Evolution in the City

July 26, 2011 • 9:31 am

by Greg Mayer

Carl Zimmer has a nice piece in today’s New York Times on studies of evolution-in-action in a variety of species in New York City. Researchers have found that the fragmentation of natural and even artificial habitats by urbanization has led to genetic isolation and differentiation, and also adaptation to the urban environment. For example, Jeff Levinton of SUNY Stony Brook has found that a worm in the Hudson near West Point evolved resistance to the toxic metal cadmium. Following a cleanup, the worms have reduced resistance, due to gene flow from surrounding populations that had not been exposed to cadmium.

Desmognathus fuscus from Highbridge Park, Manhattan. Damon Winter/New York Times.

This is a dusky salamander from Manhattan. They’re pretty small, less than a handful; about a spoonful, I suppose. John Kieran in his classic book thought it “the most common salamander within the city”. They’re known from the Bronx, Manhattan, and Staten Island, but I know of no definite records for Long Island (which includes Brooklyn and Queens). Mike Klemens of the American Museum of Natural History did not find them in surveys of Central Park, so I was surprised to see they are holding on in other parts of Manhattan.


Bishop, S.C. 1941. The salamanders of New York. New York State Museum Bulletin 324:1-365.

Gibbs, J.P., A.R. Breisch, P.K. Ducey, G. Johnson, J.L. Behler and R.C. Bothner. 2007. The Amphibians and Reptiles of New York State. Oxford University Press, New York.

Kieran, J. 1959. A Natural History of New York City. Houghton Mifflin, Boston.

Klemens, M. 1982. Herpetofaunal Inventory of Central Park. MS report, American Museum of Natural History.

10 thoughts on “Evolution in the City

  1. Thanks for posting this! Urban evolution has fascinated me since my senior year of college. Now I am studying urban cricket frog calls, comparing them to calls from less noisy environments.

  2. Thanks for the link love. I ended up cutting out the material on the salamanders from my article, which was painful–encountering a population of these critters around a spring in a Washington Heights park (where they’ve been for at least fifty years) was a magical moment.

  3. Sorry, Jerry, but your trick is easily overcome by pressing Ctrl-A to highlight all text. Firefox then displays the highlighted text in perfectly legible colors.

    As for adaptation to urban conditions: The bald eagle, a notoriously skittish critter, is recolonizing most of North America since DDT was outlawed and has gradually gotten out of the food chain. In the process, bald eagles have become more tolerant of the disturbances associated with urban life: vehicular and aircraft noise, and so on.

    The web cam at the Patricia Bay, BC, eagle nest (billed as Sidney, BC by the folks who operate it, the Hancock Wildlife Foundation) regularly shows small commuter aircraft coming in for a landing not too far behind the nest. Lots of loud noise, but the adults don’t turn a feather.

    One enthusiast has spent a great deal of time and energy photographing them, including from the ground around the nest, but also on the nearby beach, where he puts out “treatz” for the birds. He has commented that they remain quite skittish if he goes near the nest tree, even though (he believes) the adults recognize him as the nice guy who puts treatz out for them on the beach. Note that the nest is a good hundred feet up at the top of the tree.

  4. Get the sequence of the metallothionein from those resistant worms! Or is it a regulatory phenomenon of overproduction?

  5. I wondered if the mice you can spot on the London Underground are any different from their house dwelling cousins but I suppose they are not isolated enough to stop gene flow.

    I would have thought that sea levels rose too fast for the salamanders to reach long Island after the last glaciation, as with snakes in Ireland? Is Long Island deficient in other species of amphibian or reptile? I was unable to find any web page in a very quick scoot of the interweb about what wildlife the Island has/had.

  6. Thanks for the post. I’m one of the scientists interviewed in the article. We are working on the population genomics of white-footed mice in NYC, but also doing a smaller study on conservation genetics of urban dusky and two-lined salamanders (that is my collaborator, Ellen Pehek’s, hand holding the dusky above!). One side note: metallothionein is one of the gene families that may be under selection in NYC white-footed mice (although the result is preliminary at this point).

    The dusky salamander is only found in Manhattan in Highbridge park in two tiny seepages; one north and one south of the GW Bridge. There are several extant populations on Staten Island that we have sampled, but none existing in Queens, Brooklyn, or the Bronx that we know of. Mike Klemens found one dusky population in the northeastern tip of Westchester Co., but we couldn’t find them this Spring (will go back again, and sample a CT population if necessary). There is one population at the Watchung Reservation due west of the city, and perhaps some in the Palisades.

    The two-lined salamander is not in Manhattan, but has a few populations in Queens, one or two in the Bronx,several on Staten Island, and a few in Nassau Co., Long Island. Brooklyn doesn’t have much…there aren’t even red-backed salamanders in Prospect Park anymore.

  7. An example of recent adaptation to urban habitat?

    I’ve noticed a habitat expansion in the Black Phoebe in southern CA. In the 70s they were strictly associated with open water — pond and canal margins, for example, and hence were largely rural. Sometime in the 80s they began to appear around irrigated lawns, with no standing water present. Today they are a common urban bird in parks and yards.

    I wonder if there may be a genetic basis for this rapid change. Was it a variant genotype, one that didn’t insist on having a pond nearby, that was able to spread and occupy the vast open niche of suburbia? Or, maybe it’s just that some birds learned that lawns have good chow and taught their offspring.

    Evolution vs. education?

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