certainly true of camouflage.

When I saw this motionless moth, posturing oddly on a sunflower blossom, I was slow to notice the yellow spider that had paralyzed it.

The color match was almost perfect -- too perfect for the moth! How did the spider "find" the perfect background? Its species has "evolved to evolve" -- that is, it generates lots of variations, and some will be advantageous, given the right environment, or an empty "niche."

A couple years ago when I was cleaning around my outdoor cold frame, I discovered a colony of moths that were inky black, just like the exterior of the cold frame. They otherwise looked very much like the "millers" that create dust storms around bright lights in the spring. I've never seen these black ones, before or since.

If they're not a distinct species, this colony could've arisen from an individual moth parent, via a mutation in a single gene, or gene complex, that controls coloration. If the momma moth whose eggs carried this mutation laid them on a variety of surfaces, the ones on the black background will resist predation better than grey-brown ones.

Complex changes can arise from a single mutation. Modern whales still carry the gene for legs, but it's usually "turned off."

When by chance this gene is turned on -- "expressed" -- the offspring will be a whale with actual legs, just like their land-dwelling ancestors.

Set aside the fossils and molecular genetics for the moment, if you will. We can still see evolution at work in our everyday world, every day, if we pay attention. Just stop and smell the, ah, sunflowers.

* Photos by Jon Hauxwell