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Caterpillar evolves to survive in cornfields

One thing about evolution: You never know what’s going to influence it. Take the European corn borer, for instance. Researchers have just made a strong case that a certain aspect of its behavior has evolved because of human harvesting of corn.

The corn borer, Ostrinia nubilalis, is a pest caterpillar that feeds on a corn stalk before spinning a cocoon for the winter. It is almost identical to the species O. scapulalis, whose host plant is not corn, but a weed called mugwort.

In a paper in The Proceedings of the Royal Society B: Biological Sciences, biologist Vincent Calcagno and colleagues show that, behaviorally, that makes all the difference in the world. For mugwort is neither harvested nor grazed, while corn has been harvested for centuries.

In harvesting, the stalks are cut off some height – often 6 to 15 inches – above the ground. Any corn borers above that height will die when the stalks are harvested. The researchers discovered that before it stops eating and spins its cocoon, the corn borer travels down the stalk, usually reaching a height at which it is safe. O. scapulalis does not exhibit this descending behavior.

Origami-style pollen

After it’s released from a flower’s anther, a pollen grain walks a humidity tightrope. It dries up a bit as it travels through the air, the cellular material inside becoming dormant so it survives until it reaches the humid environment of another flower’s stigma. But it can’t become so dry that the material dies.

So pollen grains fold in on themselves, reducing the rate of water loss. It’s an elegant trick, and the structure of the pollen grain wall determines how it occurs, according to research published in The Proceedings of the National Academy of Sciences.

Eleni Katifori, previously at Harvard and at Rockefeller University, and colleagues studied the folding of pollen from lilies and other flowers. Katifori said the goal of the research was to discover the basic principles by which the folding occurs as a way of understanding some of the functional demands that drive the great diversity of pollen grain structures in nature. But she said the work might also prove useful to those who design structures. “I could imagine that engineers could get inspiration from just looking at pollen grains,” she said. New York Times

A purposeful cannibal

It’s a fact of life in the animal world that some fish (and other creatures) eat their young.

The three-spined stickleback, a species found around much of the globe, is one such finned cannibal. The males, who care for the eggs, are known to devour whole or parts of clutches. Sometimes, however, they might have reason to. Since sticklebacks are known to “sneak” fertilizations, another fish might be the father of some of the eggs. A study by Marion Mehlis of the University of Bonn in Germany and colleagues looked at whether a male stickleback somehow assessed the paternity of the eggs in its care in deciding whether to eat them.

As they report in The Proceedings of the Royal Society B: Biological Sciences, the answer was yes. What’s more, the researchers found that the fish made fairly fine-tuned decisions.

The researchers manipulated the clutches that individual males cared for, replacing up to 100 percent of the eggs fertilized by the male with eggs fertilized by another male. They found that the higher the percentage of “alien” eggs, the more likely the male was to completely cannibalize the clutch. New York Times

http://www.charlotteobserver.com/2010/05/03/1412088/science-briefs.html#ixzz0mr8s9Xh5