Biogeography of marine urban habitats - islands for hard bottom fauna and floraMacroecology

Robin P.M. Gauff¹, Hassan Almetwaly¹, Giada Riva¹, Davide De Battisti¹, Anna Benvenuto¹, Irene Gregori¹, Serena De Lauretis¹, Ilaria Marino¹, Nicole Macri¹, Tomaso Patarnello¹, Joana Riedel¹, Alessandro Vezzi¹, Lorenzo Zane¹, Laura Airoldi¹

¹University of Padova, Italy

Marine urban habitats constitute novel ecosystems colonized by native species, as well as a variety of introduced fauna and flora. Despite decades of research, the rules governing their community assembly and local biodiversity remain poorly understood. This gap has been attributed to the unique characteristics of these habitats, such as pollution, strong anthropogenic disturbances, and the specific ecological processes associated with species introductions. A key question, for instance, concerns the respective contributions of neutral and deterministic factors in community assembly. Using frameworks linked to the theory of island biogeography (TIB), it is possible to predict the relationship between species richness in urban habitats, the distance of these habitats from natural rocky shores, and habitat size, as well as to make inferences about community composition and the contribution of synanthropic species. These predictions were tested, along with other biogeographic theories (such as biotic homogenization), during a two-month campaign across seven biogeographic sectors of the Mediterranean Sea. In each sector, we scraped communities on natural rocky shores and in urban habitats at varying distances from these shores (0-100 km) and across different habitat sizes, identifying all fauna and flora present (>400 species total). We also sampled local limpet populations to test whether the TIB predictions held true at the genetic level. Patterns in species richness and community characteristics aligned with the predictions of the framework, while molecular analyses are ongoing. This suggests that TIB may serve as a valuable framework for predicting species richness and community assembly in marine urban habitats, advancing our understanding of these ecosystems.