Evolution in the cities

You do not have to go to exotic places like Charles Darwin did to find evidence for evolution. In an article titled Evolution right under our noses, Carl Zimmer says that Manhattan and its surrounding areas are rich in examples, such as mice responding to urban stress, fish in the Hudson river responding to pollution by becoming resistant to PCBs, worms becoming resistant to cadmium, and so on.

Cities attract only a small fraction of evolutionary biologists, who often work in lusher places like the Amazon. But urban evolution is attracting more research these days, because cities are fast-growing, and the urban environment is quickly taking over large areas of the Earth’s surface.

Biologists find a mixture of native and non-native in all the life forms they study in New York, from the trees in Central Park to the birds of Jamaica Bay. The biodiversity of New York today is the result of extinctions, invasions and adaptations. Manhattan was once home to 21 native species of orchids; today they’re all gone. In the current issue of Global Ecology and Biogeography, a team of scientists surveyed plant biodiversity in New York and 10 other cities. They found that 401 native plant species have vanished from New York since 1624, while 1,159 remain. New York’s native flora is vulnerable to extinction today in part because it was well adapted to the closed forests that once stood where the city is now.

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