Small snakes, big cities: Population genetics of urban Dekay's brown snake (Storeria dekayi) in New Jersey

Despite the unprecedented rate of global urbanization, a diverse array of
taxa are supported in urban areas. However, the long-term persistence of
urban wildlife cannot be guaranteed due to the various adverse effects
that come with urbanization, such as resource depletion and reduced gene
flow. Accordingly, it is imperative to evaluate the health and viability
of urban wildlife, particularly of species that are underrepresented in
the existing literature, like herpetofauna. Genomic techniques can provide
critical insights into urban wildlife health and population viability.
Here, we generated a ddRADseq dataset of 162 Dekay’s brown snakes
(Storeria dekayi) among 11 locations with different urbanization
magnitudes across New Jersey, USA, and examined the population genetic
patterns of this common urban reptile. While genetic diversity was not
severely reduced within those populations, we uncovered the presence of
genetic differentiation and structuring across them, especially for those
from the most urbanized areas. Deviations of interpopulation structure
from their geographic distributions might reflect either habitat
alteration or human intervention in recent history. Landscape genetic
analyses revealed the presence of an isolation-by-distance relationship
that was only significant within a short spatial distance of 1,500 m. Most
urban populations also displayed lower-than-expected historic migration
and diversity rates, but some remained genetically connected and diverse.
To conclude, our study can serve as a useful guide for population genomic
studies on urban herpetofauna. Based on our results, urbanization is
likely to impact interpopulation genetic connectivity, but to have limited
effects on intrapopulation genetic diversity of small-bodied, terrestrial
urban dwellers.