Urban Evolution Map
Illustration: Casey Chin01__EVOLVING IN A CITY NEAR YOU__: Scores of evolutionary biologists are now investigating how city-dwelling creatures have adapted to life among buildings, traffic, and discarded Big Macs. These are some of the most intriguing urban evolution studies to have emerged in recent years. —B.I.K.
Illustration: Casey Chin02**WESTERN FENCE LIZARD** (*Sceloporus occidentalis*): **Los Angeles, California** - Lizards in the most intensely developed parts of Los Angeles have fewer dorsal scales than their rural counterparts. The adaptation is believed to help them cope with the “urban heat island effect,” which makes cities several degrees hotter than their surroundings.
Illustration: Casey Chin03**WESTERN BLACK WIDOW** (*Latrodectus hesperus*): **Phoenix, Arizona** - Urban spiders produce smaller eggs but in far greater numbers than country spiders. The adaptation, possibly linked to genetic changes in the ovaries, seems designed to maximize reproduction in a high-mortality environment.
Illustration: Casey Chin04**ACORN ANT** (*Temnothorax curvispinosus*): **Cleveland, Ohio** - City ants possess a unique ability to thrive in high temperatures, perhaps due to genetic changes that facilitate the manufacture of stress-managing proteins triggered by heat.
Illustration: Casey Chin05**COYOTE** (*Canis latrans*): **Denver, Colorado** - Coyotes in the city are unusually bold and prone to exploratory behavior. Genes for boldness may have been selected over time, because these coyotes need to draw close to humans to obtain food.
Illustration: Casey Chin06**WATER FLEA** (*Daphnia magna*): **Brussels, Belgium** - Water fleas in urban ponds mature at a much faster rate than their peers in rural ponds. This allows them to produce offspring at a younger age and thus perpetuate their populations in high-stress cities where the mortality rate is high.
Illustration: Casey Chin07**ERMIN MOTH** (*Yponomeuta cagnagella*): **Basel, Switzerland** - Moths in urban settings have lost much of their species' genetic attraction to light. This means fewer urban moths perish by flying into hot light fixtures.
Illustration: Casey Chin08**CREEK CHUB** (*Semotilus atromaculatus*): **Raleigh, North Carolina** - Sparse vegetation surrounding urban waterways allows runoff to pour in at a furious rate; creek chubs in Raleigh have evolved body shapes that can help them withstand these faster currents.
Illustration: Casey Chin09**NORTHERN HOUSE MOSQUITO** (*Culex pipiens*): **London, England** - Mosquitoes that reside in the London Underground do not hibernate and can breed in confined spaces, unlike the aboveground members of their species. Some biologists believe the “London Underground mosquito” is actually a distinct species, since it has trouble breeding with other populations.
Illustration: Casey Chin10**FERAL PIGEON** (*Columba livia*): **Paris, France** - Dark feathers are the rule among pigeons in cities, likely because melanin is effective at sequestering toxic metals that abound in urban environments—especially zinc and possibly lead.
Illustration: Casey Chin11**FERAL PIGEON** (*Columba livia*): **New York, New York** - Pigeons in New York City seem to have the ability to tolerate high-sugar diets without developing hyperglycemia.
Illustration: Casey Chin12**GROVE SNAIL** (*Cepaea nemoralis*): **Leiden, the Netherlands** - Urban snails tend to have yellow shells with dark underbands, as opposed to the pink shells that predominate in the countryside. The adaptation is thought to aid in thermal regulation. Data on shell color was gathered by 1,200 citizen scientists who downloaded the SnailSnap app.
Illustration: Casey Chin13**CRESTED ANOLE** (*Anolis cristatellus*): **San Juan, Puerto Rico** - In cities, these lizards have longer limbs and larger toe pads than ones from Puerto Rico's rain forest. The adaptation makes them faster on flat surfaces and thus more apt to escape predators in environments where there is no foliage to provide cover.
Illustration: Casey Chin14**BLACK SWAN** (*Cygnus atratus*): **Melbourne, Australia** - Black swans in cities are less likely to flee when humans approach, as happens constantly in crowded urban environments. This adaptation appears to be linked to changes in a dopamine receptor gene called DRD4.
Illustration: Casey Chin15**ATLANTIC KILLIFISH** (*Fundulus heteroclitus*): **Newark, New Jersey** - Killifish in Newark Bay have rapidly evolved resistance to the toxic compound dioxin, which kills most other members of the species. The resistance is ascribed to genetic changes that “mute” dioxin's ability to overwhelm a vulnerable signaling pathway.
