Landscape connectivity and genetic structure of animal populations in urban ponds

Abstract Animal populations in urban landscapes tend to have lower genetic diversity and higher genetic differentiation than those in rural landscapes. The extent of these effects can be influenced by the dispersal rates of the organisms and the connectivity of the landscape. Here, we explore associations of landscape connectivity with genetic diversity and genetic differentiation in urban ponds in the City of Stockholm, Sweden. Our focus is on three invertebrate species and one vertebrate species, each with different dispersal rates and life-history traits. We sampled 30 ponds and collected genetic data by using double-digest restriction-site associated DNA sequencing (ddRADseq). Our results showed moderate differences in genetic diversity among populations for all species. Additionally, all populations showed a heterozygote deficiency, suggesting inbreeding. We found significant genetic structure among populations for the three species categorized as low to intermediate dispersers: Asellus aquaticus (Isopoda), Planorbis planorbis (Gastropoda) and, Rana temporaria (Amphibia). In contrast, the species with presumably the highest relative dispersal capacity, Haliplus ruficollis (Coleoptera), exhibited no significant population structure. Furthermore, genetic differentiation in A. aquaticus and P. planorbis was significantly correlated with geographic distance. For A. aquaticus , genetic differentiation was also significantly correlated with landscape connectivity across both aquatic (blue) and terrestrial (green) environmental features. Our results highlight the role of landscape connectivity and dispersal ability of species in shaping genetic structure among urban ponds.