Science Watch Site

My science writing course from this past semester has created a website of our work, including a series of blog entries chronically our class trip to the National Association of Science Writers conference in Palo Alto, CA last October. The site, know as Science Watch, is now available for public viewing. Check it out!

Honeybee bodyguards

Honeybees are extremely important for their role in plant pollination. Plus, they produce honey, that delicious childhood staple and one of man’s oldest sweeteners. But new research suggests another role for the buzzing bug: ?

A new study led by Jürgen Tautz of Biozentrum Universität Würzburg, Germany suggests that honeybees may be inadvertently serving as bodyguards for the plants they pollinate.

Caterpillars are one of the world’s most notable herbivores. The live on and around plants until they metamorphose into their adult form, and they eat leaves almost continuously. These ‘eating machines’ can consume enough to increase their bodyweights ten thousand fold in just a few months! (For those of you questioning my use of an exclamation point here, that’s equivalent to a human baby growing to the size of a tractor trailer in the same amount of time.)

One of caterpillars’ primary predators is the wasp. As wasps approach their prey, their beating wings generate air vibrations, which caterpillars can detect with small sensory hairs that cover their bodies. When they ‘hear’ an approaching wasp, the caterpillars will either stop moving or drop from the plant in an attempt to avoid detection.

Honeybees coming to pollinate the plants on which the caterpillars are feeding produce similar air disturbances to wasps that can stimulate the caterpillars’ sensory hairs. Because the caterpillars cannot distinguish between the two flying insects, they respond similarly to the approach of a honeybee, either stopping or dropping. In either case, they stop eating.

The recent study set up two tents that contained either 10 bell pepper or 10 soybean plants. In each tent, they introduced 10 beet armyworm caterpillars. The difference: one tent was connected to a beehive and included two feeders filled with a sugar solution while the second was bee-free. The result: the plants in the bee-filled tent sustained between 60 and 70% less damage. The implication: we may have stumbled upon a brand new way to defend our crops against leaf-eating pests.

So for the plants, honeybees appear to be efficient bodyguards: powerful in numbers and a heck of a lot more affordable than Kevin Costner. For us, they may prove to be a natural and affordable method of biological control.

Notes:

For more information on the study:

Tautz, Jürgen and Michael Rostás. (2008). Honeybee buzz attenuates plant damage by caterpillars. Current Biology (18) 24: 1125-1126.

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The Science of Santa

For all of you trying to cling to a belief in Santa Claus or rekindle the magic that your parents stole from you as a kid when they told you that ‘Santa isn’t real,’ here’s the story of one scientist who avidly defends the possibility that one man can indeed make toys for all the children in the world and deliver them across the globe in a single night. Dr. Silverberg claims that with a combination of nanotechnology, genetic engineering, and a handful of other scientific advances, the story of Santa may be more than a children’s tale after all.

Read more and watch videos of his interview with Discovery Canada at Dr. Silverberg’s webpage.

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Stop BUSHwhacking science

The Bush administration has instilled a lot of doubt in Americans (and the rest of the world) on a variety of issues. But one of the often overlooked blunders of Bush’s reign is its science policy and its tendency to manipulate and even ignore the evidence. Journalist Seth Shulman’s book “Undermining Science: Suppression and Distortion in the Bush Administration” addresses this ‘perpetuation of misinformation.’ For a shorter summary, read Olivia Judson’s thoughts on the importance of science and how Bush got it all wrong.

Sizing up sex

I had been back from India for less than 24 hours, and already science was coming at me from every direction. Ahh, it was good to be home.

Just before 9am the day after returning to the States, I stumbled into a quaint, little house on the north end of campus, home to the CISAB (Center for the Integrated Study of Animal Behavior). This morning was one of our monthly breakfasts, where graduate students, postdocs, and faculty from a handful of different departments gathered to discuss something relating to the theme of ‘reproductive diversity’ (i.e., sex). These were informal events, supplemented with plentiful coffee and pastries, so I decided to make the trip despite the jet-lag that had yet to release me from its groggy grasp.

Peter Cherbas was today’s speaker. Professor of Informatics here at Indiana University and director of the Center for Genomics and Bioinformatics, he had come to talk with us about the recent advances in biotechnology. Maybe it was a product of the season, but with his grayish white hair and beard and his enthusiasm for the science, I couldn’t help but imagine him as Santa Claus’ well-groomed, younger brother.

