Limited genetic structure in a wood frog (Lithobates sylvaticus) population in an urban landscape inhabiting natural and constructed wetlands

Abstract

Urbanization has been linked to amphibian population declines globally. Habitat fragmentation can negatively impact gene flow among populations but what role artificially constructed wetlands have in maintaining gene flow in urban amphibian populations remains uncertain. We assessed gene flow in a population of wood frogs (Lithobates sylvaticus) inhabiting both constructed and natural wetlands located in Edmonton, Alberta, Canada. We genotyped 10 microsatellite loci in 182 frogs from eight wetlands and tested for genetic differentiation between wetlands. We tested if bottlenecks had occurred at constructed wetlands and if there were differences in allelic richness between natural wetlands and constructed wetlands. We found no evidence of bottlenecks, no differences in allelic richness among subpopulations, and no genetic structure within the population. Although significant differences in pair-wise comparisons of allele frequency distributions between wetlands were detected, all F ST values were low (0.003-0.053) and Bayesian clustering indicated the presence of a single genetic cluster. Despite extensive urbanization within our study area, genetic homogeneity has been preserved indicating that it may be possible to use constructed wetlands to maintain amphibian populations and preserve gene flow among subpopulations living within urbanized landscapes.

Trapped within the city: integrating demography, time since isolation and population‐specific traits to assess the genetic effects of urbanization

“…), while in the wood frog ( Lithobates sylvaticus ; Furman et al . ) diversity levels were very similar to those observed in our study. In Oviedo, fire salamander populations are putatively isolated to a greater extent than these species (see below), making the observed genetic diversity even more surprising.…”

“…Other studies in urban‐dwelling amphibians have found a global F ST that varies considerably across different systems, being much lower in moor frogs on Montréal Island (Noël & Lapointe ) and in the red‐backed salamander ( Plethodon cinereus ; Furman et al . ) but quite high in the stream‐dwelling northern dusky salamander ( Desmognathus fuscus ) in New York, where population extirpation and degradation of streams likely led to a marked decrease in genetic diversity as well.…”

“…; see also Furman et al . ), and therefore, accurate testing of the effects of population history predictors in genetic diversity and structure may be compromised in regression modelling. All statistical analyses described in this section were performed in r software (R Development Core Team ).…”

When new human‐modified habitats favour the expansion of an amphibian pioneer species: Evolutionary history of the natterjack toad (Bufo calamita) in a coal basin

“…In contrast, Furman et al. () found no evidence of genetic erosion and increased genetic differentiation in natural and artificially constructed wetlands in a wood frog, despite extensive urbanization. In the same way, isolated urban populations of the Fire salamander did not exhibit lower levels of genetic diversity and showed similar N e compared to rural populations (Lourenço et al., ).…”

“…Urban environments can host trapped and isolated populations. In this context, recent studies investigated the strength of genetic drift induced by reduced functional connectivity across an urban matrix (e.g., Beninde et al., ; Furman, Scheffers, Taylor, Davis, & Paszkowski, ; Lourenço et al., ; Munshi‐South, Zak, & Pehek, ). However, it appears that new anthropogenic habitats can also promote the establishment of pioneer species in highly disturbed areas (Amici et al., ; Flavenot, Fellous, Abdelkrim, Baguette, & Coulon, ).…”