Last night, I headed down to the beautiful Bell House in the Gowanus section of Brooklyn for the monthly Secret Science Club lecture by Dr Jason Munshi-South a professor of Urban Evolutionary Biology at Baruch College and CUNY's Graduate Center. Dr Munshi-South lectured on some of the neighbors that most New Yorkers are unacquainted with.
Dr Munshi-South began his lecture with an admission that he had been somewhat surprised upon his first visit at the amount of "nature" that is present in New York City. He displayed a map of the world's biomes and indicated that, because of the activities of humans throughout the world, it was useful to think of human-altered biomes- anthromes. Because of human activity, it could be said that we are living in the age of human-dominated environments, which could be termed the Anthropocene Epoch. Even though the majority of biomes are human dominated, most ecological studies take place in protected areas. Only four percent of these studies are conducted in an urban environment.
In urban environments, biodiversity decreases. There are fewer species in urban areas, but the populations of the species that remain typically increase. While many species are "urban avoiders", the few "urban adapters" tend to thrive. Besides the ubiquitous eastern gray squirrel (we have a fairly common melanistic variety of this squirrel as well), the most common native small mammals in NYC are the white footed mouse, the meadow vole, and the northern short-tailed shrew. The mice and voles are typically caught in traps baited with birdseed, while the shrews are caught in pitfall traps. In the Q&A, Dr Munshi-South indicated that the infamous rats of the city are not included in his study because he doesn't like them, as any rats caught in the baited traps are smelly and vicious. Additionally, the rats aren't native to the region. Larger mammals, such as racoons, squirrels, striped skunks, opossums, red foxes, feral cats, and coyotes are detected with remote cameras (great images can be found at the Fauna of NYC section of the Encyclopedia of Life. The coyote pictured in the EoL was photographed on the grounds of the New York Botanical Garden in the Bronx. As an aside, coyotes are also present in Van Cortlandt Park in the Bronx. They are fairly abundant in Westchester County- I actually saw one hanging out in the driveway of a Stop-n-Shop near my workplace last Thursday night, it looked like it owned the place.
Dr Munshi-South also discussed salamander species that still inhabit New York City. Redback salamanders (and their gray-backed variety the leadback) are fairly common in parks are areas bordering golf courses. Northern two-lined salamanders and dusky salamanders are not as common, but can be found near springs and streams in extreme Northern Manhattan (being very rocky, the northern tip of Manhattan has extensive undeveloped areas).
As far as the coyote goes, the animals arrived in the New York metro area recently. It is thought that the coyote came to the city by two routes- one population arrived from the west, while another population traveled east through Canada (the reduction of the wolf population made this movement easier, and this population of coyotes engaged in interbreeding with wolves- the coyotes also occasionally interbred with dogs, so the population is more accurately described as "Northeastern wild canids"), then turned south until it established itself in the undeveloped portions of the Bronx. From time to time, a coyote will enter Manhattan, but these incidents tend to be unreported these days, probably to avoid embarrassing coverage of the authorities.
After an overview of the fauna of the city, Dr Munshi-South discussed evolution in the urban environment. The habitats of the wild critters in the city tend to be fractured (this map of the parks of the city shows that the parks are often separated by long distances though Frederick Law Olmstead did design greenbelts to connect the parks. Isolated populations gain genetic variations through the process of genetic drift- changes in allele frequency can eventually become dominant in a population. Such changes in isolated populations accumulate until each population is genetically distinct.
The white-footed mouse is the the go-to animal in urban evolutionary studies. In one study, twenty-five mice each were collected from fifteen city parks, and tissue samples were taken so eighteen locations on the genome could be compared to determine the extent of genetic variation. In the more isolated parks, the populations were distinct, while mice in connected parks showed less variation (there is an extensive green belt in eastern Brooklyn and Queens composed of parks and cemeteries). To model the movement of populations diagrams similar to circuit diagrams can be used (warning: PDF). In the case of New York City's white-footed mice, travel from one suitable habitat to another is most feasible when there is a 70% coverage of an area by the tree canopy. Lesser canopy cover results in an impeded ability to move from suitable habitat to another. Even though the isolated populations of the city's white-footed mice are genetically distinct, they have not been isolated for enough generations for allopatric speciation to occur- they are not distinct species.
Further studies compared mouse populations from more rural areas (such as Harriman State Park) to the city mouse populations (yes, the obligatory joke was made). The city mice tended to have changes in the region of the genome that influences the immune system- remember that biodiversity decreases in urban areas, but the population density of successful urban adapters tends to increase. Natural selection would result in these populations having more robust immune systems.
In the case of the dusky salamander, there are two populations separated by the insurmountable obstacle posed by the Alexander Hamilton Bridge. The populations on either side of the bridge (180th St and 167th St) are genetically distinct.
In the Q&A, Dr Munshi-South addressed such topics as the explosion in the raccoon population in New York City, and the relatively high opossum population in less developed neighborhoods in Queens and Brooklyn. He discussed the discovery of a second beaver in the Bronx (dubbed Justin Beaver). He discussed the movement of fishers from the Albany area to the south (for the record, there's a fisher at one of my worksites in northern Westchester county- luckily, it's nowhere near my primary workplace because fishers tend to kill cats and I would be really upset if anything happened to mah preshus kittehs). Some bastard in the crowd asked about conservation measures taken to protect salamander habitats in city parks and Dr Munshi-South spoke of the need to balance human recreational needs with the needs of animals... a proposed mountain biking path was scratched to protect Northern Manhattan's dusky salamanders.
The lecture was yet another stellar Secret Science Club event. For a taste of this lecture's subject matter, crack open a beer and watch this video featuring Dr Munshi-South: