Hybrid Vigor

Opinion by Holly Moeller
Oct. 30, 2013, 1:40 a.m.

FREDERICTON, CANADA — If there’s one thing I love and hate about biology, it’s that it is so very complicated. One of the things that makes it so complicated is sex.

Yes, those of us in the dating world — and, frankly, engaging in any sort of interpersonal interactions — know all about how sex complicates matters socially. But in this case, I’m thinking of the fact that sex likely evolved because, sometimes, it’s better when things are complicated.

Sex allows organisms to rearrange their genes when making the next generation. As anyone with biological siblings knows, the children born to a set of parents share a lot of traits, but each has a unique subset of them inherited from each parent.

Sex is risky: It leaves the assembly of these traits to chance. The offspring born to a particular partnership can run the gamut from particularly “fit” (the technical term that biologists use to say that an organism is well-suited to its environment and likely to survive and leave a lot of offspring itself) to weak and sickly.

One way that sex can make offspring particularly fit is through the phenomenon of “hybrid vigor”. Imagine two prospective parents, each with their own set of positive and negative attributes.

For example (familiar to many plant breeders), a wheat plant that is especially high yielding, and another wheat plant that is very short in stature. Their hybrid offspring (which formed the foundation of the “Green Revolution” that supplies much of our current food supply) don’t waste energy growing big, tough stalks, but rather invest all their efforts in producing big, hearty wheat kernels for human consumption.

Obviously, “vigor” can be measured in various ways — from the strictly biological definition of fitness (reproductive success) to various measures specific to human needs (like the production of those ears of corn).

Another example of hybrid vigor is sickle cell anemia. Humans with two copies of the sickle cell trait are very sick, humans with two copies of the alternate trait are vulnerable to malaria, and humans with one copy of each are, as Goldilocks would say, “just right.”

And, hybrid vigor doesn’t just apply to the biology of sex.

I’ve spent the last few days surrounded by scientists of both American and Canadian persuasions, at a workshop focused on how we should manage the precious resources contained in our freshwater and marine ecosystems. The main message that came across in four days of lectures and discussions was that we’re going to need a lot of hybridization.

Indeed, all of the scientists at the workshop — including me — were hybrids ourselves, using mathematical tools to solve biological problems. Fisheries, which were a major topic of interest, are particularly amenable to such combined approaches.

Their assessment requires biologists (to count fish, calculate growth rates, and determine habitat quality and needs) as well as mathematical modelers (who have been particularly successful at calculating things like maximum sustainable yield and appropriate harvest rates).

The more I work on mathematical ecology problems, the more I’m struck by the importance of hybrid vigor in this field. Many of the most prolific scientists trained in fields like physics and applied mathematics before turning their attention to biological problems. By applying the skills and techniques they’d learned in their previous work, they’ve often had great success at understanding and modeling biological problems.

When it comes to fisheries, of course, the process doesn’t stop with the combination of math and biology.

The scientific assessment is merely the first step in the management process. Regardless of what those in the ivory tower may have to say, fisheries can’t be regulated without the participation of political and social leaders. Which means that scientists like me have to think about other ways to hybridize.

For me, that often involves trying to bridge the gap with economics. For others, it means developing new monitoring and predictive tools that are quick and easy for busy managers to learn to use.  And if we reached one conclusion at our workshop, it’s that there’s still plenty of hybridization work to be done.

While this knowledge is overwhelming (and, frankly, terrifying), it’s also very exciting. After all, this is why I went into ecology — the study of how plants and animals interact with each other and their environment is about as broad and complicated a field as I can imagine.

It’s a field full of tough problems with global implications, and we can’t make scientific progress working in isolation. Ecologists have to be experts in their own focal areas, and experts in knowing how and when to turn to others for expertise.

Frankly, I can’t imagine anything better than this sort of hybridization: fixing the world, and making friends while doing it.

Holly welcomes questions, comments, and vigorous discourse via email at hollyvm ‘at’ stanford.edu

Holly is a Ph.D. student in Ecology and Evolution, with interests that range from marine microbes to trees and mushrooms to the future of human life on this swiftly tilting planet. She's been writing "Seeing Green" since 2007, and still hasn't run out of environmental issues to cover, so to stay sane she goes for long runs, communes with redwood trees and does yoga (badly).

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