Historical human activity shapes the genomic landscape of urban and
forest túngara frogs
Abstract
Urbanisation is rapidly altering ecosystems, leading to profound
biodiversity loss. To mitigate these effects, we need a better
understanding of how urbanisation impacts dispersal and reproduction.
Two contrasting population demographic models have been proposed which
predict that urbanisation either promotes (facilitation model) or
constrains (fragmentation model) gene flow and genetic diversity. Which
of these models prevails likely depends on the strength of selection on
specific phenotypic traits that influence dispersal, survival or
reproduction. Here, we examine the genomic impact of urbanisation on the
Neotropical túngara frog (Engystomops pustulosus), a species known to
adapt its reproductive traits to urban selective pressures. Using
whole-genome resequencing for multiple paired urban and forest
populations we examined genomic diversity, population connectivity and
demographic history. Contrary to both the fragmentation and facilitation
models, urban populations did not exhibit substantial changes in genomic
diversity or differentiation compared to forest populations and genomic
variation was best explained by geographic distance rather than
environmental factors. Moreover, both urban and forest populations
appear to have undergone population declines which are coincident with
extensive human-activity around the Panama Canal during the last few
centuries rather than recent urbanisation. Overall, our study
underscores the importance of considering the historical context in
urban evolution studies as anthropogenic effects may be extensive and
impact non-urban areas on both recent and older timescales. Failure to
take this into account when interpreting comparisons between urban and
non-urban areas may underestimate the impact of urbanisation.