Abstract
Urbanization affects key aspects of wildlife ecology. Dispersal in urban wildlife species may be impacted by geographical barriers but also by a species' inherent behavioural variability. There are no functional connectivity analyses using continuous individual-based sampling across an urban-rural continuum that would allow a thorough assessment of the relative importance of physical and behavioural dispersal barriers. We used 16 microsatellite loci to genotype 374 red foxes (Vulpes vulpes) from the city of Berlin and surrounding rural regions in Brandenburg in order to study genetic structure and dispersal behaviour of a mobile carnivore across the urban-rural landscape. We assessed functional connectivity by applying an individual-based landscape genetic optimization procedure. Three commonly used genetic distance measures yielded different model selection results, with only the results of an eigenvector-based multivariate analysis reasonably explaining genetic differentiation patterns. Genetic clustering methods and landscape resistance modelling supported the presence of an urban population with reduced dispersal across the city border. Artificial structures (railways, motorways) served as main dispersal corridors within the cityscape, yet urban foxes avoided densely built-up areas. We show that despite their ubiquitous presence in urban areas, their mobility and behavioural plasticity, foxes were affected in their dispersal by anthropogenic presence. Distinguishing between man-made structures and sites of human activity, rather than between natural and artificial structures, is thus essential for better understanding urban fox dispersal. This differentiation may also help to understand dispersal of other urban wildlife and to predict how behaviour can shape population genetic structure beyond physical barriers.
Highlights
Urbanization results in dramatic environmental change (Johnson & Munshi-South, 2017) and some species flourish in these semi-artificial ecosystems (Møller, 2009; Shochat, Warren, Faeth, McIntyre, & Hope, 2006)
This predicts that the urban fabric has no influence on gene flow, resulting in the absence of population and landscape genetic structure. (b) The fragmentation hypothesis posits that fox dispersal was affected by physical barriers such as rivers, built-up areas and highways
Despite differences in the resistance surface values between the models, the circuitscape current maps for the best supported model and the model with the fewest predictors were very similar, both suggesting that gene flow within the city of Berlin mostly occurred along linear landscape elements
Summary
Urbanization results in dramatic environmental change (Johnson & Munshi-South, 2017) and some species flourish in these semi-artificial ecosystems (Møller, 2009; Shochat, Warren, Faeth, McIntyre, & Hope, 2006). There is currently no thorough analysis of the population and landscape genetic structure of a vagile species in an urban-rural continuum available, using continuous individual-based sampling This would permit to identify drivers of urban gene flow, including those unrelated to the physical properties of the landscape. (a) The null hypothesis was that, due to their niche breadth and mobility, foxes disperse unhampered throughout the city and urban and adjoining rural populations are panmictic This predicts that the urban fabric has no influence on gene flow, resulting in the absence of population and landscape genetic structure. | 468 individuals within the city are habituated to manmade structures and human presence, while individuals from the rural surroundings are not and face a behavioural barrier to enter the urban area This predicts two genetic populations resulting from limited gene flow across the city border.
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