High Evolutionary Potential Maintained in Common Frog (Rana temporaria) Populations Inhabiting Urban Drainage Ponds

Abstract

Urbanisation leading to habitat change and fragmentation is a recognised global threat to biodiversity. However, it may also offer opportunities for some species. Genetic diversity, one of the three components of biodiversity, is often overlooked in conservation planning and policy. In the present study, we used a panel of seven microsatellite markers to compare the genetic structure of 34 common frog (Rana temporaria) populations residing in urban and suburban drainage ponds in Inverness (Scotland) with populations from rural surroundings. As a main finding, the levels of genetic variation were indiscernible between (sub)urban and rural populations. Significant isolation-by-distance was observed only for rural populations, with measures of pairwise genetic differentiation (Fst) that were, on average, lower than those in urban and suburban areas. The mean numbers of alleles remained stable between two temporal sets of samples collected at intervals broadly representing one R. temporaria generation, but with a tendency of decreasing allelic richness, irrespectively of the site characteristics. Taking these results together, our study revealed that the elevated levels of differentiation between R. temporaria populations inhabiting (sub)urban drainage ponds did not lead to increased levels of genetic erosion. Our findings support the importance of well-designed blue–green infrastructure in urban landscapes for the retention of within-species genetic diversity and can help to inform future biodiversity management policies.

Limited evidence for genetic differentiation or adaptation in two amphibian species across replicated rural–urban gradients

“…However, evidence for a negative influence of urbanization on genetic diversity of amphibian populations is mixed. Although many studies have reported stronger differentiation and/or erosion of genetic variability in urban populations (Arens et al., 2007; de Campos Telles et al., 2007; Fusco et al., 2021; Hitchings & Beebee, 1997, 1998; Homola, Loftin, & Kinnison, 2019; Lourenço et al., 2017; Munshi‐South et al., 2013; Noël et al., 2007; Noël & Lapointe, 2010; Vargová et al., 2023), others have found no or only a weak effect (Furman et al., 2016; Jehle et al., 2023; Schmidt & Garroway, 2021; Straub et al., 2015; Yannic et al., 2021). Schmidt and Garroway (2021) provided a synthesis for 19 North American amphibian species across rural–urban gradients and did not detect a relationship between genetic parameters and urbanization.…”

Among the trees: shade promotes the growth and higher survival of juvenile toads

“…However, progressive urbanization transforms habitats into increasingly unfavourable conditions, driving many species of amphibians towards a widespread decline mainly due to habitat loss or degradation, fragmentation, isolation or direct mortality (Baillie et al, 2004;Hamer & McDonnell, 2008). Consequently, many amphibian populations in urban areas become small, burdened with inbreeding, and more exposed to the risk of extinction (Hamer & McDonnell, 2008;Nowakowski et al, 2018;Pyron, 2018; but see Jehle et al, 2023).…”