title: Trapped within the city: integrating demography, time since isolation and population-specific traits to assess the genetic effects of urbanization.
abstract: Urbanization is a severe form of habitat fragmentation that can cause many species to be locally extirpated and many others to become trapped and isolated within an urban matrix. The role of drift in reducing genetic diversity and increasing genetic differentiation is well recognized in urban populations. However, explicit incorporation and analysis of the demographic and temporal factors promoting drift in urban environments are poorly studied. Here, we genotyped 15 microsatellites in 320 fire salamanders from the historical city of Oviedo (Est. 8th century) to assess the effects of time since isolation, demographic history (historical effective population size; Ne) and patch size on genetic diversity, population structure and contemporary Ne. Our results indicate that urban populations of fire salamanders are highly differentiated, most likely due to the recent Nedeclines, as calculated in coalescence analyses, concomitant with the urban development of Oviedo. However, urbanization only caused a small loss of genetic diversity. Regression modelling showed that patch size was positively associated with contemporary Ne, while we found only moderate support for the effects of demographic history when excluding populations with unresolved history. This highlights the interplay between different factors in determining current genetic diversity and structure. Overall, the results of our study on urban populations of fire salamanders provide some of the very first insights into the mechanisms affecting changes in genetic diversity and population differentiation via drift in urban environments, a crucial subject in a world where increasing urbanization is forecasted.
authors.affiliation: Departamento de Biologia da Faculdade de Ciências da Universidade do Porto, Rua Campo Alegre, 4169-007, Porto, Portugal.|CIBIO/InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos da Universidade do Porto, Instituto de Ciências Agrárias de Vairão, Rua Padre Armando Quintas 7, 4485-661, Vairão, Portugal.
authors.forename: André
authors.identifier: http://orcid.org/0000-0003-3650-5062
authors.initials: A
authors.lastname: Lourenço
authors.affiliation: Ecology Unit, Department of Organisms and Systems Biology, University of Oviedo, C/ Catedrático Rodrigo Uría, 33071 Oviedo, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Álvarez
authors.affiliation: Department of Environmental Science, Policy and Management, University of California, 130 Mulford Hall #3114, Berkeley, CA, 94705, USA.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Wang
authors.affiliation: CIBIO/InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos da Universidade do Porto, Instituto de Ciências Agrárias de Vairão, Rua Padre Armando Quintas 7, 4485-661, Vairão, Portugal.
authors.forename: Guillermo
authors.identifier: http://orcid.org/0000-0002-9483-5695
authors.initials: G
authors.lastname: Velo-Antón
mesh_terms: D000818:Animals; D003710:Demography; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D018895:Microsatellite Repeats; D013030:Spain; D014507:Urbanization; D014562:Caudata / Q000235:genetics*
keywords: 
  Salamandra salamandra
  ; demography; genetic drift; genetic isolation; microsatellite; population effective size