Extensive gene flow along the urban–rural gradient in a migratory colonial bird

Abstract

Urban colonization by wildlife involves a combination of several different mechanisms, including phenotype or genotype sorting, phenotypic plasticity and microevolutionary adaptation. Combination of these processes can produce a rapid phenotypic, but also genetic divergence of urban versus rural populations. Here, we examined the pattern of genetic differentiation between urban and rural populations of a colonial migratory bird, the black‐headed gull Chroicocephalus ridibundus. To this end, we sampled ca 170 individuals from six (two urban and four rural) colonies in northern Poland, and genotyped them at ten microsatellite loci. Our analysis provided evidence for negligible genetic divergence of urban and rural colonies, as assessed with fixation index FST and Nei's unbiased genetic distance D (mean pairwise urban‐rural comparisons: FST = 0.003 ± 0.001 [SE] and D = 0.012 ± 0.006 [SE]). Bayesian clustering methods provided support for homogeneous genetic structure across all urban and rural populations. Also, we found no support for reduced allelic diversity in urban versus rural colonies. These results stand in a stark contrast to the previous findings on the genetic consequences of urbanization in birds. We hypothesize that this pattern could possibly be attributed to the important life‐history characters of the black‐headed gull, including coloniality, migratoriness, and high dispersal propensity. Our study provides a novel insight into the urban landscape genetics, underlining large variation in the mechanisms of urban colonization and its genetic consequences in wild animal populations.

Genetic structure of urban and non-urban populations differs between two common parid species

“…In turn, analyzes of microsatellite data conducted by Brewer et al 19 revealed that the level of urbanization did not affect genetic diversity and genetic structure of song sparrows inhabiting patches in a gradient of urbanization around Blacksburg (USA), where pairwise F ST values ranged from 0.011 to 0.023. Similar conclusion was provided by studies on black headed gulls Chroicocephalus ridibundus in northern Poland 15 and on common kestrels Falco tinnuculus in Czech Republic 24 , where urban and rural populations did not differ genetically.…”

“…Evaluation of genetic divergence between populations of each species was conducted by calculation of Wright’s fixation index F ST . This is a classic measure of population divergence, although it is known to diminish the role of mutations in inducing genetic variation within populations 15 , 63 . Therefore, an alternative statistic R ST 63 was introduced based on the stepwise mutation model, which can more accurately reflect changes in microsatellite allele sizes 21 .…”

Urban birds’ tolerance towards humans was largely unaffected by increased variation in human levels due to COVID-19 shutdowns

“…In other words, the urban environment has filtered birds based on their inherent levels of tolerance in a similar way regardless of variation in human levels. Indeed, based on genetic studies, in some species, rural populations are a source of individuals to urban populations [58,59].…”

Prevalence and Antibiotic Resistance of Campylobacter spp. in Urban and Rural Black-Headed Gulls Chroicocephalus ridibundus

“…In 2015–2016, 330–350 pairs of black-headed gulls bred in the Bydg-IND colony, 120 pairs in Bydg-REC and 880–1200 pairs in Kusowo. The extent of anthropogenic pressure, physiographic characteristics of the areas surrounding the breeding sites and detailed information about the study area were described by Kitowski et al ( 2017 ) and Indykiewicz et al ( 2018a ).…”