Urbanization drives the acoustic diversity of mangrove anurans and avifauna in Puerto Rico

The mangroves of Puerto Rico occupy a broad gradient of urbanization that offers a chance to test hypotheses on urban faunal communities from both terrestrial and mangrove systems. These hypotheses state that urban avifaunal communities are less diverse, with greater representation by generalists, but that certain mangrove specialists can utilize urban landscapes. Much of this is said to be driven by food resources, with frugivores and nectarivores benefiting from abundant residential flowers and fruits, while insectivores are driven away by low food resources. This study used passive acoustic monitoring to identify the audible anuran and avifaunal species in mangroves across the urban gradient of Puerto Rico. Three anurans and twenty-four avian species were detected across all sites, with eighteen species found at the most diverse site, and six at the least diverse site. The most urban communities were more similar to each other and characterized by low diversity, especially of invertivores, mangrove specialists, and endemics. The least urban communities, however, were less like each other and more diverse than their more urban counterparts. Greater surrounding vegetation cover was the strongest overall predictor of increased faunal diversity, although urban coverage and population density were also strongly correlated with some guilds and species. Soundscape analyses showed that acoustic space use was a strong predictor of site diversity and is thus a sufficiently accurate faster alternative to detecting individual species. This will be an important tool in the continued monitoring of these forests, which may experience changes associated with ongoing urbanization and sea-level rise.