Rethink the Sink: Urban cores act as leaky sinks to maintain regional gene flow in coyotes

Urbanization is rapidly becoming an influential evolutionary force, but the intricate relationship between urbanization and gene flow among species like coyotes remains poorly understood. This research aims to unravel the mystery surrounding the three primary models governing urban connectivity: urban fragmentation, urban facilitation, and the urban sink hypothesis.

To test these models, researchers analyzed high-resolution RAD-capture data to conduct landscape genomics and gene flow assessments in urban coyotes (Canis latrans) across the Los Angeles metropolitan area. By examining various environmental, social-ecological, and historical aspects of the built environment, they were able to gauge the impact of urban heterogeneity on intra-city evolutionary dynamics.

The study found weak population structure in coyotes, with a strong influence from family groups. This was accompanied by extensive landscape permeability and gene flow, spanning across crucial highways. One surprising finding was the asymmetric gene flow from exurban source populations into the urban core, reinforcing the urban sink paradigm.

Contrary to previous assumptions, the urban matrix exhibited surprising functional heterogeneity. One urban core served as a "genetic sponge," absorbing unique transient alleles from several surrounding sources, while both urban cores functioned as permeable "leaky sinks," exporting vital gene flow to other populations.

The findings challenge the notion that urban sinks solely act as genetic dead-ends, revealing that urban demographic sinks can paradoxically function as essential genetic bridges. This study rejects the pure urban fragmentation model, demonstrating that genetic sink dynamics and genetic facilitation are not mutually exclusive. In essence, high-turnover urban sinks can help buffer regional biodiversity against genetic erosion, emphasizing the critical importance of promoting matrix permeability and inter-patch connectivity in urban conservation strategies.