Monday, July 25, 2011

Evolution in New York City

In today's New York times there is an article that uses New York City as an example of how large urban areas act as selective pressures that propel the process of evolution. What they report seems surprising, but makes complete sense if you consider that it is consistent with both evolution and punctuated equilibrium. For example:
The researchers inspected 50 traps laid the day before and found seven mice inside. They plopped each mouse out of its trap and into a Ziploc bag. They clipped a scale to each bag to weigh the mice. Dr. Munshi-South gently took hold of the animals so his students could measure them with a ruler along their backs.

Dr. Munshi-South and his colleagues have been analyzing the DNA of the mice. He’s been surprised to find that the populations of mice in each park are genetically distinct from the mice in others. “The amount of differences you see among populations of mice in the same borough is similar to what you’d see across the whole southeastern United States,” he said.
Consistent with what the Hardy-Weinberg principle suggests, this example of Cadmium resistant worms shows how large randomly mating pairs will eventually result in stasis:
In 1989, Jeffrey Levinton of Stony Brook University and his colleagues discovered that a population of mud-dwelling worms in the Hudson had evolved resistance to cadmium. They lived in a place called Foundry Cove near a battery factory near West Point. Dr. Levinton and his colleagues found that the worms produced huge amounts of a protein that binds cadmium and prevents it from doing harm.

In the early 1990s, the federal Environmental Protection Agency hauled away most of the cadmium-laced sediment from Foundry Cove. Over nine generations, the Foundry Cove worm populations became vulnerable again. This shift occurred, Dr. Levinton and his colleagues reported last year, as worms from less contaminated parts of the river moved in. They are interbreeding with the resident worms, and the resistant mutations are becoming rarer.
Lastly, the article shows why it is not necessarily always a good idea to be a germophobe:
Evolution is not just taking place in New York’s rivers and parks. It’s also taking place inside its hospitals. In 1997, Dr. John Quale, an infectious diseases physician at SUNY Downstate Medical Center, discovered a newly evolved strain of bacteria in the city that is resistant to most

The bacteria, known as Klebsiella pneumoniae, is often found in hospitals, where it can cause pneumonia and other life-threatening infections. Doctors typically treat Klebsiella with an antibiotic called carbapenem. Dr. Quale and his colleagues discovered carbapenem-resistant Klebsiella in four hospitals in Brooklyn. The new genetic recipe proved to be a winning solution. Dr. Quale’s surveys charted the strain as it spread from hospital to hospital throughout New York. “It’s one strain that’s adapted very well to the hospital environment, and it clearly has a survival advantage over other bacteria,” Dr. Quale said.

Once the new strain had established itself in New York, it began to spread out of the city. It’s now reached 33 other states, and has become a serious problem in other countries including France, Greece, and Israel.
Dr. Quale and his colleagues found that this new strain of Klebsiella is especially dangerous. About half of patients who get infected die. Doctors can cure some infections, but only by using toxic drugs that can cause nerve and kidney damage.
To read the entire article, CLICK HERE.

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