The city‐fox phenomenon: genetic consequences of a recent colonization of urban habitat

Abstract

The red fox (Vulpes vulpes) is one of the best-documented examples of a species that has successfully occupied cities and their suburbs during the last century. The city of Zurich (Switzerland) was colonized by red foxes 15 years ago and the number of recorded individuals has increased steadily since then. Here, we assessed the hypothesis that the fox population within the city of Zurich is isolated from adjacent rural fox populations against the alternative hypothesis that urban habitat acts as a constant sink for rural dispersers. We examined 11 microsatellite loci in 128 foxes from two urban areas, separated by the main river crossing the city, and three adjacent rural areas from the region of Zurich. Mean observed heterozygosity across individuals and the number of detected alleles were lower for foxes collected within the city as compared with their rural conspecifics. Genetic differentiation was significantly lower between rural than between rural and urban populations, and highest value of pairwise FST was recorded between the two urban areas. Our results indicate that the two urban areas were independently founded by a small number of individuals from adjacent rural areas resulting in genetic drift and genetic differentiation between rural and urban fox populations. Population admixture and immigration analysis revealed that urban-rural gene flow was higher than expected from FST statistics. In the five to seven generations since colonization, fox density has dramatically increased. Currently observed levels of migration between urban and rural populations will probably erode genetic differentiation over time.

Molecular Detection of Capillaria aerophila, an Agent of Canine and Feline Pulmonary Capillariosis

“…In particular, Vulpes vulpes and Martes foina may contribute to the spreading of C. aerophila in areas where it previously was not endemic and in companion animals. This epidemiological pattern is similar to that recorded for the cardiopulmonary worm Angiostrongylus vasorum as a likely effect of the increase of fox populations in periurban and urban areas and of movements of wild and companion animals around regions (21,32,37). More studies are warranted for evaluating the distribution of C. aerophila in wildlife and pets cohabiting the same geographic areas in order to elucidate the phylogeography of different parasite populations.…”

The spatial genetic structure of the yellow-necked mouse in an urban environment – a recent invader vs. a closely related permanent inhabitant

“…One such study investigated the population of foxes (Vulpes vulpes) in Zurich approx. 15 years after a significant increase in the number of animals within the city borders, and reported a small but significant genetic differentiation between urban and rural sampling sites, as well as slightly reduced genetic variability within urban populations, probably due to the founder effect (Wandeler et al 2003). In another such study, the genetic variability of a breeding population of European kestrel (Falco tinnunculus) recently founded (in the 1970s) in the city of Warsaw was compared with rural populations and no differences were found, suggesting undisturbed gene flow between the relatively new urban population and birds from nonurban areas (Rutkowski et al 2009).…”

“…amphibians), often related to a specific environment, such as water bodies, exhibit decreased genetic variability due to isolation and intensified genetic drift (Hitchings and Beebee 1998;Noël et al 2007;Noël and Lapointe 2010;Mikulič and Pišút 2012;Munshi-South et al 2013;Zak and Pehek 2013, but see also Saarikivi et al 2013); (ii) mobile species able to cross environmental barriers seem to maintain a high level of genetic variability, probably avoiding complete isolation between patches of habitat within the city as well as between urban and rural areas (Desender et al 2005;Gardner-Santana et al 2009;Rutkowski et al 2009;Bj rklund et al 2010;Munshi-South and Kharchenko 2010); (iii) urban populations, usually fragmented into local subpopulations inhabiting small patches of suitable habitats (e.g. green spaces), exhibit pronounced genetic structure (Rubin et al 2001;Wood and Pullin 2002;Wandeler et al 2003;Desender et al 2005;Gardner-Santana et al 2009;Bj rklund et al 2010;Delaney et al 2010;Munshi-South and Kharchenko 2010;Vangestel et al 2011;Gortat et al 2013Gortat et al , 2015aMunshi-South et al 2013;Unfried et al 2013).…”

Ecological Characteristics of Two Closely Related Rodent Species in Urban Environment—Permanent Inhabitant vs Newcomer

“…This occurs either by active penetration of species into cities from outside, or as a result of populations becoming enclosed within cities as they expand, a phenomenon known as urban trap [2].…”

“…Animal behavior has also been observed to differ in cities [11]. Different abiotic conditions in cities and the spatial structure supporting the isolation of small patches of the environment frequently lead to greater genetic differentiation between isolated local populations within cities and in comparison to natural populations [2] [12]. Additionally, within isolated local populations, genetic variability is frequently reduced and the degree of relatedness between individuals is increased [13] [14], in particular in species with a limited mobility [15] [16] for whom crossing anthropogenic barriers is difficult or impossible.…”