Urban Environments Impact Parasite Diversity and an Antipredator Response in an Amphibian Model

Urbanization is a major driver of biodiversity loss by transforming ecosystems and imposing novel selective pressures that reshape not only species but also their interspecific interactions. In urban environments, predation pressure is often altered, leading to shifts in antipredator strategies, and parasitism varies with changes in environmental quality and the introduction of novel hosts or vectors. Understanding how these processes are modified by urbanization is particularly urgent for amphibians, the most threatened group of vertebrates, as urban-driven changes may have profound consequences for fitness and population persistence. To explore these processes with an integrative perspective, we evaluated the effects of the anthropogenic footprint on the species Pelophylax perezi across six locations in central Spain with varying degrees of urbanization. We analyzed traits related to predator-prey and parasite-host interactions linked to survival and performance in altered habitats. Contrary to expectations, urban frogs had longer tibiofibulae and greater flight initiation distances, suggesting distinct selective pressures on antipredator responses in human-modified landscapes. Submersion time was unrelated to urbanization and body condition did not vary significantly, although it was greater in urban areas. Blood parasite diversity and abundance of Lankesterella, a genus of blood coccidian, increased with anthropogenic footprint. Moreover, urban frogs with worse body condition had higher loads of Lankesterella. Overall, our results show that urbanization modifies the morphology and interspecific interactions of this amphibian species, emphasizing the need to consider traits related to predator-prey and parasite-host interactions when assessing amphibian responses to urbanization and informing conservation strategies in increasingly urbanized landscapes.