Cherbas excitedly breezed through the basics of modern molecular techniques, which I will spare you here. But partway through his whirlwind oration, he mentioned something that caught my attention.

“Facultative sex gets evolutionary biologists excited,” he said. Facultatively sexual organisms sometimes reproduce sexually and sometimes asexually. He was segueing into one of biology’s most recent model systems, Daphnia (a facultatively sexual organism), but he was hitting on one of the major mysteries of evolutionary biology: why did sexual reproduction evolve?

At first glance, sex appears quite disadvantageous. (To evolutionists, that is. I have no doubt that any of you could easily compile a lengthy list of the benefits of sex.) First, there’s the cost of finding a mate, something I’m sure we can all relate to. While most of the animal kingdom may be far less picky than us humans, it still seems a helluva lot easier to just clone yourself than go through all the trouble of finding, seducing, and possibly raising offspring with another individual.

Second, if we were to reproduce asexually, we would simply be creating complete clones of ourselves. This means, we pass on our entire genome to our offspring. And after all, passing on genes is the primary goal of reproduction. As it is, we reproduce sexually, which means we package only half our genomes into our gametes (eggs for females, sperm for males). To create our progeny, our gametes must fuse with the gametes of another individual, thus passing on only half of our genes to each child. Often called the two-fold cost of sex, this is a pretty significant disadvantage in terms of our evolutionary fitness in the game of natural selection, Survival of the Fittest.

Think of it this way. If there is a group of organisms, some sexually reproducing and some asexually reproducing, each generation the asexual reproducers will pass on at least twice as many genes as their sexual counterparts. Thus, their genes, including the one for asexual reproduction, will spread more quickly through the population. In other words, the asexual outcompete the sexual such that sexual reproduction seemingly could not evolve to the prominence in which we see it in plants and animals today.

So how did sex evolve and why is it so common today? The best way to answer these questions is to examine a species that sometimes reproduces sexually and sometimes reproduces asexually and look at what the environmental conditions are like during the times of each mode of reproduction. Hence the importance of Daphnia that Peter Cherbas was getting at this morning.

A recent study does just that. By raising sexual and asexual Daphnia either together or separated by strain, scientists at Indiana University identified a benefit to sexuality: superiority in competition. When raised in isolation, the asexual lines had greater reproductive success than the sexual ones, as predicted by theory. However, when raised in competition with each other, the sexuals outcompeted the asexuals for food and produced more female offspring. (In Daphnia, female offspring are counted as the measure reproductive success because males cannot reproduce asexually.)

Thus, under at least some environmental conditions, reproducing sexually may be so beneficial in some ways that it outweighs the inherent costs sexual reproduction. So whether it be rearing conditions, as in Daphnia case, or $4 pitchers at the local pub, the environment most likely played a major role in the evolution of sex.

Notes:

Two common theories of the origin of sex:

Numerous hypotheses have been put forth by even more scientists, but two still stand out as the ones worth mentioning in an introductory evolution class. The first states that because our DNA is constantly acquiring mutations, many of which are harmful to our ability to survive and reproduce, we need a way to purge our genome every so often. If we simply cloned ourselves from generation to generation, the mutations would accumulate and the result could be disastrous. This theory regarding the ratcheting of deleterious mutations from the genome is aptly called Muller’s Ratchet.

The other common hypothesis for the origin of sexual reproduction is called the Red Queen Hypothesis. We are in a constant evolutionary arms race with the parasites that plague us. Viruses and parasitic microbes are evolving at an extraordinary pace to be able to overcome their hosts’ (our) defenses and successfully infect and reproduce. The constant pharmaceutical battle between these evolving parasites and our developing drugs is a well-known example. The Red Queen Hypothesis states that the genetic diversity generated by sexual reproduction is necessary to give sexual organisms a leg up in this evolutionary war.

For more on the recent Daphnia experiment:

Wolinska, Justyna and Curtis M. Lively. (2008)The cost of males in Daphnia pulex. Oikos 117: 1637_1646.

For more on the evolution of sexual reproduction.

For more on Daphnia.

Also, see Erika Check Hayden’s article Scandal: Sex-starved and still surviving for a great review of rotifers, the world’s only ancient asexual organism.

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