Abstract
Urbanization fragments landscapes and can impede the movement of organisms through their environment, which can decrease population connectivity. Reduction in connectivity influences gene flow and allele frequencies, and can lead to a reduction in genetic diversity and the fixation of certain alleles, with potential negative effects for populations. Previous studies have detected effects of urbanization on genetic diversity and structure in terrestrial animals living in landscapes that vary in their degree of urbanization, even over very short distances. We investigated the effects of low-intensity urbanization on genetic diversity and genetic structure in Song Sparrows (Melospiza melodia). We captured 208 Song Sparrows at seven sites along a gradient of urbanization in and around Blacksburg, VA, USA, then genotyped them using a panel of fifteen polymorphic microsatellite loci. We found that genetic diversity was comparable among the seven study sites, and there was no evidence of genetic structuring among sites. These findings suggest that over a gradient of urbanization characterized by low density urban development, Song Sparrows likely exist in a single panmictic population.
Highlights
Urbanization and habitat fragmentation are major concerns in a changing world, and can have large effects on population genetic diversity and structure
We used microsatellite genotypes to compare the genetic diversity and population genetic structure of 208 birds over approximately 15 km, surveying birds living in undisturbed riparian areas, farm land, and suburban habitats that we describe here as rural, intermediate, and suburban, respectively
Sosp012 was removed from further analysis because in addition to the linkage disequilibrium (LD), it was out of Hardy–Weinberg equilibrium (HWE) at four sites
Summary
Urbanization and habitat fragmentation are major concerns in a changing world, and can have large effects on population genetic diversity and structure. Human need for more land and resources has led to habitat fragmentation through expanded development into previously rural areas, known as urbanization. Anthropogenic factors such as highways, bridges, and gaps in natural cover may impede the movements of individuals through the environment; even highly-mobile organisms such as birds may have their movements restricted by anthropogenic habitat changes [2,3,4], which can promote genetic isolation due to restricted interactions between individuals. Reduced connectivity may lessen the genetic diversity of members of a breeding population, impact gene flow and allele frequencies, and can lead to allele fixation, with potential negative consequences for animal populations [5,6,7].
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