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Wednesday, June 21, 2006

'Niches' and Adaptive Innovation

It's interesting to think of this article about why evolution progresses at different rates both over time and across regions in terms of how competition among firms for survival drives innovation in a competitive marketplace. The term 'niche' as used below would be, for example, an industry where firms are earning greater than normal profits, or a profitable market opportunity that has not yet been exploited:

No Vacancy, No Evolution, Evolution 101, by Olivia Judson, Commentary, NY Times: Yesterday, I claimed that a major reason large evolutionary changes often don’t happen is that competition from the creatures around you stops you from changing. In other words, in environments that are already rich in different species, natural selection often prevents large changes. My piece of evidence for this was a claim that, when you take other organisms away — when you reduce competition for food, or space — evolution explodes. Today, I want to examine the truth of these claims more closely.

I want to start with a question: Why aren’t there more insects in the sea? Insects, after all, make up the bulk of all known animal species — most animals are insects — yet hardly any insects live in the sea.

It’s not because of the water. Many insects live in freshwater for at least part of their lives. Think of mayfly nymphs, or caddis fly larvae... Or think of water striders, skating along the top of a pond... Could it be the salt? No. Brine fly larvae live in the Utah’s Great Salt Lake. Some mosquito larvae do fine in salt, too — they can even live in the hypersalty Dead Sea. ...

I put it to you that the reason so few insects get beyond rock pools or dip their toes beneath the low tide mark is that the niches they would occupy in the ocean proper are taken already. Crabs, lobsters, shrimp, barnacles, water fleas (which are ... little crustaceans) and company have got all niches covered. My prediction — which I hope we won’t be testing — is that if all the crustaceans were wiped out of the oceans, insects would move straight in.

My prediction rests on the fact that it is typically difficult to evolve to occupy a niche that is already full. An invader must be better at exploiting the niche than the current occupant, who has already evolved to make effective use of it. By contrast, when a niche is empty — when seeds are falling to the ground and no one is eating them, say — it doesn’t matter if, at first, an animal is a bit inept at finding and opening the seeds.

Consistent with this idea is the observation that when new niches open up — perhaps because new islands or lakes or cave systems have formed, or because an asteroid has hit the earth and eradicated millions of species — the first organisms to become established in the new environments evolve quickly and reliably into all sorts of new species. This phenomenon is known as adaptive radiation.

Newly erupted islands are famous for this. Over and over again, archipelagos see explosive bursts of evolutionary change and the rapid appearance of species found nowhere else. New Zealand is full (and was fuller) of an amazing array of unique flightless birds... Hawaii has an abundance of unique fruit flies, spiders, silverswords ... and birds. Madagascar has all manner of lemurs... And everyone knows about the Galápagos.

Rapid bursts of evolution can also happen in new lakes... Indeed, right now, the great lakes of tropical Africa are the backdrop for the fastest known radiation of vertebrates, the cichlid fishes. Lake Victoria, for example, appears to have dried up and then refilled around 14,600 years ago. Since then, perhaps 500 different species of cichlid have evolved... Lake Victoria has cichlids that eat algae, cichlids that eat other cichlids, cichlids that eat fish eggs — cichlids, in short, that have evolved to eat everything that can be eaten. Some fish live in shallow water; others prefer the deeps...

Ideas about adaptive radiation can also be tested in experiments. ...[M]any bacteria can whiz through hundreds of generations in a month. This makes it relatively easy to use bacteria to look at radiations. Here’s what you do. You create two sets of environments, one simple, and one complex. The complex environment might have several different places to live, or a variety of sources of carbon. The simple environment has just one habitat or foodstuff. Then, since bacteria reproduce asexually, you take genetically identical individuals, and release them into the two different environments. Sure enough, mutations happen, and the bacteria rapidly evolve to exploit the different niches. After a month, you will find that bacteria from the complicated environment have become genetically diverse. Those from the simple environment, in contrast, remain unevolved.

In short, empty niches are a license for evolutionary change. Once the new niches are full, natural selection acts to stop further change, and the rate of evolutionary change slows. Fossils, islands and test tubes — they all show the same dynamics. ...

This impliess that it is not competition per se that produces rapid innovation, but competition coupled with emergent profitable 'niches.'

    Posted by on Wednesday, June 21, 2006 at 03:51 PM in Economics, Science, Technology | Permalink  TrackBack (0)  Comments (18)


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