Effect of Spatial and Temporal Urban Isolation on the Genetic Diversity, Acoustic Variation, and Morphological Characteristics of an Urban Survivor Bird Species

Urbanization modifies ecosystems by fragmenting natural habitats and increasing isolation between populations. Therefore, a reduction in gene flow among isolated populations is expected with greater distance and time since fragmentation. Changes in the structure, density, or community composition of the remaining habitats often result in species' differences in acoustic and morphological traits. However, the relationship between genetics, vocalizations, and morphological divergence in urban areas over time remains poorly understood. We analyzed ten years of genetic, acoustic, and morphological data from isolated populations of the white-eared ground-sparrow. We recorded and measured five acoustic traits, six morphological traits, and used seven microsatellites (SSRs) to compare the effect of urban expansion on the acoustics, morphology, and gene flow patterns across populations over a 10-year period. We found an increase in inbreeding, song duration, number of elements, and frequency of maximum amplitude, but a decrease in female body size and changes in male beak, decreasing size in one population and increasing in another. In general, we found changes in all characteristics studied but only found a significant correlation between genetic diversity and the acoustic characteristics of songs. Our results corroborate that urbanization acts as an important barrier for white-eared ground sparrows, which leads to significant divergence in genetic and behavioral traits.