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.

Body size plays an important role in predator-prey interactions, but its evolution is often limited due to all sorts of constraints. The arms race between bats and moths provides great opportunities to study body size evolution and associated traits across a wide range of species. Nocturnally-active moths are in particular limited in evolving larger bodies, as any increase in echo-acoustic reflective surface will put them more at risk of a bat's sonar system. Here we assessed whether moths can escape bat detection in a size-dependent way by increasing their acoustic camouflage through ultrasonic absorptive body scales. We used an automated setup to 3D scan a total of 110 moth specimen, from eight different families of Lepidoptera using a biomimetic bat head. We carried out three different ensonification experiments with intact, partially shaved and fully shaved moth specimen to relate the level of acoustic camouflage to various body size measurements. Comparing shaved versus intact specimen we found a clear reduction in target strength, although the effect strongly depends on frequency range as well as body size. The stealth coating provided by sound absorptive body scales can reduce prey detectability up to 365 cubic metres and is in particular beneficial to larger species. The level of acoustic camouflage did not covary with other anti-predator traits, such as ultrasonic ears and appears to be an all-round anti-predator strategy. Acoustic camouflage through stealth coating thus allows moths to escape from the allometric relationship between size and detection risk, thereby enabling species to evolve larger bodies.