Figure - available from: Urban Ecosystems
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Study sites with the least and most impervious cover within 1000 m. Maps show 2015 World Imagery provided by Esri (Redlands, California, USA)
Source publication
Urbanization is known to extirpate many species, but far less is known about how suburbanization may affect amphibian populations. We studied wood frogs (Lithobates sylvaticus) to test the effects of site characteristics (within-pool conditions and land cover indicative of suburbanization within 1000 m) and larval morphology on newly emerged frogle...
Citations
In urban environments, organisms often exhibit novel phenotypes, which can be attributed to phenotypic plasticity and/or evolutionary responses. Understanding the mechanism behind these phenotypic changes is essential for the effective conservation. Amphibians, being highly sensitive to environmental changes, show variation in size at metamorphosis, which impacts their fitness. We surveyed the Japanese common toad (Bufo japonicus) in and around the city of Tokyo to determine whether size at metamorphosis exhibits urban phenotypes, and if so, whether the phenotype is associated with evolutionary responses. We measured size at metamorphosis at 30 study sites over two years along an urban gradient to examine the relationship with the urbanization indicator, green cover ratio. Our results showed that toads at sites with lower green cover ratio (more urbanized) had larger sizes at metamorphosis, indicating an urban phenotype. To examine the possibility of evolutionary response in this urban phenotype, a rearing experiment was conducted. We reared tadpoles from nine sites under identical laboratory conditions and found that tadpoles from sites with lower green cover ratios (more urbanized) metamorphosed later at a larger size. These results suggest that the larger size at metamorphosis may be favored in more urbanized areas, possibly because terrestrial environments are of relatively lower quality compared to aquatic environments. We propose that maintaining aquatic environments that support larger size at metamorphosis is key for conserving urban amphibians. We also emphasize the importance of testing for evolutionary responses in urban phenotypes to correctly understand the conditions of urban amphibians and develop appropriate conservation strategies.
