Urbanization reduces gene flow but not genetic diversity of stream salamander populations in the New York City metropolitan area

Abstract

Natural landscape heterogeneity and barriers resulting from urbanization can reduce genetic connectivity between populations. The evolutionary, demographic, and ecological effects of reduced connectivity may lead to population isolation and ultimately extinction. Alteration to the terrestrial and aquatic environment caused by urban influence can affect gene flow, specifically for stream salamanders who depend on both landscapes for survival and reproduction. To examine how urbanization affects a relatively common stream salamander species, we compared genetic connectivity of Eurycea bislineata (northern two‐lined salamander) populations within and between streams in an urban, suburban, and rural habitat around the New York City (NYC) metropolitan area. We report reduced genetic connectivity between streams within the urban landscape found to correspond with potential barriers to gene flow, that is, areas with more dense urbanization (roadways, industrial buildings, and residential housing). The suburban populations also exhibited areas of reduced connectivity correlated with areas of greater human land use and greater connectivity within a preserve protected from development. Connectivity was relatively high among neighboring rural streams, but a major roadway corresponded with genetic breaks even though the habitat contained more connected green space overall. Despite greater human disturbance across the landscape, urban and suburban salamander populations maintained comparable levels of genetic diversity to their rural counterparts. Yet small effective population size in the urban habitats yielded a high probability of loss of heterozygosity due to genetic drift in the future. In conclusion, urbanization impacted connectivity among stream salamander populations where its continual influence may eventually hinder population persistence for this native species in urban habitats.

Inconsistent effects of urbanization on amphibian genetic diversity

“…S2). Other studies with data not included in our synthesis have also found that genetic diversity did not decrease with urbanization in wood frogs (Furman, Scheffers, Taylor, Davis, & Paszkowski, 2016), fire salamanders (Lourenço, Álvarez, Wang, & Velo-Antón, 2017), and northern two-lined salamanders (Fusco, Pehek, & Munshi-South, 2020). Abundance in a species of frog related to the spring peeper, the boreal chorus frog ( P. maculata ), had a positive relationship with urbanization, which may be attributed to its preference for open habitats, or potential breeding habitats near roads (Browne, Paszkowski, Foote, Moenting, & Boss, 2009).…”

A global meta-analysis reveals higher variation in breeding phenology in urban birds than in their non-urban neighbours

“…Assessing differences in phenotypic variation between urban and non-urban populations of less mobile species will be important to evaluate how biological traits (e.g., dispersal ability) determine the evolutionary impact of urban ecological conditions. Previous work in mammal and amphibian species with lower dispersal ability than birds suggests a comparable level of (genetic) variation between urban and non-urban habitats (Fusco et al . 2021; Richardson et al .…”

Urban evolution comes into its own: Emerging themes and future directions of a burgeoning field

“…In the first study, Fusco et al. (2020) examined Northern two‐lined salamanders ( Eurycea bislineata ) which are native to the New York City metropolitan area and live in urban, suburban, and rural stream environments. Fusco et al.…”

“…Fusco et al. (2020) found that populations experience reduced gene flow in urban areas, and this reduction was correlated with buildings, roadways, and residential housing. Yet, despite this disturbance and reduced gene flow due to urban development, all populations maintained similar levels of genetic diversity.…”

“…et al (2020) examined Northern two-lined salamanders (Eurycea bislineata) which are native to the New York City metropolitan area and live in urban, suburban, and rural stream environments Fusco et al (2020). found that populations experience reduced gene flow in urban areas, and this reduction was correlated with buildings, roadways, and residential housing.…”